{"version":"1.0.0","segments":[{"startTime":0.19,"endTime":2.35,"body":"- It's my very great pleasure this evening"},{"startTime":2.35,"endTime":4.74,"body":"to introduce the annual Gresham College"},{"startTime":4.74,"endTime":7.05,"body":"London Mathematical Society lecture."},{"startTime":7.05,"endTime":8.51,"body":"This is a longstanding partnership"},{"startTime":8.51,"endTime":10.58,"body":"between the society and the college,"},{"startTime":10.58,"endTime":13.17,"body":"and we have fantastic speakers every year,"},{"startTime":13.17,"endTime":14.71,"body":"and this year is no exception,"},{"startTime":14.71,"endTime":17.03,"body":"with a wonderful speaker,"},{"startTime":14.71,"endTime":17.03,"body":"Professor Hugh Hunt,"},{"startTime":17.03,"endTime":19.04,"body":"who I'm about to introduce."},{"startTime":19.04,"endTime":22.23,"body":"Hugh is professor of engineering"},{"startTime":19.04,"endTime":22.23,"body":"dynamics and vibration"},{"startTime":22.23,"endTime":23.62,"body":"at Cambridge University."},{"startTime":23.62,"endTime":26.23,"body":"His research specializes in climate change"},{"startTime":26.23,"endTime":29.05,"body":"and how we could potentially"},{"startTime":26.23,"endTime":29.05,"body":"refreeze the Arctic."},{"startTime":29.05,"endTime":30.91,"body":"Some of his other research interests"},{"startTime":30.91,"endTime":33.86,"body":"include noise and vibration"},{"startTime":30.91,"endTime":33.86,"body":"from underground trains,"},{"startTime":33.86,"endTime":35.13,"body":"pendulum clocks,"},{"startTime":35.13,"endTime":36.96,"body":"and spinning things that fly,"},{"startTime":36.96,"endTime":38.95,"body":"you're going to hear"},{"startTime":36.96,"endTime":38.95,"body":"something about those tonight."},{"startTime":38.95,"endTime":41.7,"body":"Hugh is a regular presenter"},{"startTime":38.95,"endTime":41.7,"body":"on television documentaries,"},{"speaker":"including \"Dambusters","startTime":41.7,"endTime":44.997,"body":"Building the Bouncing Bomb,\""},{"speaker":"including \"Dambusters","startTime":44.997,"endTime":47.73,"body":"\"Attack of the Zeppelins,\""},{"speaker":"including \"Dambusters","startTime":44.997,"endTime":47.73,"body":"sounds fantastic,"},{"speaker":"and \"Guy Martin","startTime":47.73,"endTime":49.55,"body":"Wall of Death,\""},{"speaker":"and \"Guy Martin","startTime":49.55,"endTime":52.39,"body":"which I think may be one"},{"speaker":"and \"Guy Martin","startTime":49.55,"endTime":52.39,"body":"of the pictures there."},{"speaker":"and \"Guy Martin","startTime":52.39,"endTime":55.19,"body":"He's also keeper of the"},{"speaker":"and \"Guy Martin","startTime":52.39,"endTime":55.19,"body":"clock at Trinity College,"},{"speaker":"and \"Guy Martin","startTime":55.19,"endTime":58.86,"body":"a clock which is the most"},{"speaker":"and \"Guy Martin","startTime":55.19,"endTime":58.86,"body":"accurate tower clock in the world."},{"speaker":"and \"Guy Martin","startTime":58.86,"endTime":60.89,"body":"He has an impressive"},{"speaker":"and \"Guy Martin","startTime":58.86,"endTime":60.89,"body":"collection of boomerangs,"},{"speaker":"and \"Guy Martin","startTime":60.89,"endTime":62.38,"body":"which he uses to inspire students"},{"speaker":"and \"Guy Martin","startTime":62.38,"endTime":64.93,"body":"in the study of dynamics and mechanics,"},{"speaker":"and \"Guy Martin","startTime":64.93,"endTime":67.04,"body":"and tonight he'll be speaking to us"},{"speaker":"and \"Guy Martin","startTime":67.04,"endTime":70.05,"body":"on the maths of gyroscopes and boomerangs."},{"speaker":"and \"Guy Martin","startTime":70.05,"endTime":71.708,"body":"Professor Hugh Hunt."},{"speaker":"and \"Guy Martin","startTime":71.708,"endTime":74.708,"body":"(audience applauds)"},{"speaker":"and \"Guy Martin","startTime":75.57,"endTime":78.76,"body":"- We're talking about things that spin,"},{"speaker":"and \"Guy Martin","startTime":78.76,"endTime":80.55,"body":"and so what I want to do"},{"speaker":"and \"Guy Martin","startTime":80.55,"endTime":83.5,"body":"is to start off with a demonstration,"},{"speaker":"and \"Guy Martin","startTime":83.5,"endTime":86.97,"body":"and the demonstration"},{"speaker":"and \"Guy Martin","startTime":83.5,"endTime":86.97,"body":"involves a bouncy ball."},{"speaker":"and \"Guy Martin","startTime":86.97,"endTime":88.97,"body":"Now, if I take a bouncy ball,"},{"speaker":"and \"Guy Martin","startTime":88.97,"endTime":91.22,"body":"you kind of expect"},{"speaker":"and \"Guy Martin","startTime":91.22,"endTime":95.07,"body":"a ball bouncing between two tables"},{"speaker":"and \"Guy Martin","startTime":95.07,"endTime":98.023,"body":"would behave like a ray of light."},{"speaker":"and \"Guy Martin","startTime":99.12,"endTime":103.73,"body":"If that was a light,"},{"speaker":"and \"Guy Martin","startTime":99.12,"endTime":103.73,"body":"photons, they're particles,"},{"speaker":"and \"Guy Martin","startTime":103.73,"endTime":104.99,"body":"bouncing between mirrors,"},{"speaker":"and \"Guy Martin","startTime":104.99,"endTime":109.42,"body":"you'd expect it to"},{"speaker":"and \"Guy Martin","startTime":104.99,"endTime":109.42,"body":"bounce kind of like that."},{"speaker":"and \"Guy Martin","startTime":109.42,"endTime":113.18,"body":"So let's now do a demonstration."},{"speaker":"and \"Guy Martin","startTime":113.18,"endTime":114.26,"body":"So I've got a table here,"},{"speaker":"and \"Guy Martin","startTime":114.26,"endTime":115.383,"body":"I can move my cat,"},{"speaker":"and \"Guy Martin","startTime":116.81,"endTime":118.25,"body":"the cat will come in later,"},{"speaker":"and \"Guy Martin","startTime":118.25,"endTime":119.353,"body":"I have a table here,"},{"speaker":"and \"Guy Martin","startTime":121.4,"endTime":122.52,"body":"so there's two tables,"},{"speaker":"and \"Guy Martin","startTime":122.52,"endTime":125.83,"body":"this is the top table and"},{"speaker":"and \"Guy Martin","startTime":122.52,"endTime":125.83,"body":"this is the bottom table,"},{"speaker":"and \"Guy Martin","startTime":125.83,"endTime":128.003,"body":"and I've got a bouncy ball."},{"speaker":"and \"Guy Martin","startTime":129.22,"endTime":130.593,"body":"Here we go, a bouncy ball."},{"speaker":"and \"Guy Martin","startTime":131.75,"endTime":136.247,"body":"And I'm going to bounce the ball."},{"speaker":"and \"Guy Martin","startTime":136.247,"endTime":137.513,"body":"Are you good at catching?"},{"speaker":"and \"Guy Martin","startTime":138.98,"endTime":142.7,"body":"I'm going to bounce the"},{"speaker":"and \"Guy Martin","startTime":138.98,"endTime":142.7,"body":"ball sort of this way."},{"speaker":"and \"Guy Martin","startTime":142.7,"endTime":147.7,"body":"You'd expect the ball to go"},{"speaker":"and \"Guy Martin","startTime":142.7,"endTime":147.7,"body":"here, here, here, and out there."},{"speaker":"and \"Guy Martin","startTime":147.96,"endTime":150.64,"body":"And it's a pretty reliable experiment,"},{"speaker":"and \"Guy Martin","startTime":150.64,"endTime":155.64,"body":"so I can make myself a bit of a target,"},{"speaker":"and \"Guy Martin","startTime":160.733,"endTime":163.507,"body":"and the ball will come back towards me."},{"speaker":"and \"Guy Martin","startTime":166.03,"endTime":168.66,"body":"Now the question is why does that happen?"},{"speaker":"and \"Guy Martin","startTime":168.66,"endTime":169.72,"body":"I'll get rid of these glasses"},{"speaker":"and \"Guy Martin","startTime":169.72,"endTime":171.91,"body":"because they're just in the way."},{"speaker":"and \"Guy Martin","startTime":171.91,"endTime":174.693,"body":"If I try that again,"},{"speaker":"and \"Guy Martin","startTime":176.42,"endTime":177.383,"body":"I can do this way."},{"speaker":"and \"Guy Martin","startTime":179.45,"endTime":181.57,"body":"Why does the ball come back to me?"},{"speaker":"and \"Guy Martin","startTime":181.57,"endTime":183.48,"body":"Now, the thing about this is"},{"speaker":"and \"Guy Martin","startTime":183.48,"endTime":185.58,"body":"anybody can do this experiment,"},{"speaker":"and \"Guy Martin","startTime":185.58,"endTime":188.09,"body":"we've probably never thought about it."},{"speaker":"and \"Guy Martin","startTime":188.09,"endTime":189.04,"body":"You can do it,"},{"speaker":"and \"Guy Martin","startTime":189.04,"endTime":190.47,"body":"you can throw the ball under a table,"},{"speaker":"and \"Guy Martin","startTime":190.47,"endTime":193.2,"body":"the ball comes back the way it came."},{"speaker":"and \"Guy Martin","startTime":193.2,"endTime":194.37,"body":"There's three bounces,"},{"speaker":"and \"Guy Martin","startTime":194.37,"endTime":195.67,"body":"which is kind of what you'd expect,"},{"speaker":"and \"Guy Martin","startTime":195.67,"endTime":196.958,"body":"you can hear that,"},{"speaker":"and \"Guy Martin","startTime":196.958,"endTime":197.791,"body":"(ball bangs)"},{"speaker":"and \"Guy Martin","startTime":197.791,"endTime":198.624,"body":"one, two, three,"},{"speaker":"and \"Guy Martin","startTime":200.48,"endTime":201.853,"body":"but why does it come back?"},{"speaker":"and \"Guy Martin","startTime":202.7,"endTime":203.533,"body":"So what we've got to do"},{"speaker":"and \"Guy Martin","startTime":203.533,"endTime":206.46,"body":"is to think about each"},{"speaker":"and \"Guy Martin","startTime":203.533,"endTime":206.46,"body":"bounce as it happens."},{"speaker":"and \"Guy Martin","startTime":206.46,"endTime":209.99,"body":"The first bounce, we"},{"speaker":"and \"Guy Martin","startTime":206.46,"endTime":209.99,"body":"get some spin happening."},{"speaker":"and \"Guy Martin","startTime":209.99,"endTime":211.17,"body":"You kind of expect that"},{"speaker":"and \"Guy Martin","startTime":211.17,"endTime":216.17,"body":"because if you imagine a"},{"speaker":"and \"Guy Martin","startTime":211.17,"endTime":216.17,"body":"plane landing on a runway,"},{"speaker":"and \"Guy Martin","startTime":219.233,"endTime":220.75,"body":"the plane comes in like this,"},{"speaker":"and \"Guy Martin","startTime":220.75,"endTime":224.163,"body":"you'd expect the wheel to start spinning."},{"speaker":"and \"Guy Martin","startTime":225.96,"endTime":226.793,"body":"If it didn't,"},{"speaker":"and \"Guy Martin","startTime":226.793,"endTime":227.95,"body":"you'd have thought the"},{"speaker":"and \"Guy Martin","startTime":226.793,"endTime":227.95,"body":"brakes were on, or something."},{"speaker":"and \"Guy Martin","startTime":227.95,"endTime":230.99,"body":"So why shouldn't that happen with a ball?"},{"speaker":"and \"Guy Martin","startTime":231.931,"endTime":234.0,"body":"So I've got my ball here,"},{"speaker":"and \"Guy Martin","startTime":234.0,"endTime":236.4,"body":"the ball starts spinning"},{"speaker":"and \"Guy Martin","startTime":234.0,"endTime":236.4,"body":"after the first bounce."},{"speaker":"and \"Guy Martin","startTime":237.36,"endTime":241.13,"body":"So straightaway, this"},{"speaker":"and \"Guy Martin","startTime":237.36,"endTime":241.13,"body":"is a problem about spin."},{"speaker":"and \"Guy Martin","startTime":241.13,"endTime":242.68,"body":"Then what happens?"},{"speaker":"and \"Guy Martin","startTime":242.68,"endTime":243.97,"body":"The thing is,"},{"speaker":"and \"Guy Martin","startTime":243.97,"endTime":246.25,"body":"we know that if I put backspin on a ball,"},{"speaker":"and \"Guy Martin","startTime":246.25,"endTime":250.7,"body":"that the ball will come back towards me,"},{"speaker":"and \"Guy Martin","startTime":250.7,"endTime":253.07,"body":"so is this backspin or topspin?"},{"speaker":"and \"Guy Martin","startTime":253.07,"endTime":254.69,"body":"All right, let's do a show hands,"},{"speaker":"and \"Guy Martin","startTime":254.69,"endTime":256.053,"body":"who thinks this is topspin?"},{"speaker":"and \"Guy Martin","startTime":257.17,"endTime":258.18,"body":"Lots of sporty people."},{"speaker":"and \"Guy Martin","startTime":258.18,"endTime":259.43,"body":"Who thinks it's backspin?"},{"speaker":"and \"Guy Martin","startTime":262.61,"endTime":263.84,"body":"It looks like topspin,"},{"speaker":"and \"Guy Martin","startTime":263.84,"endTime":265.64,"body":"but that's because we're looking at it"},{"speaker":"and \"Guy Martin","startTime":265.64,"endTime":267.76,"body":"from the perspective of the ground,"},{"speaker":"and \"Guy Martin","startTime":267.76,"endTime":269.94,"body":"let's tip it upside down."},{"speaker":"and \"Guy Martin","startTime":269.94,"endTime":274.94,"body":"Now it looks like backspin"},{"speaker":"and \"Guy Martin","startTime":269.94,"endTime":274.94,"body":"because it's spinning."},{"speaker":"and \"Guy Martin","startTime":276.69,"endTime":278.42,"body":"It is backspin,"},{"speaker":"and \"Guy Martin","startTime":278.42,"endTime":279.89,"body":"so the backspinners got that right."},{"speaker":"and \"Guy Martin","startTime":279.89,"endTime":281.78,"body":"So if we think about what happens,"},{"speaker":"and \"Guy Martin","startTime":281.78,"endTime":284.557,"body":"with backspin, the ball"},{"speaker":"and \"Guy Martin","startTime":281.78,"endTime":284.557,"body":"comes back the way it came."},{"speaker":"and \"Guy Martin","startTime":284.557,"endTime":285.86,"body":"And then, also,"},{"speaker":"and \"Guy Martin","startTime":285.86,"endTime":287.06,"body":"you've got to think,"},{"speaker":"and \"Guy Martin","startTime":287.06,"endTime":288.92,"body":"what happens to the direction of spin?"},{"speaker":"and \"Guy Martin","startTime":288.92,"endTime":289.96,"body":"If you look closely,"},{"speaker":"and \"Guy Martin","startTime":289.96,"endTime":291.063,"body":"when you take a ball,"},{"speaker":"and \"Guy Martin","startTime":291.063,"endTime":293.66,"body":"I don't know whether anybody"},{"speaker":"and \"Guy Martin","startTime":291.063,"endTime":293.66,"body":"can see what's happening,"},{"speaker":"and \"Guy Martin","startTime":293.66,"endTime":296.61,"body":"but that ball comes back towards me,"},{"speaker":"and \"Guy Martin","startTime":296.61,"endTime":299.26,"body":"but also changes the spin direction."},{"speaker":"and \"Guy Martin","startTime":299.26,"endTime":300.31,"body":"Try that for yourself,"},{"speaker":"and \"Guy Martin","startTime":300.31,"endTime":301.6,"body":"and that's quite interesting."},{"speaker":"So now let's recap","startTime":302.88,"endTime":306.17,"body":"the ball comes in, starts to spin,"},{"speaker":"So now let's recap","startTime":306.17,"endTime":307.46,"body":"comes back the way it came,"},{"speaker":"So now let's recap","startTime":307.46,"endTime":309.31,"body":"spin direction reverses,"},{"speaker":"So now let's recap","startTime":309.31,"endTime":311.49,"body":"now we've got some topspin,"},{"speaker":"So now let's recap","startTime":311.49,"endTime":312.38,"body":"and out it goes."},{"speaker":"So now let's recap","startTime":312.38,"endTime":314.62,"body":"You kind of think,"},{"speaker":"So now let's recap","startTime":314.62,"endTime":316.49,"body":"well that's not maths,"},{"speaker":"So now let's recap","startTime":316.49,"endTime":320.26,"body":"but the first thing about solving problems"},{"speaker":"So now let's recap","startTime":320.26,"endTime":322.58,"body":"is to know what problem"},{"speaker":"So now let's recap","startTime":320.26,"endTime":322.58,"body":"it is you've got to solve."},{"speaker":"So now let's recap","startTime":322.58,"endTime":324.75,"body":"And you look at this and you think,"},{"speaker":"So now let's recap","startTime":324.75,"endTime":328.62,"body":"hmm, I think I can see"},{"speaker":"So now let's recap","startTime":324.75,"endTime":328.62,"body":"what's happening here,"},{"speaker":"So now let's recap","startTime":328.62,"endTime":329.95,"body":"so now we solve the problem."},{"speaker":"So now let's recap","startTime":329.95,"endTime":331.313,"body":"The maths we want to do,"},{"speaker":"So now let's recap","startTime":333.27,"endTime":335.47,"body":"we're going to assume that the ball"},{"speaker":"So now let's recap","startTime":335.47,"endTime":340.47,"body":"is really good at conserving energy,"},{"speaker":"So now let's recap","startTime":341.56,"endTime":342.83,"body":"'cause it's a nice, bouncy ball,"},{"speaker":"So now let's recap","startTime":342.83,"endTime":347.83,"body":"so conservation of energy on each bounce,"},{"speaker":"So now let's recap","startTime":347.9,"endTime":349.67,"body":"conservation of angular momentum,"},{"speaker":"So now let's recap","startTime":349.67,"endTime":352.31,"body":"I'll talk a bit more"},{"speaker":"So now let's recap","startTime":349.67,"endTime":352.31,"body":"about that this evening,"},{"speaker":"So now let's recap","startTime":352.31,"endTime":355.28,"body":"and if we just put the"},{"speaker":"So now let's recap","startTime":352.31,"endTime":355.28,"body":"maths in for those things,"},{"speaker":"So now let's recap","startTime":355.28,"endTime":358.678,"body":"conservation of energy,"},{"speaker":"So now let's recap","startTime":355.28,"endTime":358.678,"body":"conservation of angular momentum,"},{"speaker":"then this is what happened","startTime":359.511,"endTime":361.77,"body":"ball comes in, no spin,"},{"speaker":"then this is what happened","startTime":361.77,"endTime":362.88,"body":"conservation of energy,"},{"speaker":"then this is what happened","startTime":362.88,"endTime":364.92,"body":"conservation of angular momentum there,"},{"speaker":"then this is what happened","startTime":364.92,"endTime":366.52,"body":"it starts to spin,"},{"speaker":"then this is what happened","startTime":366.52,"endTime":367.78,"body":"the equations there,"},{"speaker":"then this is what happened","startTime":367.78,"endTime":368.64,"body":"it starts to spin,"},{"speaker":"then this is what happened","startTime":368.64,"endTime":370.16,"body":"the same equations here,"},{"speaker":"then this is what happened","startTime":370.16,"endTime":371.74,"body":"it starts to spin."},{"speaker":"then this is what happened","startTime":371.74,"endTime":373.39,"body":"What's really neat"},{"speaker":"then this is what happened","startTime":373.39,"endTime":374.3,"body":"is that the equations"},{"speaker":"then this is what happened","startTime":374.3,"endTime":378.05,"body":"are just multiplying, adding, square root,"},{"speaker":"then this is what happened","startTime":378.05,"endTime":379.67,"body":"nothing very complicated,"},{"speaker":"then this is what happened","startTime":379.67,"endTime":380.91,"body":"so it's really easy to code up,"},{"speaker":"then this is what happened","startTime":380.91,"endTime":384.783,"body":"so if anyone's interested in"},{"speaker":"then this is what happened","startTime":380.91,"endTime":384.783,"body":"coding up this sort of thing."},{"speaker":"then this is what happened","startTime":386.06,"endTime":387.74,"body":"Then if you do a high-speed movie,"},{"speaker":"then this is what happened","startTime":387.74,"endTime":390.95,"body":"which you can all do with"},{"speaker":"then this is what happened","startTime":387.74,"endTime":390.95,"body":"your phones these days,"},{"speaker":"then this is what happened","startTime":390.95,"endTime":391.783,"body":"that's what it does."},{"speaker":"then this is what happened","startTime":391.783,"endTime":393.38,"body":"In it comes, up it goes,"},{"speaker":"then this is what happened","startTime":393.38,"endTime":395.493,"body":"spin direction reverses."},{"speaker":"then this is what happened","startTime":397.771,"endTime":400.697,"body":"So it's pretty amazing that"},{"speaker":"then this is what happened","startTime":397.771,"endTime":400.697,"body":"this is what's going on,"},{"speaker":"then this is what happened","startTime":400.697,"endTime":403.017,"body":"and a little bit of maths helps us do it,"},{"speaker":"then this is what happened","startTime":403.017,"endTime":404.33,"body":"but the first thing you have to do"},{"speaker":"then this is what happened","startTime":404.33,"endTime":407.04,"body":"is to observe the thing"},{"speaker":"then this is what happened","startTime":404.33,"endTime":407.04,"body":"in the first place."},{"speaker":"then this is what happened","startTime":407.04,"endTime":408.203,"body":"Why is this important?"},{"speaker":"then this is what happened","startTime":409.12,"endTime":412.42,"body":"Well if we think of ball games here,"},{"speaker":"then this is what happened","startTime":412.42,"endTime":415.55,"body":"so this ball hits the crossbar,"},{"speaker":"then this is what happened","startTime":415.55,"endTime":418.863,"body":"and that's fine."},{"speaker":"then this is what happened","startTime":419.726,"endTime":422.559,"body":"(audience laughs)"},{"speaker":"then this is what happened","startTime":424.62,"endTime":429.37,"body":"So what's happening there is"},{"speaker":"then this is what happened","startTime":424.62,"endTime":429.37,"body":"the ball hits the crossbar,"},{"speaker":"then this is what happened","startTime":429.37,"endTime":430.22,"body":"it bounces back,"},{"speaker":"then this is what happened","startTime":430.22,"endTime":431.56,"body":"but it's spinning like anything,"},{"speaker":"then this is what happened","startTime":431.56,"endTime":433.55,"body":"we know that now,"},{"speaker":"then this is what happened","startTime":433.55,"endTime":435.78,"body":"and so it's just quite fun,"},{"speaker":"then this is what happened","startTime":435.78,"endTime":438.035,"body":"now that you know about spin."},{"speaker":"then this is what happened","startTime":438.035,"endTime":441.56,"body":"I was very pleased in Cambridge,"},{"speaker":"then this is what happened","startTime":441.56,"endTime":443.25,"body":"when I first arrived there,"},{"speaker":"then this is what happened","startTime":443.25,"endTime":446.72,"body":"to find that this chap, Ken Johnson,"},{"speaker":"then this is what happened","startTime":446.72,"endTime":451.54,"body":"was just in an office just"},{"speaker":"then this is what happened","startTime":446.72,"endTime":451.54,"body":"down the corridor from me,"},{"speaker":"then this is what happened","startTime":451.54,"endTime":453.657,"body":"and he'd published this paper called"},{"speaker":"then this is what happened","startTime":453.657,"endTime":456.14,"body":"\"The Bounce of the Superball.\""},{"speaker":"then this is what happened","startTime":456.14,"endTime":460.023,"body":"And in it, at the very beginning,"},{"speaker":"then this is what happened","startTime":463.03,"endTime":465.267,"body":"he works out angular"},{"speaker":"then this is what happened","startTime":463.03,"endTime":465.267,"body":"velocities of each bounce,"},{"speaker":"then this is what happened","startTime":465.267,"endTime":466.747,"body":"\"As we will now proceed to show,"},{"speaker":"then this is what happened","startTime":466.747,"endTime":468.827,"body":"\"this behavior cannot be accounted for"},{"speaker":"then this is what happened","startTime":468.827,"endTime":472.16,"body":"\"by classical rigid"},{"speaker":"then this is what happened","startTime":468.827,"endTime":472.16,"body":"body theory of impact.\""},{"speaker":"then this is what happened","startTime":472.16,"endTime":474.15,"body":"The thing is that all I've"},{"speaker":"then this is what happened","startTime":472.16,"endTime":474.15,"body":"just been showing you now"},{"speaker":"then this is what happened","startTime":474.15,"endTime":476.6,"body":"is the classic rigid"},{"speaker":"then this is what happened","startTime":474.15,"endTime":476.6,"body":"body theory of impact,"},{"speaker":"then this is what happened","startTime":476.6,"endTime":477.59,"body":"so I was a bit worried about this."},{"speaker":"then this is what happened","startTime":477.59,"endTime":479.58,"body":"So I spoke to Ken,"},{"speaker":"then this is what happened","startTime":479.58,"endTime":482.65,"body":"and he was saying, no, it doesn't work."},{"speaker":"then this is what happened","startTime":482.65,"endTime":485.03,"body":"And then I showed him my videos,"},{"speaker":"then this is what happened","startTime":485.03,"endTime":486.75,"body":"I think it does work."},{"speaker":"then this is what happened","startTime":486.75,"endTime":491.75,"body":"He wrote a lovely paper on"},{"speaker":"then this is what happened","startTime":486.75,"endTime":491.75,"body":"the contact of elastic solids,"},{"speaker":"then this is what happened","startTime":491.88,"endTime":494.33,"body":"and he came up with this nice idea"},{"speaker":"then this is what happened","startTime":494.33,"endTime":496.4,"body":"that you take a rigid body,"},{"speaker":"then this is what happened","startTime":496.4,"endTime":500.48,"body":"a rigid ball, like a solid steel ball,"},{"speaker":"then this is what happened","startTime":500.48,"endTime":502.16,"body":"and for the impact,"},{"speaker":"then this is what happened","startTime":502.16,"endTime":504.32,"body":"you just put a tiny,"},{"speaker":"then this is what happened","startTime":502.16,"endTime":504.32,"body":"little elastic particle"},{"speaker":"then this is what happened","startTime":504.32,"endTime":506.13,"body":"at the point of impact,"},{"speaker":"then this is what happened","startTime":506.13,"endTime":509.24,"body":"and when you do that, it"},{"speaker":"then this is what happened","startTime":506.13,"endTime":509.24,"body":"all comes out very nicely."},{"speaker":"then this is what happened","startTime":509.24,"endTime":511.79,"body":"So this is pretty much the"},{"speaker":"then this is what happened","startTime":509.24,"endTime":511.79,"body":"only maths I'm going to do,"},{"speaker":"then this is what happened","startTime":511.79,"endTime":513.06,"body":"I thought I'd better put some maths in"},{"speaker":"then this is what happened","startTime":513.06,"endTime":515.64,"body":"for those who've come here for maths,"},{"speaker":"then this is what happened","startTime":515.64,"endTime":516.473,"body":"but this is,"},{"speaker":"then this is what happened","startTime":516.473,"endTime":518.31,"body":"as some people in the audience would call,"},{"speaker":"then this is what happened","startTime":518.31,"endTime":520.544,"body":"dirty maths, applied maths,"},{"speaker":"then this is what happened","startTime":520.544,"endTime":522.15,"body":"that's all I do."},{"speaker":"then this is what happened","startTime":522.15,"endTime":523.92,"body":"But what's interesting is,"},{"speaker":"then this is what happened","startTime":523.92,"endTime":528.19,"body":"if you look at the kinetic"},{"speaker":"then this is what happened","startTime":523.92,"endTime":528.19,"body":"energy for a spinning ball,"},{"speaker":"then this is what happened","startTime":528.19,"endTime":531.1,"body":"then it's a formula that"},{"speaker":"then this is what happened","startTime":528.19,"endTime":531.1,"body":"looks kind of like this,"},{"speaker":"then this is what happened","startTime":531.1,"endTime":535.04,"body":"where v is velocity, and"},{"speaker":"then this is what happened","startTime":531.1,"endTime":535.04,"body":"omega is the angular velocity,"},{"speaker":"then this is what happened","startTime":535.04,"endTime":538.2,"body":"and I've got the kinetic"},{"speaker":"then this is what happened","startTime":535.04,"endTime":538.2,"body":"energy before collision,"},{"speaker":"then this is what happened","startTime":538.2,"endTime":541.997,"body":"and the kinetic energy"},{"speaker":"then this is what happened","startTime":538.2,"endTime":541.997,"body":"afterwards must be the same,"},{"speaker":"then this is what happened","startTime":541.997,"endTime":543.99,"body":"and then I do the same"},{"speaker":"then this is what happened","startTime":541.997,"endTime":543.99,"body":"thing for angular momentum"},{"speaker":"then this is what happened","startTime":543.99,"endTime":546.09,"body":"about the contact point."},{"speaker":"then this is what happened","startTime":546.09,"endTime":548.69,"body":"And then you can solve those"},{"speaker":"then this is what happened","startTime":546.09,"endTime":548.69,"body":"equations, that's fine,"},{"speaker":"then this is what happened","startTime":550.44,"endTime":551.273,"body":"you do that."},{"speaker":"then this is what happened","startTime":551.273,"endTime":553.29,"body":"But then, the neat thing is,"},{"speaker":"then this is what happened","startTime":553.29,"endTime":555.003,"body":"you do the next collision,"},{"speaker":"then this is what happened","startTime":555.9,"endTime":559.41,"body":"and then you get the third velocity,"},{"speaker":"then this is what happened","startTime":559.41,"endTime":560.853,"body":"depending on the first one,"},{"speaker":"then this is what happened","startTime":562.41,"endTime":566.72,"body":"and this is approaching"},{"speaker":"then this is what happened","startTime":562.41,"endTime":566.72,"body":"the bottom table again,"},{"speaker":"then this is what happened","startTime":566.72,"endTime":567.553,"body":"and you think,"},{"speaker":"then this is what happened","startTime":567.553,"endTime":569.213,"body":"hmm, well now I've got,"},{"speaker":"then this is what happened","startTime":570.97,"endTime":573.34,"body":"every time it approaches"},{"speaker":"then this is what happened","startTime":570.97,"endTime":573.34,"body":"this bottom table,"},{"speaker":"then this is what happened","startTime":573.34,"endTime":575.14,"body":"I know what the velocity is"},{"speaker":"then this is what happened","startTime":575.14,"endTime":576.66,"body":"depending on what it was"},{"speaker":"then this is what happened","startTime":576.66,"endTime":578.4,"body":"the last time it approached the table."},{"speaker":"then this is what happened","startTime":578.4,"endTime":579.603,"body":"So what you have is,"},{"speaker":"then this is what happened","startTime":582.44,"endTime":583.87,"body":"it's a difference equation,"},{"speaker":"then this is what happened","startTime":583.87,"endTime":587.89,"body":"so the n+1-th velocity"},{"speaker":"then this is what happened","startTime":583.87,"endTime":587.89,"body":"and angular velocity"},{"speaker":"then this is what happened","startTime":587.89,"endTime":591.693,"body":"is related by this ridiculous matrix,"},{"speaker":"then this is what happened","startTime":593.17,"endTime":596.3,"body":"and we want it to be some"},{"speaker":"then this is what happened","startTime":593.17,"endTime":596.3,"body":"kind of proportionality,"},{"speaker":"then this is what happened","startTime":596.3,"endTime":599.11,"body":"and that leads to an eigenvalue problem,"},{"speaker":"then this is what happened","startTime":599.11,"endTime":602.8,"body":"and the problem here is you"},{"speaker":"then this is what happened","startTime":599.11,"endTime":602.8,"body":"end up with complex numbers,"},{"speaker":"then this is what happened","startTime":602.8,"endTime":604.78,"body":"you think, oh God, why do I,"},{"speaker":"then this is what happened","startTime":604.78,"endTime":607.59,"body":"there's no complex"},{"speaker":"then this is what happened","startTime":604.78,"endTime":607.59,"body":"numbers in bouncing balls,"},{"speaker":"then this is what happened","startTime":607.59,"endTime":609.35,"body":"it's a real thing."},{"speaker":"then this is what happened","startTime":609.35,"endTime":611.87,"body":"But you solve it all,"},{"speaker":"then this is what happened","startTime":609.35,"endTime":611.87,"body":"you go through the maths,"},{"speaker":"then this is what happened","startTime":611.87,"endTime":613.09,"body":"and you end up with"},{"speaker":"then this is what happened","startTime":614.57,"endTime":617.73,"body":"that the velocity and the"},{"speaker":"then this is what happened","startTime":614.57,"endTime":617.73,"body":"angular velocity are sinusoids,"},{"speaker":"then this is what happened","startTime":619.6,"endTime":620.82,"body":"and you think, okay?"},{"speaker":"then this is what happened","startTime":620.82,"endTime":622.02,"body":"So you plot it all out,"},{"speaker":"then this is what happened","startTime":622.02,"endTime":623.94,"body":"and you get these sinusoids,"},{"speaker":"then this is what happened","startTime":623.94,"endTime":627.29,"body":"but it turns out that"},{"speaker":"then this is what happened","startTime":623.94,"endTime":627.29,"body":"you sample the sinusoids"},{"speaker":"then this is what happened","startTime":627.29,"endTime":629.51,"body":"at particular points."},{"speaker":"then this is what happened","startTime":629.51,"endTime":632.533,"body":"So what it means is that if I start here,"},{"speaker":"then this is what happened","startTime":633.79,"endTime":635.52,"body":"the first collision is there,"},{"speaker":"then this is what happened","startTime":635.52,"endTime":637.98,"body":"and that's the first"},{"speaker":"then this is what happened","startTime":635.52,"endTime":637.98,"body":"little circle on the curve,"},{"speaker":"then this is what happened","startTime":637.98,"endTime":639.28,"body":"and then the next one's there,"},{"speaker":"then this is what happened","startTime":639.28,"endTime":640.91,"body":"which is the next little circle,"},{"speaker":"then this is what happened","startTime":640.91,"endTime":642.05,"body":"then the next one's here,"},{"speaker":"then this is what happened","startTime":642.05,"endTime":644.7,"body":"so that, I've shown with"},{"speaker":"then this is what happened","startTime":642.05,"endTime":644.7,"body":"the big thick lines,"},{"speaker":"then this is what happened","startTime":644.7,"endTime":646.5,"body":"is the first three bounces,"},{"speaker":"then this is what happened","startTime":646.5,"endTime":648.91,"body":"which is what we've observed."},{"speaker":"then this is what happened","startTime":648.91,"endTime":650.25,"body":"And what's really nice is"},{"speaker":"then this is what happened","startTime":650.25,"endTime":652.113,"body":"when you look at it,"},{"speaker":"then this is what happened","startTime":653.51,"endTime":656.77,"body":"it all makes sense, more or less,"},{"speaker":"then this is what happened","startTime":656.77,"endTime":658.57,"body":"it's not perfect, but it's pretty good."},{"speaker":"then this is what happened","startTime":658.57,"endTime":661.1,"body":"And you kind of imagine"},{"speaker":"then this is what happened","startTime":661.1,"endTime":662.93,"body":"if I could make the table long enough"},{"speaker":"then this is what happened","startTime":662.93,"endTime":664.583,"body":"and get rid of energy loss,"},{"speaker":"then this is what happened","startTime":665.67,"endTime":669.47,"body":"this ball would go bouncing"},{"speaker":"then this is what happened","startTime":665.67,"endTime":669.47,"body":"backwards and forwards forever,"},{"speaker":"then this is what happened","startTime":669.47,"endTime":672.44,"body":"and I just quite like that sort of stuff."},{"speaker":"then this is what happened","startTime":672.44,"endTime":676.73,"body":"But now some of you will"},{"speaker":"then this is what happened","startTime":672.44,"endTime":676.73,"body":"remember a more important goal,"},{"speaker":"then this is what happened","startTime":677.64,"endTime":679.19,"body":"do you remember this one?"},{"speaker":"then this is what happened","startTime":679.19,"endTime":683.0,"body":"So this was Frank"},{"speaker":"then this is what happened","startTime":679.19,"endTime":683.0,"body":"Lampard's disallowed goal,"},{"speaker":"then this is what happened","startTime":683.0,"endTime":687.32,"body":"and it bounced over the goal line,"},{"speaker":"then this is what happened","startTime":687.32,"endTime":690.44,"body":"and then back up."},{"speaker":"then this is what happened","startTime":690.44,"endTime":691.273,"body":"Look at him,"},{"speaker":"then this is what happened","startTime":691.273,"endTime":693.78,"body":"he's a bit older now, isn't he."},{"speaker":"then this is what happened","startTime":693.78,"endTime":697.3,"body":"So the thing about that goal"},{"speaker":"then this is what happened","startTime":697.3,"endTime":699.11,"body":"is that if you do the maths on it,"},{"speaker":"then this is what happened","startTime":699.11,"endTime":701.71,"body":"it turns out that it's impossible"},{"speaker":"then this is what happened","startTime":701.71,"endTime":704.75,"body":"for a ball to hit the crossbar twice"},{"speaker":"then this is what happened","startTime":704.75,"endTime":706.4,"body":"without going over the goal line,"},{"speaker":"then this is what happened","startTime":707.27,"endTime":710.3,"body":"and you can do the angular"},{"speaker":"then this is what happened","startTime":707.27,"endTime":710.3,"body":"momentum and energy calculations,"},{"speaker":"then this is what happened","startTime":710.3,"endTime":713.702,"body":"but the newspapers the next"},{"speaker":"then this is what happened","startTime":710.3,"endTime":713.702,"body":"day didn't mention any of that."},{"speaker":"then this is what happened","startTime":713.702,"endTime":714.82,"body":"(audience laughs)"},{"speaker":"then this is what happened","startTime":714.82,"endTime":717.68,"body":"But it's just quite fun that you can,"},{"speaker":"then this is what happened","startTime":717.68,"endTime":719.1,"body":"with very simple maths,"},{"speaker":"then this is what happened","startTime":719.1,"endTime":721.35,"body":"look at that sort of thing"},{"speaker":"then this is what happened","startTime":719.1,"endTime":721.35,"body":"and enjoy what's going on."},{"speaker":"then this is what happened","startTime":721.35,"endTime":726.083,"body":"And ultimately, it comes down"},{"speaker":"then this is what happened","startTime":721.35,"endTime":726.083,"body":"to Isaac Newton's F equals ma,"},{"speaker":"then this is what happened","startTime":726.94,"endTime":729.14,"body":"force is mass times acceleration."},{"speaker":"then this is what happened","startTime":729.14,"endTime":730.48,"body":"Before we get onto gyroscopes,"},{"speaker":"then this is what happened","startTime":730.48,"endTime":732.17,"body":"I want to tell you about"},{"speaker":"then this is what happened","startTime":730.48,"endTime":732.17,"body":"this wall of death thing,"},{"speaker":"then this is what happened","startTime":732.17,"endTime":734.27,"body":"because what was really good,"},{"speaker":"then this is what happened","startTime":734.27,"endTime":736.55,"body":"this chap, Guy Martin,"},{"speaker":"then this is what happened","startTime":736.55,"endTime":737.73,"body":"you might have seen him on the telly,"},{"speaker":"then this is what happened","startTime":737.73,"endTime":738.57,"body":"he's a bit of a nutter,"},{"speaker":"then this is what happened","startTime":738.57,"endTime":742.75,"body":"but he wanted to ride the wall of death"},{"speaker":"then this is what happened","startTime":743.69,"endTime":748.207,"body":"and set the world speed"},{"speaker":"then this is what happened","startTime":743.69,"endTime":748.207,"body":"record for the wall of death,"},{"speaker":"then this is what happened","startTime":748.207,"endTime":752.34,"body":"he wanted to go 100 miles"},{"speaker":"then this is what happened","startTime":748.207,"endTime":752.34,"body":"an hour on a wall of death."},{"speaker":"then this is what happened","startTime":752.34,"endTime":756.61,"body":"So what I did was to write"},{"speaker":"then this is what happened","startTime":752.34,"endTime":756.61,"body":"down some equations for him,"},{"speaker":"then this is what happened","startTime":756.61,"endTime":758.7,"body":"but let's have a look at"},{"speaker":"then this is what happened","startTime":756.61,"endTime":758.7,"body":"a wall of death first."},{"speaker":"then this is what happened","startTime":758.7,"endTime":762.54,"body":"This is what you might"},{"speaker":"then this is what happened","startTime":758.7,"endTime":762.54,"body":"find in a fairground,"},{"speaker":"then this is what happened","startTime":762.54,"endTime":765.56,"body":"you've got a slopy bit at the bottom,"},{"speaker":"then this is what happened","startTime":765.56,"endTime":767.02,"body":"you've got a motorbike,"},{"speaker":"then this is what happened","startTime":767.02,"endTime":769.51,"body":"and you get these motorbike riders"},{"speaker":"then this is what happened","startTime":769.51,"endTime":773.06,"body":"that will go round and round."},{"speaker":"then this is what happened","startTime":773.06,"endTime":775.41,"body":"Typically, the diameter of"},{"speaker":"then this is what happened","startTime":773.06,"endTime":775.41,"body":"this thing is four meters,"},{"speaker":"then this is what happened","startTime":775.41,"endTime":778.0,"body":"and they'll go at 25 miles an hour."},{"speaker":"then this is what happened","startTime":778.0,"endTime":781.37,"body":"And all I said to to Guy Martin was"},{"speaker":"then this is what happened","startTime":782.27,"endTime":785.9,"body":"if you want to go 100 miles an hour,"},{"speaker":"then this is what happened","startTime":785.9,"endTime":788.33,"body":"well we're going to have"},{"speaker":"then this is what happened","startTime":785.9,"endTime":788.33,"body":"to do some sums on this"},{"speaker":"then this is what happened","startTime":788.33,"endTime":793.33,"body":"because the thing that is"},{"speaker":"then this is what happened","startTime":788.33,"endTime":793.33,"body":"difficult for the rider"},{"speaker":"then this is what happened","startTime":794.79,"endTime":796.56,"body":"on this wall of death"},{"speaker":"then this is what happened","startTime":796.56,"endTime":799.0,"body":"is the forces on their body,"},{"speaker":"then this is what happened","startTime":799.0,"endTime":801.847,"body":"because you get the g-forces,"},{"speaker":"then this is what happened","startTime":801.847,"endTime":802.68,"body":"in other words,"},{"speaker":"then this is what happened","startTime":802.68,"endTime":805.593,"body":"your eyeballs sink,"},{"speaker":"then this is what happened","startTime":802.68,"endTime":805.593,"body":"and your bladder sinks,"},{"speaker":"then this is what happened","startTime":807.31,"endTime":811.03,"body":"you can die just from the g-forces."},{"speaker":"then this is what happened","startTime":811.03,"endTime":811.863,"body":"So there they are,"},{"speaker":"then this is what happened","startTime":811.863,"endTime":814.86,"body":"the g-forces are holding"},{"speaker":"then this is what happened","startTime":811.863,"endTime":814.86,"body":"the bike onto the wall,"},{"speaker":"then this is what happened","startTime":814.86,"endTime":816.28,"body":"this is the wall of death,"},{"speaker":"then this is what happened","startTime":816.28,"endTime":817.32,"body":"but otherwise, as far as I know,"},{"speaker":"then this is what happened","startTime":817.32,"endTime":820.38,"body":"nobody's ever died doing a wall of death,"},{"speaker":"then this is what happened","startTime":820.38,"endTime":822.423,"body":"so it's a bit of a misnomer."},{"speaker":"then this is what happened","startTime":823.95,"endTime":826.28,"body":"So, circular motion,"},{"speaker":"then this is what happened","startTime":826.28,"endTime":830.14,"body":"what are the forces involved"},{"speaker":"then this is what happened","startTime":826.28,"endTime":830.14,"body":"with circular motion?"},{"speaker":"then this is what happened","startTime":830.14,"endTime":832.5,"body":"Well let's just have a look at this."},{"speaker":"then this is what happened","startTime":832.5,"endTime":835.843,"body":"if I take a tennis ball,"},{"speaker":"then this is what happened","startTime":835.843,"endTime":837.89,"body":"it's a regular tennis ball,"},{"speaker":"then this is what happened","startTime":837.89,"endTime":840.183,"body":"and I've got here,"},{"speaker":"then this is what happened","startTime":841.95,"endTime":842.783,"body":"it's full of water,"},{"speaker":"then this is what happened","startTime":842.783,"endTime":845.24,"body":"so this is two kilograms,"},{"speaker":"then this is what happened","startTime":845.24,"endTime":848.32,"body":"two liters, two kilograms,"},{"speaker":"then this is what happened","startTime":848.32,"endTime":853.32,"body":"and I'm going to tie a string"},{"speaker":"then this is what happened","startTime":848.32,"endTime":853.32,"body":"to this two liters of water."},{"speaker":"then this is what happened","startTime":856.94,"endTime":860.173,"body":"Normally, a tennis ball"},{"speaker":"then this is what happened","startTime":856.94,"endTime":860.173,"body":"is 50 grams, or something."},{"speaker":"then this is what happened","startTime":861.25,"endTime":864.77,"body":"In a game of water bottle"},{"speaker":"then this is what happened","startTime":861.25,"endTime":864.77,"body":"versus tennis ball,"},{"speaker":"then this is what happened","startTime":864.77,"endTime":866.59,"body":"the water bottle wins,"},{"speaker":"then this is what happened","startTime":866.59,"endTime":868.15,"body":"but it doesn't take much"},{"speaker":"then this is what happened","startTime":871.68,"endTime":873.493,"body":"to lift the two kilograms."},{"speaker":"then this is what happened","startTime":874.37,"endTime":877.11,"body":"So you get an idea that"},{"speaker":"then this is what happened","startTime":874.37,"endTime":877.11,"body":"this centrifugal force,"},{"speaker":"then this is what happened","startTime":877.11,"endTime":879.46,"body":"this force of circular motion,"},{"speaker":"then this is what happened","startTime":879.46,"endTime":881.113,"body":"is very big."},{"speaker":"then this is what happened","startTime":882.35,"endTime":886.14,"body":"So when Guy Martin is"},{"speaker":"then this is what happened","startTime":882.35,"endTime":886.14,"body":"going round on his bike,"},{"speaker":"then this is what happened","startTime":886.14,"endTime":891.14,"body":"he wanted to know what"},{"speaker":"then this is what happened","startTime":886.14,"endTime":891.14,"body":"forces can I put up with."},{"speaker":"then this is what happened","startTime":894.32,"endTime":896.46,"body":"The force in that string"},{"speaker":"then this is what happened","startTime":896.46,"endTime":901.46,"body":"is dependent on how fast"},{"speaker":"then this is what happened","startTime":896.46,"endTime":901.46,"body":"you're going, squared,"},{"speaker":"then this is what happened","startTime":901.71,"endTime":903.693,"body":"divided by the radius of the circle."},{"speaker":"then this is what happened","startTime":905.71,"endTime":906.76,"body":"As you do for television,"},{"speaker":"then this is what happened","startTime":906.76,"endTime":909.54,"body":"you spray-paint the formulae on a wall,"},{"speaker":"then this is what happened","startTime":909.54,"endTime":911.363,"body":"and so that's what we did."},{"speaker":"then this is what happened","startTime":912.62,"endTime":917.28,"body":"The small wall, 25 miles"},{"speaker":"then this is what happened","startTime":912.62,"endTime":917.28,"body":"an hour at 4 meters,"},{"speaker":"then this is what happened","startTime":917.28,"endTime":919.69,"body":"if he wants to do 100 miles an hour,"},{"speaker":"then this is what happened","startTime":919.69,"endTime":924.69,"body":"we need a 64 meter diameter wall of death."},{"speaker":"then this is what happened","startTime":924.78,"endTime":928.553,"body":"So what are we going to do,"},{"speaker":"then this is what happened","startTime":931.36,"endTime":932.85,"body":"what do we have to do?"},{"speaker":"then this is what happened","startTime":932.85,"endTime":936.68,"body":"Let's just think a little"},{"speaker":"then this is what happened","startTime":932.85,"endTime":936.68,"body":"bit more about the force."},{"speaker":"then this is what happened","startTime":936.68,"endTime":940.23,"body":"If you imagine your bike"},{"speaker":"then this is what happened","startTime":936.68,"endTime":940.23,"body":"sitting on the ground,"},{"speaker":"then this is what happened","startTime":940.23,"endTime":942.61,"body":"you might have noticed"},{"speaker":"then this is what happened","startTime":940.23,"endTime":942.61,"body":"on the wall of death,"},{"speaker":"then this is what happened","startTime":942.61,"endTime":944.213,"body":"that the bike was at an angle,"},{"speaker":"then this is what happened","startTime":945.06,"endTime":948.0,"body":"because as you're going"},{"speaker":"then this is what happened","startTime":945.06,"endTime":948.0,"body":"around on a circle,"},{"speaker":"then this is what happened","startTime":948.0,"endTime":949.85,"body":"you need a horizontal force"},{"speaker":"then this is what happened","startTime":949.85,"endTime":951.25,"body":"to make you go around in a circle,"},{"speaker":"then this is what happened","startTime":951.25,"endTime":953.68,"body":"that's this mv-squared over r thing,"},{"speaker":"then this is what happened","startTime":953.68,"endTime":957.08,"body":"but you still have to hold your weight up."},{"speaker":"then this is what happened","startTime":957.08,"endTime":959.06,"body":"If you're up on the wall,"},{"speaker":"then this is what happened","startTime":959.06,"endTime":961.15,"body":"then this resultant force"},{"speaker":"then this is what happened","startTime":961.15,"endTime":966.15,"body":"is always along the line"},{"speaker":"then this is what happened","startTime":961.15,"endTime":966.15,"body":"of the slope of the bike."},{"speaker":"then this is what happened","startTime":969.07,"endTime":971.37,"body":"So when you're going around on a corner,"},{"speaker":"then this is what happened","startTime":971.37,"endTime":973.31,"body":"you lean your bike in,"},{"speaker":"then this is what happened","startTime":973.31,"endTime":975.3,"body":"that's what's happening."},{"speaker":"then this is what happened","startTime":975.3,"endTime":977.72,"body":"So you can see, more or less,"},{"speaker":"then this is what happened","startTime":977.72,"endTime":979.66,"body":"what the g-forces are"},{"speaker":"then this is what happened","startTime":979.66,"endTime":981.41,"body":"by the slope of the bike."},{"speaker":"then this is what happened","startTime":981.41,"endTime":983.09,"body":"And by the way,"},{"speaker":"then this is what happened","startTime":983.09,"endTime":986.06,"body":"this theta has become a q here, nevermind,"},{"speaker":"then this is what happened","startTime":986.06,"endTime":991.06,"body":"the coefficient of"},{"speaker":"then this is what happened","startTime":986.06,"endTime":991.06,"body":"friction, mu, is 10-theta."},{"speaker":"then this is what happened","startTime":991.12,"endTime":991.953,"body":"What's really nice"},{"speaker":"then this is what happened","startTime":991.953,"endTime":994.68,"body":"is that we can link the"},{"speaker":"then this is what happened","startTime":991.953,"endTime":994.68,"body":"coefficient of friction,"},{"speaker":"then this is what happened","startTime":994.68,"endTime":996.15,"body":"what coefficient of friction do you need"},{"speaker":"then this is what happened","startTime":996.15,"endTime":998.06,"body":"to hold the bike up,"},{"speaker":"then this is what happened","startTime":998.06,"endTime":1001.9,"body":"it's a nice bit of"},{"speaker":"then this is what happened","startTime":998.06,"endTime":1001.9,"body":"trigonometry, which is good."},{"speaker":"then this is what happened","startTime":1001.9,"endTime":1005.9,"body":"What it means is that you've"},{"speaker":"then this is what happened","startTime":1001.9,"endTime":1005.9,"body":"got to have a dry surface,"},{"speaker":"then this is what happened","startTime":1005.9,"endTime":1008.01,"body":"no oil on it, no water on it,"},{"speaker":"then this is what happened","startTime":1008.01,"endTime":1009.093,"body":"to hold yourself up."},{"speaker":"then this is what happened","startTime":1014.0,"endTime":1015.333,"body":"Is this video going to run?"},{"speaker":"then this is what happened","startTime":1016.53,"endTime":1017.9,"body":"- [Commentator] 70 miles an hour,"},{"speaker":"then this is what happened","startTime":1017.9,"endTime":1020.79,"body":"five-g, that's five times his body weight"},{"speaker":"then this is what happened","startTime":1020.79,"endTime":1021.81,"body":"pushing him down to the ground."},{"speaker":"then this is what happened","startTime":1021.81,"endTime":1023.56,"body":"- [Hugh] So you see how big"},{"speaker":"then this is what happened","startTime":1021.81,"endTime":1023.56,"body":"the wall has ended up being."},{"speaker":"then this is what happened","startTime":1023.56,"endTime":1026.63,"body":"- [Commentator] Pushing"},{"speaker":"then this is what happened","startTime":1023.56,"endTime":1026.63,"body":"him towards seven-g."},{"speaker":"then this is what happened","startTime":1026.63,"endTime":1030.17,"body":"- [Hugh] So we made a wall"},{"speaker":"then this is what happened","startTime":1026.63,"endTime":1030.17,"body":"of about 40 meters diameter,"},{"speaker":"then this is what happened","startTime":1030.17,"endTime":1031.673,"body":"40 meters diameter,"},{"speaker":"then this is what happened","startTime":1032.709,"endTime":1035.65,"body":"an lo and behold,"},{"speaker":"then this is what happened","startTime":1035.65,"endTime":1037.27,"body":"he gets to about 80 miles an hour,"},{"speaker":"then this is what happened","startTime":1037.27,"endTime":1038.773,"body":"'cause if you do the sums."},{"speaker":"then this is what happened","startTime":1040.81,"endTime":1043.96,"body":"So there we go, 80 miles an hour."},{"speaker":"then this is what happened","startTime":1043.96,"endTime":1045.26,"body":"So we did the sums,"},{"speaker":"then this is what happened","startTime":1045.26,"endTime":1047.253,"body":"and it all worked, it's great."},{"speaker":"then this is what happened","startTime":1048.61,"endTime":1051.02,"body":"Why do you build these big things?"},{"speaker":"then this is what happened","startTime":1051.02,"endTime":1052.58,"body":"I don't know, but it was good fun,"},{"speaker":"then this is what happened","startTime":1052.58,"endTime":1055.29,"body":"and it's good to know"},{"speaker":"then this is what happened","startTime":1052.58,"endTime":1055.29,"body":"that the maths works,"},{"speaker":"then this is what happened","startTime":1055.29,"endTime":1058.21,"body":"that's what I really"},{"speaker":"then this is what happened","startTime":1055.29,"endTime":1058.21,"body":"like to see about this."},{"speaker":"then this is what happened","startTime":1058.21,"endTime":1060.68,"body":"The other thing where"},{"speaker":"then this is what happened","startTime":1058.21,"endTime":1060.68,"body":"the maths works as well"},{"speaker":"then this is what happened","startTime":1060.68,"endTime":1062.23,"body":"is in a loop-the-loop,"},{"speaker":"then this is what happened","startTime":1062.23,"endTime":1064.58,"body":"and this was another"},{"speaker":"then this is what happened","startTime":1062.23,"endTime":1064.58,"body":"thing that we tried to do,"},{"speaker":"then this is what happened","startTime":1065.71,"endTime":1067.45,"body":"which was to build a loop-the-loop,"},{"speaker":"then this is what happened","startTime":1067.45,"endTime":1071.96,"body":"and to drive a regular car, a Toyota Aygo,"},{"speaker":"then this is what happened","startTime":1071.96,"endTime":1072.813,"body":"around the loop."},{"speaker":"then this is what happened","startTime":1073.75,"endTime":1074.583,"body":"So here we go,"},{"speaker":"then this is what happened","startTime":1074.583,"endTime":1078.02,"body":"this car heading towards the loop."},{"speaker":"then this is what happened","startTime":1078.02,"endTime":1081.563,"body":"I told the driver you had to"},{"speaker":"then this is what happened","startTime":1078.02,"endTime":1081.563,"body":"go in at 37 miles an hour,"},{"speaker":"then this is what happened","startTime":1083.08,"endTime":1084.81,"body":"I'd worked it out,"},{"speaker":"then this is what happened","startTime":1084.81,"endTime":1086.127,"body":"to be able to go around the loop,"},{"speaker":"then this is what happened","startTime":1086.127,"endTime":1087.27,"body":"and he just said,"},{"speaker":"then this is what happened","startTime":1087.27,"endTime":1089.02,"body":"you know what, I have to trust you."},{"speaker":"then this is what happened","startTime":1091.15,"endTime":1092.156,"body":"When you're doing these things,"},{"speaker":"then this is what happened","startTime":1092.156,"endTime":1096.04,"body":"you've got to do some sums,"},{"speaker":"then this is what happened","startTime":1096.04,"endTime":1097.31,"body":"and make it work,"},{"speaker":"then this is what happened","startTime":1097.31,"endTime":1100.02,"body":"exactly the same way as when"},{"speaker":"then this is what happened","startTime":1097.31,"endTime":1100.02,"body":"astronauts go to the Moon,"},{"speaker":"then this is what happened","startTime":1100.02,"endTime":1100.853,"body":"or wherever they go,"},{"speaker":"then this is what happened","startTime":1100.853,"endTime":1102.81,"body":"you do sums, it's got to work,"},{"speaker":"then this is what happened","startTime":1102.81,"endTime":1104.52,"body":"and it's just great that it works."},{"speaker":"then this is what happened","startTime":1104.52,"endTime":1106.13,"body":"But now, let's think about it,"},{"speaker":"then this is what happened","startTime":1106.13,"endTime":1108.81,"body":"why did we build a circle?"},{"speaker":"then this is what happened","startTime":1108.81,"endTime":1113.363,"body":"Because let's start looking"},{"speaker":"then this is what happened","startTime":1108.81,"endTime":1113.363,"body":"at other loop-the-loops."},{"speaker":"then this is what happened","startTime":1114.56,"endTime":1115.79,"body":"If you look closely at them,"},{"speaker":"then this is what happened","startTime":1115.79,"endTime":1117.193,"body":"they're not circles."},{"speaker":"then this is what happened","startTime":1118.04,"endTime":1119.603,"body":"Why are they not circles?"},{"speaker":"then this is what happened","startTime":1120.79,"endTime":1125.39,"body":"Humans can't withstand very high g-forces,"},{"speaker":"then this is what happened","startTime":1125.39,"endTime":1128.5,"body":"but as you go around your loop-the-loop,"},{"speaker":"then this is what happened","startTime":1128.5,"endTime":1130.42,"body":"you slow down,"},{"speaker":"then this is what happened","startTime":1130.42,"endTime":1133.07,"body":"so you can have the circle tightening up."},{"speaker":"then this is what happened","startTime":1133.07,"endTime":1134.79,"body":"So this shape,"},{"speaker":"then this is what happened","startTime":1134.79,"endTime":1136.043,"body":"it's got a funny name,"},{"speaker":"then this is what happened","startTime":1136.043,"endTime":1137.24,"body":"it's called a clothoid,"},{"speaker":"then this is what happened","startTime":1137.24,"endTime":1142.24,"body":"if ever you want to find a"},{"speaker":"then this is what happened","startTime":1137.24,"endTime":1142.24,"body":"word that nobody knows about,"},{"speaker":"then this is what happened","startTime":1142.39,"endTime":1144.27,"body":"but these are not circles."},{"speaker":"then this is what happened","startTime":1144.27,"endTime":1148.07,"body":"And if you look at places"},{"speaker":"then this is what happened","startTime":1144.27,"endTime":1148.07,"body":"where there's no track,"},{"speaker":"then this is what happened","startTime":1148.07,"endTime":1151.23,"body":"if you've got a plane"},{"speaker":"then this is what happened","startTime":1148.07,"endTime":1151.23,"body":"doing a loop-the-loop,"},{"speaker":"then this is what happened","startTime":1151.23,"endTime":1154.78,"body":"they naturally go on these shapes,"},{"speaker":"then this is what happened","startTime":1154.78,"endTime":1157.21,"body":"they're not circles."},{"speaker":"then this is what happened","startTime":1157.21,"endTime":1159.39,"body":"And you kind of think, well yeah."},{"speaker":"then this is what happened","startTime":1159.39,"endTime":1161.26,"body":"So why do we think,"},{"speaker":"then this is what happened","startTime":1161.26,"endTime":1164.813,"body":"when we have our toy"},{"speaker":"then this is what happened","startTime":1161.26,"endTime":1164.813,"body":"Mattel, whatever it is,"},{"speaker":"then this is what happened","startTime":1166.03,"endTime":1166.88,"body":"Hot Wheels thing,"},{"speaker":"then this is what happened","startTime":1166.88,"endTime":1168.66,"body":"we do circular loops,"},{"speaker":"then this is what happened","startTime":1168.66,"endTime":1170.15,"body":"when we really ought to be doing loops"},{"speaker":"then this is what happened","startTime":1170.15,"endTime":1171.42,"body":"that look a bit like this."},{"speaker":"then this is what happened","startTime":1171.42,"endTime":1174.69,"body":"So next time you go to a theme park,"},{"speaker":"then this is what happened","startTime":1174.69,"endTime":1175.72,"body":"just have a look,"},{"speaker":"then this is what happened","startTime":1175.72,"endTime":1180.063,"body":"and you'll see that the"},{"speaker":"then this is what happened","startTime":1175.72,"endTime":1180.063,"body":"circles are not circles."},{"speaker":"then this is what happened","startTime":1183.54,"endTime":1185.57,"body":"We've looked at spin"},{"speaker":"then this is what happened","startTime":1185.57,"endTime":1188.18,"body":"from a point of view of circular motion,"},{"speaker":"then this is what happened","startTime":1188.18,"endTime":1190.79,"body":"not really getting at"},{"speaker":"then this is what happened","startTime":1188.18,"endTime":1190.79,"body":"the gyroscopic effect,"},{"speaker":"then this is what happened","startTime":1190.79,"endTime":1193.593,"body":"now I want to do gyroscopic effect."},{"speaker":"then this is what happened","startTime":1196.08,"endTime":1200.09,"body":"And when we have a spinning top,"},{"speaker":"then this is what happened","startTime":1200.09,"endTime":1201.52,"body":"like this one here,"},{"speaker":"then this is what happened","startTime":1201.52,"endTime":1206.1,"body":"we know that a spinning top"},{"speaker":"then this is what happened","startTime":1201.52,"endTime":1206.1,"body":"doesn't stay up on its own,"},{"speaker":"then this is what happened","startTime":1206.1,"endTime":1209.4,"body":"and it doesn't stay up"},{"speaker":"then this is what happened","startTime":1206.1,"endTime":1209.4,"body":"unless it's spinning"},{"speaker":"then this is what happened","startTime":1214.1,"endTime":1215.76,"body":"fast enough."},{"speaker":"then this is what happened","startTime":1215.76,"endTime":1217.31,"body":"And when it's spinning fast enough,"},{"speaker":"then this is what happened","startTime":1217.31,"endTime":1218.143,"body":"what you see,"},{"speaker":"then this is what happened","startTime":1218.143,"endTime":1219.683,"body":"it starts to move around,"},{"speaker":"then this is what happened","startTime":1220.68,"endTime":1221.943,"body":"this kind of motion."},{"speaker":"then this is what happened","startTime":1223.53,"endTime":1224.65,"body":"And you think,"},{"speaker":"then this is what happened","startTime":1224.65,"endTime":1229.103,"body":"I'd like to know, why does it stay up?"},{"speaker":"then this is what happened","startTime":1231.72,"endTime":1234.77,"body":"It's one of these things that,"},{"speaker":"then this is what happened","startTime":1234.77,"endTime":1239.623,"body":"at school, we don't learn"},{"speaker":"then this is what happened","startTime":1234.77,"endTime":1239.623,"body":"about spinning tops anymore,"},{"speaker":"then this is what happened","startTime":1240.94,"endTime":1242.34,"body":"even if we ever really did,"},{"speaker":"then this is what happened","startTime":1242.34,"endTime":1244.8,"body":"because it's reckoned"},{"speaker":"then this is what happened","startTime":1242.34,"endTime":1244.8,"body":"to be too complicated,"},{"speaker":"then this is what happened","startTime":1244.8,"endTime":1249.8,"body":"but yet we do learn about"},{"speaker":"then this is what happened","startTime":1244.8,"endTime":1249.8,"body":"genetics, and double helices,"},{"speaker":"then this is what happened","startTime":1250.407,"endTime":1251.92,"body":"and all that sort of thing,"},{"speaker":"then this is what happened","startTime":1251.92,"endTime":1253.48,"body":"because, somehow,"},{"speaker":"then this is what happened","startTime":1253.48,"endTime":1256.14,"body":"biology's allowed to be complicated,"},{"speaker":"then this is what happened","startTime":1256.14,"endTime":1258.2,"body":"but physics and maths,"},{"speaker":"then this is what happened","startTime":1258.2,"endTime":1262.84,"body":"it's got to be stuff that you can explain"},{"speaker":"then this is what happened","startTime":1262.84,"endTime":1264.14,"body":"from one step to the next."},{"speaker":"then this is what happened","startTime":1265.72,"endTime":1267.34,"body":"But I think that's a"},{"speaker":"then this is what happened","startTime":1265.72,"endTime":1267.34,"body":"bit of a shame, really,"},{"speaker":"then this is what happened","startTime":1267.34,"endTime":1271.653,"body":"because there's so much fun"},{"speaker":"then this is what happened","startTime":1267.34,"endTime":1271.653,"body":"to be had with spinning tops."},{"speaker":"then this is what happened","startTime":1272.58,"endTime":1274.57,"body":"The gyroscopic effect,"},{"speaker":"then this is what happened","startTime":1274.57,"endTime":1275.99,"body":"if you want to Google this"},{"speaker":"then this is what happened","startTime":1275.99,"endTime":1278.06,"body":"and try and figure out what's going on,"},{"speaker":"then this is what happened","startTime":1278.06,"endTime":1281.0,"body":"you need words like gyroscopic effect"},{"speaker":"then this is what happened","startTime":1281.0,"endTime":1283.1,"body":"and gyroscopic precession,"},{"speaker":"then this is what happened","startTime":1283.1,"endTime":1284.79,"body":"and once you've got those words,"},{"speaker":"then this is what happened","startTime":1284.79,"endTime":1285.98,"body":"it's much easier,"},{"speaker":"then this is what happened","startTime":1285.98,"endTime":1288.26,"body":"'cause if you just Google spinning top,"},{"speaker":"then this is what happened","startTime":1288.26,"endTime":1290.42,"body":"you'll find out that you"},{"speaker":"then this is what happened","startTime":1288.26,"endTime":1290.42,"body":"can buy one from Argos"},{"speaker":"then this is what happened","startTime":1290.42,"endTime":1292.21,"body":"for 7 pounds 99,"},{"speaker":"then this is what happened","startTime":1292.21,"endTime":1294.33,"body":"and it won't tell you"},{"speaker":"then this is what happened","startTime":1292.21,"endTime":1294.33,"body":"anything about how they work,"},{"speaker":"then this is what happened","startTime":1294.33,"endTime":1296.57,"body":"so you need these words."},{"speaker":"then this is what happened","startTime":1296.57,"endTime":1297.64,"body":"But what I quite like"},{"speaker":"then this is what happened","startTime":1297.64,"endTime":1300.79,"body":"is that it's not just a spinning top"},{"speaker":"then this is what happened","startTime":1300.79,"endTime":1304.2,"body":"that behaves like a spinning top,"},{"speaker":"then this is what happened","startTime":1304.2,"endTime":1306.39,"body":"and if you get a regular bike wheel,"},{"speaker":"then this is what happened","startTime":1306.39,"endTime":1311.39,"body":"and you can go to a bike"},{"speaker":"then this is what happened","startTime":1306.39,"endTime":1311.39,"body":"shop and get a stunt peg,"},{"speaker":"then this is what happened","startTime":1311.89,"endTime":1313.62,"body":"this is a stunt peg,"},{"speaker":"then this is what happened","startTime":1313.62,"endTime":1316.71,"body":"and you can screw the"},{"speaker":"then this is what happened","startTime":1313.62,"endTime":1316.71,"body":"stunt peg on like that,"},{"speaker":"then this is what happened","startTime":1316.71,"endTime":1318.83,"body":"that gives you a handle,"},{"speaker":"then this is what happened","startTime":1318.83,"endTime":1320.17,"body":"and now, with this thing,"},{"speaker":"then this is what happened","startTime":1320.17,"endTime":1323.683,"body":"I can do exactly what"},{"speaker":"then this is what happened","startTime":1320.17,"endTime":1323.683,"body":"the spinning top does,"},{"speaker":"then this is what happened","startTime":1325.32,"endTime":1326.707,"body":"it's exactly the same,"},{"speaker":"then this is what happened","startTime":1325.32,"endTime":1326.707,"body":"it's a spinning thing,"},{"speaker":"then this is what happened","startTime":1326.707,"endTime":1329.513,"body":"and you see it's precessing around."},{"speaker":"then this is what happened","startTime":1330.83,"endTime":1335.12,"body":"But what's nice is that I"},{"speaker":"then this is what happened","startTime":1330.83,"endTime":1335.12,"body":"can make it precess around"},{"speaker":"then this is what happened","startTime":1335.12,"endTime":1336.33,"body":"at whatever angle I like"},{"speaker":"then this is what happened","startTime":1336.33,"endTime":1339.5,"body":"if I've got a piece of string"},{"speaker":"then this is what happened","startTime":1336.33,"endTime":1339.5,"body":"on the end of it there."},{"speaker":"then this is what happened","startTime":1339.5,"endTime":1344.5,"body":"And the thing here is"},{"speaker":"then this is what happened","startTime":1339.5,"endTime":1344.5,"body":"that it kind of looks like"},{"speaker":"then this is what happened","startTime":1344.69,"endTime":1347.63,"body":"that this is some kind"},{"speaker":"then this is what happened","startTime":1344.69,"endTime":1347.63,"body":"of anti-gravity device."},{"speaker":"then this is what happened","startTime":1347.63,"endTime":1352.63,"body":"There was a famous Royal"},{"speaker":"then this is what happened","startTime":1347.63,"endTime":1352.63,"body":"Institution Christmas lecture"},{"speaker":"then this is what happened","startTime":1352.72,"endTime":1355.95,"body":"in 1976, I think,"},{"speaker":"then this is what happened","startTime":1355.95,"endTime":1357.94,"body":"a chap called Eric Laithwaite,"},{"speaker":"then this is what happened","startTime":1357.94,"endTime":1361.42,"body":"and he demonstrated, basically,"},{"speaker":"then this is what happened","startTime":1361.42,"endTime":1364.87,"body":"that gyroscopes were anti-gravity devices,"},{"speaker":"then this is what happened","startTime":1364.87,"endTime":1367.62,"body":"because if they weren't,"},{"speaker":"then this is what happened","startTime":1367.62,"endTime":1369.673,"body":"then how could you do this."},{"speaker":"then this is what happened","startTime":1371.61,"endTime":1374.08,"body":"All you have to do is let go of the string"},{"speaker":"then this is what happened","startTime":1374.08,"endTime":1377.87,"body":"and you realize that it's"},{"speaker":"then this is what happened","startTime":1374.08,"endTime":1377.87,"body":"being held up by the string."},{"speaker":"then this is what happened","startTime":1377.87,"endTime":1382.82,"body":"And if you put a pair of"},{"speaker":"then this is what happened","startTime":1377.87,"endTime":1382.82,"body":"scales, a balance on here,"},{"speaker":"then this is what happened","startTime":1382.82,"endTime":1386.01,"body":"you'll see that the mass of"},{"speaker":"then this is what happened","startTime":1382.82,"endTime":1386.01,"body":"this thing hasn't changed at all"},{"speaker":"then this is what happened","startTime":1386.01,"endTime":1387.253,"body":"as it precesses around."},{"speaker":"then this is what happened","startTime":1388.27,"endTime":1389.563,"body":"So what's going on?"},{"speaker":"then this is what happened","startTime":1390.48,"endTime":1394.04,"body":"And this is where you can do"},{"speaker":"then this is what happened","startTime":1390.48,"endTime":1394.04,"body":"it with maths if you like,"},{"speaker":"then this is what happened","startTime":1394.04,"endTime":1397.56,"body":"but I quite like doing"},{"speaker":"then this is what happened","startTime":1394.04,"endTime":1397.56,"body":"it with visualizing it."},{"speaker":"then this is what happened","startTime":1397.56,"endTime":1401.323,"body":"So what we've got are two forces,"},{"speaker":"then this is what happened","startTime":1402.55,"endTime":1403.93,"body":"I like to call them a couple,"},{"speaker":"then this is what happened","startTime":1403.93,"endTime":1406.15,"body":"some people will call it a moment,"},{"speaker":"then this is what happened","startTime":1406.15,"endTime":1407.44,"body":"but if you've got two forces"},{"speaker":"then this is what happened","startTime":1407.44,"endTime":1408.71,"body":"that are not in line with each other,"},{"speaker":"then this is what happened","startTime":1408.71,"endTime":1411.29,"body":"one force is the force in the string"},{"speaker":"then this is what happened","startTime":1411.29,"endTime":1414.93,"body":"and the other force is"},{"speaker":"then this is what happened","startTime":1411.29,"endTime":1414.93,"body":"the weight of the wheel,"},{"speaker":"then this is what happened","startTime":1414.93,"endTime":1418.24,"body":"those two forces create a couple,"},{"speaker":"then this is what happened","startTime":1418.24,"endTime":1420.393,"body":"which, if the wheel is not spinning,"},{"speaker":"then this is what happened","startTime":1421.35,"endTime":1423.146,"body":"will cause the wheel to twist around"},{"speaker":"then this is what happened","startTime":1423.146,"endTime":1428.146,"body":"and develop some angular momentum,"},{"speaker":"then this is what happened","startTime":1428.46,"endTime":1430.813,"body":"but if the wheel is already spinning,"},{"speaker":"then this is what happened","startTime":1432.15,"endTime":1433.27,"body":"then there's another way"},{"speaker":"then this is what happened","startTime":1433.27,"endTime":1435.9,"body":"for this wheel to generate"},{"speaker":"then this is what happened","startTime":1433.27,"endTime":1435.9,"body":"some angular momentum."},{"speaker":"then this is what happened","startTime":1435.9,"endTime":1438.75,"body":"Which direction do I want to"},{"speaker":"then this is what happened","startTime":1435.9,"endTime":1438.75,"body":"generate the angular momentum?"},{"speaker":"then this is what happened","startTime":1438.75,"endTime":1442.15,"body":"I want to generate the"},{"speaker":"then this is what happened","startTime":1438.75,"endTime":1442.15,"body":"angular momentum that way,"},{"speaker":"then this is what happened","startTime":1442.15,"endTime":1445.14,"body":"because that's the"},{"speaker":"then this is what happened","startTime":1442.15,"endTime":1445.14,"body":"direction of the couple."},{"speaker":"then this is what happened","startTime":1445.14,"endTime":1446.693,"body":"But if it's already spinning,"},{"speaker":"then this is what happened","startTime":1448.22,"endTime":1450.37,"body":"then I can generate that angular momentum"},{"speaker":"then this is what happened","startTime":1450.37,"endTime":1453.01,"body":"by turning the wheel around to there,"},{"speaker":"then this is what happened","startTime":1453.01,"endTime":1453.843,"body":"and now it's spinning"},{"speaker":"then this is what happened","startTime":1453.843,"endTime":1456.363,"body":"in exactly the direction"},{"speaker":"then this is what happened","startTime":1453.843,"endTime":1456.363,"body":"I was wanting it to do."},{"speaker":"then this is what happened","startTime":1457.55,"endTime":1460.98,"body":"So this gyroscopic precession"},{"speaker":"then this is what happened","startTime":1460.98,"endTime":1465.98,"body":"is continually moving"},{"speaker":"then this is what happened","startTime":1460.98,"endTime":1465.98,"body":"the direction of spin,"},{"speaker":"then this is what happened","startTime":1467.78,"endTime":1469.42,"body":"it's spinning in this direction,"},{"speaker":"then this is what happened","startTime":1469.42,"endTime":1470.763,"body":"put a couple that way,"},{"speaker":"then this is what happened","startTime":1472.1,"endTime":1474.49,"body":"ah look, it's spinning that way."},{"speaker":"then this is what happened","startTime":1474.49,"endTime":1477.3,"body":"That is what's going on physically."},{"speaker":"then this is what happened","startTime":1477.3,"endTime":1478.38,"body":"Now, the maths you can do,"},{"speaker":"then this is what happened","startTime":1478.38,"endTime":1479.59,"body":"and you get at with the equations,"},{"speaker":"then this is what happened","startTime":1479.59,"endTime":1480.423,"body":"which is fine."},{"speaker":"then this is what happened","startTime":1481.32,"endTime":1483.52,"body":"We need to understand though"},{"speaker":"then this is what happened","startTime":1483.52,"endTime":1486.62,"body":"what's meant by angular momentum,"},{"speaker":"then this is what happened","startTime":1486.62,"endTime":1490.673,"body":"and for that, I'm going to do a demo here."},{"speaker":"then this is what happened","startTime":1493.235,"endTime":1495.276,"body":"It's quite handy to have a volunteer,"},{"speaker":"then this is what happened","startTime":1495.276,"endTime":1497.238,"body":"anyone want to?"},{"speaker":"then this is what happened","startTime":1497.238,"endTime":1498.071,"body":"Ah, we've got a volunteer,"},{"speaker":"then this is what happened","startTime":1498.071,"endTime":1499.26,"body":"there we go, that's good,"},{"speaker":"then this is what happened","startTime":1500.123,"endTime":1501.473,"body":"we've got a volunteer here."},{"speaker":"then this is what happened","startTime":1504.2,"endTime":1505.033,"body":"Right, yeah,"},{"speaker":"then this is what happened","startTime":1505.033,"endTime":1506.01,"body":"come up there, that's good."},{"speaker":"then this is what happened","startTime":1510.74,"endTime":1511.959,"body":"Hi, what's your name?"},{"speaker":"then this is what happened","startTime":1511.959,"endTime":1513.733,"body":"- Olly."},{"speaker":"then this is what happened","startTime":1511.959,"endTime":1513.733,"body":"- Olly, right."},{"speaker":"then this is what happened","startTime":1515.51,"endTime":1518.96,"body":"I have a swivelly stool here,"},{"speaker":"then this is what happened","startTime":1518.96,"endTime":1519.987,"body":"which you're going to stand on,"},{"speaker":"then this is what happened","startTime":1519.987,"endTime":1521.237,"body":"are you happy to do that?"},{"speaker":"then this is what happened","startTime":1521.237,"endTime":1522.07,"body":"- Yeah, that's fine."},{"speaker":"then this is what happened","startTime":1522.07,"endTime":1522.903,"body":"- Are you good at keeping balance?"},{"speaker":"then this is what happened","startTime":1522.903,"endTime":1523.736,"body":"- Yeah."},{"speaker":"then this is what happened","startTime":1523.736,"endTime":1524.569,"body":"- Right, there we go."},{"speaker":"then this is what happened","startTime":1525.553,"endTime":1528.563,"body":"So if you stand on that,"},{"speaker":"then this is what happened","startTime":1529.828,"endTime":1530.863,"body":"there you go, happy?"},{"speaker":"then this is what happened","startTime":1534.51,"endTime":1537.343,"body":"(audience laughs)"},{"speaker":"then this is what happened","startTime":1542.16,"endTime":1543.539,"body":"Yeah?"},{"speaker":"then this is what happened","startTime":1542.16,"endTime":1543.539,"body":"- Yeah, that's fine."},{"speaker":"then this is what happened","startTime":1543.539,"endTime":1545.2,"body":"- Good, that's good."},{"speaker":"then this is what happened","startTime":1545.2,"endTime":1547.18,"body":"So now what I'm going to do"},{"speaker":"then this is what happened","startTime":1547.18,"endTime":1548.71,"body":"is I'm going to give you a couple of,"},{"speaker":"then this is what happened","startTime":1548.71,"endTime":1551.51,"body":"this one's two kilograms, hold that one,"},{"speaker":"then this is what happened","startTime":1551.51,"endTime":1553.7,"body":"this one's two kilograms."},{"speaker":"then this is what happened","startTime":1553.7,"endTime":1554.59,"body":"Now what I want to do is,"},{"speaker":"then this is what happened","startTime":1554.59,"endTime":1556.813,"body":"I want you to hold those"},{"speaker":"then this is what happened","startTime":1554.59,"endTime":1556.813,"body":"in front of you like that."},{"speaker":"then this is what happened","startTime":1557.71,"endTime":1560.833,"body":"If I try to spin you around like that,"},{"speaker":"then this is what happened","startTime":1562.37,"endTime":1564.58,"body":"you have a certain angular mass,"},{"speaker":"then this is what happened","startTime":1564.58,"endTime":1566.07,"body":"I can feel that mass,"},{"speaker":"then this is what happened","startTime":1566.07,"endTime":1569.113,"body":"but now if you put your"},{"speaker":"then this is what happened","startTime":1566.07,"endTime":1569.113,"body":"arms at full stretch,"},{"speaker":"then this is what happened","startTime":1573.67,"endTime":1574.81,"body":"I know you haven't got heavier,"},{"speaker":"then this is what happened","startTime":1574.81,"endTime":1576.173,"body":"but that feels,"},{"speaker":"then this is what happened","startTime":1577.09,"endTime":1579.54,"body":"you can feel it too,"},{"speaker":"then this is what happened","startTime":1577.09,"endTime":1579.54,"body":"can't you, in your arms?"},{"speaker":"then this is what happened","startTime":1579.54,"endTime":1584.54,"body":"So it matters how far"},{"speaker":"then this is what happened","startTime":1579.54,"endTime":1584.54,"body":"out you put your arms."},{"speaker":"then this is what happened","startTime":1585.15,"endTime":1588.99,"body":"So this is what you"},{"speaker":"then this is what happened","startTime":1585.15,"endTime":1588.99,"body":"might call angular mass,"},{"speaker":"then this is what happened","startTime":1588.99,"endTime":1590.8,"body":"or we might call it moment of inertia"},{"speaker":"then this is what happened","startTime":1590.8,"endTime":1593.0,"body":"if we want to use its proper name."},{"speaker":"then this is what happened","startTime":1593.0,"endTime":1596.17,"body":"But if we think of momentum,"},{"speaker":"then this is what happened","startTime":1596.17,"endTime":1599.02,"body":"like a car is moving along a road,"},{"speaker":"then this is what happened","startTime":1599.02,"endTime":1602.18,"body":"its momentum is its"},{"speaker":"then this is what happened","startTime":1599.02,"endTime":1602.18,"body":"mass times its velocity."},{"speaker":"then this is what happened","startTime":1602.18,"endTime":1603.36,"body":"Angular momentum"},{"speaker":"then this is what happened","startTime":1603.36,"endTime":1607.443,"body":"is its angular mass times"},{"speaker":"then this is what happened","startTime":1603.36,"endTime":1607.443,"body":"its angular velocity."},{"speaker":"then this is what happened","startTime":1610.13,"endTime":1612.85,"body":"Nice frictionless stool here,"},{"speaker":"then this is what happened","startTime":1612.85,"endTime":1616.05,"body":"so we know that if a car is"},{"speaker":"then this is what happened","startTime":1612.85,"endTime":1616.05,"body":"going on a frictionless road,"},{"speaker":"then this is what happened","startTime":1616.05,"endTime":1617.55,"body":"its speed stays constant"},{"speaker":"then this is what happened","startTime":1617.55,"endTime":1620.333,"body":"because mass stays constant,"},{"speaker":"then this is what happened","startTime":1617.55,"endTime":1620.333,"body":"momentum stay constant,"},{"speaker":"then this is what happened","startTime":1621.37,"endTime":1626.217,"body":"but you can change your angular mass"},{"speaker":"then this is what happened","startTime":1627.48,"endTime":1629.163,"body":"by bringing your arms in and out."},{"speaker":"then this is what happened","startTime":1630.0,"endTime":1632.77,"body":"So if you've got constant"},{"speaker":"then this is what happened","startTime":1630.0,"endTime":1632.77,"body":"angular momentum,"},{"speaker":"then this is what happened","startTime":1632.77,"endTime":1635.573,"body":"which is angular mass"},{"speaker":"then this is what happened","startTime":1632.77,"endTime":1635.573,"body":"times angular velocity,"},{"speaker":"then this is what happened","startTime":1637.62,"endTime":1639.77,"body":"then your spin speed's going to change."},{"speaker":"then this is what happened","startTime":1639.77,"endTime":1641.41,"body":"Right, so you're going"},{"speaker":"then this is what happened","startTime":1639.77,"endTime":1641.41,"body":"to do this as a demo,"},{"speaker":"then this is what happened","startTime":1641.41,"endTime":1643.03,"body":"arms out."},{"speaker":"then this is what happened","startTime":1643.03,"endTime":1643.9,"body":"What I want you to do,"},{"speaker":"then this is what happened","startTime":1643.9,"endTime":1645.817,"body":"without any spin,"},{"speaker":"then this is what happened","startTime":1645.817,"endTime":1646.65,"body":"at this sort of rate,"},{"speaker":"then this is what happened","startTime":1646.65,"endTime":1649.067,"body":"bring your arms right to,"},{"speaker":"then this is what happened","startTime":1649.067,"endTime":1650.11,"body":"there we go."},{"speaker":"then this is what happened","startTime":1650.11,"endTime":1652.15,"body":"Now we do the same thing spinning."},{"speaker":"then this is what happened","startTime":1652.15,"endTime":1652.983,"body":"Arms out."},{"speaker":"then this is what happened","startTime":1655.18,"endTime":1656.33,"body":"Wait, wait, wait, wait."},{"speaker":"then this is what happened","startTime":1657.56,"endTime":1658.693,"body":"Okay, nice and gently,"},{"speaker":"then this is what happened","startTime":1660.232,"endTime":1661.065,"body":"all the way in, all the way,"},{"speaker":"then this is what happened","startTime":1661.972,"endTime":1662.83,"body":"all the way keep going."},{"speaker":"then this is what happened","startTime":1664.22,"endTime":1665.453,"body":"And slowly out again."},{"speaker":"then this is what happened","startTime":1666.421,"endTime":1667.53,"body":"(audience laughs)"},{"speaker":"then this is what happened","startTime":1667.53,"endTime":1668.51,"body":"Okay, we'll go backwards,"},{"speaker":"then this is what happened","startTime":1668.51,"endTime":1669.353,"body":"we'll unwind."},{"speaker":"then this is what happened","startTime":1671.428,"endTime":1672.837,"body":"You get a bit dizzy doing this, don't you."},{"speaker":"then this is what happened","startTime":1672.837,"endTime":1673.93,"body":"Are you okay?"},{"speaker":"then this is what happened","startTime":1673.93,"endTime":1674.763,"body":"Arms out."},{"speaker":"then this is what happened","startTime":1678.885,"endTime":1679.718,"body":"In you go."},{"speaker":"then this is what happened","startTime":1682.504,"endTime":1685.504,"body":"All the way in, how far can you get?"},{"speaker":"then this is what happened","startTime":1686.54,"endTime":1687.373,"body":"Very good,"},{"speaker":"then this is what happened","startTime":1687.373,"endTime":1688.84,"body":"fantastic, Olly, brilliant,"},{"speaker":"then this is what happened","startTime":1688.84,"endTime":1690.04,"body":"a big round of applause."},{"speaker":"then this is what happened","startTime":1690.91,"endTime":1693.124,"body":"You all right there?"},{"speaker":"then this is what happened","startTime":1693.124,"endTime":1694.532,"body":"Thanks very much."},{"speaker":"then this is what happened","startTime":1694.532,"endTime":1697.46,"body":"(audience applauds)"},{"speaker":"then this is what happened","startTime":1697.46,"endTime":1701.85,"body":"So that is an example of"},{"speaker":"then this is what happened","startTime":1697.46,"endTime":1701.85,"body":"conservation of angular momentum,"},{"speaker":"then this is what happened","startTime":1701.85,"endTime":1706.4,"body":"and we can see that with ice skaters."},{"speaker":"then this is what happened","startTime":1706.4,"endTime":1707.91,"body":"This ice skater here,"},{"speaker":"then this is what happened","startTime":1707.91,"endTime":1711.5,"body":"with not much friction at"},{"speaker":"then this is what happened","startTime":1707.91,"endTime":1711.5,"body":"the contact with the ice,"},{"speaker":"then this is what happened","startTime":1711.5,"endTime":1713.68,"body":"she can move her arms in and out"},{"speaker":"then this is what happened","startTime":1714.52,"endTime":1716.14,"body":"to change her angular velocity."},{"speaker":"then this is what happened","startTime":1716.14,"endTime":1717.35,"body":"She's given herself a kick here,"},{"speaker":"then this is what happened","startTime":1717.35,"endTime":1719.607,"body":"she's still got her bum"},{"speaker":"then this is what happened","startTime":1717.35,"endTime":1719.607,"body":"stuck out like that,"},{"speaker":"then this is what happened","startTime":1719.607,"endTime":1721.81,"body":"and now she stands up thin"},{"speaker":"then this is what happened","startTime":1722.89,"endTime":1725.25,"body":"and spins around really fast,"},{"speaker":"then this is what happened","startTime":1725.25,"endTime":1727.01,"body":"conservation of angular momentum,"},{"speaker":"then this is what happened","startTime":1727.01,"endTime":1731.93,"body":"so you don't need extra"},{"speaker":"then this is what happened","startTime":1727.01,"endTime":1731.93,"body":"weights to be holding."},{"speaker":"then this is what happened","startTime":1733.22,"endTime":1734.61,"body":"So if I try to do this,"},{"speaker":"then this is what happened","startTime":1734.61,"endTime":1736.913,"body":"I can stand on here,"},{"speaker":"then this is what happened","startTime":1738.001,"endTime":1739.95,"body":"with my bum stuck out like she had,"},{"speaker":"then this is what happened","startTime":1739.95,"endTime":1740.783,"body":"and then."},{"speaker":"then this is what happened","startTime":1743.414,"endTime":1744.247,"body":"(audience laughs)"},{"speaker":"then this is what happened","startTime":1744.247,"endTime":1746.16,"body":"So all I have to do is stand up straight,"},{"speaker":"then this is what happened","startTime":1746.16,"endTime":1749.223,"body":"and I start to spin around faster."},{"speaker":"then this is what happened","startTime":1750.54,"endTime":1755.373,"body":"So now this thing, conservation"},{"speaker":"then this is what happened","startTime":1750.54,"endTime":1755.373,"body":"of angular momentum,"},{"speaker":"then this is what happened","startTime":1756.87,"endTime":1758.66,"body":"you might kind of think"},{"speaker":"then this is what happened","startTime":1758.66,"endTime":1759.86,"body":"it's only to do with"},{"speaker":"then this is what happened","startTime":1762.16,"endTime":1765.08,"body":"ice skaters, and ballet"},{"speaker":"then this is what happened","startTime":1762.16,"endTime":1765.08,"body":"dancers, and stuff,"},{"speaker":"then this is what happened","startTime":1765.08,"endTime":1768.0,"body":"but it's a really useful"},{"speaker":"then this is what happened","startTime":1765.08,"endTime":1768.0,"body":"thing out in space."},{"speaker":"then this is what happened","startTime":1768.0,"endTime":1770.313,"body":"So let's suppose I'm out in space,"},{"speaker":"then this is what happened","startTime":1771.15,"endTime":1775.513,"body":"and I want to point a telescope."},{"speaker":"then this is what happened","startTime":1777.502,"endTime":1782.502,"body":"All right, let's imagine"},{"speaker":"then this is what happened","startTime":1777.502,"endTime":1782.502,"body":"I've got a telescope here,"},{"speaker":"then this is what happened","startTime":1786.358,"endTime":1787.383,"body":"and I would like,"},{"speaker":"then this is what happened","startTime":1789.103,"endTime":1790.403,"body":"there's a star over there,"},{"speaker":"then this is what happened","startTime":1791.41,"endTime":1794.143,"body":"but there's a better"},{"speaker":"then this is what happened","startTime":1791.41,"endTime":1794.143,"body":"looking star over there."},{"speaker":"then this is what happened","startTime":1800.92,"endTime":1801.863,"body":"How do I?"},{"speaker":"then this is what happened","startTime":1803.27,"endTime":1804.68,"body":"Conservation of angular momentum,"},{"speaker":"then this is what happened","startTime":1804.68,"endTime":1808.27,"body":"I can't point my telescope over there."},{"speaker":"then this is what happened","startTime":1808.27,"endTime":1810.693,"body":"But if I've got a wheel,"},{"speaker":"then this is what happened","startTime":1812.22,"endTime":1813.67,"body":"then I can do some fun things."},{"speaker":"then this is what happened","startTime":1813.67,"endTime":1816.933,"body":"So the first thing I can do is,"},{"speaker":"then this is what happened","startTime":1818.07,"endTime":1820.48,"body":"if I start my wheel spinning,"},{"speaker":"then this is what happened","startTime":1820.48,"endTime":1823.56,"body":"then if the wheel is turning clockwise,"},{"speaker":"then this is what happened","startTime":1823.56,"endTime":1826.6,"body":"then I have to turn anticlockwise,"},{"speaker":"then this is what happened","startTime":1826.6,"endTime":1828.15,"body":"and I can stop wherever I want,"},{"speaker":"then this is what happened","startTime":1829.0,"endTime":1832.063,"body":"and that is conservation"},{"speaker":"then this is what happened","startTime":1829.0,"endTime":1832.063,"body":"of angular momentum."},{"speaker":"then this is what happened","startTime":1833.02,"endTime":1838.02,"body":"If I start and stop"},{"speaker":"then this is what happened","startTime":1833.02,"endTime":1838.02,"body":"the wheel, that's fine,"},{"speaker":"then this is what happened","startTime":1839.55,"endTime":1844.157,"body":"but what if I start the"},{"speaker":"then this is what happened","startTime":1839.55,"endTime":1844.157,"body":"wheel spinning clockwise,"},{"speaker":"then this is what happened","startTime":1847.942,"endTime":1851.277,"body":"and what if I were to"},{"speaker":"then this is what happened","startTime":1847.942,"endTime":1851.277,"body":"tip the wheel like this?"},{"speaker":"then this is what happened","startTime":1854.18,"endTime":1857.99,"body":"Because now the wheel is"},{"speaker":"then this is what happened","startTime":1854.18,"endTime":1857.99,"body":"spinning anticlockwise,"},{"speaker":"then this is what happened","startTime":1857.99,"endTime":1860.55,"body":"it's now spinning in"},{"speaker":"then this is what happened","startTime":1857.99,"endTime":1860.55,"body":"the opposite direction."},{"speaker":"then this is what happened","startTime":1860.55,"endTime":1863.21,"body":"So what would you expect to happen?"},{"speaker":"then this is what happened","startTime":1863.21,"endTime":1864.733,"body":"So I'll get on my stool here,"},{"speaker":"then this is what happened","startTime":1865.91,"endTime":1870.653,"body":"so I'll start the wheel"},{"speaker":"then this is what happened","startTime":1865.91,"endTime":1870.653,"body":"spinning clockwise,"},{"speaker":"then this is what happened","startTime":1872.13,"endTime":1874.563,"body":"and now turn it around,"},{"speaker":"then this is what happened","startTime":1875.84,"endTime":1877.39,"body":"and I'll spin it anticlockwise,"},{"speaker":"then this is what happened","startTime":1878.55,"endTime":1882.38,"body":"and now I'll go back up there."},{"speaker":"then this is what happened","startTime":1882.38,"endTime":1887.38,"body":"So what it means is that I can"},{"speaker":"then this is what happened","startTime":1882.38,"endTime":1887.38,"body":"use this as a steering wheel"},{"speaker":"then this is what happened","startTime":1889.11,"endTime":1890.253,"body":"when I'm out in space."},{"speaker":"then this is what happened","startTime":1891.55,"endTime":1892.523,"body":"Anyone want to come up and try,"},{"speaker":"then this is what happened","startTime":1892.523,"endTime":1894.34,"body":"another volunteer from anywhere?"},{"speaker":"then this is what happened","startTime":1894.34,"endTime":1896.19,"body":"Ooh, we've got one up there, come on."},{"speaker":"then this is what happened","startTime":1897.34,"endTime":1901.9,"body":"So this is just to prove"},{"speaker":"then this is what happened","startTime":1897.34,"endTime":1901.9,"body":"that I'm not cheating here,"},{"speaker":"then this is what happened","startTime":1901.9,"endTime":1905.7,"body":"so here we go, very good."},{"speaker":"then this is what happened","startTime":1905.7,"endTime":1907.478,"body":"Your name is?"},{"speaker":"then this is what happened","startTime":1905.7,"endTime":1907.478,"body":"- Premjo."},{"speaker":"then this is what happened","startTime":1907.478,"endTime":1908.712,"body":"- Cranjo?"},{"speaker":"then this is what happened","startTime":1907.478,"endTime":1908.712,"body":"- Premjo."},{"speaker":"then this is what happened","startTime":1908.712,"endTime":1909.99,"body":"- Premjo, great."},{"speaker":"then this is what happened","startTime":1909.99,"endTime":1913.93,"body":"So what I want you to do is"},{"speaker":"then this is what happened","startTime":1909.99,"endTime":1913.93,"body":"stand on my swivelly stool,"},{"speaker":"then this is what happened","startTime":1913.93,"endTime":1915.579,"body":"there we go."},{"speaker":"then this is what happened","startTime":1915.579,"endTime":1916.462,"body":"Are you happy with that?"},{"speaker":"then this is what happened","startTime":1916.462,"endTime":1919.58,"body":"- Yeah."},{"speaker":"then this is what happened","startTime":1919.58,"endTime":1920.73,"body":"- Good with that?"},{"speaker":"then this is what happened","startTime":1920.73,"endTime":1924.313,"body":"So what I'm going to do is"},{"speaker":"then this is what happened","startTime":1920.73,"endTime":1924.313,"body":"I'm going to spin this up,"},{"speaker":"then this is what happened","startTime":1925.706,"endTime":1929.02,"body":"and what I'd you to do is to"},{"speaker":"then this is what happened","startTime":1925.706,"endTime":1929.02,"body":"grab that with both hands,"},{"speaker":"then this is what happened","startTime":1929.02,"endTime":1930.493,"body":"and now you can tip it up,"},{"speaker":"then this is what happened","startTime":1931.73,"endTime":1933.11,"body":"and you can tip it down a bit,"},{"speaker":"then this is what happened","startTime":1933.11,"endTime":1935.1,"body":"now point it downwards,"},{"speaker":"then this is what happened","startTime":1935.1,"endTime":1937.13,"body":"keep pointing downwards."},{"speaker":"then this is what happened","startTime":1937.13,"endTime":1938.313,"body":"Yeah, that's it."},{"speaker":"then this is what happened","startTime":1943.356,"endTime":1945.939,"body":"There we go, and back up again."},{"speaker":"then this is what happened","startTime":1947.44,"endTime":1948.63,"body":"It feels pretty strange, doesn't it?"},{"speaker":"then this is what happened","startTime":1948.63,"endTime":1950.76,"body":"- [Premjo] Yeah."},{"speaker":"then this is what happened","startTime":1950.76,"endTime":1951.593,"body":"- The thing is,"},{"speaker":"then this is what happened","startTime":1951.593,"endTime":1953.4,"body":"it feels stranger than it looks."},{"speaker":"then this is what happened","startTime":1953.4,"endTime":1957.67,"body":"So there we go, conservation"},{"speaker":"then this is what happened","startTime":1953.4,"endTime":1957.67,"body":"of angular momentum."},{"speaker":"then this is what happened","startTime":1957.67,"endTime":1958.503,"body":"Very good, Premjo,"},{"speaker":"then this is what happened","startTime":1958.503,"endTime":1960.033,"body":"thank you very much."},{"speaker":"then this is what happened","startTime":1960.033,"endTime":1963.033,"body":"(audience applauds)"},{"speaker":"then this is what happened","startTime":1964.733,"endTime":1965.75,"body":"So they key thing here"},{"speaker":"then this is what happened","startTime":1965.75,"endTime":1969.66,"body":"is that because we're on a swivelly stool,"},{"speaker":"then this is what happened","startTime":1969.66,"endTime":1974.23,"body":"as you change the angle of"},{"speaker":"then this is what happened","startTime":1969.66,"endTime":1974.23,"body":"a rotor in your spaceship,"},{"speaker":"then this is what happened","startTime":1974.23,"endTime":1977.67,"body":"you can change the direction"},{"speaker":"then this is what happened","startTime":1974.23,"endTime":1977.67,"body":"that you're spinning,"},{"speaker":"then this is what happened","startTime":1977.67,"endTime":1979.723,"body":"conservation of angular momentum."},{"speaker":"then this is what happened","startTime":1981.75,"endTime":1983.65,"body":"Conservation of angular momentum, again,"},{"speaker":"then this is what happened","startTime":1983.65,"endTime":1986.2,"body":"happens in places you least expect it."},{"speaker":"then this is what happened","startTime":1986.2,"endTime":1987.793,"body":"If I take this tennis racket,"},{"speaker":"then this is what happened","startTime":1988.695,"endTime":1993.063,"body":"it's painted red facing you there,"},{"speaker":"then this is what happened","startTime":1993.063,"endTime":1995.26,"body":"and it's white on the other side."},{"speaker":"then this is what happened","startTime":1995.26,"endTime":1997.15,"body":"Normally, you'd kind of expect,"},{"speaker":"then this is what happened","startTime":1997.15,"endTime":1999.363,"body":"if I toss the tennis racket up in the air,"},{"speaker":"then this is what happened","startTime":2000.37,"endTime":2005.37,"body":"you would expect the white"},{"speaker":"then this is what happened","startTime":2000.37,"endTime":2005.37,"body":"is facing you all the time,"},{"speaker":"then this is what happened","startTime":2005.59,"endTime":2008.89,"body":"that's what conservation of"},{"speaker":"then this is what happened","startTime":2005.59,"endTime":2008.89,"body":"angular momentum would do,"},{"speaker":"then this is what happened","startTime":2008.89,"endTime":2011.86,"body":"you wouldn't expect it to tumble around."},{"speaker":"then this is what happened","startTime":2011.86,"endTime":2015.17,"body":"Well unfortunately, that's"},{"speaker":"then this is what happened","startTime":2011.86,"endTime":2015.17,"body":"exactly what does happen."},{"speaker":"then this is what happened","startTime":2015.17,"endTime":2018.6,"body":"If I take my tennis racket"},{"speaker":"then this is what happened","startTime":2015.17,"endTime":2018.6,"body":"and spin it this way,"},{"speaker":"then this is what happened","startTime":2018.6,"endTime":2020.52,"body":"red facing you,"},{"speaker":"then this is what happened","startTime":2020.52,"endTime":2022.08,"body":"toss it up,"},{"speaker":"then this is what happened","startTime":2022.08,"endTime":2023.51,"body":"now it's white facing you."},{"speaker":"then this is what happened","startTime":2023.51,"endTime":2024.97,"body":"White facing you,"},{"speaker":"then this is what happened","startTime":2024.97,"endTime":2027.18,"body":"toss it up, and now it's red,"},{"speaker":"then this is what happened","startTime":2027.18,"endTime":2028.113,"body":"toss it up again."},{"speaker":"then this is what happened","startTime":2029.43,"endTime":2032.53,"body":"And this is just one of"},{"speaker":"then this is what happened","startTime":2029.43,"endTime":2032.53,"body":"these things that happens"},{"speaker":"then this is what happened","startTime":2032.53,"endTime":2035.07,"body":"when you do the maths of a spinning body,"},{"speaker":"then this is what happened","startTime":2035.07,"endTime":2036.84,"body":"it turns out that,"},{"speaker":"then this is what happened","startTime":2036.84,"endTime":2038.74,"body":"it doesn't have to be a tennis racket,"},{"speaker":"then this is what happened","startTime":2038.74,"endTime":2040.93,"body":"it can be a book,"},{"speaker":"then this is what happened","startTime":2040.93,"endTime":2042.083,"body":"I've got a book here,"},{"speaker":"then this is what happened","startTime":2043.62,"endTime":2046.37,"body":"and a rubber band on it to"},{"speaker":"then this is what happened","startTime":2043.62,"endTime":2046.37,"body":"stop the pages from opening."},{"speaker":"then this is what happened","startTime":2047.81,"endTime":2049.64,"body":"If I spin the book like this,"},{"speaker":"then this is what happened","startTime":2049.64,"endTime":2051.98,"body":"it's pointing upwards,"},{"speaker":"then this is what happened","startTime":2051.98,"endTime":2053.9,"body":"toss it up, catch it,"},{"speaker":"then this is what happened","startTime":2053.9,"endTime":2055.75,"body":"and it's now upside down,"},{"speaker":"then this is what happened","startTime":2055.75,"endTime":2056.583,"body":"toss it up,"},{"speaker":"then this is what happened","startTime":2056.583,"endTime":2057.84,"body":"it's now back the right way up."},{"speaker":"then this is what happened","startTime":2057.84,"endTime":2059.59,"body":"In fact, if I do it high enough,"},{"speaker":"then this is what happened","startTime":2059.59,"endTime":2061.15,"body":"I might be able to get a double flip."},{"speaker":"then this is what happened","startTime":2061.15,"endTime":2062.4,"body":"So it's the right way up,"},{"speaker":"then this is what happened","startTime":2065.31,"endTime":2067.27,"body":"it's back the right way up."},{"speaker":"then this is what happened","startTime":2067.27,"endTime":2069.015,"body":"Why is this happening?"},{"speaker":"then this is what happened","startTime":2069.015,"endTime":2072.72,"body":"I can show you a bit of"},{"speaker":"then this is what happened","startTime":2069.015,"endTime":2072.72,"body":"the maths of that later on"},{"speaker":"then this is what happened","startTime":2072.72,"endTime":2074.24,"body":"if you want,"},{"speaker":"then this is what happened","startTime":2074.24,"endTime":2076.01,"body":"but what's really interesting is"},{"speaker":"then this is what happened","startTime":2076.01,"endTime":2078.14,"body":"the maths isn't too difficult,"},{"speaker":"then this is what happened","startTime":2078.14,"endTime":2081.94,"body":"and it's why we study maths,"},{"speaker":"then this is what happened","startTime":2081.94,"endTime":2085.97,"body":"because it's only by getting"},{"speaker":"then this is what happened","startTime":2081.94,"endTime":2085.97,"body":"into the maths of things"},{"speaker":"then this is what happened","startTime":2085.97,"endTime":2090.85,"body":"that we start to understand"},{"speaker":"then this is what happened","startTime":2085.97,"endTime":2090.85,"body":"crazy things like that."},{"speaker":"then this is what happened","startTime":2090.85,"endTime":2092.87,"body":"There's even a crazier one,"},{"speaker":"then this is what happened","startTime":2092.87,"endTime":2095.97,"body":"which, again, is conservation"},{"speaker":"then this is what happened","startTime":2092.87,"endTime":2095.97,"body":"of angular momentum,"},{"speaker":"then this is what happened","startTime":2095.97,"endTime":2098.993,"body":"which is why my cat,"},{"speaker":"then this is what happened","startTime":2099.92,"endTime":2102.14,"body":"if dropped upside-down,"},{"speaker":"then this is what happened","startTime":2102.14,"endTime":2103.32,"body":"will land on its feet."},{"speaker":"then this is what happened","startTime":2103.32,"endTime":2107.575,"body":"Unfortunately, this"},{"speaker":"then this is what happened","startTime":2103.32,"endTime":2107.575,"body":"one is a defective cat,"},{"speaker":"then this is what happened","startTime":2107.575,"endTime":2109.957,"body":"(audience laughs)"},{"speaker":"then this is what happened","startTime":2109.957,"endTime":2113.79,"body":"but this one is a non-defective cat,"},{"speaker":"then this is what happened","startTime":2113.79,"endTime":2115.743,"body":"this is a real cat."},{"speaker":"then this is what happened","startTime":2116.8,"endTime":2118.05,"body":"I'll show this NASA video,"},{"speaker":"then this is what happened","startTime":2118.05,"endTime":2119.45,"body":"'cause if anyone's got any complaints,"},{"speaker":"then this is what happened","startTime":2119.45,"endTime":2121.34,"body":"they should contact NASA."},{"speaker":"then this is what happened","startTime":2121.34,"endTime":2123.403,"body":"But here is the cat,"},{"speaker":"then this is what happened","startTime":2124.287,"endTime":2125.903,"body":"that was reversed, by the way."},{"speaker":"then this is what happened","startTime":2126.763,"endTime":2128.83,"body":"(audience laughs)"},{"speaker":"So let's see what's happening","startTime":2130.29,"endTime":2134.063,"body":"the cat is being dropped upside-down,"},{"speaker":"So let's see what's happening","startTime":2135.31,"endTime":2138.88,"body":"and the back end of the cat,"},{"speaker":"So let's see what's happening","startTime":2138.88,"endTime":2140.93,"body":"the tail and the hind legs,"},{"speaker":"So let's see what's happening","startTime":2140.93,"endTime":2142.45,"body":"are going, say, clockwise,"},{"speaker":"So let's see what's happening","startTime":2142.45,"endTime":2146.04,"body":"and the front end is a cat"},{"speaker":"So let's see what's happening","startTime":2142.45,"endTime":2146.04,"body":"is going anticlockwise,"},{"speaker":"So let's see what's happening","startTime":2146.04,"endTime":2147.91,"body":"and then the cat does a bit of a maneuver"},{"speaker":"So let's see what's happening","startTime":2147.91,"endTime":2150.06,"body":"to get the legs in the right place,"},{"speaker":"So let's see what's happening","startTime":2150.06,"endTime":2151.493,"body":"and lands on its feet."},{"speaker":"So let's see what's happening","startTime":2152.89,"endTime":2153.723,"body":"And of course,"},{"speaker":"So let's see what's happening","startTime":2153.723,"endTime":2157.433,"body":"cats have worked out how to"},{"speaker":"So let's see what's happening","startTime":2153.723,"endTime":2157.433,"body":"do this over generations."},{"speaker":"So let's see what's happening","startTime":2158.96,"endTime":2163.96,"body":"This is a picture taken"},{"speaker":"So let's see what's happening","startTime":2158.96,"endTime":2163.96,"body":"about 120 years ago,"},{"speaker":"So let's see what's happening","startTime":2163.98,"endTime":2166.97,"body":"a series of flash photographs,"},{"speaker":"So let's see what's happening","startTime":2166.97,"endTime":2167.803,"body":"but the problem was"},{"speaker":"So let's see what's happening","startTime":2167.803,"endTime":2170.81,"body":"that the cat had to be"},{"speaker":"So let's see what's happening","startTime":2167.803,"endTime":2170.81,"body":"dropped a few hundred times"},{"speaker":"So let's see what's happening","startTime":2170.81,"endTime":2172.91,"body":"to get this sequence of photographs,"},{"speaker":"So let's see what's happening","startTime":2172.91,"endTime":2174.93,"body":"it's good that we've"},{"speaker":"So let's see what's happening","startTime":2172.91,"endTime":2174.93,"body":"got video cameras now,"},{"speaker":"So let's see what's happening","startTime":2174.93,"endTime":2176.93,"body":"cats are in a happier place."},{"speaker":"So let's see what's happening","startTime":2176.93,"endTime":2179.993,"body":"But I think I can do"},{"speaker":"So let's see what's happening","startTime":2176.93,"endTime":2179.993,"body":"what the cat is doing,"},{"speaker":"So let's see what's happening","startTime":2182.17,"endTime":2183.003,"body":"sort of,"},{"speaker":"So let's see what's happening","startTime":2183.003,"endTime":2184.13,"body":"let me just demonstrate."},{"speaker":"So let's see what's happening","startTime":2184.13,"endTime":2186.65,"body":"If I put my arms out at a distance,"},{"speaker":"So let's see what's happening","startTime":2186.65,"endTime":2191.09,"body":"I get large angular mass,"},{"speaker":"So let's see what's happening","startTime":2191.09,"endTime":2196.09,"body":"and my body moves quite a lot,"},{"speaker":"So let's see what's happening","startTime":2197.56,"endTime":2198.69,"body":"and my arms don't move that much,"},{"speaker":"So let's see what's happening","startTime":2198.69,"endTime":2201.12,"body":"whereas if I put my arms in,"},{"speaker":"So let's see what's happening","startTime":2201.12,"endTime":2204.3,"body":"small angular mass, my"},{"speaker":"So let's see what's happening","startTime":2201.12,"endTime":2204.3,"body":"body doesn't move at all."},{"speaker":"So let's see what's happening","startTime":2204.3,"endTime":2206.71,"body":"So that means I can go around one way"},{"speaker":"So let's see what's happening","startTime":2206.71,"endTime":2208.04,"body":"with a large angular mass,"},{"speaker":"So let's see what's happening","startTime":2208.04,"endTime":2209.933,"body":"bring my arms in, go back out."},{"speaker":"So let's see what's happening","startTime":2213.98,"endTime":2215.63,"body":"So that is what the cat is doing,"},{"speaker":"So let's see what's happening","startTime":2216.82,"endTime":2220.55,"body":"it's kind of swimming around in a circle."},{"speaker":"So let's see what's happening","startTime":2220.55,"endTime":2221.383,"body":"And again,"},{"speaker":"So let's see what's happening","startTime":2221.383,"endTime":2223.66,"body":"it's really nice to be"},{"speaker":"So let's see what's happening","startTime":2221.383,"endTime":2223.66,"body":"able to see how that works."},{"speaker":"So let's see what's happening","startTime":2223.66,"endTime":2225.77,"body":"And maybe some of you are trampolinists,"},{"speaker":"So let's see what's happening","startTime":2225.77,"endTime":2230.42,"body":"or maybe some of you have"},{"speaker":"So let's see what's happening","startTime":2225.77,"endTime":2230.42,"body":"done any kind of acrobatics,"},{"speaker":"So let's see what's happening","startTime":2230.42,"endTime":2232.42,"body":"you can tumble around."},{"speaker":"So let's see what's happening","startTime":2232.42,"endTime":2234.913,"body":"You watch this with"},{"speaker":"So let's see what's happening","startTime":2232.42,"endTime":2234.913,"body":"diving in the Olympics,"},{"speaker":"So let's see what's happening","startTime":2236.855,"endTime":2237.688,"body":"you think,"},{"speaker":"So let's see what's happening","startTime":2237.688,"endTime":2240.75,"body":"how is it that this diver has"},{"speaker":"So let's see what's happening","startTime":2237.688,"endTime":2240.75,"body":"managed to start off this way,"},{"speaker":"So let's see what's happening","startTime":2240.75,"endTime":2243.63,"body":"but lands in the pool"},{"speaker":"So let's see what's happening","startTime":2240.75,"endTime":2243.63,"body":"pointing the other way?"},{"speaker":"So let's see what's happening","startTime":2243.63,"endTime":2244.555,"body":"Well there you go,"},{"speaker":"So let's see what's happening","startTime":2244.555,"endTime":2247.73,"body":"that's all this conservation"},{"speaker":"So let's see what's happening","startTime":2244.555,"endTime":2247.73,"body":"of angular momentum stuff."},{"speaker":"So let's see what's happening","startTime":2247.73,"endTime":2248.563,"body":"I'm going to wind up now"},{"speaker":"So let's see what's happening","startTime":2248.563,"endTime":2253.08,"body":"on my favorite bit of gyroscopic stuff,"},{"speaker":"So let's see what's happening","startTime":2253.08,"endTime":2256.9,"body":"on boomerangs, and how they work."},{"speaker":"So let's see what's happening","startTime":2256.9,"endTime":2259.293,"body":"We have to accept that wings work,"},{"speaker":"So let's see what's happening","startTime":2260.54,"endTime":2263.52,"body":"airflow over a wing generates lift."},{"speaker":"So let's see what's happening","startTime":2263.52,"endTime":2267.57,"body":"If ever anybody asks"},{"speaker":"So let's see what's happening","startTime":2263.52,"endTime":2267.57,"body":"you why is there lift,"},{"speaker":"So let's see what's happening","startTime":2267.57,"endTime":2270.943,"body":"if you start to talk about Bernoulli,"},{"speaker":"So let's see what's happening","startTime":2272.29,"endTime":2274.12,"body":"that's the complicated"},{"speaker":"So let's see what's happening","startTime":2272.29,"endTime":2274.12,"body":"way to think about it,"},{"speaker":"So let's see what's happening","startTime":2274.12,"endTime":2276.69,"body":"because there's nothing at all,"},{"speaker":"So let's see what's happening","startTime":2276.69,"endTime":2277.92,"body":"by looking at that diagram,"},{"speaker":"So let's see what's happening","startTime":2277.92,"endTime":2280.47,"body":"to say that the air moves"},{"speaker":"So let's see what's happening","startTime":2277.92,"endTime":2280.47,"body":"over one side of the wing"},{"speaker":"So let's see what's happening","startTime":2280.47,"endTime":2282.41,"body":"faster or slower than the other,"},{"speaker":"So let's see what's happening","startTime":2282.41,"endTime":2284.56,"body":"but the easy thing to think about"},{"speaker":"So let's see what's happening","startTime":2284.56,"endTime":2287.47,"body":"is that the wing deflects air downwards,"},{"speaker":"So let's see what's happening","startTime":2287.47,"endTime":2289.92,"body":"and every action has an"},{"speaker":"So let's see what's happening","startTime":2287.47,"endTime":2289.92,"body":"equal and opposite reaction,"},{"speaker":"So let's see what's happening","startTime":2289.92,"endTime":2291.8,"body":"so if I'm deflecting air downwards,"},{"speaker":"So let's see what's happening","startTime":2291.8,"endTime":2294.19,"body":"there's got to be a"},{"speaker":"So let's see what's happening","startTime":2291.8,"endTime":2294.19,"body":"lift force on the wing."},{"speaker":"So let's see what's happening","startTime":2294.19,"endTime":2297.1,"body":"And we know that the lift"},{"speaker":"So let's see what's happening","startTime":2294.19,"endTime":2297.1,"body":"force on the wing is bigger"},{"speaker":"So let's see what's happening","startTime":2297.1,"endTime":2299.61,"body":"the faster the air is moving."},{"speaker":"So let's see what's happening","startTime":2299.61,"endTime":2301.59,"body":"So how does that relate to a boomerang?"},{"speaker":"So let's see what's happening","startTime":2301.59,"endTime":2302.84,"body":"The first thing is,"},{"speaker":"So let's see what's happening","startTime":2302.84,"endTime":2307.84,"body":"the boomerang I've shown"},{"speaker":"So let's see what's happening","startTime":2302.84,"endTime":2307.84,"body":"there is, if you like,"},{"speaker":"So let's see what's happening","startTime":2308.14,"endTime":2311.69,"body":"two of these regular"},{"speaker":"So let's see what's happening","startTime":2308.14,"endTime":2311.69,"body":"boomerangs joined together"},{"speaker":"So let's see what's happening","startTime":2311.69,"endTime":2313.653,"body":"to make a kind of cross shape."},{"speaker":"So let's see what's happening","startTime":2314.56,"endTime":2316.49,"body":"It turns out they're easier to analyze,"},{"speaker":"So let's see what's happening","startTime":2316.49,"endTime":2317.51,"body":"they're easier to make,"},{"speaker":"So let's see what's happening","startTime":2317.51,"endTime":2320.92,"body":"they're easier to think about generally."},{"speaker":"So let's see what's happening","startTime":2320.92,"endTime":2323.63,"body":"And what we do is we have some spin,"},{"speaker":"So let's see what's happening","startTime":2323.63,"endTime":2325.31,"body":"just like our spinning wheel,"},{"speaker":"So let's see what's happening","startTime":2325.31,"endTime":2328.81,"body":"and we're going to throw the"},{"speaker":"So let's see what's happening","startTime":2325.31,"endTime":2328.81,"body":"boomerang in a certain direction."},{"speaker":"So let's see what's happening","startTime":2328.81,"endTime":2330.78,"body":"And what you'll notice"},{"speaker":"So let's see what's happening","startTime":2330.78,"endTime":2335.78,"body":"is that because we've got"},{"speaker":"So let's see what's happening","startTime":2330.78,"endTime":2335.78,"body":"spin and moving forwards"},{"speaker":"So let's see what's happening","startTime":2336.23,"endTime":2337.393,"body":"at the same time,"},{"speaker":"So let's see what's happening","startTime":2338.23,"endTime":2341.53,"body":"our boomerang is,"},{"speaker":"So let's see what's happening","startTime":2341.53,"endTime":2343.64,"body":"well, if the middle is"},{"speaker":"So let's see what's happening","startTime":2341.53,"endTime":2343.64,"body":"going at a certain speed,"},{"speaker":"So let's see what's happening","startTime":2343.64,"endTime":2344.933,"body":"and it's spinning,"},{"speaker":"So let's see what's happening","startTime":2346.16,"endTime":2351.16,"body":"then the top is moving forwards"},{"speaker":"So let's see what's happening","startTime":2346.16,"endTime":2351.16,"body":"faster than the middle,"},{"speaker":"So let's see what's happening","startTime":2351.26,"endTime":2353.62,"body":"and the bottom is going backwards a bit,"},{"speaker":"So let's see what's happening","startTime":2353.62,"endTime":2356.25,"body":"so it's moving forwards"},{"speaker":"So let's see what's happening","startTime":2353.62,"endTime":2356.25,"body":"slower than the middle."},{"speaker":"So let's see what's happening","startTime":2356.25,"endTime":2357.4,"body":"So when moving through the air,"},{"speaker":"So let's see what's happening","startTime":2357.4,"endTime":2359.13,"body":"this bit of wing,"},{"speaker":"So let's see what's happening","startTime":2359.13,"endTime":2363.4,"body":"because the boomerang's"},{"speaker":"So let's see what's happening","startTime":2359.13,"endTime":2363.4,"body":"got wing-shaped surfaces,"},{"speaker":"So let's see what's happening","startTime":2363.4,"endTime":2364.483,"body":"this bit of wing,"},{"speaker":"So let's see what's happening","startTime":2365.94,"endTime":2368.01,"body":"the faster one has got more lift,"},{"speaker":"So let's see what's happening","startTime":2368.01,"endTime":2370.003,"body":"the slower bit has got less lift."},{"speaker":"So let's see what's happening","startTime":2372.3,"endTime":2376.07,"body":"That means we've got an"},{"speaker":"So let's see what's happening","startTime":2372.3,"endTime":2376.07,"body":"unbalanced set of forces,"},{"speaker":"So let's see what's happening","startTime":2376.07,"endTime":2378.98,"body":"which was just like on the bicycle wheel,"},{"speaker":"So let's see what's happening","startTime":2378.98,"endTime":2381.12,"body":"we have this couple,"},{"speaker":"So let's see what's happening","startTime":2381.12,"endTime":2383.21,"body":"more force at the top, less at the bottom."},{"speaker":"So let's see what's happening","startTime":2383.21,"endTime":2387.173,"body":"And when we've got a couple"},{"speaker":"So let's see what's happening","startTime":2383.21,"endTime":2387.173,"body":"acting on a spinning object,"},{"speaker":"So let's see what's happening","startTime":2388.09,"endTime":2391.31,"body":"well here's our couple"},{"speaker":"So let's see what's happening","startTime":2388.09,"endTime":2391.31,"body":"acting on a spinning object,"},{"speaker":"So let's see what's happening","startTime":2391.31,"endTime":2393.96,"body":"we get this gyroscopic precession,"},{"speaker":"So let's see what's happening","startTime":2393.96,"endTime":2397.583,"body":"it wants to go around"},{"speaker":"So let's see what's happening","startTime":2393.96,"endTime":2397.583,"body":"to change its direction."},{"speaker":"So let's see what's happening","startTime":2400.17,"endTime":2402.513,"body":"Does that happen with our boomerang?"},{"speaker":"So let's see what's happening","startTime":2403.439,"endTime":2404.989,"body":"And the answer is yes, it does."},{"speaker":"So let's see what's happening","startTime":2407.51,"endTime":2408.343,"body":"There we go,"},{"speaker":"So let's see what's happening","startTime":2408.343,"endTime":2413.0,"body":"it's gone round on a curved path"},{"speaker":"So let's see what's happening","startTime":2413.0,"endTime":2416.763,"body":"because of this gyroscopic effect."},{"speaker":"So let's see what's happening","startTime":2417.63,"endTime":2420.8,"body":"You might notice that it levels out a bit"},{"speaker":"So let's see what's happening","startTime":2420.8,"endTime":2425.61,"body":"because there's a bit"},{"speaker":"So let's see what's happening","startTime":2420.8,"endTime":2425.61,"body":"of drag, it slows down,"},{"speaker":"So let's see what's happening","startTime":2425.61,"endTime":2426.443,"body":"various effects,"},{"speaker":"So let's see what's happening","startTime":2426.443,"endTime":2429.85,"body":"but actually, it's very handy"},{"speaker":"So let's see what's happening","startTime":2426.443,"endTime":2429.85,"body":"if it does level out a bit"},{"speaker":"So let's see what's happening","startTime":2429.85,"endTime":2432.217,"body":"because when it comes back to me,"},{"speaker":"So let's see what's happening","startTime":2432.217,"endTime":2433.79,"body":"it makes it nice and easy to catch."},{"speaker":"So let's see what's happening","startTime":2433.79,"endTime":2435.64,"body":"I've got other ones here,"},{"speaker":"So let's see what's happening","startTime":2435.64,"endTime":2437.04,"body":"this one's a left,"},{"speaker":"So let's see what's happening","startTime":2437.04,"endTime":2438.15,"body":"oh no, where's my left-handed?"},{"speaker":"So let's see what's happening","startTime":2438.15,"endTime":2440.72,"body":"This is a left-handed boomerang,"},{"speaker":"So let's see what's happening","startTime":2440.72,"endTime":2441.913,"body":"mirror image,"},{"speaker":"So let's see what's happening","startTime":2445.23,"endTime":2446.88,"body":"it should go round the other way."},{"speaker":"So let's see what's happening","startTime":2448.84,"endTime":2450.005,"body":"It goes round a bit fast."},{"speaker":"So let's see what's happening","startTime":2450.005,"endTime":2452.16,"body":"And then this one,"},{"speaker":"So let's see what's happening","startTime":2452.16,"endTime":2453.16,"body":"these are quite fun."},{"speaker":"So let's see what's happening","startTime":2455.47,"endTime":2457.28,"body":"And you can make these yourself,"},{"speaker":"So let's see what's happening","startTime":2457.28,"endTime":2460.123,"body":"they're nice, easy things to do."},{"speaker":"So let's see what's happening","startTime":2463.94,"endTime":2465.89,"body":"If you do the maths on them,"},{"speaker":"So let's see what's happening","startTime":2465.89,"endTime":2470.113,"body":"it turns out that the radius"},{"speaker":"So let's see what's happening","startTime":2465.89,"endTime":2470.113,"body":"of the flight of a boomerang,"},{"speaker":"So let's see what's happening","startTime":2470.97,"endTime":2475.95,"body":"it doesn't depend on"},{"speaker":"So let's see what's happening","startTime":2470.97,"endTime":2475.95,"body":"how hard you throw it,"},{"speaker":"So let's see what's happening","startTime":2475.95,"endTime":2478.24,"body":"the radius of the flight of the boomerang,"},{"speaker":"So let's see what's happening","startTime":2478.24,"endTime":2479.84,"body":"that's big R,"},{"speaker":"So let's see what's happening","startTime":2479.84,"endTime":2482.16,"body":"depends on our angular mass, J,"},{"speaker":"So let's see what's happening","startTime":2482.16,"endTime":2483.86,"body":"the moment of inertia,"},{"speaker":"So let's see what's happening","startTime":2483.86,"endTime":2487.86,"body":"density of air, the lift"},{"speaker":"So let's see what's happening","startTime":2483.86,"endTime":2487.86,"body":"coefficient of the wing,"},{"speaker":"So let's see what's happening","startTime":2487.86,"endTime":2490.01,"body":"pi, which is three,"},{"speaker":"So let's see what's happening","startTime":2490.01,"endTime":2493.41,"body":"and how big the boomerang is."},{"speaker":"So let's see what's happening","startTime":2493.41,"endTime":2495.6,"body":"The radius doesn't depend"},{"speaker":"So let's see what's happening","startTime":2493.41,"endTime":2495.6,"body":"on how hard I throw it,"},{"speaker":"So let's see what's happening","startTime":2495.6,"endTime":2497.453,"body":"so if I throw it gently,"},{"speaker":"So let's see what's happening","startTime":2498.84,"endTime":2500.883,"body":"it kind of comes back to me,"},{"speaker":"So let's see what's happening","startTime":2502.078,"endTime":2504.731,"body":"and it goes two or three rows back."},{"speaker":"So let's see what's happening","startTime":2504.731,"endTime":2505.681,"body":"If I throw it hard,"},{"speaker":"So let's see what's happening","startTime":2506.67,"endTime":2509.863,"body":"it comes back on the same path radius."},{"speaker":"So let's see what's happening","startTime":2511.28,"endTime":2513.4,"body":"Surely, throwing it"},{"speaker":"So let's see what's happening","startTime":2511.28,"endTime":2513.4,"body":"hard makes a difference?"},{"speaker":"So let's see what's happening","startTime":2513.4,"endTime":2516.373,"body":"Well you need this flick of the wrist,"},{"speaker":"So let's see what's happening","startTime":2517.897,"endTime":2518.73,"body":"the faster you throw it,"},{"speaker":"So let's see what's happening","startTime":2518.73,"endTime":2520.38,"body":"the more you need to spin it,"},{"speaker":"So let's see what's happening","startTime":2520.38,"endTime":2521.213,"body":"and that's the thing"},{"speaker":"So let's see what's happening","startTime":2521.213,"endTime":2523.71,"body":"about learning how to throw a boomerang."},{"speaker":"So let's see what's happening","startTime":2523.71,"endTime":2527.6,"body":"So I've given you a bit"},{"speaker":"So let's see what's happening","startTime":2523.71,"endTime":2527.6,"body":"of a whistle-stop tour"},{"speaker":"So let's see what's happening","startTime":2527.6,"endTime":2529.01,"body":"of gyroscopes and boomerangs."},{"speaker":"So let's see what's happening","startTime":2529.01,"endTime":2530.27,"body":"The maths?"},{"speaker":"So let's see what's happening","startTime":2530.27,"endTime":2532.64,"body":"Well it's all buried in underneath,"},{"speaker":"So let's see what's happening","startTime":2532.64,"endTime":2536.09,"body":"but I hope you enjoyed"},{"speaker":"So let's see what's happening","startTime":2532.64,"endTime":2536.09,"body":"seeing some of these demos,"},{"speaker":"So let's see what's happening","startTime":2536.09,"endTime":2537.93,"body":"thank you very much."},{"speaker":"So let's see what's happening","startTime":2537.93,"endTime":2540.93,"body":"(audience applauds)"},{"speaker":"So let's see what's happening","startTime":2546.994,"endTime":2547.827,"body":"- Professor Hunt,"},{"speaker":"So let's see what's happening","startTime":2547.827,"endTime":2550.09,"body":"that was fascinating, entertaining,"},{"speaker":"So let's see what's happening","startTime":2550.09,"endTime":2552.01,"body":"it looked like miracles and magic"},{"speaker":"So let's see what's happening","startTime":2552.01,"endTime":2552.843,"body":"from where I was sitting."},{"speaker":"So let's see what's happening","startTime":2552.843,"endTime":2554.13,"body":"- But no maths."},{"speaker":"So let's see what's happening","startTime":2554.13,"endTime":2555.24,"body":"- No, there was maths as well,"},{"speaker":"So let's see what's happening","startTime":2555.24,"endTime":2557.51,"body":"and we have some questions."},{"speaker":"So let's see what's happening","startTime":2557.51,"endTime":2559.3,"body":"We have some questions"},{"speaker":"So let's see what's happening","startTime":2557.51,"endTime":2559.3,"body":"from the online audience,"},{"speaker":"So let's see what's happening","startTime":2559.3,"endTime":2561.22,"body":"and I'm sure we'll have some questions"},{"speaker":"So let's see what's happening","startTime":2561.22,"endTime":2562.4,"body":"from the room as well,"},{"speaker":"So let's see what's happening","startTime":2562.4,"endTime":2566.28,"body":"and I'm going to start off with"},{"speaker":"So let's see what's happening","startTime":2562.4,"endTime":2566.28,"body":"one of the online questions,"},{"speaker":"which is this","startTime":2567.997,"endTime":2571.267,"body":"\"With gyroscopes pointing telescopes,"},{"speaker":"which is this","startTime":2571.267,"endTime":2574.517,"body":"\"why do they eventually"},{"speaker":"which is this","startTime":2571.267,"endTime":2574.517,"body":"run out of capacity"},{"speaker":"which is this","startTime":2574.517,"endTime":2578.617,"body":"\"and have to realign the"},{"speaker":"which is this","startTime":2574.517,"endTime":2578.617,"body":"spin with thrusters?\""},{"speaker":"which is this","startTime":2579.53,"endTime":2583.53,"body":"- When you've got a gyroscope."},{"speaker":"which is this","startTime":2583.53,"endTime":2584.493,"body":"- Should I get out of"},{"speaker":"which is this","startTime":2583.53,"endTime":2584.493,"body":"the way so that you can?"},{"speaker":"which is this","startTime":2587.386,"endTime":2588.219,"body":"- So imagine,"},{"speaker":"which is this","startTime":2590.87,"endTime":2594.023,"body":"if you've got a spinning wheel,"},{"speaker":"which is this","startTime":2595.19,"endTime":2599.197,"body":"the effect you want to get is best"},{"speaker":"which is this","startTime":2603.49,"endTime":2606.04,"body":"when the spin is at right angles"},{"speaker":"which is this","startTime":2606.04,"endTime":2611.04,"body":"to the motion you want to change."},{"speaker":"which is this","startTime":2611.27,"endTime":2612.46,"body":"So on a spacecraft,"},{"speaker":"which is this","startTime":2612.46,"endTime":2614.11,"body":"you're going to have"},{"speaker":"which is this","startTime":2612.46,"endTime":2614.11,"body":"three of these things,"},{"speaker":"which is this","startTime":2614.11,"endTime":2617.08,"body":"one in this direction,"},{"speaker":"which is this","startTime":2617.08,"endTime":2618.83,"body":"one in this direction,"},{"speaker":"which is this","startTime":2618.83,"endTime":2622.06,"body":"and a third one in that direction,"},{"speaker":"which is this","startTime":2622.06,"endTime":2623.72,"body":"and hopefully then, with any luck,"},{"speaker":"which is this","startTime":2623.72,"endTime":2625.35,"body":"you can use them"},{"speaker":"which is this","startTime":2625.35,"endTime":2628.773,"body":"to do fully three-dimensional"},{"speaker":"which is this","startTime":2625.35,"endTime":2628.773,"body":"aligning of your spacecraft."},{"speaker":"which is this","startTime":2630.27,"endTime":2632.6,"body":"But what happens if,"},{"speaker":"which is this","startTime":2632.6,"endTime":2636.34,"body":"there I am, I'm doing fantastic"},{"speaker":"which is this","startTime":2632.6,"endTime":2636.34,"body":"alignment of my spacecraft,"},{"speaker":"which is this","startTime":2636.34,"endTime":2637.34,"body":"but what happens if,"},{"speaker":"which is this","startTime":2637.34,"endTime":2639.04,"body":"for one reason or another,"},{"speaker":"which is this","startTime":2639.04,"endTime":2642.49,"body":"this one has ended up"},{"speaker":"which is this","startTime":2639.04,"endTime":2642.49,"body":"pointing up this way,"},{"speaker":"which is this","startTime":2642.49,"endTime":2645.203,"body":"in exactly the same"},{"speaker":"which is this","startTime":2642.49,"endTime":2645.203,"body":"direction as the other one?"},{"speaker":"which is this","startTime":2646.09,"endTime":2649.41,"body":"So now I've got one direction"},{"speaker":"which is this","startTime":2646.09,"endTime":2649.41,"body":"which I can't control."},{"speaker":"which is this","startTime":2649.41,"endTime":2650.69,"body":"So what I've got to do,"},{"speaker":"which is this","startTime":2650.69,"endTime":2653.09,"body":"turn off my gyro,"},{"speaker":"which is this","startTime":2653.09,"endTime":2655.9,"body":"get it aligned back to where it is,"},{"speaker":"which is this","startTime":2655.9,"endTime":2659.08,"body":"use my thrusters to get"},{"speaker":"which is this","startTime":2655.9,"endTime":2659.08,"body":"everything lined up properly,"},{"speaker":"which is this","startTime":2659.08,"endTime":2660.72,"body":"and start up again."},{"speaker":"which is this","startTime":2660.72,"endTime":2665.073,"body":"There was a famous bit in"},{"speaker":"which is this","startTime":2660.72,"endTime":2665.073,"body":"\"Apollo 13,\" the movie,"},{"speaker":"which is this","startTime":2666.26,"endTime":2670.683,"body":"where they turned off their"},{"speaker":"which is this","startTime":2666.26,"endTime":2670.683,"body":"inertial navigation system."},{"speaker":"which is this","startTime":2671.84,"endTime":2672.82,"body":"That was a scary moment,"},{"speaker":"which is this","startTime":2672.82,"endTime":2673.653,"body":"you're out in space,"},{"speaker":"which is this","startTime":2673.653,"endTime":2674.95,"body":"the one thing you don't want to lose"},{"speaker":"which is this","startTime":2674.95,"endTime":2677.25,"body":"is your inertial navigation system,"},{"speaker":"which is this","startTime":2677.25,"endTime":2678.94,"body":"but they had to turn it off,"},{"speaker":"which is this","startTime":2678.94,"endTime":2680.62,"body":"and then you turn it on again,"},{"speaker":"which is this","startTime":2680.62,"endTime":2681.453,"body":"and then, yes,"},{"speaker":"which is this","startTime":2681.453,"endTime":2683.43,"body":"they had to use their thrusters to line up"},{"speaker":"which is this","startTime":2683.43,"endTime":2685.27,"body":"and switch everything back on again."},{"speaker":"which is this","startTime":2685.27,"endTime":2686.7,"body":"- [Questioner] Thank you"},{"speaker":"which is this","startTime":2685.27,"endTime":2686.7,"body":"very much, Professor Hunt,"},{"speaker":"which is this","startTime":2686.7,"endTime":2688.47,"body":"for a most interesting lecture."},{"speaker":"which is this","startTime":2689.55,"endTime":2691.08,"body":"I didn't realize a boomerang"},{"speaker":"which is this","startTime":2691.08,"endTime":2694.62,"body":"would actually have four"},{"speaker":"which is this","startTime":2691.08,"endTime":2694.62,"body":"arms of equal length."},{"speaker":"which is this","startTime":2694.62,"endTime":2696.84,"body":"I tried, actually throwing a boomerang"},{"speaker":"which is this","startTime":2696.84,"endTime":2698.14,"body":"when I was in Australia,"},{"speaker":"which is this","startTime":2698.14,"endTime":2699.483,"body":"I was completely hopeless at it."},{"speaker":"which is this","startTime":2699.483,"endTime":2700.85,"body":"- Well that's because it's"},{"speaker":"which is this","startTime":2699.483,"endTime":2700.85,"body":"in the Southern Hemisphere,"},{"speaker":"which is this","startTime":2700.85,"endTime":2703.717,"body":"it would have been fine if you were here."},{"speaker":"which is this","startTime":2703.717,"endTime":2705.49,"body":"(audience laughs)"},{"speaker":"which is this","startTime":2705.49,"endTime":2708.92,"body":"- [Questioner] With a"},{"speaker":"which is this","startTime":2705.49,"endTime":2708.92,"body":"traditional Aboriginal boomerang,"},{"speaker":"which is this","startTime":2708.92,"endTime":2711.09,"body":"does that involve far more skill"},{"speaker":"which is this","startTime":2711.09,"endTime":2714.782,"body":"than the boomerang you've used?"},{"speaker":"which is this","startTime":2714.782,"endTime":2719.782,"body":"- If you buy a boomerang,"},{"speaker":"which is this","startTime":2720.1,"endTime":2724.31,"body":"or get a boomerang from a tourist shop,"},{"speaker":"which is this","startTime":2724.31,"endTime":2727.81,"body":"you're probably going to find"},{"speaker":"which is this","startTime":2724.31,"endTime":2727.81,"body":"that it's not going to work,"},{"speaker":"which is this","startTime":2727.81,"endTime":2728.862,"body":"or if it does work,"},{"speaker":"which is this","startTime":2728.862,"endTime":2732.8,"body":"it's going to take a bit of practice."},{"speaker":"which is this","startTime":2732.8,"endTime":2736.82,"body":"The best boomerangs to get are online."},{"speaker":"which is this","startTime":2736.82,"endTime":2738.65,"body":"If you go to,"},{"speaker":"which is this","startTime":2738.65,"endTime":2742.197,"body":"believe it or not, the"},{"speaker":"which is this","startTime":2738.65,"endTime":2742.197,"body":"best boomerang society"},{"speaker":"which is this","startTime":2744.7,"endTime":2747.32,"body":"is the British Boomerang"},{"speaker":"which is this","startTime":2744.7,"endTime":2747.32,"body":"Society, there you go,"},{"speaker":"which is this","startTime":2747.32,"endTime":2749.43,"body":"and if you go to the"},{"speaker":"which is this","startTime":2747.32,"endTime":2749.43,"body":"British Boomerang Society,"},{"speaker":"which is this","startTime":2749.43,"endTime":2754.43,"body":"they've got a fantastic list"},{"speaker":"which is this","startTime":2749.43,"endTime":2754.43,"body":"of where to get a boomerang,"},{"speaker":"which is this","startTime":2755.3,"endTime":2756.81,"body":"and you can get little ones,"},{"speaker":"which is this","startTime":2756.81,"endTime":2757.75,"body":"tiny, weeny ones,"},{"speaker":"which is this","startTime":2757.75,"endTime":2760.45,"body":"big ones, left-handed"},{"speaker":"which is this","startTime":2757.75,"endTime":2760.45,"body":"ones, right-handed ones,"},{"speaker":"which is this","startTime":2760.45,"endTime":2763.5,"body":"lead-weighted ones that go for miles,"},{"speaker":"which is this","startTime":2763.5,"endTime":2765.18,"body":"there are sport boomerangs"},{"speaker":"which is this","startTime":2765.18,"endTime":2767.13,"body":"where they go really quickly"},{"speaker":"which is this","startTime":2767.13,"endTime":2768.43,"body":"so you can do a record"},{"speaker":"which is this","startTime":2768.43,"endTime":2770.603,"body":"of how many throws can you do in a minute,"},{"speaker":"which is this","startTime":2771.49,"endTime":2772.943,"body":"those are easy to throw."},{"speaker":"which is this","startTime":2773.97,"endTime":2776.25,"body":"Probably, you just had one"},{"speaker":"which is this","startTime":2773.97,"endTime":2776.25,"body":"that was hard to throw,"},{"speaker":"which is this","startTime":2776.25,"endTime":2778.67,"body":"it ought not to be difficult."},{"speaker":"which is this","startTime":2778.67,"endTime":2779.87,"body":"So what's the key?"},{"speaker":"which is this","startTime":2779.87,"endTime":2781.34,"body":"Firstly, make sure you know"},{"speaker":"which is this","startTime":2781.34,"endTime":2783.33,"body":"whether it's a left-handed"},{"speaker":"which is this","startTime":2781.34,"endTime":2783.33,"body":"or a right-handed boomerang."},{"speaker":"which is this","startTime":2783.33,"endTime":2785.11,"body":"If it's a right-handed boomerang,"},{"speaker":"which is this","startTime":2785.11,"endTime":2785.943,"body":"it's going to go around that way,"},{"speaker":"which is this","startTime":2785.943,"endTime":2787.68,"body":"if it's a left-handed boomerang,"},{"speaker":"which is this","startTime":2787.68,"endTime":2789.75,"body":"it's go around that way."},{"speaker":"which is this","startTime":2789.75,"endTime":2791.91,"body":"You can throw a left-handed"},{"speaker":"which is this","startTime":2789.75,"endTime":2791.91,"body":"boomerang right-handed,"},{"speaker":"which is this","startTime":2791.91,"endTime":2794.323,"body":"but it's going to go around the other way."},{"speaker":"which is this","startTime":2795.38,"endTime":2797.093,"body":"Hold it in the vertical plane,"},{"speaker":"which is this","startTime":2798.6,"endTime":2799.82,"body":"and lots of spin."},{"speaker":"which is this","startTime":2799.82,"endTime":2801.67,"body":"You don't want to hold it"},{"speaker":"which is this","startTime":2799.82,"endTime":2801.67,"body":"in the horizontal plane"},{"speaker":"which is this","startTime":2801.67,"endTime":2803.92,"body":"because then it's going to"},{"speaker":"which is this","startTime":2801.67,"endTime":2803.92,"body":"lift up and go straight up."},{"speaker":"which is this","startTime":2803.92,"endTime":2806.2,"body":"Vertical plane, lots of spin,"},{"speaker":"which is this","startTime":2806.2,"endTime":2807.85,"body":"you've got to get the spin going."},{"speaker":"which is this","startTime":2809.01,"endTime":2811.274,"body":"Have you still got the boomerang?"},{"speaker":"which is this","startTime":2811.274,"endTime":2813.215,"body":"- [Questioner] I haven't."},{"speaker":"which is this","startTime":2813.215,"endTime":2815.298,"body":"What about an Aboriginal?"},{"speaker":"which is this","startTime":2817.903,"endTime":2819.89,"body":"- They're probably quite"},{"speaker":"which is this","startTime":2817.903,"endTime":2819.89,"body":"good at throwing it."},{"speaker":"which is this","startTime":2819.89,"endTime":2821.42,"body":"Anyway, there you go,"},{"speaker":"which is this","startTime":2821.42,"endTime":2823.1,"body":"it ought to be possible."},{"speaker":"which is this","startTime":2823.1,"endTime":2823.933,"body":"- [Questioner] If you don't mind,"},{"speaker":"which is this","startTime":2823.933,"endTime":2825.023,"body":"this is not on your lecture,"},{"speaker":"which is this","startTime":2825.023,"endTime":2827.11,"body":"it's just a question that I'd like to ask,"},{"speaker":"which is this","startTime":2827.11,"endTime":2828.69,"body":"but it does involve you."},{"speaker":"which is this","startTime":2828.69,"endTime":2830.15,"body":"The \"Today\" program,"},{"speaker":"which is this","startTime":2830.15,"endTime":2831.73,"body":"which, I'm sure you know,"},{"speaker":"which is this","startTime":2831.73,"endTime":2834.31,"body":"comes on between six"},{"speaker":"which is this","startTime":2831.73,"endTime":2834.31,"body":"and nine in the morning,"},{"speaker":"which is this","startTime":2834.31,"endTime":2836.09,"body":"up until about two years ago,"},{"speaker":"which is this","startTime":2836.09,"endTime":2841.09,"body":"it used to have a bit that"},{"speaker":"which is this","startTime":2836.09,"endTime":2841.09,"body":"was called Puzzle for the Day."},{"speaker":"which is this","startTime":2843.09,"endTime":2844.35,"body":"You used to set questions for that,"},{"speaker":"which is this","startTime":2844.35,"endTime":2845.183,"body":"- Yeah, I did."},{"speaker":"which is this","startTime":2845.183,"endTime":2846.64,"body":"- [Questioner] and they were"},{"speaker":"which is this","startTime":2845.183,"endTime":2846.64,"body":"always the most challenging,"},{"speaker":"which is this","startTime":2846.64,"endTime":2847.473,"body":"I enjoyed them."},{"speaker":"which is this","startTime":2847.473,"endTime":2849.033,"body":"Why did those questions stop?"},{"speaker":"which is this","startTime":2852.424,"endTime":2855.18,"body":"- It might be perhaps equally interesting"},{"speaker":"which is this","startTime":2855.18,"endTime":2856.683,"body":"as to why they started,"},{"speaker":"which is this","startTime":2858.05,"endTime":2860.45,"body":"and I think that it was thought"},{"speaker":"which is this","startTime":2858.05,"endTime":2860.45,"body":"that it would be a good idea"},{"speaker":"which is this","startTime":2860.45,"endTime":2861.68,"body":"to promote maths,"},{"speaker":"which is this","startTime":2861.68,"endTime":2864.053,"body":"and to have these puzzles for the day."},{"speaker":"which is this","startTime":2865.4,"endTime":2868.28,"body":"I'm not sure that they"},{"speaker":"which is this","startTime":2865.4,"endTime":2868.28,"body":"quite thought through"},{"speaker":"which is this","startTime":2868.28,"endTime":2869.87,"body":"how it was going to work,"},{"speaker":"which is this","startTime":2869.87,"endTime":2871.593,"body":"having a new puzzle every day,"},{"speaker":"which is this","startTime":2873.305,"endTime":2874.25,"body":"it was quite a challenge,"},{"speaker":"which is this","startTime":2874.25,"endTime":2876.07,"body":"and I think the quality was variable,"},{"speaker":"which is this","startTime":2876.07,"endTime":2878.57,"body":"and it got more and more"},{"speaker":"which is this","startTime":2876.07,"endTime":2878.57,"body":"variable as time went on,"},{"speaker":"which is this","startTime":2879.76,"endTime":2881.23,"body":"and it got to the point"},{"speaker":"which is this","startTime":2881.23,"endTime":2882.73,"body":"where there weren't that many."},{"speaker":"which is this","startTime":2883.93,"endTime":2884.82,"body":"What I think was hoped"},{"speaker":"which is this","startTime":2884.82,"endTime":2887.16,"body":"was there'd be a much"},{"speaker":"which is this","startTime":2884.82,"endTime":2887.16,"body":"bigger pool of people"},{"speaker":"which is this","startTime":2887.16,"endTime":2888.883,"body":"coming in to set these puzzles,"},{"speaker":"which is this","startTime":2890.13,"endTime":2891.25,"body":"but they decided to stop it."},{"speaker":"which is this","startTime":2891.25,"endTime":2893.51,"body":"I think it was probably the right thing."},{"speaker":"which is this","startTime":2893.51,"endTime":2896.86,"body":"One thing that I found"},{"speaker":"which is this","startTime":2893.51,"endTime":2896.86,"body":"slightly frustrating"},{"speaker":"which is this","startTime":2896.86,"endTime":2901.86,"body":"was that there was an answer online,"},{"speaker":"which is this","startTime":2903.73,"endTime":2906.472,"body":"so if you wanted to figure"},{"speaker":"which is this","startTime":2903.73,"endTime":2906.472,"body":"out what the answer was,"},{"speaker":"which is this","startTime":2906.472,"endTime":2908.623,"body":"you would look online the next day,"},{"speaker":"which is this","startTime":2909.8,"endTime":2912.12,"body":"but I think not many people did,"},{"speaker":"which is this","startTime":2912.12,"endTime":2914.26,"body":"and I would rather have"},{"speaker":"which is this","startTime":2912.12,"endTime":2914.26,"body":"had something like,"},{"speaker":"which is this","startTime":2914.26,"endTime":2916.47,"body":"where you have puzzle for the day,"},{"speaker":"which is this","startTime":2916.47,"endTime":2920.26,"body":"and then half an hour later, you say,"},{"speaker":"which is this","startTime":2920.26,"endTime":2922.444,"body":"right, have you figured it out?"},{"speaker":"which is this","startTime":2922.444,"endTime":2925.48,"body":"Here is the explanation,"},{"speaker":"which is this","startTime":2925.48,"endTime":2929.13,"body":"and actually have it read"},{"speaker":"which is this","startTime":2925.48,"endTime":2929.13,"body":"out by the person who set it."},{"speaker":"which is this","startTime":2929.13,"endTime":2932.72,"body":"So I think it was difficult,"},{"speaker":"which is this","startTime":2932.72,"endTime":2935.093,"body":"some of the presenters didn't really,"},{"speaker":"which is this","startTime":2938.31,"endTime":2940.66,"body":"sometimes, they say things about maths"},{"speaker":"which is this","startTime":2940.66,"endTime":2944.193,"body":"which they really ought not"},{"speaker":"which is this","startTime":2940.66,"endTime":2944.193,"body":"to say on a radio program."},{"speaker":"which is this","startTime":2947.68,"endTime":2948.82,"body":"I'm sad it stopped,"},{"speaker":"which is this","startTime":2948.82,"endTime":2951.3,"body":"but it was fun while it lasted."},{"speaker":"which is this","startTime":2951.3,"endTime":2954.323,"body":"- Okay, we've got some more"},{"speaker":"which is this","startTime":2951.3,"endTime":2954.323,"body":"questions flooding in online."},{"speaker":"Here's a question about motorbikes","startTime":2957.867,"endTime":2961.927,"body":"\"To initiate a left"},{"speaker":"Here's a question about motorbikes","startTime":2957.867,"endTime":2961.927,"body":"turn with a motorcycle,"},{"speaker":"Here's a question about motorbikes","startTime":2961.927,"endTime":2965.047,"body":"\"you need to turn the"},{"speaker":"Here's a question about motorbikes","startTime":2961.927,"endTime":2965.047,"body":"handlebars to the right."},{"speaker":"Here's a question about motorbikes","startTime":2965.047,"endTime":2967.813,"body":"\"Could you please explain this.\""},{"speaker":"Here's a question about motorbikes","startTime":2967.813,"endTime":2970.12,"body":"- This is an extraordinary thing,"},{"speaker":"Here's a question about motorbikes","startTime":2970.12,"endTime":2971.44,"body":"and it's not just on a motorbike,"},{"speaker":"Here's a question about motorbikes","startTime":2971.44,"endTime":2973.603,"body":"it's on a regular bike as well."},{"speaker":"Here's a question about motorbikes","startTime":2975.06,"endTime":2976.763,"body":"It's called the counter-steer,"},{"speaker":"Here's a question about motorbikes","startTime":2977.65,"endTime":2979.52,"body":"and it's counterintuitive."},{"speaker":"Here's a question about motorbikes","startTime":2979.52,"endTime":2983.423,"body":"Imagine you are riding in"},{"speaker":"Here's a question about motorbikes","startTime":2979.52,"endTime":2983.423,"body":"a straight line on a bike,"},{"speaker":"Here's a question about motorbikes","startTime":2984.67,"endTime":2988.191,"body":"and then imagine you want to"},{"speaker":"Here's a question about motorbikes","startTime":2984.67,"endTime":2988.191,"body":"get from that straight line"},{"speaker":"Here's a question about motorbikes","startTime":2988.191,"endTime":2992.667,"body":"to going around on a corner."},{"speaker":"Here's a question about motorbikes","startTime":2994.29,"endTime":2996.67,"body":"If you want to be going"},{"speaker":"Here's a question about motorbikes","startTime":2994.29,"endTime":2996.67,"body":"around on a corner,"},{"speaker":"Here's a question about motorbikes","startTime":2996.67,"endTime":2998.273,"body":"you want to be tilted over,"},{"speaker":"Here's a question about motorbikes","startTime":2999.49,"endTime":3001.713,"body":"but actually, you don't need to steer,"},{"speaker":"Here's a question about motorbikes","startTime":3003.7,"endTime":3006.98,"body":"being tilted over is really all you need"},{"speaker":"Here's a question about motorbikes","startTime":3006.98,"endTime":3008.493,"body":"to go around this corner,"},{"speaker":"Here's a question about motorbikes","startTime":3009.797,"endTime":3010.89,"body":"that's just what's going to happen,"},{"speaker":"Here's a question about motorbikes","startTime":3010.89,"endTime":3012.85,"body":"you hardly need steer."},{"speaker":"Here's a question about motorbikes","startTime":3012.85,"endTime":3017.43,"body":"How are you going to get from"},{"speaker":"Here's a question about motorbikes","startTime":3012.85,"endTime":3017.43,"body":"this point to this point?"},{"speaker":"Here's a question about motorbikes","startTime":3017.43,"endTime":3020.25,"body":"And the easiest way to do that,"},{"speaker":"Here's a question about motorbikes","startTime":3020.25,"endTime":3021.8,"body":"if you've got a spinning wheel,"},{"speaker":"Here's a question about motorbikes","startTime":3023.6,"endTime":3026.65,"body":"is if I want to tilt the wheel that way,"},{"speaker":"Here's a question about motorbikes","startTime":3026.65,"endTime":3028.41,"body":"the easiest way is to,"},{"speaker":"Here's a question about motorbikes","startTime":3028.41,"endTime":3030.973,"body":"I'm actually trying to push"},{"speaker":"Here's a question about motorbikes","startTime":3028.41,"endTime":3030.973,"body":"the wheel to the right."},{"speaker":"Here's a question about motorbikes","startTime":3033.824,"endTime":3035.283,"body":"I'm trying to do this,"},{"speaker":"Here's a question about motorbikes","startTime":3036.329,"endTime":3038.029,"body":"but because it's a spinning wheel,"},{"speaker":"Here's a question about motorbikes","startTime":3039.194,"endTime":3040.19,"body":"and the gyroscopic effect,"},{"speaker":"Here's a question about motorbikes","startTime":3040.19,"endTime":3041.65,"body":"I'm trying to turn it to the right,"},{"speaker":"Here's a question about motorbikes","startTime":3041.65,"endTime":3043.59,"body":"and look what it does, it tilts over,"},{"speaker":"Here's a question about motorbikes","startTime":3043.59,"endTime":3045.73,"body":"which is what I wanted to do."},{"speaker":"Here's a question about motorbikes","startTime":3045.73,"endTime":3050.73,"body":"So the quickest way to"},{"speaker":"Here's a question about motorbikes","startTime":3045.73,"endTime":3050.73,"body":"get onto that corner,"},{"speaker":"Here's a question about motorbikes","startTime":3050.8,"endTime":3052.37,"body":"turning to the left,"},{"speaker":"Here's a question about motorbikes","startTime":3052.37,"endTime":3054.38,"body":"is to do a quick turn to the right,"},{"speaker":"Here's a question about motorbikes","startTime":3054.38,"endTime":3055.52,"body":"and it's really weird."},{"speaker":"Here's a question about motorbikes","startTime":3055.52,"endTime":3057.447,"body":"And it's what we all do,"},{"speaker":"Here's a question about motorbikes","startTime":3057.447,"endTime":3059.34,"body":"you might not have noticed it,"},{"speaker":"Here's a question about motorbikes","startTime":3059.34,"endTime":3060.54,"body":"but it's what we all do."},{"speaker":"Here's a question about motorbikes","startTime":3061.71,"endTime":3063.78,"body":"If you suddenly need to turn left,"},{"speaker":"Here's a question about motorbikes","startTime":3063.78,"endTime":3065.67,"body":"you do a quick turn to the right,"},{"speaker":"Here's a question about motorbikes","startTime":3065.67,"endTime":3066.67,"body":"it's amazing stuff."},{"speaker":"Here's a question about motorbikes","startTime":3066.67,"endTime":3070.05,"body":"- [Questioner] In the formula"},{"speaker":"Here's a question about motorbikes","startTime":3066.67,"endTime":3070.05,"body":"for the radius of the flight,"},{"speaker":"Here's a question about motorbikes","startTime":3070.05,"endTime":3072.76,"body":"you had inertia over the"},{"speaker":"Here's a question about motorbikes","startTime":3070.05,"endTime":3072.76,"body":"size of the boomerang."},{"speaker":"Here's a question about motorbikes","startTime":3072.76,"endTime":3074.58,"body":"Would that not cancel out"},{"speaker":"Here's a question about motorbikes","startTime":3074.58,"endTime":3078.53,"body":"because the size of the"},{"speaker":"Here's a question about motorbikes","startTime":3074.58,"endTime":3078.53,"body":"arms of the boomerang"},{"speaker":"Here's a question about motorbikes","startTime":3078.53,"endTime":3079.61,"body":"would cancel,"},{"speaker":"Here's a question about motorbikes","startTime":3079.61,"endTime":3081.76,"body":"what is meant by the"},{"speaker":"Here's a question about motorbikes","startTime":3079.61,"endTime":3081.76,"body":"size of the boomerang?"},{"speaker":"Here's a question about motorbikes","startTime":3083.86,"endTime":3087.037,"body":"- The size in my formula"},{"speaker":"Here's a question about motorbikes","startTime":3083.86,"endTime":3087.037,"body":"there was the radius."},{"speaker":"Here's a question about motorbikes","startTime":3094.98,"endTime":3096.22,"body":"There's a nice thing you can do,"},{"speaker":"Here's a question about motorbikes","startTime":3096.22,"endTime":3099.623,"body":"which is dimensional analysis."},{"speaker":"Here's a question about motorbikes","startTime":3102.52,"endTime":3107.37,"body":"These are the only parameters"},{"speaker":"Here's a question about motorbikes","startTime":3102.52,"endTime":3107.37,"body":"that can be put together"},{"speaker":"Here's a question about motorbikes","startTime":3107.37,"endTime":3112.19,"body":"to create a formula for the"},{"speaker":"Here's a question about motorbikes","startTime":3107.37,"endTime":3112.19,"body":"radius of the boomerang."},{"speaker":"Here's a question about motorbikes","startTime":3112.19,"endTime":3116.13,"body":"Let's assume that the speed"},{"speaker":"Here's a question about motorbikes","startTime":3112.19,"endTime":3116.13,"body":"of light doesn't matter,"},{"speaker":"Here's a question about motorbikes","startTime":3116.13,"endTime":3119.0,"body":"and let's say that"},{"speaker":"Here's a question about motorbikes","startTime":3116.13,"endTime":3119.0,"body":"viscosity doesn't matter,"},{"speaker":"Here's a question about motorbikes","startTime":3119.0,"endTime":3121.36,"body":"and let's suppose that"},{"speaker":"Here's a question about motorbikes","startTime":3119.0,"endTime":3121.36,"body":"temperature doesn't matter,"},{"speaker":"Here's a question about motorbikes","startTime":3121.36,"endTime":3122.93,"body":"various things don't matter,"},{"speaker":"Here's a question about motorbikes","startTime":3122.93,"endTime":3124.92,"body":"these things all matter,"},{"speaker":"Here's a question about motorbikes","startTime":3124.92,"endTime":3127.45,"body":"and it turns out that these two formulae"},{"speaker":"Here's a question about motorbikes","startTime":3128.3,"endTime":3130.99,"body":"are the only way that you"},{"speaker":"Here's a question about motorbikes","startTime":3128.3,"endTime":3130.99,"body":"can put them together,"},{"speaker":"Here's a question about motorbikes","startTime":3130.99,"endTime":3134.473,"body":"so you're going to need a size parameter."},{"speaker":"Here's a question about motorbikes","startTime":3136.186,"endTime":3137.35,"body":"When you say things cancel out,"},{"speaker":"Here's a question about motorbikes","startTime":3137.35,"endTime":3138.45,"body":"well they can't cancel out"},{"speaker":"Here's a question about motorbikes","startTime":3138.45,"endTime":3143.45,"body":"because otherwise you won't"},{"speaker":"Here's a question about motorbikes","startTime":3138.45,"endTime":3143.45,"body":"get dimensional consistency."},{"speaker":"Here's a question about motorbikes","startTime":3144.09,"endTime":3147.09,"body":"But I think what you have to bear in mind"},{"speaker":"Here's a question about motorbikes","startTime":3147.09,"endTime":3151.87,"body":"is that the gyroscopic effect"},{"speaker":"Here's a question about motorbikes","startTime":3147.09,"endTime":3151.87,"body":"if one thing that's happening,"},{"speaker":"Here's a question about motorbikes","startTime":3151.87,"endTime":3154.28,"body":"the other thing that's"},{"speaker":"Here's a question about motorbikes","startTime":3151.87,"endTime":3154.28,"body":"happening is circular motion,"},{"speaker":"Here's a question about motorbikes","startTime":3154.28,"endTime":3156.36,"body":"mv-squared over r,"},{"speaker":"Here's a question about motorbikes","startTime":3156.36,"endTime":3158.08,"body":"and I think if you go"},{"speaker":"Here's a question about motorbikes","startTime":3156.36,"endTime":3158.08,"body":"through the maths on it,"},{"speaker":"Here's a question about motorbikes","startTime":3158.08,"endTime":3161.78,"body":"you'll find that this does work out."},{"speaker":"Here's a question about motorbikes","startTime":3161.78,"endTime":3163.21,"body":"But I'm glad you're"},{"speaker":"Here's a question about motorbikes","startTime":3161.78,"endTime":3163.21,"body":"thinking about the maths,"},{"speaker":"Here's a question about motorbikes","startTime":3163.21,"endTime":3168.02,"body":"that's exactly what we want in this room."},{"speaker":"Here's a question about motorbikes","startTime":3168.02,"endTime":3170.533,"body":"- Your next-door neighbor"},{"speaker":"Here's a question about motorbikes","startTime":3168.02,"endTime":3170.533,"body":"had a question as well."},{"speaker":"Here's a question about motorbikes","startTime":3172.65,"endTime":3176.26,"body":"- [Questioner] I had a question"},{"speaker":"Here's a question about motorbikes","startTime":3172.65,"endTime":3176.26,"body":"about the wall of death,"},{"speaker":"Here's a question about motorbikes","startTime":3176.26,"endTime":3178.04,"body":"you said that because of the g-forces,"},{"speaker":"Here's a question about motorbikes","startTime":3178.04,"endTime":3181.18,"body":"the driver wouldn't survive"},{"speaker":"Here's a question about motorbikes","startTime":3178.04,"endTime":3181.18,"body":"if the radius was too small,"},{"speaker":"Here's a question about motorbikes","startTime":3181.18,"endTime":3182.013,"body":"so what would happen"},{"speaker":"Here's a question about motorbikes","startTime":3182.013,"endTime":3183.73,"body":"if you put a robot, or something on there"},{"speaker":"Here's a question about motorbikes","startTime":3183.73,"endTime":3185.1,"body":"that could survive the g-force,"},{"speaker":"Here's a question about motorbikes","startTime":3185.1,"endTime":3187.48,"body":"would it be able to go"},{"speaker":"Here's a question about motorbikes","startTime":3185.1,"endTime":3187.48,"body":"at 100 miles an hour"},{"speaker":"Here's a question about motorbikes","startTime":3187.48,"endTime":3188.75,"body":"around a radius of 20?"},{"speaker":"Here's a question about motorbikes","startTime":3188.75,"endTime":3190.48,"body":"- Yeah, absolutely."},{"speaker":"Here's a question about motorbikes","startTime":3190.48,"endTime":3194.67,"body":"If you want to do a wall of death,"},{"speaker":"Here's a question about motorbikes","startTime":3194.67,"endTime":3198.133,"body":"if you want to get a slot car thing,"},{"speaker":"Here's a question about motorbikes","startTime":3199.96,"endTime":3203.563,"body":"if you imagine a velodrome,"},{"speaker":"Here's a question about motorbikes","startTime":3204.4,"endTime":3206.29,"body":"and you're on a bike,"},{"speaker":"Here's a question about motorbikes","startTime":3206.29,"endTime":3208.14,"body":"and you're going around, and it slopes up,"},{"speaker":"Here's a question about motorbikes","startTime":3208.14,"endTime":3209.61,"body":"you can imagine getting to the point"},{"speaker":"Here's a question about motorbikes","startTime":3209.61,"endTime":3211.72,"body":"where it's pretty much vertical,"},{"speaker":"Here's a question about motorbikes","startTime":3211.72,"endTime":3213.903,"body":"and if you got a"},{"speaker":"Here's a question about motorbikes","startTime":3211.72,"endTime":3213.903,"body":"driverless car to do that,"},{"speaker":"Here's a question about motorbikes","startTime":3213.903,"endTime":3215.763,"body":"you can go as fast as you like,"},{"speaker":"Here's a question about motorbikes","startTime":3217.682,"endTime":3219.6,"body":"and the g-forces can"},{"speaker":"Here's a question about motorbikes","startTime":3217.682,"endTime":3219.6,"body":"be as fast as you like."},{"speaker":"Here's a question about motorbikes","startTime":3219.6,"endTime":3222.07,"body":"That tennis ball was experiencing,"},{"speaker":"Here's a question about motorbikes","startTime":3222.07,"endTime":3225.59,"body":"because 2 kilograms, a"},{"speaker":"Here's a question about motorbikes","startTime":3222.07,"endTime":3225.59,"body":"tennis ball is 50 grams,"},{"speaker":"Here's a question about motorbikes","startTime":3225.59,"endTime":3229.64,"body":"so that tennis ball was"},{"speaker":"Here's a question about motorbikes","startTime":3225.59,"endTime":3229.64,"body":"experiencing g-forces of 80-g,"},{"speaker":"Here's a question about motorbikes","startTime":3232.39,"endTime":3235.083,"body":"and because it's not a person, it's okay."},{"speaker":"Here's a question about motorbikes","startTime":3236.07,"endTime":3237.41,"body":"So yeah, you're right,"},{"speaker":"Here's a question about motorbikes","startTime":3237.41,"endTime":3240.49,"body":"if you could do it with a robot vehicle,"},{"speaker":"Here's a question about motorbikes","startTime":3240.49,"endTime":3241.323,"body":"that'd be good."},{"speaker":"Here's a question about motorbikes","startTime":3243.88,"endTime":3247.053,"body":"Guy Martin did try to go faster,"},{"speaker":"Here's a question about motorbikes","startTime":3247.93,"endTime":3252.615,"body":"but he just found that"},{"speaker":"Here's a question about motorbikes","startTime":3247.93,"endTime":3252.615,"body":"his vision got blurred,"},{"speaker":"Here's a question about motorbikes","startTime":3252.615,"endTime":3256.91,"body":"and that's one of the classic"},{"speaker":"Here's a question about motorbikes","startTime":3252.615,"endTime":3256.91,"body":"things with fighter pilots,"},{"speaker":"Here's a question about motorbikes","startTime":3256.91,"endTime":3261.91,"body":"that they have to train how"},{"speaker":"Here's a question about motorbikes","startTime":3256.91,"endTime":3261.91,"body":"to deal with the g-forces,"},{"speaker":"Here's a question about motorbikes","startTime":3262.3,"endTime":3263.9,"body":"you really have to train for it."},{"speaker":"Here's a question about motorbikes","startTime":3265.78,"endTime":3267.11,"body":"Good question."},{"speaker":"Here's a question about motorbikes","startTime":3267.11,"endTime":3270.213,"body":"- There's a related question here,"},{"speaker":"Here's a question about motorbikes","startTime":3270.213,"endTime":3271.99,"body":"a couple of questions about fluids,"},{"speaker":"Here's a question about motorbikes","startTime":3271.99,"endTime":3273.39,"body":"and this one is about fluids"},{"speaker":"Here's a question about motorbikes","startTime":3273.39,"endTime":3274.54,"body":"and the capability of the human body,"},{"speaker":"Here's a question about motorbikes","startTime":3274.54,"endTime":3277.06,"body":"which is a bit what you're saying."},{"speaker":"Here's a question about motorbikes","startTime":3277.06,"endTime":3278.157,"body":"The question is,"},{"speaker":"Here's a question about motorbikes","startTime":3278.157,"endTime":3282.56,"body":"\"What happens to the fluid"},{"speaker":"Here's a question about motorbikes","startTime":3278.157,"endTime":3282.56,"body":"within an ice skater's ears,\""},{"speaker":"Here's a question about motorbikes","startTime":3282.56,"endTime":3283.997,"body":"the cochlear fluid,"},{"speaker":"Here's a question about motorbikes","startTime":3283.997,"endTime":3285.377,"body":"\"when they spin,"},{"speaker":"Here's a question about motorbikes","startTime":3285.377,"endTime":3289.177,"body":"\"and does this affect their"},{"speaker":"Here's a question about motorbikes","startTime":3285.377,"endTime":3289.177,"body":"ability to continue a spin?\""},{"speaker":"Here's a question about motorbikes","startTime":3291.33,"endTime":3296.33,"body":"- I'm told that ice"},{"speaker":"Here's a question about motorbikes","startTime":3291.33,"endTime":3296.33,"body":"skaters and ballet dancers"},{"speaker":"Here's a question about motorbikes","startTime":3296.38,"endTime":3298.7,"body":"who do a lot of these spins,"},{"speaker":"Here's a question about motorbikes","startTime":3298.7,"endTime":3302.433,"body":"they become immune to"},{"speaker":"Here's a question about motorbikes","startTime":3298.7,"endTime":3302.433,"body":"it, they don't get dizzy,"},{"speaker":"Here's a question about motorbikes","startTime":3305.629,"endTime":3307.363,"body":"whereas most of us, we do."},{"speaker":"Here's a question about motorbikes","startTime":3309.58,"endTime":3312.373,"body":"I don't know whether Olly"},{"speaker":"Here's a question about motorbikes","startTime":3309.58,"endTime":3312.373,"body":"is still feeling a bit,"},{"speaker":"Here's a question about motorbikes","startTime":3313.724,"endTime":3314.69,"body":"(Simon laughs)"},{"speaker":"Here's a question about motorbikes","startTime":3314.69,"endTime":3319.02,"body":"but you notice it for quite"},{"speaker":"Here's a question about motorbikes","startTime":3314.69,"endTime":3319.02,"body":"a few minutes afterwards."},{"speaker":"Here's a question about motorbikes","startTime":3319.02,"endTime":3320.713,"body":"Is that true, did you notice it?"},{"speaker":"Here's a question about motorbikes","startTime":3322.07,"endTime":3324.0,"body":"For those of use who"},{"speaker":"Here's a question about motorbikes","startTime":3322.07,"endTime":3324.0,"body":"don't do it all the time,"},{"speaker":"Here's a question about motorbikes","startTime":3324.0,"endTime":3325.44,"body":"but if you do it all the time,"},{"speaker":"Here's a question about motorbikes","startTime":3325.44,"endTime":3327.7,"body":"I'm told it's something"},{"speaker":"Here's a question about motorbikes","startTime":3325.44,"endTime":3327.7,"body":"you just get used to."},{"speaker":"Here's a question about motorbikes","startTime":3327.7,"endTime":3332.7,"body":"The cochlea is a very"},{"speaker":"Here's a question about motorbikes","startTime":3327.7,"endTime":3332.7,"body":"multi-talented organ in our body,"},{"speaker":"Here's a question about motorbikes","startTime":3333.46,"endTime":3334.713,"body":"it's used for hearing,"},{"speaker":"Here's a question about motorbikes","startTime":3335.82,"endTime":3338.36,"body":"but it's got fluid in it which,"},{"speaker":"Here's a question about motorbikes","startTime":3338.36,"endTime":3340.3,"body":"when you spin around,"},{"speaker":"Here's a question about motorbikes","startTime":3340.3,"endTime":3342.66,"body":"the pressures in the cochlea"},{"speaker":"Here's a question about motorbikes","startTime":3342.66,"endTime":3344.553,"body":"can tell you that you are spinning,"},{"speaker":"Here's a question about motorbikes","startTime":3346.24,"endTime":3351.24,"body":"and that's where we get dizzy from."},{"speaker":"Here's a question about motorbikes","startTime":3351.61,"endTime":3355.08,"body":"- [Questioner] You"},{"speaker":"Here's a question about motorbikes","startTime":3351.61,"endTime":3355.08,"body":"described the bicycle wheel"},{"speaker":"Here's a question about motorbikes","startTime":3355.08,"endTime":3359.36,"body":"spinning on the end of a string"},{"speaker":"Here's a question about motorbikes","startTime":3355.08,"endTime":3359.36,"body":"as an anti-gravity device."},{"speaker":"Here's a question about motorbikes","startTime":3359.36,"endTime":3364.36,"body":"Is that similar to how"},{"speaker":"Here's a question about motorbikes","startTime":3359.36,"endTime":3364.36,"body":"astronauts simulate zero gravity"},{"speaker":"Here's a question about motorbikes","startTime":3364.77,"endTime":3366.553,"body":"by spinning around a plane?"},{"speaker":"Here's a question about motorbikes","startTime":3368.5,"endTime":3370.2,"body":"- When they simulate zero gravity,"},{"speaker":"Here's a question about motorbikes","startTime":3371.89,"endTime":3375.427,"body":"what's the film, it's one of those films?"},{"speaker":"Here's a question about motorbikes","startTime":3375.427,"endTime":3379.58,"body":"\"Interstellar,\" or"},{"speaker":"Here's a question about motorbikes","startTime":3375.427,"endTime":3379.58,"body":"\"Gravity,\" or \"The Martian,\""},{"speaker":"Here's a question about motorbikes","startTime":3379.58,"endTime":3381.859,"body":"where they've got a spin."},{"speaker":"Here's a question about motorbikes","startTime":3381.859,"endTime":3382.92,"body":"- [Audience Member] \"2001.\""},{"speaker":"Here's a question about motorbikes","startTime":3382.92,"endTime":3383.753,"body":"- That one too,"},{"speaker":"Here's a question about motorbikes","startTime":3383.753,"endTime":3386.78,"body":"but this audience doesn't know,"},{"speaker":"Here's a question about motorbikes","startTime":3386.78,"endTime":3387.613,"body":"yes, but it's true."},{"speaker":"Here's a question about motorbikes","startTime":3387.613,"endTime":3391.397,"body":"But they've got this spinning spacecraft"},{"speaker":"Here's a question about motorbikes","startTime":3393.25,"endTime":3398.233,"body":"so that you can have gravity out in space."},{"speaker":"Here's a question about motorbikes","startTime":3401.01,"endTime":3404.83,"body":"But if you want to get rid of"},{"speaker":"Here's a question about motorbikes","startTime":3401.01,"endTime":3404.83,"body":"gravity when you're on Earth,"},{"speaker":"Here's a question about motorbikes","startTime":3404.83,"endTime":3406.373,"body":"that's really difficult."},{"speaker":"Here's a question about motorbikes","startTime":3407.75,"endTime":3408.83,"body":"There's two ways of doing it,"},{"speaker":"Here's a question about motorbikes","startTime":3408.83,"endTime":3412.573,"body":"one is to go up into a plane,"},{"speaker":"Here's a question about motorbikes","startTime":3415.34,"endTime":3416.173,"body":"go up as high as you can"},{"speaker":"Here's a question about motorbikes","startTime":3416.173,"endTime":3417.88,"body":"so you've got plenty of"},{"speaker":"Here's a question about motorbikes","startTime":3416.173,"endTime":3417.88,"body":"time for the experiment,"},{"speaker":"Here's a question about motorbikes","startTime":3417.88,"endTime":3422.88,"body":"and then the plane falls"},{"speaker":"Here's a question about motorbikes","startTime":3417.88,"endTime":3422.88,"body":"down, projectile motion,"},{"speaker":"Here's a question about motorbikes","startTime":3427.41,"endTime":3430.16,"body":"Stephen Hawking went up"},{"speaker":"Here's a question about motorbikes","startTime":3427.41,"endTime":3430.16,"body":"in one of these things,"},{"speaker":"Here's a question about motorbikes","startTime":3430.16,"endTime":3433.52,"body":"you can feel weightlessness"},{"speaker":"Here's a question about motorbikes","startTime":3430.16,"endTime":3433.52,"body":"for not very long,"},{"speaker":"Here's a question about motorbikes","startTime":3433.52,"endTime":3435.56,"body":"because you've only got"},{"speaker":"Here's a question about motorbikes","startTime":3433.52,"endTime":3435.56,"body":"a certain amount of time"},{"speaker":"Here's a question about motorbikes","startTime":3435.56,"endTime":3436.96,"body":"before you get to the Earth."},{"speaker":"Here's a question about motorbikes","startTime":3437.91,"endTime":3442.69,"body":"But then what they did a lot"},{"speaker":"Here's a question about motorbikes","startTime":3437.91,"endTime":3442.69,"body":"of in the Apollo program,"},{"speaker":"Here's a question about motorbikes","startTime":3442.69,"endTime":3444.48,"body":"and in the shuttle program"},{"speaker":"Here's a question about motorbikes","startTime":3444.48,"endTime":3449.48,"body":"was to practice being weightless"},{"speaker":"Here's a question about motorbikes","startTime":3444.48,"endTime":3449.48,"body":"by being in water tanks,"},{"speaker":"Here's a question about motorbikes","startTime":3452.26,"endTime":3456.64,"body":"so where your buoyancy is"},{"speaker":"Here's a question about motorbikes","startTime":3452.26,"endTime":3456.64,"body":"equal and opposite to gravity,"},{"speaker":"Here's a question about motorbikes","startTime":3456.64,"endTime":3458.99,"body":"but it's still not the"},{"speaker":"Here's a question about motorbikes","startTime":3456.64,"endTime":3458.99,"body":"same as being out in space."},{"speaker":"Here's a question about motorbikes","startTime":3458.99,"endTime":3461.04,"body":"I don't know whether that"},{"speaker":"Here's a question about motorbikes","startTime":3458.99,"endTime":3461.04,"body":"answers your question,"},{"speaker":"Here's a question about motorbikes","startTime":3461.04,"endTime":3464.6,"body":"but the spin is to create"},{"speaker":"Here's a question about motorbikes","startTime":3461.04,"endTime":3464.6,"body":"gravity when you're out in space"},{"speaker":"Here's a question about motorbikes","startTime":3464.6,"endTime":3467.31,"body":"rather than to get rid of"},{"speaker":"Here's a question about motorbikes","startTime":3464.6,"endTime":3467.31,"body":"gravity when you're on Earth."},{"speaker":"Here's a question about motorbikes","startTime":3467.31,"endTime":3468.77,"body":"- Fantastic, thank you very much"},{"speaker":"Here's a question about motorbikes","startTime":3468.77,"endTime":3469.91,"body":"for answering those questions."},{"speaker":"Here's a question about motorbikes","startTime":3469.91,"endTime":3472.173,"body":"We are now going to move"},{"speaker":"Here's a question about motorbikes","startTime":3469.91,"endTime":3472.173,"body":"to a vote of thanks."},{"speaker":"Here's a question about motorbikes","startTime":3475.08,"endTime":3475.913,"body":"- I hope I've turned that on,"},{"speaker":"Here's a question about motorbikes","startTime":3475.913,"endTime":3479.3,"body":"and I can hear myself I"},{"speaker":"Here's a question about motorbikes","startTime":3475.913,"endTime":3479.3,"body":"think, so that's good."},{"speaker":"Here's a question about motorbikes","startTime":3479.3,"endTime":3481.03,"body":"First of all, I'm Kevin Houston,"},{"speaker":"Here's a question about motorbikes","startTime":3481.03,"endTime":3482.85,"body":"I'm the education secretary"},{"speaker":"Here's a question about motorbikes","startTime":3482.85,"endTime":3485.11,"body":"of the London Mathematical Society,"},{"speaker":"Here's a question about motorbikes","startTime":3485.11,"endTime":3488.13,"body":"and normally, what I do"},{"speaker":"Here's a question about motorbikes","startTime":3485.11,"endTime":3488.13,"body":"at these events is say"},{"speaker":"Here's a question about motorbikes","startTime":3488.13,"endTime":3492.57,"body":"the London Mathematical Society"},{"speaker":"Here's a question about motorbikes","startTime":3488.13,"endTime":3492.57,"body":"is a very old institution,"},{"speaker":"Here's a question about motorbikes","startTime":3492.57,"endTime":3494.41,"body":"and goes back other 1865,"},{"speaker":"Here's a question about motorbikes","startTime":3494.41,"endTime":3496.24,"body":"but I always feel that"},{"speaker":"Here's a question about motorbikes","startTime":3494.41,"endTime":3496.24,"body":"when I come to Gresham,"},{"speaker":"Here's a question about motorbikes","startTime":3496.24,"endTime":3498.2,"body":"that that no longer cuts is,"},{"speaker":"Here's a question about motorbikes","startTime":3498.2,"endTime":3502.48,"body":"as Gresham is at least twice as old."},{"speaker":"Here's a question about motorbikes","startTime":3502.48,"endTime":3507.48,"body":"But the talks that"},{"speaker":"Here's a question about motorbikes","startTime":3502.48,"endTime":3507.48,"body":"we've had over the years"},{"speaker":"Here's a question about motorbikes","startTime":3507.6,"endTime":3509.32,"body":"go back maybe 15 years or so"},{"speaker":"Here's a question about motorbikes","startTime":3509.32,"endTime":3513.8,"body":"with this connection between"},{"speaker":"Here's a question about motorbikes","startTime":3509.32,"endTime":3513.8,"body":"the two institutions,"},{"speaker":"Here's a question about motorbikes","startTime":3513.8,"endTime":3514.633,"body":"has been fantastic,"},{"speaker":"Here's a question about motorbikes","startTime":3514.633,"endTime":3518.003,"body":"and we've had another"},{"speaker":"Here's a question about motorbikes","startTime":3514.633,"endTime":3518.003,"body":"fantastic talk here today."},{"speaker":"Here's a question about motorbikes","startTime":3519.47,"endTime":3520.31,"body":"I was glad to see,"},{"speaker":"Here's a question about motorbikes","startTime":3520.31,"endTime":3521.71,"body":"it was very dangerous,"},{"speaker":"Here's a question about motorbikes","startTime":3521.71,"endTime":3522.87,"body":"there were all sorts of things"},{"speaker":"Here's a question about motorbikes","startTime":3522.87,"endTime":3526.15,"body":"which could have ended in disaster,"},{"speaker":"Here's a question about motorbikes","startTime":3526.15,"endTime":3527.57,"body":"so it's good to see that,"},{"speaker":"Here's a question about motorbikes","startTime":3527.57,"endTime":3530.611,"body":"because coming back to being in person,"},{"speaker":"Here's a question about motorbikes","startTime":3530.611,"endTime":3533.59,"body":"(audience laughs)"},{"speaker":"Here's a question about motorbikes","startTime":3533.59,"endTime":3536.552,"body":"online, you don't really"},{"speaker":"Here's a question about motorbikes","startTime":3533.59,"endTime":3536.552,"body":"get that feeling of danger,"},{"speaker":"Here's a question about motorbikes","startTime":3536.552,"endTime":3539.54,"body":"so it's great, indeed,"},{"speaker":"Here's a question about motorbikes","startTime":3539.54,"endTime":3542.16,"body":"it's great to see so"},{"speaker":"Here's a question about motorbikes","startTime":3539.54,"endTime":3542.16,"body":"many people coming out,"},{"speaker":"Here's a question about motorbikes","startTime":3542.16,"endTime":3544.63,"body":"and I'm assured that"},{"speaker":"Here's a question about motorbikes","startTime":3542.16,"endTime":3544.63,"body":"there are people online,"},{"speaker":"Here's a question about motorbikes","startTime":3544.63,"endTime":3546.43,"body":"so hello to the people online,"},{"speaker":"Here's a question about motorbikes","startTime":3546.43,"endTime":3550.58,"body":"I hope everyone has"},{"speaker":"Here's a question about motorbikes","startTime":3546.43,"endTime":3550.58,"body":"enjoyed the talk today."},{"speaker":"Here's a question about motorbikes","startTime":3550.58,"endTime":3554.28,"body":"I would like you to join me"},{"speaker":"Here's a question about motorbikes","startTime":3550.58,"endTime":3554.28,"body":"in thanking Professor Hunt"},{"speaker":"Here's a question about motorbikes","startTime":3554.28,"endTime":3556.053,"body":"for such a fantastic talk."},{"speaker":"Here's a question about motorbikes","startTime":3557.042,"endTime":3558.855,"body":"- Thank you very much."},{"speaker":"Here's a question about motorbikes","startTime":3558.855,"endTime":3561.855,"body":"(audience applauds)"}]}