{"version":"1.0.0","segments":[{"startTime":0.134,"endTime":2.884,"body":"(dramatic music)"},{"startTime":4.86,"endTime":6.723,"body":"- Good evening everybody."},{"startTime":7.56,"endTime":9.24,"body":"I'm Katherine Blundell,"},{"startTime":9.24,"endTime":12.45,"body":"Gresham Professor of Astronomy number 38."},{"startTime":12.45,"endTime":15.6,"body":"The focus of tonight's"},{"startTime":12.45,"endTime":15.6,"body":"lecture is number nine,"},{"startTime":15.6,"endTime":16.983,"body":"Sir Christopher Wren."},{"startTime":17.94,"endTime":21.87,"body":"Christopher Wren was born in 1632,"},{"startTime":21.87,"endTime":23.55,"body":"which was 150 years"},{"startTime":23.55,"endTime":27.153,"body":"before the United States"},{"startTime":23.55,"endTime":27.153,"body":"of America was a thing."},{"startTime":28.65,"endTime":31.47,"body":"It was 12 years after"},{"startTime":28.65,"endTime":31.47,"body":"the Mayflower set sail"},{"startTime":31.47,"endTime":34.59,"body":"across the Atlantic that he was born,"},{"startTime":34.59,"endTime":38.613,"body":"and the Copernican Principle"},{"startTime":34.59,"endTime":38.613,"body":"hadn't fully taken hold."},{"startTime":39.63,"endTime":42.54,"body":"So enter Christopher Wren."},{"startTime":42.54,"endTime":45.42,"body":"But before we get too"},{"startTime":42.54,"endTime":45.42,"body":"much into his life story,"},{"startTime":45.42,"endTime":47.913,"body":"I want to pose the following question."},{"startTime":49.14,"endTime":53.34,"body":"What does it mean to be an influencer?"},{"startTime":53.34,"endTime":56.49,"body":"Indeed, can you be an influencer"},{"startTime":56.49,"endTime":59.31,"body":"if you don't care about likes,"},{"startTime":59.31,"endTime":62.943,"body":"and if you don't indulge"},{"startTime":59.31,"endTime":62.943,"body":"in self-aggrandizement?"},{"startTime":64.11,"endTime":69.06,"body":"We'll see tonight that"},{"startTime":64.11,"endTime":69.06,"body":"despite a remarkable lack"},{"startTime":69.06,"endTime":72.39,"body":"of the use of first person pronouns"},{"startTime":72.39,"endTime":74.46,"body":"on the part of Christopher Wren,"},{"startTime":74.46,"endTime":77.583,"body":"he was a tremendous influencer."},{"startTime":79.17,"endTime":83.403,"body":"Yet his childhood, though"},{"startTime":79.17,"endTime":83.403,"body":"not without many blessings,"},{"startTime":84.3,"endTime":87.99,"body":"was pretty traumatic in a number of ways."},{"startTime":87.99,"endTime":90.963,"body":"Five of his siblings died."},{"startTime":92.1,"endTime":95.283,"body":"His mother died when he"},{"startTime":92.1,"endTime":95.283,"body":"was a young little boy."},{"startTime":96.48,"endTime":99.45,"body":"War broke out when he was a 10 year old,"},{"startTime":99.45,"endTime":102.36,"body":"and that lasted for nine years."},{"startTime":102.36,"endTime":103.193,"body":"Prior to that,"},{"startTime":103.193,"endTime":106.98,"body":"the family had been on friendly"},{"startTime":103.193,"endTime":106.98,"body":"terms with the Royal Family."},{"startTime":106.98,"endTime":108.69,"body":"Christopher Wren Senior,"},{"startTime":108.69,"endTime":112.32,"body":"our Christopher Wren's"},{"startTime":108.69,"endTime":112.32,"body":"father was Dean of Windsor."},{"startTime":112.32,"endTime":113.73,"body":"They were favored by the kings"},{"startTime":113.73,"endTime":116.55,"body":"and indeed they were staunch royalists."},{"startTime":116.55,"endTime":119.76,"body":"But war broke out, as I said,"},{"startTime":119.76,"endTime":122.13,"body":"when Wren was a mere 10 year old,"},{"startTime":122.13,"endTime":125.91,"body":"and some pretty ghastly things"},{"startTime":122.13,"endTime":125.91,"body":"happened to him as a child."},{"startTime":125.91,"endTime":129.693,"body":"Yet he was not defined by"},{"startTime":125.91,"endTime":129.693,"body":"any of those bad things."},{"startTime":130.71,"endTime":133.26,"body":"It must have been heart rendering though"},{"startTime":133.26,"endTime":135.78,"body":"to see what happened to Charles I,"},{"startTime":135.78,"endTime":139.56,"body":"who must surely have attended"},{"startTime":135.78,"endTime":139.56,"body":"his father's services"},{"startTime":139.56,"endTime":143.04,"body":"in St. George's Chapel in Windsor Castle."},{"startTime":143.04,"endTime":147.303,"body":"This is Charles I with"},{"startTime":143.04,"endTime":147.303,"body":"his head and without."},{"startTime":149.43,"endTime":151.23,"body":"Sorry for anyone who's squeamish."},{"startTime":151.23,"endTime":155.973,"body":"So this took place on the"},{"startTime":151.23,"endTime":155.973,"body":"30th of January, 1649."},{"startTime":157.68,"endTime":160.47,"body":"We'll be seeing tonight"},{"startTime":157.68,"endTime":160.47,"body":"that Sir Christopher Wren"},{"startTime":160.47,"endTime":162.96,"body":"was the most remarkable polymath,"},{"startTime":162.96,"endTime":167.07,"body":"and a lot of his work concerned"},{"startTime":162.96,"endTime":167.07,"body":"mathematics and architecture"},{"startTime":167.07,"endTime":169.74,"body":"as well as mathematics and astronomy."},{"startTime":169.74,"endTime":171.54,"body":"Mathematics and architecture"},{"startTime":171.54,"endTime":173.37,"body":"is going to be covered by my colleague,"},{"startTime":173.37,"endTime":176.46,"body":"the Gresham Professor"},{"startTime":173.37,"endTime":176.46,"body":"of Geometry, Sarah Hart,"},{"startTime":176.46,"endTime":178.65,"body":"in a lecture in a couple of weeks' time."},{"startTime":178.65,"endTime":183.65,"body":"So I'll be leaving her to"},{"startTime":178.65,"endTime":183.65,"body":"address aspects of his brilliance"},{"startTime":184.5,"endTime":188.01,"body":"as they applied to architecture."},{"startTime":188.01,"endTime":191.01,"body":"I'll also draw to your"},{"startTime":188.01,"endTime":191.01,"body":"attention that this Saturday,"},{"startTime":191.01,"endTime":194.52,"body":"there is a special service"},{"startTime":191.01,"endTime":194.52,"body":"at St. Paul's Cathedral,"},{"startTime":194.52,"endTime":197.373,"body":"all dedicated to Sir Christopher Wren."},{"startTime":198.81,"endTime":200.97,"body":"So let's turn our attention now"},{"startTime":200.97,"endTime":205.35,"body":"to what Christopher Wren"},{"startTime":200.97,"endTime":205.35,"body":"focused on in the cosmos"},{"startTime":205.35,"endTime":207.603,"body":"and how he went about it."},{"startTime":208.77,"endTime":212.67,"body":"How do you begin to understand the cosmos?"},{"startTime":212.67,"endTime":215.28,"body":"It's a very hard thing to do in any case,"},{"startTime":215.28,"endTime":218.373,"body":"but telescopes of the time"},{"startTime":215.28,"endTime":218.373,"body":"were very poor quality."},{"startTime":219.51,"endTime":224.34,"body":"Wren's Cosmos, however, spanned"},{"startTime":219.51,"endTime":224.34,"body":"all different length scales,"},{"startTime":224.34,"endTime":226.05,"body":"from the microscopic,"},{"startTime":226.05,"endTime":228.84,"body":"that which you could see"},{"startTime":226.05,"endTime":228.84,"body":"through a microscope,"},{"startTime":228.84,"endTime":230.73,"body":"to the macroscopic,"},{"startTime":230.73,"endTime":233.13,"body":"that which you could sort of see through"},{"startTime":233.13,"endTime":236.073,"body":"the not great telescopes of the day."},{"startTime":237.39,"endTime":239.34,"body":"It's a great challenge in any case,"},{"startTime":239.34,"endTime":242.16,"body":"even with modern instrumentation"},{"startTime":242.16,"endTime":245.55,"body":"from the vantage point"},{"startTime":242.16,"endTime":245.55,"body":"of this rocky planet,"},{"startTime":245.55,"endTime":249.9,"body":"to think that we might be"},{"startTime":245.55,"endTime":249.9,"body":"able to explain and elucidate"},{"startTime":249.9,"endTime":253.83,"body":"the universe and the way that it evolves."},{"startTime":253.83,"endTime":257.82,"body":"But it was especially hard"},{"startTime":253.83,"endTime":257.82,"body":"with the limited optics"},{"startTime":257.82,"endTime":260.31,"body":"that were available at the time,"},{"startTime":260.31,"endTime":263.7,"body":"and the limitations of the"},{"startTime":260.31,"endTime":263.7,"body":"worldviews and paradigms"},{"startTime":263.7,"endTime":265.5,"body":"that couldn't be anything else"},{"startTime":265.5,"endTime":268.953,"body":"given what was known and"},{"startTime":265.5,"endTime":268.953,"body":"understandable at the time."},{"startTime":270.24,"endTime":273.6,"body":"Telescopes were truly poor quality then."},{"startTime":273.6,"endTime":275.65,"body":"Single elements of glass"},{"startTime":276.66,"endTime":280.29,"body":"were involved in the very"},{"startTime":276.66,"endTime":280.29,"body":"simple telescopes they had,"},{"startTime":280.29,"endTime":283.32,"body":"hence all sorts of aberrations abounded,"},{"startTime":283.32,"endTime":286.08,"body":"spherical aberration,"},{"startTime":283.32,"endTime":286.08,"body":"chromatic aberration,"},{"startTime":286.08,"endTime":290.61,"body":"all of them serving to degrade"},{"startTime":286.08,"endTime":290.61,"body":"the quality of any images"},{"startTime":290.61,"endTime":292.143,"body":"that were obtainable."},{"startTime":293.58,"endTime":296.43,"body":"In order to provide a very"},{"startTime":293.58,"endTime":296.43,"body":"high focal length lens,"},{"startTime":296.43,"endTime":300.27,"body":"you would need really,"},{"startTime":296.43,"endTime":300.27,"body":"really accurate surfaces,"},{"startTime":300.27,"endTime":303.27,"body":"and it was very hard to"},{"startTime":300.27,"endTime":303.27,"body":"grind surfaces to be,"},{"startTime":303.27,"endTime":306.81,"body":"to have a very accurate"},{"startTime":303.27,"endTime":306.81,"body":"curvature in those days."},{"startTime":306.81,"endTime":310.95,"body":"Microscopes on the other"},{"startTime":306.81,"endTime":310.95,"body":"hand, were much easier."},{"startTime":310.95,"endTime":312.57,"body":"They had abundant light,"},{"startTime":312.57,"endTime":315.6,"body":"you could illuminate them"},{"startTime":312.57,"endTime":315.6,"body":"with nearby light sources,"},{"startTime":315.6,"endTime":316.62,"body":"and to be honest,"},{"startTime":316.62,"endTime":319.89,"body":"you only needed to"},{"startTime":316.62,"endTime":319.89,"body":"magnify by about 20 times"},{"startTime":319.89,"endTime":323.52,"body":"in order to learn more"},{"startTime":319.89,"endTime":323.52,"body":"about what was going on."},{"startTime":323.52,"endTime":326.16,"body":"So even with relatively poor lenses,"},{"startTime":326.16,"endTime":330.843,"body":"microscopy was superior"},{"startTime":326.16,"endTime":330.843,"body":"to telescopy at the time."},{"startTime":332.79,"endTime":335.61,"body":"Christopher Wren fully understood"},{"startTime":335.61,"endTime":340.08,"body":"that innovation in"},{"startTime":335.61,"endTime":340.08,"body":"instrumentation was crucial"},{"startTime":340.08,"endTime":344.283,"body":"to lead to advance an"},{"startTime":340.08,"endTime":344.283,"body":"understanding and in discovery."},{"startTime":345.3,"endTime":350.3,"body":"Christopher Wren was no mere"},{"startTime":345.3,"endTime":350.3,"body":"hypothesizer in an ivory tower."},{"startTime":350.55,"endTime":353.22,"body":"Rather, he rolled up his sleeves"},{"startTime":353.22,"endTime":356.25,"body":"and invented devices, and instruments,"},{"startTime":356.25,"endTime":358.83,"body":"and new ways to make instruments"},{"startTime":358.83,"endTime":361.953,"body":"to overcome the limitations of the time."},{"startTime":362.91,"endTime":366.96,"body":"Here is one such device,"},{"startTime":362.91,"endTime":366.96,"body":"he called it an engine,"},{"startTime":366.96,"endTime":369.57,"body":"that he developed to help with the problem"},{"startTime":369.57,"endTime":374.4,"body":"of grinding the surfaces of"},{"startTime":369.57,"endTime":374.4,"body":"lenses very, very accurately."},{"startTime":374.4,"endTime":379.2,"body":"He used a hyperboloid shape"},{"startTime":374.4,"endTime":379.2,"body":"running over the glass lens"},{"startTime":379.2,"endTime":380.73,"body":"that he was trying to shape"},{"startTime":380.73,"endTime":383.1,"body":"to grind it very, very accurately."},{"startTime":383.1,"endTime":385.95,"body":"Of course, this was a labor of love"},{"startTime":385.95,"endTime":389.973,"body":"and would've taken many,"},{"startTime":385.95,"endTime":389.973,"body":"many, many months to build,"},{"startTime":390.99,"endTime":393.81,"body":"but this was the kind of"},{"startTime":390.99,"endTime":393.81,"body":"device that was needed"},{"startTime":393.81,"endTime":396.75,"body":"to get an even halfway decent lens"},{"startTime":396.75,"endTime":399.873,"body":"to get a good window on the universe."},{"startTime":400.86,"endTime":402.9,"body":"The problem is that big bits of glass"},{"startTime":402.9,"endTime":405.96,"body":"that you need for high curvature"},{"startTime":402.9,"endTime":405.96,"body":"and short focal lengths"},{"startTime":405.96,"endTime":410.61,"body":"were very hard to obtain"},{"startTime":405.96,"endTime":410.61,"body":"without impurities and defects."},{"startTime":410.61,"endTime":414.36,"body":"Whereas if you wanted long focal"},{"startTime":410.61,"endTime":414.36,"body":"lengths to see fine detail,"},{"startTime":414.36,"endTime":416.76,"body":"for example, to delineate the shape"},{"startTime":416.76,"endTime":419.04,"body":"or the surface features of a planet,"},{"startTime":419.04,"endTime":421.86,"body":"then you needed very,"},{"startTime":419.04,"endTime":421.86,"body":"very shallow surfaces"},{"startTime":421.86,"endTime":423.63,"body":"of immense accuracy."},{"startTime":423.63,"endTime":427.65,"body":"Immense accuracy here meaning"},{"startTime":423.63,"endTime":427.65,"body":"to better than a micron,"},{"startTime":427.65,"endTime":432.65,"body":"that is better to, better"},{"startTime":427.65,"endTime":432.65,"body":"than 1000th of one millimeter."},{"startTime":434.13,"endTime":437.283,"body":"Making it smooth and"},{"startTime":434.13,"endTime":437.283,"body":"correct was really tricky."},{"startTime":438.51,"endTime":441.42,"body":"But nonetheless, Christopher"},{"startTime":438.51,"endTime":441.42,"body":"Wren's perseverance"},{"startTime":441.42,"endTime":445.14,"body":"and ingenuity got him a very long way."},{"startTime":445.14,"endTime":449.31,"body":"He built a lot of these as a"},{"startTime":445.14,"endTime":449.31,"body":"child, and then as a student,"},{"startTime":449.31,"endTime":452.04,"body":"he was a student at Oxford."},{"startTime":452.04,"endTime":455.25,"body":"His connections with Oxford"},{"startTime":452.04,"endTime":455.25,"body":"preceded him arriving there"},{"startTime":455.25,"endTime":456.513,"body":"as an undergraduate."},{"startTime":457.53,"endTime":460.32,"body":"In fact, his father"},{"startTime":457.53,"endTime":460.32,"body":"attended St. John's College,"},{"startTime":460.32,"endTime":462.75,"body":"which happens to be my college."},{"startTime":462.75,"endTime":465.18,"body":"And there, Christopher Wren Senior,"},{"startTime":465.18,"endTime":466.89,"body":"our Christopher Wren's father,"},{"startTime":466.89,"endTime":469.8,"body":"left his mark in the old library"},{"startTime":469.8,"endTime":472.83,"body":"in these stained glass windows."},{"startTime":472.83,"endTime":475.56,"body":"Just below that central"},{"startTime":472.83,"endTime":475.56,"body":"dagger in this window,"},{"startTime":475.56,"endTime":478.47,"body":"I don't know whether you are"},{"startTime":475.56,"endTime":478.47,"body":"quite able to make it out."},{"startTime":478.47,"endTime":482.01,"body":"He's etched his autograph."},{"startTime":482.01,"endTime":484.41,"body":"For some reason, I have no idea why,"},{"startTime":484.41,"endTime":485.61,"body":"he's altered the font"},{"startTime":485.61,"endTime":488.82,"body":"between the penultimate E of Christopher,"},{"startTime":488.82,"endTime":491.43,"body":"and the penultimate E of Wren."},{"startTime":491.43,"endTime":495.036,"body":"I also have no idea how"},{"startTime":491.43,"endTime":495.036,"body":"you go about etching"},{"startTime":495.036,"endTime":495.869,"body":"a stained glass window."},{"startTime":495.869,"endTime":497.94,"body":"Maybe you use a diamond or something."},{"startTime":497.94,"endTime":499.83,"body":"But anyway, Christopher Wren Senior"},{"startTime":499.83,"endTime":502.83,"body":"left his mark at my college at St. John's,"},{"startTime":502.83,"endTime":506.28,"body":"but our Christopher Wren"},{"startTime":502.83,"endTime":506.28,"body":"went to Wadham College"},{"startTime":506.28,"endTime":508.14,"body":"where he was an undergraduate."},{"startTime":508.14,"endTime":511.14,"body":"He was later a fellow"},{"startTime":508.14,"endTime":511.14,"body":"at All Souls College."},{"startTime":511.14,"endTime":515.97,"body":"But at Wadham, his curiosity"},{"startTime":511.14,"endTime":515.97,"body":"and his voracious appetite"},{"startTime":515.97,"endTime":518.253,"body":"for knowledge were well fed."},{"startTime":519.18,"endTime":521.73,"body":"Wren contributed enthusiastically"},{"startTime":521.73,"endTime":525.183,"body":"to discussions with many fellows,"},{"startTime":526.41,"endTime":530.46,"body":"and formed a key part"},{"startTime":526.41,"endTime":530.46,"body":"of the group of people"},{"startTime":530.46,"endTime":534.03,"body":"that were the proto Royal Society."},{"startTime":534.03,"endTime":537.87,"body":"That all had its origins"},{"startTime":534.03,"endTime":537.87,"body":"at Wadham College."},{"startTime":537.87,"endTime":542.13,"body":"And what they discussed there"},{"startTime":537.87,"endTime":542.13,"body":"wasn't just the universe,"},{"startTime":542.13,"endTime":543.93,"body":"they went beyond astronomy,"},{"startTime":543.93,"endTime":546.96,"body":"to botany, to zoology, to mathematics."},{"startTime":546.96,"endTime":550.623,"body":"Truly, they had an"},{"startTime":546.96,"endTime":550.623,"body":"intellectually rich diet."},{"startTime":551.82,"endTime":554.4,"body":"At Wadham, Christopher Wren invented"},{"startTime":554.4,"endTime":555.93,"body":"all sorts of crazy things,"},{"startTime":555.93,"endTime":559.263,"body":"not the least of which was"},{"startTime":555.93,"endTime":559.263,"body":"the transparent beehive."},{"startTime":560.25,"endTime":563.37,"body":"I think it shows a remarkable creativity"},{"startTime":563.37,"endTime":565.02,"body":"and zest for knowledge,"},{"startTime":565.02,"endTime":569.1,"body":"to think of being sufficiently inquisitive"},{"startTime":569.1,"endTime":573.6,"body":"that you should build a beehive"},{"startTime":569.1,"endTime":573.6,"body":"that gives bees no privacy,"},{"startTime":573.6,"endTime":575.4,"body":"yet you can see what's going on"},{"startTime":575.4,"endTime":577.923,"body":"and how they breed and so on."},{"startTime":579.18,"endTime":580.05,"body":"But of course,"},{"startTime":580.05,"endTime":583.41,"body":"tonight's focus is about"},{"startTime":580.05,"endTime":583.41,"body":"Christopher Wen's astronomy,"},{"startTime":583.41,"endTime":584.88,"body":"not merely his botany,"},{"startTime":584.88,"endTime":587.79,"body":"about which you probably could"},{"startTime":584.88,"endTime":587.79,"body":"fill a lecture by the way,"},{"startTime":587.79,"endTime":590.613,"body":"but I'm not a botanist, so"},{"startTime":587.79,"endTime":590.613,"body":"I'm going to stop there."},{"startTime":591.84,"endTime":596.13,"body":"Christopher Wren followed the"},{"startTime":591.84,"endTime":596.13,"body":"patterns of our nearest star,"},{"startTime":596.13,"endTime":599.61,"body":"and he designed and loved many sundials."},{"startTime":599.61,"endTime":601.5,"body":"There's a particularly famous one"},{"startTime":601.5,"endTime":604.8,"body":"that's attributed to him"},{"startTime":601.5,"endTime":604.8,"body":"in All Souls College."},{"startTime":604.8,"endTime":607.89,"body":"There are actually two"},{"startTime":604.8,"endTime":607.89,"body":"sundials in this picture."},{"startTime":607.89,"endTime":610.53,"body":"This one is nothing to"},{"startTime":607.89,"endTime":610.53,"body":"do with Christopher Wren,"},{"startTime":610.53,"endTime":613.53,"body":"but this one is attributed to him."},{"startTime":613.53,"endTime":616.53,"body":"He was bursar of All Souls at the time."},{"startTime":616.53,"endTime":618.99,"body":"If you're the bursar of an Oxford College,"},{"startTime":618.99,"endTime":620.7,"body":"you hold a lot of power"},{"startTime":620.7,"endTime":624.66,"body":"and you get to oversee"},{"startTime":620.7,"endTime":624.66,"body":"projects in all their details."},{"startTime":624.66,"endTime":629.31,"body":"And so I'm sure he had a huge"},{"startTime":624.66,"endTime":629.31,"body":"involvement in this sundial."},{"startTime":629.31,"endTime":631.29,"body":"Sundials are absolutely lovely things"},{"startTime":631.29,"endTime":632.31,"body":"because they reflect,"},{"startTime":632.31,"endTime":634.17,"body":"if you've properly designed them"},{"startTime":634.17,"endTime":637.86,"body":"for their latitude and their position,"},{"startTime":637.86,"endTime":640.11,"body":"they enable you to calculate the time"},{"startTime":640.11,"endTime":642.87,"body":"just from the shadow of the sun,"},{"startTime":642.87,"endTime":645.81,"body":"given the way the sundial is set up."},{"startTime":645.81,"endTime":647.4,"body":"Of course, it doesn't"},{"startTime":645.81,"endTime":647.4,"body":"always work in Oxford"},{"startTime":647.4,"endTime":650.25,"body":"because the sky's are"},{"startTime":647.4,"endTime":650.25,"body":"pretty cloudy in Oxford,"},{"startTime":650.25,"endTime":653.79,"body":"but it's a beautiful thing,"},{"startTime":650.25,"endTime":653.79,"body":"and it's a great idea,"},{"startTime":653.79,"endTime":656.58,"body":"and it speaks of"},{"startTime":653.79,"endTime":656.58,"body":"Christopher hen's interests"},{"startTime":656.58,"endTime":659.94,"body":"in the patterns, and"},{"startTime":656.58,"endTime":659.94,"body":"mathematics, and rhythms"},{"startTime":659.94,"endTime":662.763,"body":"of the rising of the sun"},{"startTime":659.94,"endTime":662.763,"body":"and the setting of the sun."},{"startTime":664.02,"endTime":667.35,"body":"But I want to turn now to our next,"},{"startTime":667.35,"endTime":671.79,"body":"our nearest celestial"},{"startTime":667.35,"endTime":671.79,"body":"body, which is the moon."},{"startTime":671.79,"endTime":675.78,"body":"Christopher Wren took"},{"startTime":671.79,"endTime":675.78,"body":"great interest in the moon,"},{"startTime":675.78,"endTime":679.56,"body":"which is of course our"},{"startTime":675.78,"endTime":679.56,"body":"nearest natural satellite."},{"startTime":679.56,"endTime":683.94,"body":"Of course, the moon has inspired"},{"startTime":679.56,"endTime":683.94,"body":"poetry, and art, and music"},{"startTime":683.94,"endTime":685.86,"body":"through the centuries."},{"startTime":685.86,"endTime":689.34,"body":"But what Christopher Wren did"},{"startTime":685.86,"endTime":689.34,"body":"was something pretty special."},{"startTime":689.34,"endTime":691.29,"body":"He didn't just look at the moon,"},{"startTime":691.29,"endTime":693.93,"body":"he didn't just think of"},{"startTime":691.29,"endTime":693.93,"body":"it as a piece of art,"},{"startTime":693.93,"endTime":695.61,"body":"though it is in some ways,"},{"startTime":695.61,"endTime":699.27,"body":"but scientifically it's pretty important."},{"startTime":699.27,"endTime":702.12,"body":"Christopher Wren was"},{"startTime":699.27,"endTime":702.12,"body":"really the first person"},{"startTime":702.12,"endTime":705.03,"body":"to seriously map the moon."},{"startTime":705.03,"endTime":707.37,"body":"He developed an eye piece micrometer"},{"startTime":707.37,"endTime":710.19,"body":"so that he could accurately track across,"},{"startTime":710.19,"endTime":712.653,"body":"and relay that into a drawing."},{"startTime":713.7,"endTime":718.59,"body":"He made a model of the moon,"},{"startTime":713.7,"endTime":718.59,"body":"a 3D model out of pasteboard,"},{"startTime":718.59,"endTime":722.64,"body":"which I believe is some kind"},{"startTime":718.59,"endTime":722.64,"body":"of old-fashioned paper mache,"},{"startTime":722.64,"endTime":726.24,"body":"sort of glued together cardboard stuff."},{"startTime":726.24,"endTime":729.06,"body":"He made a model for the king"},{"startTime":729.06,"endTime":732.3,"body":"after the restoration of"},{"startTime":729.06,"endTime":732.3,"body":"the monarchy, Charles II,"},{"startTime":732.3,"endTime":735.84,"body":"to have a model of the moon."},{"startTime":735.84,"endTime":738.66,"body":"And that was something very,"},{"startTime":735.84,"endTime":738.66,"body":"very special for the king,"},{"startTime":738.66,"endTime":742.98,"body":"and apparently he showed"},{"startTime":738.66,"endTime":742.98,"body":"it off to all his friends."},{"startTime":742.98,"endTime":746.43,"body":"Sadly, being made of"},{"startTime":742.98,"endTime":746.43,"body":"pasteboard, it didn't survive."},{"startTime":746.43,"endTime":749.73,"body":"But there is photograph,"},{"startTime":749.73,"endTime":751.26,"body":"sorry, not photographic,"},{"startTime":751.26,"endTime":756.26,"body":"pictorial evidence of"},{"startTime":751.26,"endTime":756.26,"body":"this model of the moon."},{"startTime":756.3,"endTime":759.24,"body":"In this portrait of Christopher Wren,"},{"startTime":759.24,"endTime":761.16,"body":"which about a month ago,"},{"startTime":761.16,"endTime":763.35,"body":"I suddenly realized I was sitting opposite"},{"startTime":763.35,"endTime":766.443,"body":"when I was in the Sheldonian"},{"startTime":763.35,"endTime":766.443,"body":"Theater in Oxford,"},{"startTime":767.4,"endTime":771.84,"body":"which was built and designed"},{"startTime":767.4,"endTime":771.84,"body":"by Sir Christopher Wren."},{"startTime":771.84,"endTime":773.25,"body":"I was in the Sheldonian Theater"},{"startTime":773.25,"endTime":775.11,"body":"for the occasion of the admission"},{"startTime":775.11,"endTime":778.08,"body":"of our new Vice Chancellor, Irene Tracy."},{"startTime":778.08,"endTime":780.12,"body":"And while we were waiting"},{"startTime":778.08,"endTime":780.12,"body":"for the ceremony to begin,"},{"startTime":780.12,"endTime":783.69,"body":"I suddenly realized I was"},{"startTime":780.12,"endTime":783.69,"body":"sitting opposite this portrait,"},{"startTime":783.69,"endTime":786.12,"body":"and I gazed at it intently,"},{"startTime":786.12,"endTime":789.15,"body":"trying to take in as"},{"startTime":786.12,"endTime":789.15,"body":"much detail as I could."},{"startTime":789.15,"endTime":792.153,"body":"So this was painted in 1708,"},{"startTime":793.5,"endTime":795.24,"body":"and it gives lots of different evidence"},{"startTime":795.24,"endTime":799.02,"body":"of various different domes"},{"startTime":795.24,"endTime":799.02,"body":"and steeples of churches"},{"startTime":799.02,"endTime":800.523,"body":"that Christopher Wren built."},{"startTime":801.48,"endTime":806.48,"body":"It's signed by no fewer"},{"startTime":801.48,"endTime":806.48,"body":"than three artists."},{"startTime":806.79,"endTime":810.9,"body":"So clearly it's a labor of love, again,"},{"startTime":810.9,"endTime":814.74,"body":"lots of people contributing"},{"startTime":810.9,"endTime":814.74,"body":"to it and collaborating on it."},{"startTime":814.74,"endTime":819.54,"body":"They were Verio, and Nella, and Thornhill"},{"startTime":819.54,"endTime":821.493,"body":"who all contributed to this painting."},{"startTime":822.36,"endTime":824.85,"body":"But what's of interest to us tonight"},{"startTime":824.85,"endTime":828.84,"body":"is that in the bottom"},{"startTime":824.85,"endTime":828.84,"body":"corner, there are two globes."},{"startTime":828.84,"endTime":832.26,"body":"And the one on the left"},{"startTime":828.84,"endTime":832.26,"body":"is a celestial globe,"},{"startTime":832.26,"endTime":835.14,"body":"the sort of thing that has the plow on it,"},{"startTime":835.14,"endTime":839.19,"body":"the constellations of the stars"},{"startTime":835.14,"endTime":839.19,"body":"as they could be understood."},{"startTime":839.19,"endTime":841.14,"body":"So there were quite a few of those around."},{"startTime":841.14,"endTime":844.98,"body":"But this on the left, on the right rather,"},{"startTime":844.98,"endTime":849.98,"body":"is a picture of the 3D model"},{"startTime":844.98,"endTime":849.98,"body":"pasteboard model of the moon"},{"startTime":851.16,"endTime":852.273,"body":"given to the king."},{"startTime":853.17,"endTime":856.68,"body":"Now, you may be thinking, why"},{"startTime":853.17,"endTime":856.68,"body":"is the moon such a big deal?"},{"startTime":856.68,"endTime":859.02,"body":"Why were people excited about the moon?"},{"startTime":859.02,"endTime":861.21,"body":"It's our nearest celestial neighbor."},{"startTime":861.21,"endTime":863.7,"body":"It rocks through the sky the whole time."},{"startTime":863.7,"endTime":864.72,"body":"Why is it exciting?"},{"startTime":864.72,"endTime":866.1,"body":"Why is it special?"},{"startTime":866.1,"endTime":868.5,"body":"Why did the king show off this beautiful"},{"startTime":868.5,"endTime":871.62,"body":"first model of the moon"},{"startTime":868.5,"endTime":871.62,"body":"to all his friends?"},{"startTime":871.62,"endTime":873.993,"body":"Well, the moon is pretty special,"},{"startTime":874.92,"endTime":878.79,"body":"and its structure is remarkable."},{"startTime":878.79,"endTime":882.57,"body":"And I'm going to tell you"},{"startTime":878.79,"endTime":882.57,"body":"now a very, very brief story"},{"startTime":882.57,"endTime":884.73,"body":"about something that happened to me once"},{"startTime":884.73,"endTime":887.58,"body":"when I was working at my observatory"},{"startTime":887.58,"endTime":889.47,"body":"in rural southern India."},{"startTime":889.47,"endTime":890.91,"body":"This is one of my domes."},{"startTime":890.91,"endTime":893.373,"body":"I don't have as many"},{"startTime":890.91,"endTime":893.373,"body":"domes as Christopher Wren."},{"startTime":894.36,"endTime":897.03,"body":"This is the observatory in the"},{"startTime":894.36,"endTime":897.03,"body":"heart of the school in India"},{"startTime":897.03,"endTime":900.87,"body":"where I was working"},{"startTime":897.03,"endTime":900.87,"body":"just last week in fact."},{"startTime":900.87,"endTime":903.72,"body":"Now, when you commission a telescope,"},{"startTime":903.72,"endTime":905.52,"body":"the very first image that you take"},{"startTime":905.52,"endTime":907.95,"body":"is called your first light image."},{"startTime":907.95,"endTime":910.29,"body":"And it's really special, because it is."},{"startTime":910.29,"endTime":911.67,"body":"You've got light through the telescope,"},{"startTime":911.67,"endTime":913.5,"body":"you see an astronomical object."},{"startTime":913.5,"endTime":916.77,"body":"Everyone's very happy, all good."},{"startTime":916.77,"endTime":918.03,"body":"Now, shortly after that,"},{"startTime":918.03,"endTime":921.6,"body":"I was asked to give a"},{"startTime":918.03,"endTime":921.6,"body":"talk to school teachers"},{"startTime":921.6,"endTime":922.89,"body":"who were visiting the school"},{"startTime":922.89,"endTime":925.053,"body":"where my observatory in India is."},{"startTime":925.95,"endTime":927.87,"body":"And I didn't have a whole lot of notice"},{"startTime":927.87,"endTime":929.25,"body":"before giving this talk,"},{"startTime":929.25,"endTime":931.8,"body":"so I pulled together"},{"startTime":929.25,"endTime":931.8,"body":"some astronomical images"},{"startTime":931.8,"endTime":933.48,"body":"taken from this telescope,"},{"startTime":933.48,"endTime":934.95,"body":"of which the first one was the moon."},{"startTime":934.95,"endTime":938.01,"body":"And I explained it was"},{"startTime":934.95,"endTime":938.01,"body":"our first light image"},{"startTime":938.01,"endTime":939.18,"body":"from the telescope,"},{"startTime":939.18,"endTime":943.26,"body":"and how excited we were to"},{"startTime":939.18,"endTime":943.26,"body":"be able to see in detail"},{"startTime":943.26,"endTime":944.97,"body":"the craters on the moon."},{"startTime":944.97,"endTime":948.12,"body":"And as I was infusing about"},{"startTime":944.97,"endTime":948.12,"body":"these craters on the moon,"},{"startTime":948.12,"endTime":950.28,"body":"I suddenly got a sense"},{"startTime":950.28,"endTime":954.51,"body":"that two thirds of my"},{"startTime":950.28,"endTime":954.51,"body":"audience were in tears."},{"startTime":954.51,"endTime":956.763,"body":"I truly hope that isn't happening tonight."},{"startTime":957.9,"endTime":962.07,"body":"But let me tell you why it"},{"startTime":957.9,"endTime":962.07,"body":"was such a moving experience"},{"startTime":962.07,"endTime":964.323,"body":"for those teachers from"},{"startTime":962.07,"endTime":964.323,"body":"rural southern India."},{"startTime":965.16,"endTime":967.14,"body":"In that part of the world,"},{"startTime":967.14,"endTime":969.3,"body":"retina screen iPads aren't a thing,"},{"startTime":969.3,"endTime":972.81,"body":"glossy magazines aren't a thing."},{"startTime":972.81,"endTime":974.13,"body":"Televisions aren't a thing."},{"startTime":974.13,"endTime":976.53,"body":"They hadn't ever seen a picture"},{"startTime":976.53,"endTime":978.567,"body":"of the surface of the moon before."},{"startTime":978.567,"endTime":980.97,"body":"And so to actually see it,"},{"startTime":980.97,"endTime":983.55,"body":"to be able to connect the"},{"startTime":980.97,"endTime":983.55,"body":"sort of slightly dark patches"},{"startTime":983.55,"endTime":986.46,"body":"you can see on a very clear night"},{"startTime":986.46,"endTime":988.71,"body":"with an actual image"},{"startTime":988.71,"endTime":992.43,"body":"that tells you about genuine"},{"startTime":988.71,"endTime":992.43,"body":"structure on the moon"},{"startTime":992.43,"endTime":995.73,"body":"was moving for those teachers."},{"startTime":995.73,"endTime":998.37,"body":"If we haven't been exposed to the moon"},{"startTime":998.37,"endTime":999.9,"body":"in earlier parts of our life,"},{"startTime":999.9,"endTime":1004.04,"body":"when we suddenly see it as"},{"startTime":999.9,"endTime":1004.04,"body":"became possible for people"},{"startTime":1004.04,"endTime":1007.553,"body":"in Christopher Wren's time,"},{"startTime":1004.04,"endTime":1007.553,"body":"it's really pretty special."},{"startTime":1009.41,"endTime":1012.68,"body":"So this is all the more,"},{"startTime":1012.68,"endTime":1016.52,"body":"this is the only pictorial"},{"startTime":1012.68,"endTime":1016.52,"body":"record that we have,"},{"startTime":1016.52,"endTime":1019.04,"body":"it's only a 2D record that we have"},{"startTime":1019.04,"endTime":1020.63,"body":"of this model of the moon."},{"startTime":1020.63,"endTime":1024.02,"body":"But I want to emphasize"},{"startTime":1020.63,"endTime":1024.02,"body":"Christopher Wren wanted to map it."},{"startTime":1024.02,"endTime":1026.96,"body":"He didn't just want to do a piece of art,"},{"startTime":1026.96,"endTime":1029.69,"body":"he wanted to map it, he"},{"startTime":1026.96,"endTime":1029.69,"body":"wanted to measure it."},{"startTime":1029.69,"endTime":1031.64,"body":"And I feel sure that this fed"},{"startTime":1031.64,"endTime":1034.31,"body":"into his enthusiasm and commitment"},{"startTime":1034.31,"endTime":1037.52,"body":"to the Longitude Project"},{"startTime":1034.31,"endTime":1037.52,"body":"to which he contributed"},{"startTime":1037.52,"endTime":1039.53,"body":"in later life."},{"startTime":1039.53,"endTime":1042.71,"body":"The whole business of seeing"},{"startTime":1039.53,"endTime":1042.71,"body":"these craters on the moon"},{"startTime":1042.71,"endTime":1047.63,"body":"is quite eye-opening"},{"startTime":1042.71,"endTime":1047.63,"body":"for inhabitants of Earth"},{"startTime":1048.53,"endTime":1051.83,"body":"because they remind us that"},{"startTime":1048.53,"endTime":1051.83,"body":"one of the very special things"},{"startTime":1051.83,"endTime":1055.43,"body":"about living on this planet"},{"startTime":1051.83,"endTime":1055.43,"body":"is that we have an atmosphere."},{"startTime":1055.43,"endTime":1059.33,"body":"And this atmosphere, which"},{"startTime":1055.43,"endTime":1059.33,"body":"the moon does not have,"},{"startTime":1059.33,"endTime":1063.89,"body":"protects Earth from being"},{"startTime":1059.33,"endTime":1063.89,"body":"splatted with meteorites,"},{"startTime":1063.89,"endTime":1066.06,"body":"which give rise to these craters"},{"startTime":1066.98,"endTime":1068.42,"body":"than is the case on the moon."},{"startTime":1068.42,"endTime":1070.61,"body":"The moon has no atmosphere."},{"startTime":1070.61,"endTime":1074.164,"body":"So if a meteorite rocks up"},{"startTime":1070.61,"endTime":1074.164,"body":"and goes splat, there you go,"},{"startTime":1074.164,"endTime":1077.51,"body":"you have a crater."},{"startTime":1077.51,"endTime":1078.343,"body":"So it's a reminder,"},{"startTime":1078.343,"endTime":1079.79,"body":"I mean the atmosphere is, of course,"},{"startTime":1079.79,"endTime":1081.44,"body":"super useful for breathing,"},{"startTime":1081.44,"endTime":1084.44,"body":"but the atmosphere is very"},{"startTime":1081.44,"endTime":1084.44,"body":"useful for protecting us"},{"startTime":1084.44,"endTime":1088.13,"body":"from meteorites, because"},{"startTime":1084.44,"endTime":1088.13,"body":"under frictional heating,"},{"startTime":1088.13,"endTime":1090.59,"body":"most of them burn up."},{"startTime":1090.59,"endTime":1092.24,"body":"That's not always the case."},{"startTime":1092.24,"endTime":1094.94,"body":"And it's the subject of my next lecture,"},{"startTime":1094.94,"endTime":1097.823,"body":"which will be how life on"},{"startTime":1094.94,"endTime":1097.823,"body":"Earth might be wiped out,"},{"startTime":1098.69,"endTime":1099.83,"body":"that I'll be addressing that."},{"startTime":1099.83,"endTime":1104.6,"body":"But let's stay on cheery matters today."},{"startTime":1104.6,"endTime":1106.19,"body":"Earth's gravity is sufficiently strong"},{"startTime":1106.19,"endTime":1108.56,"body":"so that we have an atmosphere"},{"startTime":1106.19,"endTime":1108.56,"body":"and life can be sustained,"},{"startTime":1108.56,"endTime":1110.03,"body":"not so for the moon."},{"startTime":1110.03,"endTime":1112.22,"body":"So in seeing the moon,"},{"startTime":1112.22,"endTime":1116.81,"body":"we get a sense of the reality"},{"startTime":1112.22,"endTime":1116.81,"body":"of the brutal existence"},{"startTime":1116.81,"endTime":1117.89,"body":"that is out of space"},{"startTime":1117.89,"endTime":1120.923,"body":"when there is no atmosphere to protect us."},{"startTime":1122.33,"endTime":1125.72,"body":"Let's now move on to"},{"startTime":1122.33,"endTime":1125.72,"body":"Wren and Saturn's rings."},{"startTime":1125.72,"endTime":1129.23,"body":"So at the time there"},{"startTime":1125.72,"endTime":1129.23,"body":"wasn't a clear picture"},{"startTime":1129.23,"endTime":1131.45,"body":"or a clear acceptance"},{"startTime":1131.45,"endTime":1134.24,"body":"that all the planets in the solar system"},{"startTime":1134.24,"endTime":1136.61,"body":"orbited around the moon."},{"startTime":1136.61,"endTime":1139.16,"body":"Heliocentrism was becoming a thing"},{"startTime":1139.16,"endTime":1142.52,"body":"thanks to Galileo and Copernicus,"},{"startTime":1142.52,"endTime":1145.37,"body":"but it hadn't fully clicked in"},{"startTime":1145.37,"endTime":1149.21,"body":"with all the modern thinkers of the time."},{"startTime":1149.21,"endTime":1151.91,"body":"So we've all had the picture in our minds"},{"startTime":1151.91,"endTime":1155.0,"body":"of the planets orbiting around the sun"},{"startTime":1155.0,"endTime":1157.97,"body":"very happily for a"},{"startTime":1155.0,"endTime":1157.97,"body":"couple of centuries now."},{"startTime":1157.97,"endTime":1160.94,"body":"But the picture then was far from clear."},{"startTime":1160.94,"endTime":1165.2,"body":"And one of the most"},{"startTime":1160.94,"endTime":1165.2,"body":"mysterious was planet Saturn."},{"startTime":1165.2,"endTime":1169.31,"body":"That perplexed and"},{"startTime":1165.2,"endTime":1169.31,"body":"fascinated Galileo, and Wren,"},{"startTime":1169.31,"endTime":1171.623,"body":"and Huygens amongst others."},{"startTime":1172.52,"endTime":1176.903,"body":"We have a fairly good"},{"startTime":1172.52,"endTime":1176.903,"body":"understanding of Saturn today."},{"startTime":1177.825,"endTime":1180.98,"body":"We now know that there are rings"},{"startTime":1180.98,"endTime":1183.74,"body":"in a pretty similar plane to moons,"},{"startTime":1183.74,"endTime":1186.56,"body":"which also orbit around it."},{"startTime":1186.56,"endTime":1189.26,"body":"It's almost like Saturn is"},{"startTime":1186.56,"endTime":1189.26,"body":"its own little solar system"},{"startTime":1189.26,"endTime":1193.19,"body":"orbiting within the solar"},{"startTime":1189.26,"endTime":1193.19,"body":"system around the sun."},{"startTime":1193.19,"endTime":1195.8,"body":"They had none of that, of course."},{"startTime":1195.8,"endTime":1199.04,"body":"They couldn't do computational"},{"startTime":1195.8,"endTime":1199.04,"body":"calculations that we could do"},{"startTime":1199.04,"endTime":1203.24,"body":"and they certainly couldn't"},{"startTime":1199.04,"endTime":1203.24,"body":"produce images of this quality."},{"startTime":1203.24,"endTime":1206.21,"body":"This is another image taken"},{"startTime":1203.24,"endTime":1206.21,"body":"at my telescope in India"},{"startTime":1206.21,"endTime":1209.36,"body":"that I referred to a few moments ago."},{"startTime":1209.36,"endTime":1214.36,"body":"I took this image on the"},{"startTime":1209.36,"endTime":1214.36,"body":"20th of December, 2020,"},{"startTime":1215.54,"endTime":1219.65,"body":"the first Christmas of lockdown."},{"startTime":1219.65,"endTime":1223.817,"body":"Jupiter and Saturn were doing"},{"startTime":1219.65,"endTime":1223.817,"body":"an unusually close encounter."},{"startTime":1225.23,"endTime":1229.67,"body":"These images are taken 24 hours apart"},{"startTime":1229.67,"endTime":1231.89,"body":"and they're unusually close in the sky."},{"startTime":1231.89,"endTime":1233.51,"body":"They hadn't been this close in the sky"},{"startTime":1233.51,"endTime":1236.66,"body":"for about eight centuries."},{"startTime":1236.66,"endTime":1238.16,"body":"But you get a a little bit of,"},{"startTime":1238.16,"endTime":1242.72,"body":"you can see Jupiter's"},{"startTime":1238.16,"endTime":1242.72,"body":"Galliean moons there,"},{"startTime":1242.72,"endTime":1246.74,"body":"and a couple of the"},{"startTime":1242.72,"endTime":1246.74,"body":"satellites also in Saturn."},{"startTime":1246.74,"endTime":1248.78,"body":"It's an absolute joy to be able to image"},{"startTime":1248.78,"endTime":1252.35,"body":"these beautiful planets"},{"startTime":1248.78,"endTime":1252.35,"body":"in such detail now,"},{"startTime":1252.35,"endTime":1256.04,"body":"but that absolutely was"},{"startTime":1252.35,"endTime":1256.04,"body":"not possible at the time."},{"startTime":1256.04,"endTime":1260.0,"body":"It was much harder to"},{"startTime":1256.04,"endTime":1260.0,"body":"interpret what was going on"},{"startTime":1260.0,"endTime":1262.37,"body":"as far as Saturn was concerned"},{"startTime":1262.37,"endTime":1263.51,"body":"because of the aforementioned"},{"startTime":1263.51,"endTime":1265.88,"body":"poor quality optics that they had."},{"startTime":1265.88,"endTime":1269.57,"body":"Sure it was possible to see"},{"startTime":1265.88,"endTime":1269.57,"body":"distinct points of light"},{"startTime":1269.57,"endTime":1271.76,"body":"that orbited around Jupiter."},{"startTime":1271.76,"endTime":1274.1,"body":"But in terms of image quality,"},{"startTime":1274.1,"endTime":1276.68,"body":"in terms of revealing stripes on Jupiter,"},{"startTime":1276.68,"endTime":1278.12,"body":"that wasn't possible."},{"startTime":1278.12,"endTime":1282.29,"body":"In terms of deconstructing"},{"startTime":1278.12,"endTime":1282.29,"body":"what was the shape,"},{"startTime":1282.29,"endTime":1285.23,"body":"the underlying physical"},{"startTime":1282.29,"endTime":1285.23,"body":"structure of Saturn,"},{"startTime":1285.23,"endTime":1287.09,"body":"that wasn't possible."},{"startTime":1287.09,"endTime":1288.68,"body":"It was partly because"},{"startTime":1287.09,"endTime":1288.68,"body":"of the image quality,"},{"startTime":1288.68,"endTime":1293.39,"body":"but also Saturn changes with time."},{"startTime":1293.39,"endTime":1297.47,"body":"Now Wren was very much on the"},{"startTime":1293.39,"endTime":1297.47,"body":"right lines with his thinking,"},{"startTime":1297.47,"endTime":1300.92,"body":"although in fact he"},{"startTime":1297.47,"endTime":1300.92,"body":"favored elliptical rings"},{"startTime":1300.92,"endTime":1302.54,"body":"being around Saturn."},{"startTime":1302.54,"endTime":1306.5,"body":"He was very much on the"},{"startTime":1302.54,"endTime":1306.5,"body":"right lines, but in fact,"},{"startTime":1306.5,"endTime":1310.043,"body":"really the person who"},{"startTime":1306.5,"endTime":1310.043,"body":"nailed it was Huygens."},{"startTime":1311.48,"endTime":1313.94,"body":"But Wren was utterly gracious"},{"startTime":1313.94,"endTime":1317.84,"body":"and utterly admiring of Huygens' model"},{"startTime":1317.84,"endTime":1319.073,"body":"and said the following,"},{"startTime":1320.487,"endTime":1324.027,"body":"\"I confesse I was so fond of the neatness"},{"startTime":1324.027,"endTime":1327.237,"body":"\"of Huygens' idea and"},{"startTime":1324.027,"endTime":1327.237,"body":"the simplicity of it,"},{"startTime":1327.237,"endTime":1329.307,"body":"\"agreeing so well with the physical causes"},{"startTime":1329.307,"endTime":1332.427,"body":"\"of the heavenly bodies"},{"startTime":1329.307,"endTime":1332.427,"body":"that I loved his invention"},{"startTime":1332.427,"endTime":1333.86,"body":"\"beyond my own.\""},{"startTime":1333.86,"endTime":1336.56,"body":"That's a beautifully"},{"startTime":1333.86,"endTime":1336.56,"body":"gracious thing to say,"},{"startTime":1336.56,"endTime":1339.35,"body":"even though Wren himself"},{"startTime":1336.56,"endTime":1339.35,"body":"was very, very close."},{"startTime":1339.35,"endTime":1342.89,"body":"Not for him going after the credit,"},{"startTime":1342.89,"endTime":1345.95,"body":"much more taking joy in what was out there"},{"startTime":1345.95,"endTime":1348.35,"body":"and what had been understood."},{"startTime":1348.35,"endTime":1349.88,"body":"Of course, we have it easy today"},{"startTime":1349.88,"endTime":1354.41,"body":"with the Hubble Space telescope"},{"startTime":1349.88,"endTime":1354.41,"body":"launched by NASA and ISSA,"},{"startTime":1354.41,"endTime":1359.09,"body":"which has made some really"},{"startTime":1354.41,"endTime":1359.09,"body":"beautiful images of Saturn."},{"startTime":1359.09,"endTime":1360.56,"body":"The Hubble Space Telescope, by the way,"},{"startTime":1360.56,"endTime":1364.4,"body":"has the mass of two"},{"startTime":1360.56,"endTime":1364.4,"body":"adult African telescopes."},{"startTime":1364.4,"endTime":1366.5,"body":"It's obviously orbiting the Earth,"},{"startTime":1366.5,"endTime":1368.273,"body":"orbiting above us right now."},{"startTime":1369.2,"endTime":1374.2,"body":"And this telescope gave rise"},{"startTime":1369.2,"endTime":1374.2,"body":"to these even sharper images."},{"startTime":1374.78,"endTime":1377.75,"body":"This is December, 1994,"},{"startTime":1377.75,"endTime":1382.213,"body":"and this image is May, 1995."},{"startTime":1384.11,"endTime":1387.59,"body":"And you'll notice that Saturn's rings"},{"startTime":1387.59,"endTime":1391.46,"body":"are presenting a very different"},{"startTime":1387.59,"endTime":1391.46,"body":"inclination towards us."},{"startTime":1391.46,"endTime":1393.71,"body":"So what's going on here?"},{"startTime":1393.71,"endTime":1398.71,"body":"In fact, it's because Saturn's obliquity,"},{"startTime":1398.72,"endTime":1402.68,"body":"its tilt with respect to"},{"startTime":1398.72,"endTime":1402.68,"body":"its orbit around the sun"},{"startTime":1402.68,"endTime":1404.21,"body":"is quite significant."},{"startTime":1404.21,"endTime":1406.43,"body":"It's about 27 degrees."},{"startTime":1406.43,"endTime":1409.7,"body":"And so as we orbit around the sun,"},{"startTime":1409.7,"endTime":1412.52,"body":"and as Saturn orbits around the sun,"},{"startTime":1412.52,"endTime":1416.21,"body":"it's a subtly different"},{"startTime":1412.52,"endTime":1416.21,"body":"angle from time to time,"},{"startTime":1416.21,"endTime":1420.59,"body":"we go slightly above and"},{"startTime":1416.21,"endTime":1420.59,"body":"slightly below Saturn's planes."},{"startTime":1420.59,"endTime":1423.17,"body":"And at these times it's possible"},{"startTime":1423.17,"endTime":1426.5,"body":"to see the rings at different angles."},{"startTime":1426.5,"endTime":1430.55,"body":"The Saturnian year is about 27 years."},{"startTime":1430.55,"endTime":1433.37,"body":"And so roughly speaking, these crossings,"},{"startTime":1433.37,"endTime":1436.88,"body":"when Earth's orbit crosses Saturn's orbit,"},{"startTime":1436.88,"endTime":1439.13,"body":"it's about twice per Saturnian year."},{"startTime":1439.13,"endTime":1442.58,"body":"It's the details of the orbit mean"},{"startTime":1442.58,"endTime":1444.65,"body":"that it varies between about 13 years,"},{"startTime":1444.65,"endTime":1446.63,"body":"sometimes up to 15 years."},{"startTime":1446.63,"endTime":1449.27,"body":"But these are the different shapes"},{"startTime":1449.27,"endTime":1453.47,"body":"that Saturn's rings are"},{"startTime":1449.27,"endTime":1453.47,"body":"present to us on Earth"},{"startTime":1453.47,"endTime":1455.99,"body":"over the course of a decade or more."},{"startTime":1455.99,"endTime":1459.74,"body":"So imagine what it must be like"},{"startTime":1455.99,"endTime":1459.74,"body":"with a very low resolution,"},{"startTime":1459.74,"endTime":1462.5,"body":"blurry, imperfect telescope"},{"startTime":1462.5,"endTime":1467.5,"body":"to see bulges on either"},{"startTime":1462.5,"endTime":1467.5,"body":"side of Saturn's main body"},{"startTime":1469.88,"endTime":1471.2,"body":"on one occasion,"},{"startTime":1471.2,"endTime":1475.04,"body":"and then suddenly to realize"},{"startTime":1471.2,"endTime":1475.04,"body":"that they're all disappearing."},{"startTime":1475.04,"endTime":1478.13,"body":"This must have compounded"},{"startTime":1475.04,"endTime":1478.13,"body":"the development of models"},{"startTime":1478.13,"endTime":1482.93,"body":"by all sorts of people,"},{"startTime":1478.13,"endTime":1482.93,"body":"Huygens and Wren at the time."},{"startTime":1482.93,"endTime":1485.21,"body":"There's no doubt that Saturn's rings,"},{"startTime":1485.21,"endTime":1488.63,"body":"the obliquity of Saturn"},{"startTime":1485.21,"endTime":1488.63,"body":"with respect to its orbit"},{"startTime":1488.63,"endTime":1491.24,"body":"caused serious confusion."},{"startTime":1491.24,"endTime":1493.853,"body":"But as I say, twice per Saturnian year,"},{"startTime":1494.87,"endTime":1498.35,"body":"we are exactly in plane with the rings,"},{"startTime":1498.35,"endTime":1501.05,"body":"and so we see them just as a line,"},{"startTime":1501.05,"endTime":1503.72,"body":"and that is what Wren"},{"startTime":1501.05,"endTime":1503.72,"body":"and Huygens would've seen"},{"startTime":1503.72,"endTime":1506.21,"body":"as rings disappeared."},{"startTime":1506.21,"endTime":1508.76,"body":"They would just have seen"},{"startTime":1506.21,"endTime":1508.76,"body":"something that resembled"},{"startTime":1508.76,"endTime":1511.043,"body":"all the other planets or the larger ones."},{"startTime":1512.21,"endTime":1517.21,"body":"The mass of Saturn's rings"},{"startTime":1512.21,"endTime":1517.21,"body":"is relatively slender"},{"startTime":1517.22,"endTime":1519.17,"body":"depending on your definition of slender."},{"startTime":1519.17,"endTime":1524.17,"body":"It's about half the mass of"},{"startTime":1519.17,"endTime":1524.17,"body":"the ice shelf in Antarctica"},{"startTime":1526.04,"endTime":1526.873,"body":"on planet Earth,"},{"startTime":1526.873,"endTime":1531.82,"body":"but it's distributed over"},{"startTime":1526.873,"endTime":1531.82,"body":"really thin surface area."},{"startTime":1533.18,"endTime":1535.61,"body":"That area being about 80 times"},{"startTime":1535.61,"endTime":1538.16,"body":"the surface area of the Earth."},{"startTime":1538.16,"endTime":1539.06,"body":"They're really thin,"},{"startTime":1539.06,"endTime":1542.6,"body":"so that's why when you see"},{"startTime":1539.06,"endTime":1542.6,"body":"Saturn's rings edge on,"},{"startTime":1542.6,"endTime":1544.7,"body":"they seemingly disappear."},{"startTime":1544.7,"endTime":1548.72,"body":"And we certainly know that"},{"startTime":1544.7,"endTime":1548.72,"body":"that caused serious confusion"},{"startTime":1548.72,"endTime":1552.953,"body":"to Galileo back in the"},{"startTime":1548.72,"endTime":1552.953,"body":"day when he was observing."},{"startTime":1553.82,"endTime":1555.323,"body":"Moving further afield now,"},{"startTime":1556.19,"endTime":1559.7,"body":"now out to about 444"},{"startTime":1556.19,"endTime":1559.7,"body":"light years from Earth,"},{"startTime":1559.7,"endTime":1563.81,"body":"we're now looking at"},{"startTime":1559.7,"endTime":1563.81,"body":"Wren and the Pleiades."},{"startTime":1563.81,"endTime":1566.3,"body":"The Pleiades are fairly"},{"startTime":1563.81,"endTime":1566.3,"body":"well known in the night sky."},{"startTime":1566.3,"endTime":1568.25,"body":"If you start with Orion,"},{"startTime":1568.25,"endTime":1572.9,"body":"which is a very well known constellation,"},{"startTime":1572.9,"endTime":1575.45,"body":"produce the line that form his belt,"},{"startTime":1575.45,"endTime":1578.24,"body":"go via the bright star,"},{"startTime":1575.45,"endTime":1578.24,"body":"which is Aldebaran,"},{"startTime":1578.24,"endTime":1580.07,"body":"and then you see a collection of stars"},{"startTime":1580.07,"endTime":1581.15,"body":"and that's the Pleiades."},{"startTime":1581.15,"endTime":1582.533,"body":"That's how you find it."},{"startTime":1583.79,"endTime":1586.91,"body":"Wren made some of the most accurate images"},{"startTime":1586.91,"endTime":1591.23,"body":"of this star cluster that"},{"startTime":1586.91,"endTime":1591.23,"body":"persisted for quite a long time."},{"startTime":1591.23,"endTime":1593.84,"body":"Again, his emphasis on measurement,"},{"startTime":1593.84,"endTime":1596.03,"body":"on quantitative observation,"},{"startTime":1596.03,"endTime":1600.5,"body":"not just an arty feel-good"},{"startTime":1596.03,"endTime":1600.5,"body":"image, if you like,"},{"startTime":1600.5,"endTime":1602.99,"body":"was extraordinarily impressive."},{"startTime":1602.99,"endTime":1604.97,"body":"If you have good eyesight,"},{"startTime":1604.97,"endTime":1608.09,"body":"and you're at a dark site"},{"startTime":1604.97,"endTime":1608.09,"body":"and there are no clouds,"},{"startTime":1608.09,"endTime":1611.69,"body":"chances are you may be"},{"startTime":1608.09,"endTime":1611.69,"body":"able to see six stars"},{"startTime":1611.69,"endTime":1614.36,"body":"with the naked eye in"},{"startTime":1611.69,"endTime":1614.36,"body":"the Pleiades cluster,"},{"startTime":1614.36,"endTime":1617.6,"body":"seven if you've got really sharp eyesight."},{"startTime":1617.6,"endTime":1620.15,"body":"With the limited telescopes of the day,"},{"startTime":1620.15,"endTime":1623.36,"body":"but with Wren's micrometer eye pieces,"},{"startTime":1623.36,"endTime":1626.45,"body":"he was able to actually"},{"startTime":1623.36,"endTime":1626.45,"body":"measure the positions"},{"startTime":1626.45,"endTime":1630.65,"body":"of 40 stars in the Pleiades"},{"startTime":1630.65,"endTime":1634.163,"body":"using the technique of"},{"startTime":1630.65,"endTime":1634.163,"body":"measuring and mapping."},{"startTime":1635.48,"endTime":1636.83,"body":"This is a modern day image"},{"startTime":1636.83,"endTime":1639.14,"body":"taken by my friend and"},{"startTime":1636.83,"endTime":1639.14,"body":"colleague, Steve Lee,"},{"startTime":1639.14,"endTime":1642.11,"body":"in Australia of the Pleiades star cluster."},{"startTime":1642.11,"endTime":1643.43,"body":"And with such modern images,"},{"startTime":1643.43,"endTime":1647.54,"body":"you can see that in fact"},{"startTime":1643.43,"endTime":1647.54,"body":"there are about 3,000 stars"},{"startTime":1647.54,"endTime":1649.07,"body":"in this little cluster."},{"startTime":1649.07,"endTime":1651.26,"body":"It's like a mini galaxy on its own"},{"startTime":1651.26,"endTime":1653.723,"body":"embedded within the Milky Way."},{"startTime":1655.07,"endTime":1657.17,"body":"One of the many other things"},{"startTime":1657.17,"endTime":1659.42,"body":"that is impressive about Christopher Wren"},{"startTime":1659.42,"endTime":1661.82,"body":"is that he built friendships"},{"startTime":1661.82,"endTime":1665.663,"body":"even with people who were"},{"startTime":1661.82,"endTime":1665.663,"body":"hard to make friends with."},{"startTime":1666.77,"endTime":1671.48,"body":"Robert Hooke, the Oxford Polymath"},{"startTime":1666.77,"endTime":1671.48,"body":"was famously disputatious."},{"startTime":1671.48,"endTime":1674.45,"body":"He was pretty cranky, more of that later."},{"startTime":1674.45,"endTime":1677.54,"body":"But these two built an extraordinary bond"},{"startTime":1677.54,"endTime":1681.953,"body":"that lasted for decades,"},{"startTime":1677.54,"endTime":1681.953,"body":"and was enormously fruitful."},{"startTime":1683.45,"endTime":1685.67,"body":"There were quite a few opinions differ"},{"startTime":1685.67,"endTime":1689.42,"body":"on which things should be"},{"startTime":1685.67,"endTime":1689.42,"body":"attributed and credited to Hook,"},{"startTime":1689.42,"endTime":1692.15,"body":"and which should be attributed"},{"startTime":1689.42,"endTime":1692.15,"body":"and credited to Wren."},{"startTime":1692.15,"endTime":1696.92,"body":"It seems to me that a whole"},{"startTime":1692.15,"endTime":1696.92,"body":"lot of dialogue and stimulation"},{"startTime":1696.92,"endTime":1699.323,"body":"went on in both directions."},{"startTime":1700.37,"endTime":1703.19,"body":"This is what Hooke has to say about Wren"},{"startTime":1703.19,"endTime":1707.42,"body":"in the context of microscopy,"},{"startTime":1703.19,"endTime":1707.42,"body":"talking about some drawings,"},{"startTime":1707.42,"endTime":1710.24,"body":"which Hooke did on the using again,"},{"startTime":1710.24,"endTime":1713.693,"body":"this clever micrometer"},{"startTime":1710.24,"endTime":1713.693,"body":"that Wren had developed."},{"startTime":1715.347,"endTime":1718.797,"body":"\"As the hazard of coming"},{"startTime":1715.347,"endTime":1718.797,"body":"after Dr. Wren did afright me,"},{"startTime":1718.797,"endTime":1722.427,"body":"\"for of him I must affirm that"},{"startTime":1718.797,"endTime":1722.427,"body":"since the time of Archimedes,"},{"startTime":1722.427,"endTime":1727.427,"body":"\"there scarce ever met in one"},{"startTime":1722.427,"endTime":1727.427,"body":"man in so great a perfection,"},{"startTime":1727.917,"endTime":1729.717,"body":"\"such a mechanical mind"},{"startTime":1729.717,"endTime":1732.687,"body":"\"so good at inventing"},{"startTime":1729.717,"endTime":1732.687,"body":"things and building things,"},{"startTime":1732.687,"endTime":1737.687,"body":"\"and so philosophical a mind,"},{"startTime":1732.687,"endTime":1737.687,"body":"so creative in his thinking.\""},{"startTime":1737.93,"endTime":1741.02,"body":"And this from Hooke who was,"},{"startTime":1741.02,"endTime":1744.5,"body":"you know, better known for"},{"startTime":1741.02,"endTime":1744.5,"body":"being pretty cantankerous,"},{"startTime":1744.5,"endTime":1746.99,"body":"to be so gracious about Wren,"},{"startTime":1746.99,"endTime":1751.61,"body":"I think is a tribute to"},{"startTime":1746.99,"endTime":1751.61,"body":"Wren's character himself."},{"startTime":1751.61,"endTime":1753.53,"body":"Let me just show you this book then,"},{"startTime":1753.53,"endTime":1756.62,"body":"which is attributed to Hooke,"},{"startTime":1756.62,"endTime":1761.62,"body":"but has such these gracious"},{"startTime":1756.62,"endTime":1761.62,"body":"words in the acknowledgements."},{"startTime":1764.6,"endTime":1766.01,"body":"Slightly grandiose title of,"},{"startTime":1766.01,"endTime":1768.23,"body":"Some Physiological"},{"startTime":1766.01,"endTime":1768.23,"body":"Descriptions of Minute Bodies"},{"startTime":1768.23,"endTime":1769.91,"body":"Made by Magnifying Glasses"},{"startTime":1769.91,"endTime":1773.33,"body":"with Observations and Inquiries Thereupon."},{"startTime":1773.33,"endTime":1776.93,"body":"We are not allowed such"},{"startTime":1773.33,"endTime":1776.93,"body":"flowery titles these days."},{"startTime":1776.93,"endTime":1778.64,"body":"But actually they're slightly justified"},{"startTime":1778.64,"endTime":1781.79,"body":"when you see the beauty of these images,"},{"startTime":1781.79,"endTime":1786.74,"body":"drawn from what was seen"},{"startTime":1781.79,"endTime":1786.74,"body":"under a microscope by Hooke."},{"startTime":1786.74,"endTime":1790.7,"body":"But Hooke foolsomely"},{"startTime":1786.74,"endTime":1790.7,"body":"attributes this technique"},{"startTime":1790.7,"endTime":1792.593,"body":"and similar drawings to Wren."},{"startTime":1793.58,"endTime":1796.52,"body":"The detail is absolutely exquisite"},{"startTime":1796.52,"endTime":1798.68,"body":"if that is you like fleas."},{"startTime":1798.68,"endTime":1800.57,"body":"I'm not so keen on them myself."},{"startTime":1800.57,"endTime":1803.75,"body":"This is a fly with its compound eyes."},{"startTime":1803.75,"endTime":1806.39,"body":"The detail is absolutely beautiful."},{"startTime":1806.39,"endTime":1811.39,"body":"Microscopy in the 17th century"},{"startTime":1806.39,"endTime":1811.39,"body":"was really very remarkable."},{"startTime":1811.46,"endTime":1815.903,"body":"Not matched by commensurate"},{"startTime":1811.46,"endTime":1815.903,"body":"prowess in telescopy,"},{"startTime":1817.01,"endTime":1821.87,"body":"but nonetheless still"},{"startTime":1817.01,"endTime":1821.87,"body":"enough to enrich and enlarge"},{"startTime":1821.87,"endTime":1824.153,"body":"the cosmos at the time."},{"startTime":1825.2,"endTime":1827.42,"body":"Talking of things that enlarge the cosmos,"},{"startTime":1827.42,"endTime":1832.42,"body":"let's now turn to Christopher"},{"startTime":1827.42,"endTime":1832.42,"body":"Wren and the comet of 1664."},{"startTime":1832.94,"endTime":1837.77,"body":"This is even mentioned in"},{"startTime":1832.94,"endTime":1837.77,"body":"Samuel Pepys's diary entry"},{"startTime":1837.77,"endTime":1841.61,"body":"on Thursday the 15th of"},{"startTime":1837.77,"endTime":1841.61,"body":"December over coffee,"},{"startTime":1841.61,"endTime":1842.57,"body":"much like the modern day,"},{"startTime":1842.57,"endTime":1844.25,"body":"a lot of scientific thinking"},{"startTime":1844.25,"endTime":1846.923,"body":"takes place over discussions over coffee."},{"startTime":1847.85,"endTime":1849.77,"body":"So in the coffee shops of the day,"},{"startTime":1849.77,"endTime":1852.02,"body":"there was great talk of the comet."},{"startTime":1852.02,"endTime":1853.31,"body":"It was a big deal."},{"startTime":1853.31,"endTime":1855.62,"body":"More people noticed it and saw it,"},{"startTime":1855.62,"endTime":1859.7,"body":"because of course, light"},{"startTime":1855.62,"endTime":1859.7,"body":"pollution was much lower in London"},{"startTime":1859.7,"endTime":1863.15,"body":"three and a half centuries"},{"startTime":1859.7,"endTime":1863.15,"body":"ago than it is today."},{"startTime":1863.15,"endTime":1865.25,"body":"So these are some of the"},{"startTime":1863.15,"endTime":1865.25,"body":"depictions that we have,"},{"startTime":1865.25,"endTime":1870.25,"body":"this is a German one of that"},{"startTime":1865.25,"endTime":1870.25,"body":"particular comet in 1664."},{"startTime":1873.02,"endTime":1876.863,"body":"Now as a drawing, it's"},{"startTime":1873.02,"endTime":1876.863,"body":"obviously somewhat stylized."},{"startTime":1877.88,"endTime":1882.029,"body":"The actual halo is possibly"},{"startTime":1877.88,"endTime":1882.029,"body":"not very authentic,"},{"startTime":1882.029,"endTime":1886.04,"body":"but one can appreciate what"},{"startTime":1882.029,"endTime":1886.04,"body":"the artist is trying to draw."},{"startTime":1886.04,"endTime":1889.25,"body":"There's a resemblance"},{"startTime":1886.04,"endTime":1889.25,"body":"with modern day comets."},{"startTime":1889.25,"endTime":1892.91,"body":"This is Comet NEOWISE"},{"startTime":1889.25,"endTime":1892.91,"body":"photographed from my back garden"},{"startTime":1892.91,"endTime":1894.653,"body":"during July of lockdown."},{"startTime":1895.52,"endTime":1899.42,"body":"And as you can see, there's"},{"startTime":1895.52,"endTime":1899.42,"body":"actually a little meteor"},{"startTime":1899.42,"endTime":1902.12,"body":"that's rocked up there on the left."},{"startTime":1902.12,"endTime":1906.35,"body":"But as you can see qualitatively,"},{"startTime":1906.35,"endTime":1910.64,"body":"this comet matches the drawings of 1664,"},{"startTime":1911.84,"endTime":1913.07,"body":"especially if I zoom in."},{"startTime":1913.07,"endTime":1918.07,"body":"So a number of people at the"},{"startTime":1913.07,"endTime":1918.07,"body":"time in Europe drew this comet."},{"startTime":1918.11,"endTime":1919.97,"body":"It was one of the brightest ones"},{"startTime":1919.97,"endTime":1922.913,"body":"that had been known at the time."},{"startTime":1924.47,"endTime":1927.47,"body":"But Wren's interest was in measuring it."},{"startTime":1927.47,"endTime":1931.46,"body":"Wren's interest was in"},{"startTime":1927.47,"endTime":1931.46,"body":"mapping its trajectory."},{"startTime":1931.46,"endTime":1933.8,"body":"And so what he did was to start to think,"},{"startTime":1933.8,"endTime":1936.2,"body":"well, what could its trajectory be?"},{"startTime":1936.2,"endTime":1938.243,"body":"What could its orbital path be?"},{"startTime":1940.1,"endTime":1941.54,"body":"If I fold that back,"},{"startTime":1941.54,"endTime":1944.48,"body":"if I reverse engineer it to reconstruct"},{"startTime":1944.48,"endTime":1946.76,"body":"what was the trajectory"},{"startTime":1944.48,"endTime":1946.76,"body":"given that we're on an Earth,"},{"startTime":1946.76,"endTime":1950.12,"body":"which is moving through space"},{"startTime":1946.76,"endTime":1950.12,"body":"in orbit around the sun,"},{"startTime":1950.12,"endTime":1952.43,"body":"because we believe that the"},{"startTime":1950.12,"endTime":1952.43,"body":"Earth goes around the sun,"},{"startTime":1952.43,"endTime":1953.78,"body":"don't we?"},{"startTime":1953.78,"endTime":1958.34,"body":"This was his attempt at"},{"startTime":1953.78,"endTime":1958.34,"body":"interpreting the passage"},{"startTime":1958.34,"endTime":1959.96,"body":"of that comet."},{"startTime":1959.96,"endTime":1961.94,"body":"Now, aspects of it are not correct."},{"startTime":1961.94,"endTime":1965.39,"body":"It was predicated on the notion"},{"startTime":1965.39,"endTime":1967.1,"body":"that was prevalent at the time"},{"startTime":1967.1,"endTime":1969.92,"body":"that comets move in rectilinear motion,"},{"startTime":1969.92,"endTime":1971.9,"body":"they move in straight lines."},{"startTime":1971.9,"endTime":1975.89,"body":"Now we now know that they follow orbits"},{"startTime":1975.89,"endTime":1979.55,"body":"that we collectively refer"},{"startTime":1975.89,"endTime":1979.55,"body":"to as conic sections."},{"startTime":1979.55,"endTime":1982.19,"body":"I'll come back to that later in my talk,"},{"startTime":1982.19,"endTime":1984.32,"body":"which obey Kepler's laws."},{"startTime":1984.32,"endTime":1988.31,"body":"But actually small segments"},{"startTime":1984.32,"endTime":1988.31,"body":"of comet trajectories"},{"startTime":1988.31,"endTime":1991.07,"body":"can sometimes be treated"},{"startTime":1988.31,"endTime":1991.07,"body":"as straight lines."},{"startTime":1991.07,"endTime":1993.26,"body":"And this gives an interesting insight"},{"startTime":1993.26,"endTime":1996.68,"body":"into what Christopher Wren thirsted for."},{"startTime":1996.68,"endTime":1998.99,"body":"For him, measuring things"},{"startTime":1998.99,"endTime":2001.54,"body":"and taking a quantitative observation"},{"startTime":2001.54,"endTime":2003.373,"body":"were really what mattered."},{"startTime":2005.08,"endTime":2008.44,"body":"Not everything in"},{"startTime":2005.08,"endTime":2008.44,"body":"Christopher Wren's adult life"},{"startTime":2008.44,"endTime":2012.4,"body":"was as happy as the joyful"},{"startTime":2008.44,"endTime":2012.4,"body":"observation of a comet."},{"startTime":2012.4,"endTime":2015.673,"body":"Three of his four children died."},{"startTime":2016.6,"endTime":2020.71,"body":"Two, he married twice"},{"startTime":2016.6,"endTime":2020.71,"body":"and was widowed twice"},{"startTime":2020.71,"endTime":2025.71,"body":"a few years after the marriage"},{"startTime":2020.71,"endTime":2025.71,"body":"and the birth of children"},{"startTime":2025.75,"endTime":2027.46,"body":"in each case."},{"startTime":2027.46,"endTime":2029.68,"body":"He lived through a pandemic,"},{"startTime":2029.68,"endTime":2033.79,"body":"he lived through the"},{"startTime":2029.68,"endTime":2033.79,"body":"dreadful Fire of London,"},{"startTime":2033.79,"endTime":2035.5,"body":"which we'll come to now."},{"startTime":2035.5,"endTime":2038.05,"body":"Again, terrible things to endure,"},{"startTime":2038.05,"endTime":2040.0,"body":"but he was not defined by them."},{"startTime":2040.0,"endTime":2043.33,"body":"And his activities show that he thrived"},{"startTime":2043.33,"endTime":2046.003,"body":"despite these terrible things."},{"startTime":2048.16,"endTime":2051.623,"body":"Christopher Wren, like a certain other"},{"startTime":2051.623,"endTime":2053.71,"body":"Gresham Professor of Astronomy,"},{"startTime":2053.71,"endTime":2055.63,"body":"developed a real taste for eclipses."},{"startTime":2055.63,"endTime":2057.343,"body":"I love eclipses."},{"startTime":2058.69,"endTime":2063.43,"body":"By remarkable coincidence, our"},{"startTime":2058.69,"endTime":2063.43,"body":"nearest satellite, the moon,"},{"startTime":2063.43,"endTime":2066.19,"body":"although it's physically"},{"startTime":2063.43,"endTime":2066.19,"body":"got a much smaller diameter"},{"startTime":2066.19,"endTime":2067.48,"body":"than the sun,"},{"startTime":2067.48,"endTime":2069.73,"body":"its distance from us is such"},{"startTime":2069.73,"endTime":2073.57,"body":"that it subtends the same"},{"startTime":2069.73,"endTime":2073.57,"body":"solid angle as the sun."},{"startTime":2073.57,"endTime":2075.22,"body":"It's a remarkable coincidence."},{"startTime":2075.22,"endTime":2077.05,"body":"And this means there are times"},{"startTime":2077.05,"endTime":2079.3,"body":"when everything aligns appropriately"},{"startTime":2079.3,"endTime":2082.06,"body":"that it can exactly block out the sun."},{"startTime":2082.06,"endTime":2087.06,"body":"And this is what happened in"},{"startTime":2082.06,"endTime":2087.06,"body":"2019 just before our pandemic,"},{"startTime":2088.21,"endTime":2093.21,"body":"when the moon moved across"},{"startTime":2088.21,"endTime":2093.21,"body":"the disk of the sun."},{"startTime":2095.65,"endTime":2099.58,"body":"It's truly a thrilling thing"},{"startTime":2095.65,"endTime":2099.58,"body":"to watch a solar eclipse."},{"startTime":2099.58,"endTime":2101.71,"body":"It's not just geometry."},{"startTime":2101.71,"endTime":2104.8,"body":"You get a strong sense"},{"startTime":2101.71,"endTime":2104.8,"body":"of being in outer space,"},{"startTime":2104.8,"endTime":2107.83,"body":"which we are all of the time, of course."},{"startTime":2107.83,"endTime":2112.24,"body":"But to have this sense of"},{"startTime":2107.83,"endTime":2112.24,"body":"celestial bodies moving"},{"startTime":2112.24,"endTime":2113.92,"body":"is just remarkable."},{"startTime":2113.92,"endTime":2116.08,"body":"And I really recommend if"},{"startTime":2113.92,"endTime":2116.08,"body":"you get the opportunity"},{"startTime":2116.08,"endTime":2119.173,"body":"to witness an eclipse that you take it up."},{"startTime":2120.22,"endTime":2125.22,"body":"Christopher Wren watched the"},{"startTime":2120.22,"endTime":2125.22,"body":"solar eclipse in 1654 in Oxford"},{"startTime":2126.97,"endTime":2129.97,"body":"assisting Richard Rawlinson and others."},{"startTime":2129.97,"endTime":2134.68,"body":"And this is the path"},{"startTime":2129.97,"endTime":2134.68,"body":"that the eclipse took."},{"startTime":2134.68,"endTime":2137.2,"body":"I'll just zoom in on the United Kingdom."},{"startTime":2137.2,"endTime":2139.06,"body":"So it didn't actually go through Oxford,"},{"startTime":2139.06,"endTime":2141.34,"body":"it went through the north of Scotland."},{"startTime":2141.34,"endTime":2142.173,"body":"But nonetheless,"},{"startTime":2142.173,"endTime":2144.46,"body":"just seeing a partial solar eclipse"},{"startTime":2144.46,"endTime":2147.37,"body":"would've been a pretty"},{"startTime":2144.46,"endTime":2147.37,"body":"exciting phenomenon."},{"startTime":2147.37,"endTime":2151.09,"body":"Again, feeding his thirst for geometry,"},{"startTime":2151.09,"endTime":2156.09,"body":"and understanding orbits,"},{"startTime":2151.09,"endTime":2156.09,"body":"and quantitative observation."},{"startTime":2157.06,"endTime":2162.06,"body":"This is a calculation of just"},{"startTime":2157.06,"endTime":2162.06,"body":"how much of the eclipsed sun"},{"startTime":2163.27,"endTime":2166.93,"body":"Christopher Wren would've"},{"startTime":2163.27,"endTime":2166.93,"body":"been able to see from Oxford"},{"startTime":2166.93,"endTime":2168.67,"body":"in that eclipse."},{"startTime":2168.67,"endTime":2172.48,"body":"So definitely an appreciator"},{"startTime":2168.67,"endTime":2172.48,"body":"of the finer things in life,"},{"startTime":2172.48,"endTime":2174.013,"body":"by which I mean eclipses."},{"startTime":2176.56,"endTime":2179.2,"body":"Now let's turn to something"},{"startTime":2176.56,"endTime":2179.2,"body":"else a bit quantitative,"},{"startTime":2179.2,"endTime":2181.48,"body":"stellar parallax."},{"startTime":2181.48,"endTime":2184.99,"body":"So in order to understand"},{"startTime":2181.48,"endTime":2184.99,"body":"the nature of the cosmos"},{"startTime":2184.99,"endTime":2188.92,"body":"and remember how small their"},{"startTime":2184.99,"endTime":2188.92,"body":"cosmos was at the time,"},{"startTime":2188.92,"endTime":2190.87,"body":"they didn't really know"},{"startTime":2188.92,"endTime":2190.87,"body":"about other galaxies."},{"startTime":2190.87,"endTime":2194.2,"body":"They knew about nebulosity"},{"startTime":2190.87,"endTime":2194.2,"body":"and patches of fuzz"},{"startTime":2194.2,"endTime":2195.033,"body":"in the night sky,"},{"startTime":2195.033,"endTime":2198.97,"body":"but they didn't know about"},{"startTime":2195.033,"endTime":2198.97,"body":"the extra galactic universe."},{"startTime":2198.97,"endTime":2201.52,"body":"But in order to advance that knowledge"},{"startTime":2201.52,"endTime":2203.14,"body":"and that understanding,"},{"startTime":2203.14,"endTime":2207.88,"body":"and deepen their picture of"},{"startTime":2203.14,"endTime":2207.88,"body":"the nature of the cosmos,"},{"startTime":2207.88,"endTime":2209.23,"body":"it was necessary to understand"},{"startTime":2209.23,"endTime":2212.32,"body":"how far things were away from Earth."},{"startTime":2212.32,"endTime":2216.04,"body":"Only then when you know"},{"startTime":2212.32,"endTime":2216.04,"body":"how distant things are,"},{"startTime":2216.04,"endTime":2219.1,"body":"can you work sizes and energies,"},{"startTime":2219.1,"endTime":2222.67,"body":"and only then can you"},{"startTime":2219.1,"endTime":2222.67,"body":"calculate the scale of cosmos."},{"startTime":2222.67,"endTime":2224.74,"body":"So for all sorts of reasons,"},{"startTime":2224.74,"endTime":2228.46,"body":"being able to measure"},{"startTime":2224.74,"endTime":2228.46,"body":"distances was really important."},{"startTime":2228.46,"endTime":2232.69,"body":"Christopher Wren was interested"},{"startTime":2228.46,"endTime":2232.69,"body":"in parallax all his life."},{"startTime":2232.69,"endTime":2233.68,"body":"So what is parallax"},{"startTime":2233.68,"endTime":2237.013,"body":"and how does it connect with"},{"startTime":2233.68,"endTime":2237.013,"body":"what Christopher Wren measured?"},{"startTime":2237.91,"endTime":2241.06,"body":"So a key prediction of Copernican theory"},{"startTime":2241.06,"endTime":2244.33,"body":"is that if you've got the"},{"startTime":2241.06,"endTime":2244.33,"body":"Earth moving around the sun,"},{"startTime":2244.33,"endTime":2246.28,"body":"then when the Earth is here,"},{"startTime":2246.28,"endTime":2248.35,"body":"it will see nearby stars aligned"},{"startTime":2248.35,"endTime":2250.42,"body":"with distant stars over there."},{"startTime":2250.42,"endTime":2251.397,"body":"But when the Earth is here,"},{"startTime":2251.397,"endTime":2254.62,"body":"you'll see the nearby star"},{"startTime":2251.397,"endTime":2254.62,"body":"aligned with distant stars"},{"startTime":2254.62,"endTime":2255.88,"body":"over here."},{"startTime":2255.88,"endTime":2259.75,"body":"I hope this diagram"},{"startTime":2255.88,"endTime":2259.75,"body":"illustrates what happens."},{"startTime":2259.75,"endTime":2262.96,"body":"So when the Earth is on the opposite side"},{"startTime":2262.96,"endTime":2265.963,"body":"of its orbital path around"},{"startTime":2262.96,"endTime":2265.963,"body":"the sun six months later,"},{"startTime":2266.95,"endTime":2270.28,"body":"you will see any nearby star"},{"startTime":2270.28,"endTime":2272.53,"body":"to be shifted by a parallatic angle,"},{"startTime":2272.53,"endTime":2275.17,"body":"an angle of parallax, alpha here,"},{"startTime":2275.17,"endTime":2277.42,"body":"given by how much it's moved"},{"startTime":2277.42,"endTime":2281.713,"body":"as a function of Earth's annual motion."},{"startTime":2283.15,"endTime":2285.94,"body":"So this is quite a well-posed problem."},{"startTime":2285.94,"endTime":2288.79,"body":"You look at the positions"},{"startTime":2285.94,"endTime":2288.79,"body":"of stars and you say,"},{"startTime":2288.79,"endTime":2291.97,"body":"how much do they move apart"},{"startTime":2291.97,"endTime":2295.57,"body":"by when you measure them"},{"startTime":2291.97,"endTime":2295.57,"body":"at six month intervals"},{"startTime":2295.57,"endTime":2297.73,"body":"against the background"},{"startTime":2295.57,"endTime":2297.73,"body":"of very distant stars,"},{"startTime":2297.73,"endTime":2301.12,"body":"which you are hardly going"},{"startTime":2297.73,"endTime":2301.12,"body":"to see any movement in."},{"startTime":2301.12,"endTime":2303.733,"body":"It's relatively simply posed,"},{"startTime":2304.6,"endTime":2305.433,"body":"but in practice,"},{"startTime":2305.433,"endTime":2307.57,"body":"the change in angle is"},{"startTime":2305.433,"endTime":2307.57,"body":"different to measure"},{"startTime":2307.57,"endTime":2310.39,"body":"for all sorts of natural"},{"startTime":2307.57,"endTime":2310.39,"body":"reasons like something,"},{"startTime":2310.39,"endTime":2313.69,"body":"a phenomenon that was"},{"startTime":2310.39,"endTime":2313.69,"body":"understood some decades later"},{"startTime":2313.69,"endTime":2315.31,"body":"called stellar aberration,"},{"startTime":2315.31,"endTime":2317.92,"body":"which is to do with the fact"},{"startTime":2315.31,"endTime":2317.92,"body":"that the stars themselves"},{"startTime":2317.92,"endTime":2321.913,"body":"are moving with respect to"},{"startTime":2317.92,"endTime":2321.913,"body":"Earth and the solar system."},{"startTime":2322.78,"endTime":2326.05,"body":"It's also hard to"},{"startTime":2322.78,"endTime":2326.05,"body":"measure stellar parallax,"},{"startTime":2326.05,"endTime":2329.83,"body":"and these small angles due"},{"startTime":2326.05,"endTime":2329.83,"body":"to the mutation and wobble"},{"startTime":2329.83,"endTime":2331.36,"body":"of Earth's axis,"},{"startTime":2331.36,"endTime":2333.22,"body":"and perhaps principally"},{"startTime":2333.22,"endTime":2336.4,"body":"due to the proper motions"},{"startTime":2333.22,"endTime":2336.4,"body":"of stars themselves."},{"startTime":2336.4,"endTime":2340.48,"body":"Stars are shooting through"},{"startTime":2336.4,"endTime":2340.48,"body":"our galaxy the whole time"},{"startTime":2340.48,"endTime":2344.62,"body":"with a non-zero motion with"},{"startTime":2340.48,"endTime":2344.62,"body":"respect to the solar system."},{"startTime":2344.62,"endTime":2346.39,"body":"And so that rather stuffs up"},{"startTime":2346.39,"endTime":2348.04,"body":"what you think might be going on."},{"startTime":2348.91,"endTime":2351.01,"body":"But more prosaically,"},{"startTime":2351.01,"endTime":2352.96,"body":"there are difficulties with telescopes"},{"startTime":2352.96,"endTime":2354.4,"body":"and the technology of the day."},{"startTime":2354.4,"endTime":2358.96,"body":"Flex in telescopes was a"},{"startTime":2354.4,"endTime":2358.96,"body":"major, major hindrance."},{"startTime":2358.96,"endTime":2362.71,"body":"You couldn't point telescopes"},{"startTime":2358.96,"endTime":2362.71,"body":"in any meaningful way."},{"startTime":2362.71,"endTime":2365.41,"body":"There was no such thing as tracking."},{"startTime":2365.41,"endTime":2370.39,"body":"Modern telescopes absolutely"},{"startTime":2365.41,"endTime":2370.39,"body":"rely on good gear boxes,"},{"startTime":2370.39,"endTime":2372.58,"body":"precision engineered, we call them mounts,"},{"startTime":2372.58,"endTime":2374.74,"body":"but they're basically gear boxes"},{"startTime":2374.74,"endTime":2378.103,"body":"to take account of the"},{"startTime":2374.74,"endTime":2378.103,"body":"pointing and the tracking."},{"startTime":2379.06,"endTime":2380.413,"body":"No such thing then."},{"startTime":2381.28,"endTime":2385.12,"body":"So the strategy that was"},{"startTime":2381.28,"endTime":2385.12,"body":"employed by Wren and by Hooke"},{"startTime":2385.12,"endTime":2388.84,"body":"was to try and build what"},{"startTime":2385.12,"endTime":2388.84,"body":"are called zenith telescopes."},{"startTime":2388.84,"endTime":2390.37,"body":"A zenith telescope is a telescope"},{"startTime":2390.37,"endTime":2391.96,"body":"that only looks at the zenith."},{"startTime":2391.96,"endTime":2396.19,"body":"The zenith is the bit of sky"},{"startTime":2391.96,"endTime":2396.19,"body":"that's directly over our heads."},{"startTime":2396.19,"endTime":2399.58,"body":"And of course, as the"},{"startTime":2396.19,"endTime":2399.58,"body":"sky rotates above us,"},{"startTime":2399.58,"endTime":2402.73,"body":"I mean it's really the Earth"},{"startTime":2399.58,"endTime":2402.73,"body":"spinning, but as the sky,"},{"startTime":2402.73,"endTime":2404.8,"body":"as the stars move through the sky,"},{"startTime":2404.8,"endTime":2408.58,"body":"that telescope will"},{"startTime":2404.8,"endTime":2408.58,"body":"only be able to observe"},{"startTime":2408.58,"endTime":2411.79,"body":"the stars that move through"},{"startTime":2408.58,"endTime":2411.79,"body":"that particular path."},{"startTime":2411.79,"endTime":2414.76,"body":"But that's a zenith telescope for you."},{"startTime":2414.76,"endTime":2418.06,"body":"But the strategy was that if you built"},{"startTime":2418.06,"endTime":2423.06,"body":"a very, very rigid zenith telescope,"},{"startTime":2423.22,"endTime":2425.92,"body":"then maybe for the stars that you did,"},{"startTime":2425.92,"endTime":2427.72,"body":"it would be rigid so"},{"startTime":2425.92,"endTime":2427.72,"body":"you didn't have to worry"},{"startTime":2427.72,"endTime":2430.96,"body":"about pointing and tracking,"},{"startTime":2427.72,"endTime":2430.96,"body":"you'd just build it rigidly,"},{"startTime":2430.96,"endTime":2434.41,"body":"then maybe you could hope"},{"startTime":2430.96,"endTime":2434.41,"body":"to see movements of stars."},{"startTime":2434.41,"endTime":2437.53,"body":"What you'd need was a"},{"startTime":2434.41,"endTime":2437.53,"body":"really, really tall telescope"},{"startTime":2437.53,"endTime":2442.53,"body":"so that you could get the kind"},{"startTime":2437.53,"endTime":2442.53,"body":"of precision that you needed."},{"startTime":2442.57,"endTime":2444.4,"body":"And I think there were"},{"startTime":2442.57,"endTime":2444.4,"body":"various early attempts."},{"startTime":2444.4,"endTime":2447.79,"body":"Hooke was involved with building,"},{"startTime":2447.79,"endTime":2450.76,"body":"I think a 35 foot telescope."},{"startTime":2450.76,"endTime":2453.49,"body":"He cut a hole in the"},{"startTime":2450.76,"endTime":2453.49,"body":"roof of Gresham College."},{"startTime":2453.49,"endTime":2455.83,"body":"Gresham College has never let me do"},{"startTime":2455.83,"endTime":2457.993,"body":"any telescope building through their roof."},{"startTime":2459.01,"endTime":2460.63,"body":"Not sure what that's all about,"},{"startTime":2460.63,"endTime":2463.273,"body":"but actually it was"},{"startTime":2460.63,"endTime":2463.273,"body":"completely insufficient."},{"startTime":2464.41,"endTime":2466.9,"body":"But when the monument came along,"},{"startTime":2466.9,"endTime":2470.17,"body":"that amazing monument to"},{"startTime":2466.9,"endTime":2470.17,"body":"the Great Fire of London,"},{"startTime":2470.17,"endTime":2475.17,"body":"the apocalypse that happened"},{"startTime":2470.17,"endTime":2475.17,"body":"in September of 1666,"},{"startTime":2475.36,"endTime":2480.36,"body":"Wren and Hooke seized the"},{"startTime":2475.36,"endTime":2480.36,"body":"opportunity to turn this monument"},{"startTime":2480.37,"endTime":2481.72,"body":"into not only something"},{"startTime":2481.72,"endTime":2485.17,"body":"which recognized the"},{"startTime":2481.72,"endTime":2485.17,"body":"truly awful experience"},{"startTime":2485.17,"endTime":2486.943,"body":"that London had been through,"},{"startTime":2487.93,"endTime":2490.72,"body":"the fire lasted for four days,"},{"startTime":2490.72,"endTime":2494.53,"body":"two thirds of the city was destroyed,"},{"startTime":2494.53,"endTime":2497.8,"body":"13,200 houses were destroyed,"},{"startTime":2497.8,"endTime":2500.14,"body":"and 87 churches were destroyed."},{"startTime":2500.14,"endTime":2503.32,"body":"Not only was it marking"},{"startTime":2500.14,"endTime":2503.32,"body":"that dreadful thing"},{"startTime":2503.32,"endTime":2505.03,"body":"that had happened,"},{"startTime":2505.03,"endTime":2507.91,"body":"but it was turning it into"},{"startTime":2505.03,"endTime":2507.91,"body":"an opportunity to say,"},{"startTime":2507.91,"endTime":2510.493,"body":"let's learn more about our cosmos."},{"startTime":2511.63,"endTime":2513.61,"body":"Christopher Wren didn't get rich"},{"startTime":2513.61,"endTime":2516.49,"body":"after the Great Fire of London,"},{"startTime":2516.49,"endTime":2519.19,"body":"but he and the then professor of Gresham,"},{"startTime":2519.19,"endTime":2520.843,"body":"Professor of Astronomy, Hooke,"},{"startTime":2521.71,"endTime":2525.61,"body":"took it upon themselves to"},{"startTime":2521.71,"endTime":2525.61,"body":"design lots of churches,"},{"startTime":2525.61,"endTime":2528.37,"body":"St. Paul's Cathedral and other buildings"},{"startTime":2528.37,"endTime":2532.39,"body":"to rebuild London, to rebuild the society."},{"startTime":2532.39,"endTime":2535.54,"body":"And the monument is the most"},{"startTime":2532.39,"endTime":2535.54,"body":"striking example of that."},{"startTime":2535.54,"endTime":2538.123,"body":"This is Wren's initial design."},{"startTime":2539.77,"endTime":2544.77,"body":"So it had a lot going for"},{"startTime":2539.77,"endTime":2544.77,"body":"it, it's over 200 feet tall."},{"startTime":2546.19,"endTime":2549.88,"body":"And they planned it quite"},{"startTime":2546.19,"endTime":2549.88,"body":"carefully, Hooke and Wren,"},{"startTime":2549.88,"endTime":2553.333,"body":"using this monument or"},{"startTime":2549.88,"endTime":2553.333,"body":"rather this monument,"},{"startTime":2554.29,"endTime":2555.7,"body":"to actually, there wasn't,"},{"startTime":2555.7,"endTime":2558.49,"body":"you could remove the lid at"},{"startTime":2555.7,"endTime":2558.49,"body":"the time so you could see out,"},{"startTime":2558.49,"endTime":2560.09,"body":"always important for telescopes."},{"startTime":2561.1,"endTime":2564.52,"body":"So what they planned was"},{"startTime":2561.1,"endTime":2564.52,"body":"to study a particular star,"},{"startTime":2564.52,"endTime":2566.62,"body":"which goes by the name of Gamma Draconis."},{"startTime":2566.62,"endTime":2569.23,"body":"It's the bright star in the middle."},{"startTime":2569.23,"endTime":2571.9,"body":"So crucially, it's bright"},{"startTime":2569.23,"endTime":2571.9,"body":"enough to be able to see"},{"startTime":2571.9,"endTime":2576.9,"body":"from London skies, so long"},{"startTime":2571.9,"endTime":2576.9,"body":"as there isn't a cloud."},{"startTime":2577.3,"endTime":2579.49,"body":"I'm going to show you a little"},{"startTime":2577.3,"endTime":2579.49,"body":"bit of a data sheet now,"},{"startTime":2579.49,"endTime":2580.72,"body":"it's a little bit busy,"},{"startTime":2580.72,"endTime":2583.3,"body":"but let me show you the"},{"startTime":2580.72,"endTime":2583.3,"body":"crucial point of information,"},{"startTime":2583.3,"endTime":2586.0,"body":"which is why this star, Gamma Draconis,"},{"startTime":2586.0,"endTime":2589.51,"body":"was important for Wren and for Hooke."},{"startTime":2589.51,"endTime":2591.19,"body":"It's declination,"},{"startTime":2591.19,"endTime":2593.42,"body":"and you can think of declination as being"},{"startTime":2596.08,"endTime":2598.153,"body":"celestial latitude,"},{"startTime":2599.11,"endTime":2602.92,"body":"is plus 51 and a half degrees."},{"startTime":2602.92,"endTime":2607.663,"body":"So that's pretty much"},{"startTime":2602.92,"endTime":2607.663,"body":"the latitude of London."},{"startTime":2608.77,"endTime":2611.65,"body":"So that means that it should pass overhead"},{"startTime":2611.65,"endTime":2613.27,"body":"of this zenith telescope"},{"startTime":2613.27,"endTime":2616.39,"body":"that couldn't track and"},{"startTime":2613.27,"endTime":2616.39,"body":"point like normal telescopes"},{"startTime":2616.39,"endTime":2617.803,"body":"or modern telescopes."},{"startTime":2619.15,"endTime":2620.38,"body":"This is its right ascension,"},{"startTime":2620.38,"endTime":2623.41,"body":"right ascension maps to"},{"startTime":2620.38,"endTime":2623.41,"body":"you can think of that"},{"startTime":2623.41,"endTime":2625.09,"body":"as celestial longitude,"},{"startTime":2625.09,"endTime":2627.82,"body":"and a right ascension of nearly 18 hours"},{"startTime":2627.82,"endTime":2632.41,"body":"means that this particular"},{"startTime":2627.82,"endTime":2632.41,"body":"star is up in the night sky"},{"startTime":2632.41,"endTime":2636.34,"body":"over London in the northern summer."},{"startTime":2636.34,"endTime":2637.173,"body":"So it should work."},{"startTime":2637.173,"endTime":2639.76,"body":"It's, although the London skies,"},{"startTime":2639.76,"endTime":2644.47,"body":"the UK skies never get truly"},{"startTime":2639.76,"endTime":2644.47,"body":"technically astronomically dark"},{"startTime":2644.47,"endTime":2646.9,"body":"in the northern summer,"},{"startTime":2646.9,"endTime":2648.79,"body":"nonetheless with a brightness"},{"startTime":2648.79,"endTime":2652.18,"body":"of about one magnitude in the red band,"},{"startTime":2652.18,"endTime":2654.64,"body":"plenty bright enough to be able to see"},{"startTime":2654.64,"endTime":2656.533,"body":"even in a twilight sky."},{"startTime":2657.73,"endTime":2662.32,"body":"Now the measurements"},{"startTime":2657.73,"endTime":2662.32,"body":"didn't happen, didn't work,"},{"startTime":2662.32,"endTime":2665.5,"body":"didn't lead to the results"},{"startTime":2662.32,"endTime":2665.5,"body":"that were hoped for"},{"startTime":2665.5,"endTime":2667.0,"body":"and longed for."},{"startTime":2667.0,"endTime":2671.5,"body":"Hooke claimed a parallax angle of,"},{"startTime":2671.5,"endTime":2676.33,"body":"I think it was half a"},{"startTime":2671.5,"endTime":2676.33,"body":"minute of arc or something,"},{"startTime":2676.33,"endTime":2679.21,"body":"which would've been extraordinarily large,"},{"startTime":2679.21,"endTime":2682.6,"body":"and had the implication"},{"startTime":2679.21,"endTime":2682.6,"body":"that Gamma Draconis"},{"startTime":2682.6,"endTime":2686.26,"body":"would've been remarkably close to Earth,"},{"startTime":2686.26,"endTime":2689.173,"body":"which wouldn't have"},{"startTime":2686.26,"endTime":2689.173,"body":"agreed with other things."},{"startTime":2691.06,"endTime":2692.2,"body":"There were a lot of problems."},{"startTime":2692.2,"endTime":2695.86,"body":"There were horses going clip"},{"startTime":2692.2,"endTime":2695.86,"body":"clop on the roads outside,"},{"startTime":2695.86,"endTime":2699.01,"body":"and all the vibrations"},{"startTime":2695.86,"endTime":2699.01,"body":"from London traffic."},{"startTime":2699.01,"endTime":2702.49,"body":"The inherent flex in the"},{"startTime":2699.01,"endTime":2702.49,"body":"building was just insufficient"},{"startTime":2702.49,"endTime":2705.67,"body":"to be able to measure the"},{"startTime":2702.49,"endTime":2705.67,"body":"true parallax of this star,"},{"startTime":2705.67,"endTime":2708.943,"body":"which is actually just 21 milliarcseconds."},{"startTime":2710.74,"endTime":2714.443,"body":"So an arc second is"},{"startTime":2710.74,"endTime":2714.443,"body":"one 3600th of a degree,"},{"startTime":2716.89,"endTime":2718.18,"body":"and a milliarcsecond"},{"startTime":2718.18,"endTime":2722.23,"body":"is one 1000th of that very small angle."},{"startTime":2722.23,"endTime":2723.4,"body":"There was no hope."},{"startTime":2723.4,"endTime":2728.09,"body":"It was a 200 foot building in noisy London"},{"startTime":2729.52,"endTime":2731.35,"body":"with even the presumably"},{"startTime":2731.35,"endTime":2734.11,"body":"relatively light traffic"},{"startTime":2731.35,"endTime":2734.11,"body":"of the day going past"},{"startTime":2734.11,"endTime":2735.79,"body":"that you had the slightest chances"},{"startTime":2735.79,"endTime":2739.42,"body":"of being able to measure"},{"startTime":2735.79,"endTime":2739.42,"body":"accurate positions."},{"startTime":2739.42,"endTime":2742.723,"body":"So it didn't happen, but"},{"startTime":2739.42,"endTime":2742.723,"body":"it was a brave attempt."},{"startTime":2743.83,"endTime":2745.6,"body":"It was a brave attempt that really,"},{"startTime":2745.6,"endTime":2748.06,"body":"you could interpret it as a null result."},{"startTime":2748.06,"endTime":2753.04,"body":"You didn't see systematic"},{"startTime":2748.06,"endTime":2753.04,"body":"repeatable, parallactic angle,"},{"startTime":2753.04,"endTime":2755.203,"body":"parallax angle changes."},{"startTime":2757.03,"endTime":2760.87,"body":"So this null result is"},{"startTime":2757.03,"endTime":2760.87,"body":"actually the real reason"},{"startTime":2760.87,"endTime":2762.97,"body":"why it wasn't possible for them"},{"startTime":2762.97,"endTime":2765.73,"body":"with the technology that"},{"startTime":2762.97,"endTime":2765.73,"body":"they had at the time"},{"startTime":2765.73,"endTime":2769.03,"body":"to determine the size"},{"startTime":2765.73,"endTime":2769.03,"body":"scale to the nearby stars,"},{"startTime":2769.03,"endTime":2773.11,"body":"and hence to get a grasp"},{"startTime":2769.03,"endTime":2773.11,"body":"on how big the cosmos was"},{"startTime":2773.11,"endTime":2775.663,"body":"because it was bigger"},{"startTime":2773.11,"endTime":2775.663,"body":"than they had thought."},{"startTime":2776.68,"endTime":2779.65,"body":"Probably they wouldn't have"},{"startTime":2776.68,"endTime":2779.65,"body":"attempted the experiment"},{"startTime":2779.65,"endTime":2783.21,"body":"had they had any instinct"},{"startTime":2779.65,"endTime":2783.21,"body":"that the idea was only one,"},{"startTime":2783.21,"endTime":2788.21,"body":"it was only 21000ths of"},{"startTime":2783.21,"endTime":2788.21,"body":"one 3600th of one degree."},{"startTime":2791.56,"endTime":2793.24,"body":"So at least it gave them a sense,"},{"startTime":2793.24,"endTime":2796.21,"body":"well, the stars have to"},{"startTime":2793.24,"endTime":2796.21,"body":"be further away than this."},{"startTime":2796.21,"endTime":2798.673,"body":"The cosmos has to be bigger than this."},{"startTime":2800.26,"endTime":2804.13,"body":"Let me now talk about planetary orbits."},{"startTime":2804.13,"endTime":2806.38,"body":"Wren keenly used telescopes"},{"startTime":2806.38,"endTime":2810.01,"body":"wherever he could in Wadham College."},{"startTime":2810.01,"endTime":2811.993,"body":"I believe in New College in Oxford,"},{"startTime":2812.98,"endTime":2816.13,"body":"here in Gresham, and elsewhere."},{"startTime":2816.13,"endTime":2817.93,"body":"And planets were clearly something"},{"startTime":2817.93,"endTime":2820.9,"body":"people studied a lot at the time"},{"startTime":2820.9,"endTime":2824.53,"body":"because they moved through"},{"startTime":2820.9,"endTime":2824.53,"body":"the sky relatively rapidly,"},{"startTime":2824.53,"endTime":2829.03,"body":"at least compared with the"},{"startTime":2824.53,"endTime":2829.03,"body":"distance stellar background."},{"startTime":2829.03,"endTime":2832.123,"body":"What we know now is that orbital paths,"},{"startTime":2833.56,"endTime":2837.88,"body":"which I described in my Gresham"},{"startTime":2833.56,"endTime":2837.88,"body":"lecture in my first year,"},{"startTime":2837.88,"endTime":2840.223,"body":"entitled Shapes of Free Fall,"},{"startTime":2841.36,"endTime":2844.9,"body":"orbital paths now followed"},{"startTime":2841.36,"endTime":2844.9,"body":"by celestial objects"},{"startTime":2844.9,"endTime":2846.47,"body":"orbiting around stars"},{"startTime":2847.45,"endTime":2852.45,"body":"are given by this beautiful"},{"startTime":2847.45,"endTime":2852.45,"body":"yet very simple equation"},{"startTime":2852.88,"endTime":2856.78,"body":"that all of the different geometric shapes"},{"startTime":2856.78,"endTime":2859.63,"body":"that you can get by"},{"startTime":2856.78,"endTime":2859.63,"body":"putting in different values"},{"startTime":2859.63,"endTime":2861.613,"body":"of the letter either,"},{"startTime":2862.66,"endTime":2865.81,"body":"this entire equation describes"},{"startTime":2865.81,"endTime":2868.84,"body":"all the different shapes"},{"startTime":2865.81,"endTime":2868.84,"body":"you can get for all orbits,"},{"startTime":2868.84,"endTime":2870.37,"body":"for comets, for planets,"},{"startTime":2870.37,"endTime":2872.74,"body":"for stars orbiting around one another."},{"startTime":2872.74,"endTime":2874.213,"body":"It's truly beautiful."},{"startTime":2875.11,"endTime":2878.68,"body":"Now various people were already on the way"},{"startTime":2878.68,"endTime":2881.41,"body":"to working out how,"},{"startTime":2881.41,"endTime":2884.11,"body":"what the orbital paths must be,"},{"startTime":2884.11,"endTime":2886.93,"body":"particularly as the decades went by."},{"startTime":2886.93,"endTime":2889.0,"body":"And telescopes did improve a little bit,"},{"startTime":2889.0,"endTime":2892.423,"body":"although not in pointing and in tracking."},{"startTime":2893.68,"endTime":2897.34,"body":"Hooke's own 1670 Gresham lecture"},{"startTime":2897.34,"endTime":2899.56,"body":"had certainly grasped that gravity,"},{"startTime":2899.56,"endTime":2904.33,"body":"gravitational attraction"},{"startTime":2899.56,"endTime":2904.33,"body":"applied to all celestial bodies."},{"startTime":2904.33,"endTime":2908.71,"body":"And he also discussed"},{"startTime":2904.33,"endTime":2908.71,"body":"the fact that he thought,"},{"startTime":2908.71,"endTime":2910.51,"body":"or some years later,"},{"startTime":2910.51,"endTime":2912.19,"body":"he discussed the fact that he thought"},{"startTime":2912.19,"endTime":2915.1,"body":"there was an inverse square dependence"},{"startTime":2915.1,"endTime":2917.263,"body":"on that gravitational attraction,"},{"startTime":2918.34,"endTime":2922.813,"body":"which he communicated in"},{"startTime":2918.34,"endTime":2922.813,"body":"a letter to Isaac Newton."},{"startTime":2923.83,"endTime":2925.9,"body":"Isaac Newton is the person"},{"startTime":2925.9,"endTime":2929.11,"body":"who gets all the credit"},{"startTime":2925.9,"endTime":2929.11,"body":"for this particular law,"},{"startTime":2929.11,"endTime":2932.44,"body":"which is very famous and"},{"startTime":2929.11,"endTime":2932.44,"body":"used every day in physics,"},{"startTime":2932.44,"endTime":2935.113,"body":"the inverse square law of gravity."},{"startTime":2935.98,"endTime":2939.07,"body":"It simply says that any"},{"startTime":2935.98,"endTime":2939.07,"body":"acceleration that you feel"},{"startTime":2939.07,"endTime":2941.2,"body":"goes as the square of the distance"},{"startTime":2941.2,"endTime":2943.663,"body":"between the two bodies involved."},{"startTime":2944.8,"endTime":2948.763,"body":"And the graphical form"},{"startTime":2944.8,"endTime":2948.763,"body":"takes that sort of shape."},{"startTime":2949.72,"endTime":2952.57,"body":"Now what Newton did was to make the link"},{"startTime":2952.57,"endTime":2955.78,"body":"between this inverse square law"},{"startTime":2955.78,"endTime":2959.59,"body":"and those orbital shapes"},{"startTime":2955.78,"endTime":2959.59,"body":"known as the conic sections"},{"startTime":2959.59,"endTime":2962.77,"body":"that I mentioned a couple of minutes ago."},{"startTime":2962.77,"endTime":2964.39,"body":"He had to invent new maths to do it,"},{"startTime":2964.39,"endTime":2967.603,"body":"but he did it and it was"},{"startTime":2964.39,"endTime":2967.603,"body":"a massive achievement."},{"startTime":2968.53,"endTime":2970.9,"body":"But one of the remarkable things"},{"startTime":2970.9,"endTime":2975.88,"body":"is that Hooke actually"},{"startTime":2970.9,"endTime":2975.88,"body":"wasn't the only person"},{"startTime":2975.88,"endTime":2978.76,"body":"to discern the inverse square law"},{"startTime":2978.76,"endTime":2981.46,"body":"of gravitational attraction."},{"startTime":2981.46,"endTime":2983.29,"body":"Wren himself did."},{"startTime":2983.29,"endTime":2988.24,"body":"Hooke also himself did"},{"startTime":2983.29,"endTime":2988.24,"body":"independently of Newton."},{"startTime":2988.24,"endTime":2990.913,"body":"And Newton does actually acknowledge this."},{"startTime":2991.78,"endTime":2996.78,"body":"And I think the very fact"},{"startTime":2991.78,"endTime":2996.78,"body":"that Wren's mind was so agile"},{"startTime":2998.11,"endTime":2999.88,"body":"that in the face of all the tragedies"},{"startTime":2999.88,"endTime":3002.01,"body":"that happened in his life,"},{"startTime":3002.01,"endTime":3007.01,"body":"the pain and anguish of war on"},{"startTime":3002.01,"endTime":3007.01,"body":"his doorstep in his homeland,"},{"startTime":3007.98,"endTime":3010.353,"body":"losing close family members,"},{"startTime":3011.28,"endTime":3014.52,"body":"yet he could look out of his horizons"},{"startTime":3014.52,"endTime":3017.52,"body":"and build, think about building churches"},{"startTime":3017.52,"endTime":3019.2,"body":"and building society,"},{"startTime":3019.2,"endTime":3023.01,"body":"think about how planetary orbits"},{"startTime":3019.2,"endTime":3023.01,"body":"worked in our solar system"},{"startTime":3023.01,"endTime":3024.72,"body":"and beyond."},{"startTime":3024.72,"endTime":3027.81,"body":"Christopher Wren's mind"},{"startTime":3024.72,"endTime":3027.81,"body":"could span the cosmos"},{"startTime":3027.81,"endTime":3032.283,"body":"as it was known then with ease"},{"startTime":3027.81,"endTime":3032.283,"body":"and with joyful curiosity."},{"startTime":3033.3,"endTime":3038.1,"body":"Christopher Wren didn't seek"},{"startTime":3033.3,"endTime":3038.1,"body":"acknowledgement or credit"},{"startTime":3038.1,"endTime":3039.72,"body":"for having come up with"},{"startTime":3039.72,"endTime":3044.72,"body":"this foundational fundamental"},{"startTime":3039.72,"endTime":3044.72,"body":"inverse square law of physics."},{"startTime":3046.02,"endTime":3050.49,"body":"And yet he was a joyful contributor to it."},{"startTime":3050.49,"endTime":3052.77,"body":"Isaac Newton was another of those"},{"startTime":3052.77,"endTime":3057.3,"body":"somewhat cantankerous"},{"startTime":3052.77,"endTime":3057.3,"body":"scientists of history."},{"startTime":3057.3,"endTime":3061.35,"body":"And yet Christopher Wren"},{"startTime":3057.3,"endTime":3061.35,"body":"could acknowledge graciously"},{"startTime":3061.35,"endTime":3065.64,"body":"and engage with all the"},{"startTime":3061.35,"endTime":3065.64,"body":"discoveries and the inventions"},{"startTime":3065.64,"endTime":3070.263,"body":"of Isaac Newton as well"},{"startTime":3065.64,"endTime":3070.263,"body":"as Hooke and others."},{"startTime":3071.58,"endTime":3075.24,"body":"Christopher Wren's Cosmos"},{"startTime":3071.58,"endTime":3075.24,"body":"was smaller than ours"},{"startTime":3075.24,"endTime":3080.24,"body":"as the non-success of the"},{"startTime":3075.24,"endTime":3080.24,"body":"zenith telescope demonstrated."},{"startTime":3081.63,"endTime":3085.98,"body":"They knew about fewer"},{"startTime":3081.63,"endTime":3085.98,"body":"planets than we know now."},{"startTime":3085.98,"endTime":3088.47,"body":"Obviously they only knew"},{"startTime":3085.98,"endTime":3088.47,"body":"about the solar system,"},{"startTime":3088.47,"endTime":3091.47,"body":"but Uranus and Neptune"},{"startTime":3088.47,"endTime":3091.47,"body":"hadn't been discovered."},{"startTime":3091.47,"endTime":3093.33,"body":"That was to come later."},{"startTime":3093.33,"endTime":3095.07,"body":"The number of galaxies known at the time"},{"startTime":3095.07,"endTime":3097.08,"body":"was pretty close to one."},{"startTime":3097.08,"endTime":3099.123,"body":"That didn't come until Herschel."},{"startTime":3100.08,"endTime":3102.6,"body":"But the expanse of Christopher Wen's mind,"},{"startTime":3102.6,"endTime":3105.33,"body":"his polymath approach to life,"},{"startTime":3105.33,"endTime":3109.98,"body":"showed that he was not in"},{"startTime":3105.33,"endTime":3109.98,"body":"some narrow disciplinary silo."},{"startTime":3109.98,"endTime":3111.6,"body":"He was truly collaborative."},{"startTime":3111.6,"endTime":3115.65,"body":"He was not seizing credit,"},{"startTime":3111.6,"endTime":3115.65,"body":"he was outward-looking,"},{"startTime":3115.65,"endTime":3118.86,"body":"manifestly church"},{"startTime":3115.65,"endTime":3118.86,"body":"building, society building"},{"startTime":3118.86,"endTime":3122.22,"body":"after the dreadful apocalypse"},{"startTime":3118.86,"endTime":3122.22,"body":"that hit London in 1666."},{"startTime":3125.25,"endTime":3129.153,"body":"I only learnt yesterday,"},{"startTime":3125.25,"endTime":3129.153,"body":"Christopher Wren was an MP."},{"startTime":3130.14,"endTime":3132.123,"body":"How outward-looking is that?"},{"startTime":3133.38,"endTime":3138.123,"body":"Truly Christopher Wren's"},{"startTime":3133.38,"endTime":3138.123,"body":"Cosmos was larger than ours."},{"startTime":3140.97,"endTime":3143.61,"body":"So there is a memorial to Christopher Wren"},{"startTime":3143.61,"endTime":3145.32,"body":"in St. Paul's Cathedral."},{"startTime":3145.32,"endTime":3147.54,"body":"I'm going to make sure I take a look at it"},{"startTime":3147.54,"endTime":3150.42,"body":"at the service on Saturday."},{"startTime":3150.42,"endTime":3152.4,"body":"And I just want to draw your attention"},{"startTime":3152.4,"endTime":3154.743,"body":"to this little bit at the end."},{"startTime":3156.54,"endTime":3161.54,"body":"Reader, if you require"},{"startTime":3156.54,"endTime":3161.54,"body":"a monument, look around."},{"startTime":3165.75,"endTime":3168.78,"body":"Christopher Wren lived more than 90 years,"},{"startTime":3168.78,"endTime":3171.033,"body":"and as his memorial says,"},{"startTime":3173.04,"endTime":3177.54,"body":"not for himself but for the public good."},{"startTime":3177.54,"endTime":3182.54,"body":"Truly, Christopher Wren's"},{"startTime":3177.54,"endTime":3182.54,"body":"Cosmos was enormous,"},{"startTime":3182.76,"endTime":3185.553,"body":"and truly he was an influencer."},{"startTime":3186.72,"endTime":3188.166,"body":"And that's all, thank you."},{"startTime":3188.166,"endTime":3191.333,"body":"(audience applauding)"},{"startTime":3195.639,"endTime":3198.75,"body":"- Do I see any hands up in the audience?"},{"startTime":3198.75,"endTime":3200.22,"body":"I should just briefly warn you"},{"startTime":3200.22,"endTime":3201.72,"body":"that we're in an"},{"startTime":3200.22,"endTime":3201.72,"body":"educational establishment,"},{"startTime":3201.72,"endTime":3205.5,"body":"which always means we have to"},{"startTime":3201.72,"endTime":3205.5,"body":"finish precisely on the hour."},{"startTime":3205.5,"endTime":3207.96,"body":"I do have a couple of questions online"},{"startTime":3207.96,"endTime":3210.033,"body":"which I will just pick up."},{"startTime":3210.93,"endTime":3211.763,"body":"The first one I think"},{"startTime":3211.763,"endTime":3214.05,"body":"is just a sort of matter"},{"startTime":3211.763,"endTime":3214.05,"body":"of fact question, which is,"},{"startTime":3214.05,"endTime":3216.78,"body":"is there any evidence as to"},{"startTime":3214.05,"endTime":3216.78,"body":"whether the far side of the moon"},{"startTime":3216.78,"endTime":3220.86,"body":"in Wren's model had any"},{"startTime":3216.78,"endTime":3220.86,"body":"features, or was it featureless,"},{"startTime":3220.86,"endTime":3223.26,"body":"asked someone masquerading"},{"startTime":3223.26,"endTime":3226.32,"body":"under the name of Meta Mathematics online."},{"startTime":3226.32,"endTime":3227.7,"body":"- Goodness, an interesting question"},{"startTime":3227.7,"endTime":3229.143,"body":"from Meta Mathematics then."},{"startTime":3230.1,"endTime":3232.56,"body":"Christopher Wren couldn't"},{"startTime":3230.1,"endTime":3232.56,"body":"have known anything"},{"startTime":3232.56,"endTime":3234.9,"body":"about the far side of the moon."},{"startTime":3234.9,"endTime":3237.78,"body":"It's tightly locked with respect to Earth."},{"startTime":3237.78,"endTime":3240.78,"body":"The far side of the moon is"},{"startTime":3237.78,"endTime":3240.78,"body":"always the far side of the moon."},{"startTime":3240.78,"endTime":3242.01,"body":"It has erroneously been called"},{"startTime":3242.01,"endTime":3243.84,"body":"the dark side of the moon by the way,"},{"startTime":3243.84,"endTime":3246.51,"body":"but it isn't dark when"},{"startTime":3243.84,"endTime":3246.51,"body":"it's new moon on Earth."},{"startTime":3246.51,"endTime":3247.83,"body":"So that's not true."},{"startTime":3247.83,"endTime":3251.37,"body":"Christopher Wren had no means of knowing"},{"startTime":3251.37,"endTime":3252.54,"body":"what was on the far side."},{"startTime":3252.54,"endTime":3255.42,"body":"It's only today with lunar"},{"startTime":3252.54,"endTime":3255.42,"body":"reconnaissance missions"},{"startTime":3255.42,"endTime":3257.7,"body":"that we have access to that information,"},{"startTime":3257.7,"endTime":3262.65,"body":"and that feature of the lunar model"},{"startTime":3262.65,"endTime":3264.84,"body":"in the bottom right corner of"},{"startTime":3262.65,"endTime":3264.84,"body":"that portrait that I showed,"},{"startTime":3264.84,"endTime":3267.72,"body":"that's in the Sheldonian"},{"startTime":3264.84,"endTime":3267.72,"body":"Theater, we only see the front."},{"startTime":3267.72,"endTime":3269.82,"body":"- [Host] Yeah, okay, we only see one side."},{"startTime":3271.32,"endTime":3272.27,"body":"The gentleman here."},{"startTime":3274.663,"endTime":3275.496,"body":"- Thank you."},{"startTime":3275.496,"endTime":3277.41,"body":"- Can you give us a sense"},{"startTime":3275.496,"endTime":3277.41,"body":"of the size and scale"},{"startTime":3277.41,"endTime":3280.41,"body":"of the lenses that they were"},{"startTime":3277.41,"endTime":3280.41,"body":"endeavoring to grind out"},{"startTime":3280.41,"endTime":3281.881,"body":"in those days?"},{"startTime":3281.881,"endTime":3285.18,"body":"And what quality of images"},{"startTime":3285.18,"endTime":3287.1,"body":"would they have perhaps seen through them,"},{"startTime":3287.1,"endTime":3288.64,"body":"if you could just give a"},{"startTime":3287.1,"endTime":3288.64,"body":"sense of that that'd be great,"},{"startTime":3288.64,"endTime":3289.473,"body":"thank you."},{"startTime":3290.46,"endTime":3293.7,"body":"- So I think the size"},{"startTime":3290.46,"endTime":3293.7,"body":"scales of the lenses,"},{"startTime":3293.7,"endTime":3295.2,"body":"there would be quite a bit of variety."},{"startTime":3295.2,"endTime":3298.743,"body":"In microscopes, of course, they"},{"startTime":3295.2,"endTime":3298.743,"body":"would probably be very tiny."},{"startTime":3299.97,"endTime":3303.33,"body":"But for doing astronomy, you"},{"startTime":3299.97,"endTime":3303.33,"body":"need lots of collecting area,"},{"startTime":3303.33,"endTime":3305.16,"body":"which means big lenses."},{"startTime":3305.16,"endTime":3309.63,"body":"And getting uniformity and"},{"startTime":3305.16,"endTime":3309.63,"body":"homogeneity in the glass"},{"startTime":3309.63,"endTime":3311.43,"body":"was hard, nevermind, you know,"},{"startTime":3311.43,"endTime":3313.71,"body":"in the density of the glass was hard,"},{"startTime":3313.71,"endTime":3317.58,"body":"nevermind grinding the"},{"startTime":3313.71,"endTime":3317.58,"body":"surface to a smoothness"},{"startTime":3317.58,"endTime":3321.3,"body":"that depending on what focal"},{"startTime":3317.58,"endTime":3321.3,"body":"length you are interested in,"},{"startTime":3321.3,"endTime":3324.573,"body":"has to be better than a very"},{"startTime":3321.3,"endTime":3324.573,"body":"small fraction of a millimeter."},{"startTime":3326.168,"endTime":3329.52,"body":"But the, I've not been in"},{"startTime":3326.168,"endTime":3329.52,"body":"the monument in London,"},{"startTime":3329.52,"endTime":3331.92,"body":"but I think my impression is"},{"startTime":3331.92,"endTime":3334.8,"body":"it was a couple of feet"},{"startTime":3331.92,"endTime":3334.8,"body":"or three or four feet,"},{"startTime":3334.8,"endTime":3335.633,"body":"something like that."},{"startTime":3335.633,"endTime":3339.03,"body":"So non-trivial to make,"},{"startTime":3339.03,"endTime":3342.48,"body":"very, very difficult to make in fact."},{"startTime":3342.48,"endTime":3344.13,"body":"Sorry, I think you had another"},{"startTime":3342.48,"endTime":3344.13,"body":"question right at the end."},{"startTime":3344.13,"endTime":3346.59,"body":"- [Speaker 2] The quality of the images"},{"startTime":3346.59,"endTime":3348.143,"body":"that they able to see,"},{"startTime":3348.143,"endTime":3349.65,"body":"or the lack of quality of"},{"startTime":3348.143,"endTime":3349.65,"body":"the image I should say."},{"startTime":3349.65,"endTime":3352.14,"body":"- Yeah, so I think our best handle"},{"startTime":3352.14,"endTime":3353.97,"body":"on the quality of the images,"},{"startTime":3353.97,"endTime":3356.01,"body":"'cause obviously that image of the comet"},{"startTime":3356.01,"endTime":3358.68,"body":"that I showed you, comets are really big,"},{"startTime":3358.68,"endTime":3362.64,"body":"and I'm sure people didn't use"},{"startTime":3358.68,"endTime":3362.64,"body":"telescopes very much at all"},{"startTime":3362.64,"endTime":3367.623,"body":"to, other than the sort of"},{"startTime":3362.64,"endTime":3367.623,"body":"the actual measuring the path."},{"startTime":3368.55,"endTime":3370.863,"body":"That was a naked eye drawing."},{"startTime":3373.41,"endTime":3376.74,"body":"But the best handle we have"},{"startTime":3373.41,"endTime":3376.74,"body":"on the quality of the images"},{"startTime":3376.74,"endTime":3380.52,"body":"is the fact that they couldn't discern"},{"startTime":3380.52,"endTime":3383.79,"body":"Saturn's rings as rings."},{"startTime":3383.79,"endTime":3388.05,"body":"I mean even with a"},{"startTime":3383.79,"endTime":3388.05,"body":"relatively straightforward,"},{"startTime":3388.05,"endTime":3392.07,"body":"very inexpensive telescope"},{"startTime":3388.05,"endTime":3392.07,"body":"that could be, you know,"},{"startTime":3392.07,"endTime":3395.52,"body":"a child's Christmas present or something."},{"startTime":3395.52,"endTime":3399.15,"body":"You can see the rings of Saturn as rings."},{"startTime":3399.15,"endTime":3401.73,"body":"I mean maybe it helps"},{"startTime":3399.15,"endTime":3401.73,"body":"that you know the answer"},{"startTime":3401.73,"endTime":3403.11,"body":"and you know what you're looking for."},{"startTime":3403.11,"endTime":3408.11,"body":"But the very fact that"},{"startTime":3403.11,"endTime":3408.11,"body":"people referred to Saturn"},{"startTime":3408.66,"endTime":3411.18,"body":"as being a three body planet."},{"startTime":3411.18,"endTime":3412.17,"body":"There was the main body"},{"startTime":3412.17,"endTime":3414.96,"body":"and then there were these"},{"startTime":3412.17,"endTime":3414.96,"body":"two bulges either side,"},{"startTime":3414.96,"endTime":3415.83,"body":"which I think is what led"},{"startTime":3415.83,"endTime":3419.553,"body":"to Wren's elliptical ring interpretation,"},{"startTime":3420.87,"endTime":3423.06,"body":"and then understandably"},{"startTime":3420.87,"endTime":3423.06,"body":"being very startled"},{"startTime":3423.06,"endTime":3426.09,"body":"when the rings became edge on,"},{"startTime":3426.09,"endTime":3430.35,"body":"and so invisible given the"},{"startTime":3426.09,"endTime":3430.35,"body":"collecting area of the day."},{"startTime":3430.35,"endTime":3431.82,"body":"I think the best handle we have"},{"startTime":3431.82,"endTime":3436.05,"body":"is just imagine the image"},{"startTime":3431.82,"endTime":3436.05,"body":"quality that you would get"},{"startTime":3436.05,"endTime":3440.07,"body":"if you had a sufficiently low-grade optics"},{"startTime":3440.07,"endTime":3443.49,"body":"and blurred telescope that"},{"startTime":3440.07,"endTime":3443.49,"body":"you could see it was elongated"},{"startTime":3443.49,"endTime":3446.7,"body":"and a little bit bulgy"},{"startTime":3443.49,"endTime":3446.7,"body":"here, but not so bulgy"},{"startTime":3446.7,"endTime":3448.35,"body":"you couldn't tell the bigger"},{"startTime":3446.7,"endTime":3448.35,"body":"bit was in the middle."},{"startTime":3448.35,"endTime":3450.663,"body":"I think that's what we're talking about."},{"startTime":3451.53,"endTime":3454.26,"body":"And yet he was transfixed by it,"},{"startTime":3454.26,"endTime":3455.79,"body":"and committed to making"},{"startTime":3455.79,"endTime":3458.103,"body":"lots and lots and lots of measurements."},{"startTime":3460.02,"endTime":3460.853,"body":"- Super answer."},{"startTime":3460.853,"endTime":3463.593,"body":"Yeah, I'm afraid time is going"},{"startTime":3460.853,"endTime":3463.593,"body":"to press on us, I'm afraid."},{"startTime":3465.21,"endTime":3467.22,"body":"It's a rare treat"},{"startTime":3465.21,"endTime":3467.22,"body":"listening to that lecture."},{"startTime":3467.22,"endTime":3469.29,"body":"I mean, I've never heard a lecture"},{"startTime":3469.29,"endTime":3472.59,"body":"about Wren's astronomy"},{"startTime":3469.29,"endTime":3472.59,"body":"before, so that was rare."},{"startTime":3472.59,"endTime":3476.31,"body":"To hear it from a professional"},{"startTime":3472.59,"endTime":3476.31,"body":"astronomer is double rare."},{"startTime":3476.31,"endTime":3479.49,"body":"To hear it from a research"},{"startTime":3476.31,"endTime":3479.49,"body":"active professional astronomer"},{"startTime":3479.49,"endTime":3481.17,"body":"on the top of her career,"},{"startTime":3481.17,"endTime":3482.52,"body":"I mean that is going some."},{"startTime":3482.52,"endTime":3484.86,"body":"So that was just an amazing evening,"},{"startTime":3484.86,"endTime":3486.18,"body":"Katherine, thank you very much."},{"startTime":3486.18,"endTime":3487.215,"body":"Thank you."},{"startTime":3487.215,"endTime":3490.382,"body":"(audience applauding)"}]}