{"version":"1.0.0","segments":[{"startTime":0.23,"endTime":4.34,"body":"- Hello and welcome to this"},{"startTime":0.23,"endTime":4.34,"body":"Gresham College lecture"},{"startTime":4.34,"endTime":7.253,"body":"on the broken cosmic distance ladder."},{"startTime":8.39,"endTime":10.07,"body":"My name is Roberto Trotta,"},{"startTime":10.07,"endTime":13.3,"body":"I'm a visiting professor of"},{"startTime":10.07,"endTime":13.3,"body":"cosmology at Gresham College"},{"startTime":13.3,"endTime":15.15,"body":"and a professor of astro-statistics"},{"startTime":15.15,"endTime":16.9,"body":"at Imperial College London,"},{"startTime":16.9,"endTime":18.57,"body":"currently on leave of absence,"},{"startTime":18.57,"endTime":22.11,"body":"and visiting the International"},{"startTime":18.57,"endTime":22.11,"body":"School for Advanced Studies"},{"startTime":22.11,"endTime":23.95,"body":"in Trieste, Italy,"},{"startTime":23.95,"endTime":26.963,"body":"from where I'm giving this lecture today."},{"startTime":29.93,"endTime":31.72,"body":"We're going to talk about"},{"startTime":31.72,"endTime":35.2,"body":"how to measure distances in the universe,"},{"startTime":35.2,"endTime":38.7,"body":"which is a surprisingly hard problem."},{"startTime":38.7,"endTime":41.74,"body":"In fact, if we look to"},{"startTime":38.7,"endTime":41.74,"body":"the Moon in the sky,"},{"startTime":41.74,"endTime":44.443,"body":"sometimes it appears so close,"},{"startTime":45.4,"endTime":48.05,"body":"it feels as if almost"},{"startTime":45.4,"endTime":48.05,"body":"we could just touch it,"},{"startTime":48.05,"endTime":51.94,"body":"and reach out to it, and"},{"startTime":48.05,"endTime":51.94,"body":"pluck it out of the sky,"},{"startTime":51.94,"endTime":53.63,"body":"it appears so close to us,"},{"startTime":53.63,"endTime":56.43,"body":"we can make out all sorts"},{"startTime":53.63,"endTime":56.43,"body":"of things on its face"},{"startTime":56.43,"endTime":57.95,"body":"when it's fully illuminated."},{"startTime":57.95,"endTime":61.35,"body":"Some people see a rabbit"},{"startTime":57.95,"endTime":61.35,"body":"on the face of the Moon,"},{"startTime":61.35,"endTime":63.86,"body":"some cultures see a toad, a lady,"},{"startTime":63.86,"endTime":67.21,"body":"a man with a bundle on his"},{"startTime":63.86,"endTime":67.21,"body":"back, even a man's face,"},{"startTime":67.21,"endTime":70.48,"body":"which I never quite could understand"},{"startTime":70.48,"endTime":72.79,"body":"and could never quite make out."},{"startTime":72.79,"endTime":76.52,"body":"So how far is the Moon,"},{"startTime":72.79,"endTime":76.52,"body":"and how can we tell,"},{"startTime":76.52,"endTime":78.26,"body":"especially in antiquity,"},{"startTime":78.26,"endTime":79.94,"body":"when technology and science"},{"startTime":79.94,"endTime":82.43,"body":"were not quite so advanced"},{"startTime":79.94,"endTime":82.43,"body":"as they are today,"},{"startTime":82.43,"endTime":85.74,"body":"and determining distances"},{"startTime":82.43,"endTime":85.74,"body":"to objects in the sky"},{"startTime":85.74,"endTime":88.78,"body":"was always a big challenge?"},{"startTime":88.78,"endTime":90.08,"body":"And in fact,"},{"startTime":90.08,"endTime":92.12,"body":"while the Moon seems tantalizingly close,"},{"startTime":92.12,"endTime":94.81,"body":"sometimes, the stars, on the other hand,"},{"startTime":94.81,"endTime":98.07,"body":"appear always to be forever out of reach,"},{"startTime":98.07,"endTime":102.26,"body":"aloof and distant, and"},{"startTime":98.07,"endTime":102.26,"body":"forever unreachable."},{"startTime":102.26,"endTime":104.41,"body":"In fact, so unreachable and so aloof"},{"startTime":104.41,"endTime":108.56,"body":"that W.H. Auden, in his"},{"startTime":104.41,"endTime":108.56,"body":"poem \"The More Loving One\""},{"speaker":"described them thus","startTime":111.167,"endTime":113.977,"body":"\"How should we like it were stars to burn"},{"speaker":"described them thus","startTime":113.977,"endTime":117.547,"body":"\"with a passion for us"},{"speaker":"described them thus","startTime":113.977,"endTime":117.547,"body":"we could not return?"},{"speaker":"described them thus","startTime":117.547,"endTime":120.257,"body":"\"If equal affection cannot be,"},{"speaker":"described them thus","startTime":120.257,"endTime":122.033,"body":"\"let the more loving one be me."},{"speaker":"described them thus","startTime":123.117,"endTime":125.187,"body":"\"Admirer, as I think I am,"},{"speaker":"described them thus","startTime":125.187,"endTime":127.417,"body":"\"of stars that do not give a damn,"},{"speaker":"described them thus","startTime":127.417,"endTime":129.797,"body":"\"I cannot, now I see them, say,"},{"speaker":"described them thus","startTime":129.797,"endTime":131.717,"body":"\"I have missed one terribly all day.\""},{"speaker":"described them thus","startTime":132.99,"endTime":134.52,"body":"So stars are distant,"},{"speaker":"described them thus","startTime":134.52,"endTime":139.09,"body":"stars are really out of reach of us,"},{"speaker":"described them thus","startTime":139.09,"endTime":142.02,"body":"except when perhaps we"},{"speaker":"described them thus","startTime":139.09,"endTime":142.02,"body":"see a shooting star,"},{"speaker":"described them thus","startTime":142.02,"endTime":143.74,"body":"which of course is not a star at all,"},{"speaker":"described them thus","startTime":143.74,"endTime":146.21,"body":"it's just a little piece"},{"speaker":"described them thus","startTime":143.74,"endTime":146.21,"body":"of rock, a meteorite,"},{"speaker":"described them thus","startTime":146.21,"endTime":147.58,"body":"burning up in the atmosphere,"},{"speaker":"described them thus","startTime":147.58,"endTime":151.12,"body":"which however does give us"},{"speaker":"described them thus","startTime":147.58,"endTime":151.12,"body":"the illusion that stars,"},{"speaker":"described them thus","startTime":151.12,"endTime":153.27,"body":"for a fleetingly short moment,"},{"speaker":"described them thus","startTime":153.27,"endTime":154.943,"body":"come to within our reach."},{"speaker":"described them thus","startTime":156.37,"endTime":160.74,"body":"So how far away is the Moon, and the Sun,"},{"speaker":"described them thus","startTime":160.74,"endTime":163.69,"body":"and the thousands of stars"},{"speaker":"described them thus","startTime":160.74,"endTime":163.69,"body":"that bejewel the night?"},{"speaker":"described them thus","startTime":163.69,"endTime":165.38,"body":"And what about nebulae,"},{"speaker":"described them thus","startTime":165.38,"endTime":167.79,"body":"those fuzzy, glowing patches of light"},{"speaker":"described them thus","startTime":167.79,"endTime":170.6,"body":"that only the big telescopes"},{"speaker":"described them thus","startTime":167.79,"endTime":170.6,"body":"of the 20th century"},{"speaker":"described them thus","startTime":170.6,"endTime":172.98,"body":"could reveal with some clarity,"},{"speaker":"described them thus","startTime":172.98,"endTime":173.95,"body":"how far are they?"},{"speaker":"described them thus","startTime":174.99,"endTime":176.42,"body":"And can our human eye,"},{"speaker":"described them thus","startTime":176.42,"endTime":178.86,"body":"combined with the powers"},{"speaker":"described them thus","startTime":176.42,"endTime":178.86,"body":"of our imagination,"},{"speaker":"described them thus","startTime":178.86,"endTime":180.59,"body":"and of science and technology,"},{"speaker":"described them thus","startTime":180.59,"endTime":184.0,"body":"reach all the way to the"},{"speaker":"described them thus","startTime":180.59,"endTime":184.0,"body":"far end of the universe"},{"speaker":"described them thus","startTime":184.0,"endTime":186.81,"body":"and stretch a cosmic ruler"},{"speaker":"described them thus","startTime":186.81,"endTime":190.16,"body":"to measure distances out in space?"},{"speaker":"described them thus","startTime":190.16,"endTime":192.26,"body":"Can we build a cosmic distance ladder"},{"speaker":"described them thus","startTime":192.26,"endTime":193.3,"body":"that, rung after rung,"},{"speaker":"described them thus","startTime":193.3,"endTime":197.09,"body":"will take us all the way to the"},{"speaker":"described them thus","startTime":193.3,"endTime":197.09,"body":"end of the visible universe?"},{"speaker":"described them thus","startTime":197.09,"endTime":199.63,"body":"We will today explore"},{"speaker":"described them thus","startTime":197.09,"endTime":199.63,"body":"all of those questions"},{"speaker":"described them thus","startTime":199.63,"endTime":201.71,"body":"and see that, mysteriously,"},{"speaker":"described them thus","startTime":201.71,"endTime":203.1,"body":"the cosmic distance ladder"},{"speaker":"described them thus","startTime":203.1,"endTime":206.09,"body":"that we have built over"},{"speaker":"described them thus","startTime":203.1,"endTime":206.09,"body":"centuries and millennia"},{"speaker":"described them thus","startTime":206.09,"endTime":208.483,"body":"appears today to be broken."},{"speaker":"described them thus","startTime":210.95,"endTime":211.93,"body":"The earliest method"},{"speaker":"described them thus","startTime":211.93,"endTime":215.24,"body":"to establish distances"},{"speaker":"described them thus","startTime":211.93,"endTime":215.24,"body":"for a faraway object"},{"speaker":"described them thus","startTime":215.24,"endTime":218.36,"body":"is one that remains"},{"speaker":"described them thus","startTime":215.24,"endTime":218.36,"body":"very much useful today,"},{"speaker":"described them thus","startTime":218.36,"endTime":220.953,"body":"and it is literally at your fingertips."},{"speaker":"described them thus","startTime":221.83,"endTime":224.06,"body":"If you stretch your arm in front of you"},{"speaker":"described them thus","startTime":224.06,"endTime":226.34,"body":"and put up your index finger, like this,"},{"speaker":"described them thus","startTime":226.34,"endTime":228.16,"body":"and you look at the finger"},{"speaker":"described them thus","startTime":228.16,"endTime":231.07,"body":"by closing one eye,"},{"speaker":"described them thus","startTime":228.16,"endTime":231.07,"body":"and then the other eye,"},{"speaker":"described them thus","startTime":231.07,"endTime":232.98,"body":"you will see the position of the finger"},{"speaker":"described them thus","startTime":232.98,"endTime":236.92,"body":"appear to jump with respect"},{"speaker":"described them thus","startTime":232.98,"endTime":236.92,"body":"to a distant background."},{"speaker":"described them thus","startTime":236.92,"endTime":238.51,"body":"My finger is moving here,"},{"speaker":"described them thus","startTime":238.51,"endTime":240.16,"body":"but if you just close, alternatively,"},{"speaker":"described them thus","startTime":240.16,"endTime":241.77,"body":"the left and right eye,"},{"speaker":"described them thus","startTime":241.77,"endTime":243.07,"body":"the appearance of movement"},{"speaker":"described them thus","startTime":244.324,"endTime":247.34,"body":"will be due to the"},{"speaker":"described them thus","startTime":244.324,"endTime":247.34,"body":"different vantage point,"},{"speaker":"described them thus","startTime":247.34,"endTime":249.72,"body":"about 10 or so centimeters apart,"},{"speaker":"described them thus","startTime":249.72,"endTime":251.873,"body":"from each one of your two eyes."},{"speaker":"described them thus","startTime":252.89,"endTime":256.01,"body":"This phenomenon is called parallax,"},{"speaker":"described them thus","startTime":256.01,"endTime":261.01,"body":"parallax coming from an old"},{"speaker":"described them thus","startTime":256.01,"endTime":261.01,"body":"Greek word which means a change."},{"speaker":"described them thus","startTime":262.42,"endTime":264.74,"body":"And if you move now your finger"},{"speaker":"described them thus","startTime":264.74,"endTime":266.04,"body":"closer to the tip of your nose,"},{"speaker":"described them thus","startTime":266.04,"endTime":267.64,"body":"and you do the same experiment again,"},{"speaker":"described them thus","startTime":267.64,"endTime":270.05,"body":"by alternating the eye that you close,"},{"speaker":"described them thus","startTime":270.05,"endTime":272.7,"body":"you will see that the parallax"},{"speaker":"described them thus","startTime":270.05,"endTime":272.7,"body":"is now much increased."},{"speaker":"described them thus","startTime":273.84,"endTime":275.22,"body":"So the closer by the object,"},{"speaker":"described them thus","startTime":275.22,"endTime":278.7,"body":"the bigger the apparent"},{"speaker":"described them thus","startTime":275.22,"endTime":278.7,"body":"angle by which it jumps"},{"speaker":"described them thus","startTime":278.7,"endTime":281.36,"body":"with respect to a distant background,"},{"speaker":"described them thus","startTime":281.36,"endTime":282.193,"body":"and conversely,"},{"speaker":"described them thus","startTime":282.193,"endTime":283.52,"body":"the farther away, the smaller the angle."},{"speaker":"described them thus","startTime":283.52,"endTime":285.69,"body":"So if, conceivably,"},{"speaker":"described them thus","startTime":285.69,"endTime":289.95,"body":"we can measure the parallax"},{"speaker":"described them thus","startTime":285.69,"endTime":289.95,"body":"angles of objects in the sky"},{"speaker":"described them thus","startTime":289.95,"endTime":293.27,"body":"by looking at them from"},{"speaker":"described them thus","startTime":289.95,"endTime":293.27,"body":"different vantage points,"},{"speaker":"described them thus","startTime":293.27,"endTime":295.61,"body":"then we can, in principle, hopefully,"},{"speaker":"described them thus","startTime":295.61,"endTime":298.783,"body":"measure their distance"},{"speaker":"described them thus","startTime":295.61,"endTime":298.783,"body":"using simple trigonometry."},{"speaker":"described them thus","startTime":300.54,"endTime":302.06,"body":"So it is a great tool"},{"speaker":"described them thus","startTime":302.06,"endTime":304.74,"body":"to measure distances to objects"},{"speaker":"described them thus","startTime":302.06,"endTime":304.74,"body":"that are relatively nearby"},{"speaker":"described them thus","startTime":304.74,"endTime":307.17,"body":"provided we have a backdrop"},{"speaker":"described them thus","startTime":307.17,"endTime":311.04,"body":"by which to judge their"},{"speaker":"described them thus","startTime":307.17,"endTime":311.04,"body":"apparent change in position."},{"speaker":"described them thus","startTime":311.04,"endTime":312.34,"body":"Also, we can already predict"},{"speaker":"described them thus","startTime":312.34,"endTime":314.06,"body":"that if objects are too far away,"},{"speaker":"described them thus","startTime":314.06,"endTime":315.64,"body":"the parallax angle will be there,"},{"speaker":"described them thus","startTime":315.64,"endTime":318.8,"body":"but it will be too small to be measurable,"},{"speaker":"described them thus","startTime":318.8,"endTime":319.79,"body":"so at some point,"},{"speaker":"described them thus","startTime":319.79,"endTime":321.373,"body":"parallax will stop working."},{"speaker":"described them thus","startTime":322.89,"endTime":324.76,"body":"The first person to use parallax"},{"speaker":"described them thus","startTime":324.76,"endTime":328.58,"body":"to try and measure the distance"},{"speaker":"described them thus","startTime":324.76,"endTime":328.58,"body":"to the Sun and the Moon"},{"speaker":"described them thus","startTime":328.58,"endTime":331.846,"body":"was the ancient Greek"},{"speaker":"described them thus","startTime":328.58,"endTime":331.846,"body":"astronomer and mathematician"},{"speaker":"described them thus","startTime":331.846,"endTime":334.35,"body":"Hipparchus of Nicaea,"},{"speaker":"described them thus","startTime":334.35,"endTime":336.013,"body":"which is in modern-day Turkey."},{"speaker":"described them thus","startTime":337.11,"endTime":339.944,"body":"Hipparchus lived in the 2nd century BC,"},{"speaker":"described them thus","startTime":339.944,"endTime":341.51,"body":"and he's the inventor of trigonometry,"},{"speaker":"described them thus","startTime":341.51,"endTime":344.27,"body":"he's also considered"},{"speaker":"described them thus","startTime":341.51,"endTime":344.27,"body":"the father of astronomy,"},{"speaker":"described them thus","startTime":344.27,"endTime":345.25,"body":"by many, he's considered"},{"speaker":"described them thus","startTime":345.25,"endTime":348.423,"body":"the greatest astronomer"},{"speaker":"described them thus","startTime":345.25,"endTime":348.423,"body":"and observer in antiquity."},{"speaker":"described them thus","startTime":349.56,"endTime":351.11,"body":"He made many discoveries,"},{"speaker":"described them thus","startTime":351.11,"endTime":353.87,"body":"which included the"},{"speaker":"described them thus","startTime":351.11,"endTime":353.87,"body":"procession of the equinoxes,"},{"speaker":"described them thus","startTime":353.87,"endTime":358.49,"body":"the fact that seasons"},{"speaker":"described them thus","startTime":353.87,"endTime":358.49,"body":"are of an equal length,"},{"speaker":"described them thus","startTime":358.49,"endTime":361.96,"body":"and he also perfected a"},{"speaker":"described them thus","startTime":358.49,"endTime":361.96,"body":"method to predict eclipses"},{"speaker":"described them thus","startTime":361.96,"endTime":365.0,"body":"more accurately than was possible before,"},{"speaker":"described them thus","startTime":365.0,"endTime":368.37,"body":"he created the first"},{"speaker":"described them thus","startTime":365.0,"endTime":368.37,"body":"astronomical catalog of stars,"},{"speaker":"described them thus","startTime":368.37,"endTime":370.98,"body":"measuring the brightness and position"},{"speaker":"described them thus","startTime":370.98,"endTime":373.93,"body":"of about 850 stars in the sky."},{"speaker":"described them thus","startTime":375.44,"endTime":377.1,"body":"And when considering the question"},{"speaker":"described them thus","startTime":377.1,"endTime":379.48,"body":"of how far away is the Moon,"},{"speaker":"described them thus","startTime":379.48,"endTime":382.543,"body":"Hipparchus used the fact"},{"speaker":"described them thus","startTime":379.48,"endTime":382.543,"body":"that a total solar eclipse,"},{"speaker":"described them thus","startTime":383.49,"endTime":385.57,"body":"which is one in which, as we know,"},{"speaker":"described them thus","startTime":385.57,"endTime":387.73,"body":"the Earth, the Moon, and"},{"speaker":"described them thus","startTime":385.57,"endTime":387.73,"body":"the Sun are lined up,"},{"speaker":"described them thus","startTime":387.73,"endTime":390.223,"body":"like in this diagram here,"},{"speaker":"described them thus","startTime":392.72,"endTime":397.39,"body":"the fact that the Sun was"},{"speaker":"described them thus","startTime":392.72,"endTime":397.39,"body":"completely covered by the Moon,"},{"speaker":"described them thus","startTime":397.39,"endTime":400.19,"body":"if you were looking at the solar eclipse"},{"speaker":"described them thus","startTime":400.19,"endTime":401.743,"body":"from his hometown, Nicaea,"},{"speaker":"described them thus","startTime":402.72,"endTime":405.33,"body":"so the line of sight to the rim of the Sun"},{"speaker":"described them thus","startTime":405.33,"endTime":407.66,"body":"was the red one in this diagram,"},{"speaker":"described them thus","startTime":407.66,"endTime":409.93,"body":"while the eclipse was partial,"},{"speaker":"described them thus","startTime":409.93,"endTime":412.89,"body":"as seen from the city"},{"speaker":"described them thus","startTime":409.93,"endTime":412.89,"body":"of Alexandria, in Egypt,"},{"speaker":"described them thus","startTime":412.89,"endTime":416.07,"body":"which was on the same meridian as Nicaea,"},{"speaker":"described them thus","startTime":416.07,"endTime":417.983,"body":"but nine degrees further south."},{"speaker":"described them thus","startTime":419.07,"endTime":421.33,"body":"So by using this fact,"},{"speaker":"described them thus","startTime":421.33,"endTime":424.07,"body":"and the fact that the Sun"},{"speaker":"described them thus","startTime":421.33,"endTime":424.07,"body":"was sufficiently far away"},{"speaker":"described them thus","startTime":424.07,"endTime":428.63,"body":"so as to not exhibit"},{"speaker":"described them thus","startTime":424.07,"endTime":428.63,"body":"any noticeable parallax,"},{"speaker":"described them thus","startTime":428.63,"endTime":430.55,"body":"he was able to estimate the angle"},{"speaker":"described them thus","startTime":430.55,"endTime":432.79,"body":"between the red and the green line,"},{"speaker":"described them thus","startTime":432.79,"endTime":434.34,"body":"and with some mathematics,"},{"speaker":"described them thus","startTime":434.34,"endTime":436.56,"body":"therefore establish the distance"},{"speaker":"described them thus","startTime":436.56,"endTime":439.18,"body":"between the Earth and the Moon,"},{"speaker":"described them thus","startTime":439.18,"endTime":441.81,"body":"correctly attributing the"},{"speaker":"described them thus","startTime":439.18,"endTime":441.81,"body":"difference in appearance"},{"speaker":"described them thus","startTime":441.81,"endTime":442.91,"body":"of the solar eclipse"},{"speaker":"described them thus","startTime":442.91,"endTime":445.15,"body":"to the parallax phenomenon"},{"speaker":"described them thus","startTime":445.15,"endTime":446.793,"body":"as applied to the Moon."},{"speaker":"described them thus","startTime":447.78,"endTime":449.9,"body":"He eventually arrived at a figure"},{"speaker":"described them thus","startTime":449.9,"endTime":452.46,"body":"for the distance between"},{"speaker":"described them thus","startTime":449.9,"endTime":452.46,"body":"the Earth and the Moon"},{"speaker":"described them thus","startTime":452.46,"endTime":454.693,"body":"of 63 Earth radii."},{"speaker":"described them thus","startTime":456.834,"endTime":458.29,"body":"In order to convert this distance,"},{"speaker":"described them thus","startTime":458.29,"endTime":460.61,"body":"which was remarkably"},{"speaker":"described them thus","startTime":458.29,"endTime":460.61,"body":"close to the right value,"},{"speaker":"described them thus","startTime":460.61,"endTime":463.07,"body":"which is about 60 radii,"},{"speaker":"described them thus","startTime":463.07,"endTime":468.07,"body":"in order to convert this"},{"speaker":"described them thus","startTime":463.07,"endTime":468.07,"body":"value to an actual distance,"},{"speaker":"described them thus","startTime":468.24,"endTime":469.08,"body":"one needed to know"},{"speaker":"described them thus","startTime":469.08,"endTime":471.1,"body":"what was the radius of the Earth,"},{"speaker":"described them thus","startTime":471.1,"endTime":473.35,"body":"and therefore the"},{"speaker":"described them thus","startTime":471.1,"endTime":473.35,"body":"circumference of the Earth."},{"speaker":"described them thus","startTime":474.33,"endTime":477.893,"body":"This had been done already 50"},{"speaker":"described them thus","startTime":474.33,"endTime":477.893,"body":"years earlier by Eratosthenes,"},{"speaker":"described them thus","startTime":478.79,"endTime":483.79,"body":"who had heard from a traveler"},{"speaker":"described them thus","startTime":478.79,"endTime":483.79,"body":"that on the summer equinox,"},{"speaker":"described them thus","startTime":483.87,"endTime":486.53,"body":"the Sun's rays at noon"},{"speaker":"described them thus","startTime":486.53,"endTime":488.76,"body":"illuminated the bottom of a well"},{"speaker":"described them thus","startTime":488.76,"endTime":492.06,"body":"in the city of Syene, in modern-day Egypt,"},{"speaker":"described them thus","startTime":492.06,"endTime":494.52,"body":"without casting any shadows."},{"speaker":"described them thus","startTime":494.52,"endTime":496.37,"body":"This meant that, at that point in time,"},{"speaker":"described them thus","startTime":496.37,"endTime":498.743,"body":"the Sun was directly overhead that city."},{"speaker":"described them thus","startTime":499.84,"endTime":500.93,"body":"On the same day,"},{"speaker":"described them thus","startTime":500.93,"endTime":502.51,"body":"he measured the length of a shadow"},{"speaker":"described them thus","startTime":502.51,"endTime":505.38,"body":"cast by a stick in Alexandria,"},{"speaker":"described them thus","startTime":505.38,"endTime":509.78,"body":"and therefore, by comparing"},{"speaker":"described them thus","startTime":505.38,"endTime":509.78,"body":"the angle that the Sun made"},{"speaker":"described them thus","startTime":509.78,"endTime":512.22,"body":"in Alexandria and in Syene,"},{"speaker":"described them thus","startTime":512.22,"endTime":514.91,"body":"he was able to find the"},{"speaker":"described them thus","startTime":512.22,"endTime":514.91,"body":"difference in latitude"},{"speaker":"described them thus","startTime":514.91,"endTime":516.49,"body":"between the two cities,"},{"speaker":"described them thus","startTime":516.49,"endTime":520.563,"body":"which he estimated as being"},{"speaker":"described them thus","startTime":516.49,"endTime":520.563,"body":"1/50 of a full circle."},{"speaker":"described them thus","startTime":521.96,"endTime":523.73,"body":"If he had the difference in latitude,"},{"speaker":"described them thus","startTime":523.73,"endTime":524.6,"body":"all he needed to do"},{"speaker":"described them thus","startTime":524.6,"endTime":528.35,"body":"was to measure the physical"},{"speaker":"described them thus","startTime":524.6,"endTime":528.35,"body":"distance between the two cities,"},{"speaker":"described them thus","startTime":528.35,"endTime":531.04,"body":"and so he hired professional surveyors"},{"speaker":"described them thus","startTime":531.04,"endTime":534.99,"body":"who walked with equally-spaced"},{"speaker":"described them thus","startTime":531.04,"endTime":534.99,"body":"steps between the two cities,"},{"speaker":"described them thus","startTime":534.99,"endTime":538.003,"body":"reporting a distance of 5,000 stadia."},{"speaker":"described them thus","startTime":539.178,"endTime":540.18,"body":"And he concluded, therefore,"},{"speaker":"described them thus","startTime":540.18,"endTime":543.92,"body":"that the circumference of our"},{"speaker":"described them thus","startTime":540.18,"endTime":543.92,"body":"planet was 250,000 stadia,"},{"speaker":"described them thus","startTime":543.92,"endTime":545.77,"body":"50 times as much,"},{"speaker":"described them thus","startTime":545.77,"endTime":546.603,"body":"which is a number"},{"speaker":"described them thus","startTime":546.603,"endTime":549.11,"body":"that's a little difficult to"},{"speaker":"described them thus","startTime":546.603,"endTime":549.11,"body":"translate in today's units,"},{"speaker":"described them thus","startTime":549.11,"endTime":551.04,"body":"because a stadium as a unit of measure"},{"speaker":"described them thus","startTime":551.04,"endTime":552.943,"body":"was not uniform throughout antiquity."},{"speaker":"described them thus","startTime":553.87,"endTime":556.38,"body":"If we put 10 stadia to the mile,"},{"speaker":"described them thus","startTime":556.38,"endTime":558.47,"body":"then Eratosthenes estimates,"},{"speaker":"described them thus","startTime":558.47,"endTime":559.86,"body":"for the circumference of the Earth"},{"speaker":"described them thus","startTime":559.86,"endTime":562.15,"body":"will be 25,000 miles,"},{"speaker":"described them thus","startTime":562.15,"endTime":563.86,"body":"which puts the Earth radius,"},{"speaker":"described them thus","startTime":563.86,"endTime":566.686,"body":"if we assume the Earth"},{"speaker":"described them thus","startTime":563.86,"endTime":566.686,"body":"to be a perfect sphere,"},{"speaker":"described them thus","startTime":566.686,"endTime":567.94,"body":"which it isn't,"},{"speaker":"described them thus","startTime":567.94,"endTime":572.94,"body":"to 3,980 miles, or 6,400 kilometers,"},{"speaker":"described them thus","startTime":573.29,"endTime":577.42,"body":"which is very close to the"},{"speaker":"described them thus","startTime":573.29,"endTime":577.42,"body":"actual value of 6,378 kilometers."},{"speaker":"described them thus","startTime":580.72,"endTime":583.45,"body":"Given this estimate of"},{"speaker":"described them thus","startTime":580.72,"endTime":583.45,"body":"the size of the Earth,"},{"speaker":"described them thus","startTime":583.45,"endTime":586.23,"body":"it is clear that 63 Earth radii,"},{"speaker":"described them thus","startTime":586.23,"endTime":587.55,"body":"Hipparchus' estimate"},{"speaker":"described them thus","startTime":587.55,"endTime":590.07,"body":"for the distance of the Earth to the Moon,"},{"speaker":"described them thus","startTime":590.07,"endTime":593.96,"body":"did put the Moon out of reach"},{"speaker":"described them thus","startTime":590.07,"endTime":593.96,"body":"of even the tallest ladder"},{"speaker":"described them thus","startTime":593.96,"endTime":596.73,"body":"on top of the tallest of mountains."},{"speaker":"described them thus","startTime":596.73,"endTime":601.023,"body":"This measurement"},{"speaker":"described them thus","startTime":596.73,"endTime":601.023,"body":"established, 200 years BC,"},{"speaker":"described them thus","startTime":602.7,"endTime":604.91,"body":"the first rung in our distance ladder,"},{"speaker":"described them thus","startTime":604.91,"endTime":608.25,"body":"which, today, sits at"},{"speaker":"described them thus","startTime":604.91,"endTime":608.25,"body":"about 384,000 kilometers,"},{"speaker":"described them thus","startTime":608.25,"endTime":611.07,"body":"that's the mean distance"},{"speaker":"described them thus","startTime":608.25,"endTime":611.07,"body":"between the Earth and the Moon,"},{"speaker":"described them thus","startTime":611.07,"endTime":612.59,"body":"the actual distance varies"},{"speaker":"described them thus","startTime":612.59,"endTime":616.12,"body":"as the orbit of the Moon"},{"speaker":"described them thus","startTime":612.59,"endTime":616.12,"body":"is not a perfect circle."},{"speaker":"described them thus","startTime":616.12,"endTime":617.61,"body":"So this was our first rung,"},{"speaker":"described them thus","startTime":617.61,"endTime":619.6,"body":"what about the next rung,"},{"speaker":"described them thus","startTime":619.6,"endTime":621.05,"body":"the distance to the Sun?"},{"speaker":"described them thus","startTime":623.385,"endTime":626.45,"body":"Hipparchus tried to measure the"},{"speaker":"described them thus","startTime":623.385,"endTime":626.45,"body":"distance to the Sun as well,"},{"speaker":"described them thus","startTime":626.45,"endTime":629.66,"body":"but his method gave a"},{"speaker":"described them thus","startTime":626.45,"endTime":629.66,"body":"hopelessly low estimate,"},{"speaker":"described them thus","startTime":629.66,"endTime":632.71,"body":"much, much lower than what it is,"},{"speaker":"described them thus","startTime":632.71,"endTime":636.535,"body":"he estimated it as 490 Earth radii,"},{"speaker":"described them thus","startTime":636.535,"endTime":638.89,"body":"which is too small by a large factor,"},{"speaker":"described them thus","startTime":638.89,"endTime":640.92,"body":"the actual distance, Earth-Sun,"},{"speaker":"described them thus","startTime":640.92,"endTime":645.1,"body":"is about 23,400 times to the Earth radius,"},{"speaker":"described them thus","startTime":645.1,"endTime":646.783,"body":"or 150 million kilometers."},{"speaker":"described them thus","startTime":647.65,"endTime":651.963,"body":"So how could we then measure"},{"speaker":"described them thus","startTime":647.65,"endTime":651.963,"body":"the distance to the Sun?"},{"speaker":"described them thus","startTime":653.97,"endTime":655.663,"body":"By the 17th century,"},{"speaker":"described them thus","startTime":657.32,"endTime":660.8,"body":"the Copernican and Keplerian revolutions"},{"speaker":"described them thus","startTime":660.8,"endTime":662.42,"body":"in terms of our understanding"},{"speaker":"described them thus","startTime":662.42,"endTime":664.79,"body":"of the orbits and the"},{"speaker":"described them thus","startTime":662.42,"endTime":664.79,"body":"structure of the solar system"},{"speaker":"described them thus","startTime":664.79,"endTime":668.52,"body":"had been completed and was in full swing."},{"speaker":"described them thus","startTime":668.52,"endTime":670.2,"body":"In particular, Kepler told us"},{"speaker":"described them thus","startTime":670.2,"endTime":674.9,"body":"that the orbits of planets"},{"speaker":"described them thus","startTime":670.2,"endTime":674.9,"body":"going around the Sun"},{"speaker":"described them thus","startTime":674.9,"endTime":676.55,"body":"are ellipses,"},{"speaker":"described them thus","startTime":676.55,"endTime":677.75,"body":"and those ellipses,"},{"speaker":"described them thus","startTime":677.75,"endTime":679.87,"body":"which are a kind of stretched circle,"},{"speaker":"described them thus","startTime":679.87,"endTime":681.42,"body":"had several properties,"},{"speaker":"described them thus","startTime":681.42,"endTime":683.48,"body":"that are encapsulated"},{"speaker":"described them thus","startTime":683.48,"endTime":686.26,"body":"in Kepler's \"Laws of Planetary Motion,\""},{"speaker":"described them thus","startTime":686.26,"endTime":688.47,"body":"that Newton would, a few decades later,"},{"speaker":"described them thus","startTime":688.47,"endTime":692.233,"body":"reinterpret and explain"},{"speaker":"described them thus","startTime":688.47,"endTime":692.233,"body":"in terms of gravity."},{"speaker":"described them thus","startTime":693.182,"endTime":696.34,"body":"In particular, Kepler's third law tells us"},{"speaker":"described them thus","startTime":696.34,"endTime":699.62,"body":"that the orbital period squared"},{"speaker":"described them thus","startTime":699.62,"endTime":701.86,"body":"of a planet going around the Sun"},{"speaker":"described them thus","startTime":701.86,"endTime":705.35,"body":"divided the semi-major"},{"speaker":"described them thus","startTime":701.86,"endTime":705.35,"body":"axis of the ellipse,"},{"speaker":"described them thus","startTime":705.35,"endTime":709.21,"body":"which is the long part of the ellipse,"},{"speaker":"described them thus","startTime":709.21,"endTime":710.823,"body":"in blue in this diagram,"},{"speaker":"described them thus","startTime":711.67,"endTime":712.84,"body":"the orbital period squared"},{"speaker":"described them thus","startTime":712.84,"endTime":715.84,"body":"divided by the semi-major axis cubed"},{"speaker":"described them thus","startTime":715.84,"endTime":717.74,"body":"is a constant for all planets,"},{"speaker":"described them thus","startTime":717.74,"endTime":720.583,"body":"indeed for all bodies"},{"speaker":"described them thus","startTime":717.74,"endTime":720.583,"body":"orbiting another body."},{"speaker":"described them thus","startTime":721.66,"endTime":723.12,"body":"And that, in turn,"},{"speaker":"described them thus","startTime":723.12,"endTime":726.01,"body":"because we know the"},{"speaker":"described them thus","startTime":723.12,"endTime":726.01,"body":"period of all the planets,"},{"speaker":"described them thus","startTime":726.01,"endTime":729.53,"body":"at least all the planets that"},{"speaker":"described them thus","startTime":726.01,"endTime":729.53,"body":"were known at Kepler's time,"},{"speaker":"described them thus","startTime":729.53,"endTime":733.07,"body":"that in turn gives us"},{"speaker":"described them thus","startTime":729.53,"endTime":733.07,"body":"the relative distances"},{"speaker":"described them thus","startTime":733.07,"endTime":735.22,"body":"of the planets to the Sun."},{"speaker":"described them thus","startTime":735.22,"endTime":736.58,"body":"So if we take the Earth"},{"speaker":"described them thus","startTime":736.58,"endTime":738.64,"body":"to define the standard of distance,"},{"speaker":"described them thus","startTime":738.64,"endTime":741.7,"body":"the AU, the astronomical unit,"},{"speaker":"described them thus","startTime":741.7,"endTime":745.97,"body":"and we say that the Earth-Sun"},{"speaker":"described them thus","startTime":741.7,"endTime":745.97,"body":"average distance is one AU,"},{"speaker":"described them thus","startTime":745.97,"endTime":749.04,"body":"then you see, on the right,"},{"speaker":"described them thus","startTime":745.97,"endTime":749.04,"body":"that all of the other planets,"},{"speaker":"described them thus","startTime":749.04,"endTime":750.4,"body":"thanks to Kepler's third law,"},{"speaker":"described them thus","startTime":750.4,"endTime":753.769,"body":"can be put at relative"},{"speaker":"described them thus","startTime":750.4,"endTime":753.769,"body":"distances from the Sun,"},{"speaker":"described them thus","startTime":753.769,"endTime":755.68,"body":"Mercury, 0.39 AU,"},{"speaker":"described them thus","startTime":755.68,"endTime":757.62,"body":"Venus, 0.72 AU,"},{"speaker":"described them thus","startTime":757.62,"endTime":759.22,"body":"Mars, 1.5 AU,"},{"speaker":"described them thus","startTime":759.22,"endTime":761.18,"body":"and so on, and so forth."},{"speaker":"described them thus","startTime":761.18,"endTime":765.59,"body":"So Kepler gave us a way of"},{"speaker":"described them thus","startTime":761.18,"endTime":765.59,"body":"measuring the relative distances"},{"speaker":"described them thus","startTime":765.59,"endTime":767.07,"body":"of the planets to the Sun,"},{"speaker":"described them thus","startTime":767.07,"endTime":767.903,"body":"and therefore,"},{"speaker":"described them thus","startTime":767.903,"endTime":770.42,"body":"to measure the relative"},{"speaker":"described them thus","startTime":767.903,"endTime":770.42,"body":"size of the solar system,"},{"speaker":"described them thus","startTime":770.42,"endTime":773.33,"body":"but we still didn't know what the AU was,"},{"speaker":"described them thus","startTime":773.33,"endTime":776.46,"body":"how big was this astronomical unit"},{"speaker":"described them thus","startTime":776.46,"endTime":779.42,"body":"in units of which all"},{"speaker":"described them thus","startTime":776.46,"endTime":779.42,"body":"of the other distances"},{"speaker":"described them thus","startTime":779.42,"endTime":781.633,"body":"of the solar system could be measured."},{"speaker":"described them thus","startTime":783.66,"endTime":786.62,"body":"And that's where Edmund Halley comes in."},{"speaker":"described them thus","startTime":786.62,"endTime":791.62,"body":"In 1716, the famous astronomer"},{"speaker":"described them thus","startTime":786.62,"endTime":791.62,"body":"issued a real call-to-arms"},{"speaker":"described them thus","startTime":793.11,"endTime":796.95,"body":"to all the diligent"},{"speaker":"described them thus","startTime":793.11,"endTime":796.95,"body":"searchers of the heavens"},{"speaker":"described them thus","startTime":796.95,"endTime":800.81,"body":"to take advantage of a very"},{"speaker":"described them thus","startTime":796.95,"endTime":800.81,"body":"rare astronomical phenomenon"},{"speaker":"described them thus","startTime":800.81,"endTime":804.32,"body":"that would happen a few decades later"},{"speaker":"described them thus","startTime":804.32,"endTime":808.11,"body":"in order to finally pinpoint down the AU,"},{"speaker":"described them thus","startTime":808.11,"endTime":809.283,"body":"the astronomical unit."},{"speaker":"described them thus","startTime":810.19,"endTime":812.05,"body":"The phenomenon that"},{"speaker":"described them thus","startTime":810.19,"endTime":812.05,"body":"Halley was interested in"},{"speaker":"described them thus","startTime":812.05,"endTime":814.37,"body":"was a transit of Venus."},{"speaker":"described them thus","startTime":814.37,"endTime":816.43,"body":"Venus is one of the inferior planets,"},{"speaker":"described them thus","startTime":816.43,"endTime":820.407,"body":"one of the planets that orbit"},{"speaker":"described them thus","startTime":816.43,"endTime":820.407,"body":"inside the orbit of the Earth,"},{"speaker":"described them thus","startTime":820.407,"endTime":821.24,"body":"and as such,"},{"speaker":"described them thus","startTime":821.24,"endTime":824.31,"body":"it goes around the Sun"},{"speaker":"described them thus","startTime":821.24,"endTime":824.31,"body":"faster than the Earth does,"},{"speaker":"described them thus","startTime":824.31,"endTime":825.64,"body":"and as it does so,"},{"speaker":"described them thus","startTime":825.64,"endTime":828.95,"body":"the Earth and Venus line up several times"},{"speaker":"described them thus","startTime":828.95,"endTime":833.7,"body":"in the course of their"},{"speaker":"described them thus","startTime":828.95,"endTime":833.7,"body":"orbits around the Sun."},{"speaker":"described them thus","startTime":833.7,"endTime":835.85,"body":"However, because the orbit of Venus"},{"speaker":"described them thus","startTime":835.85,"endTime":837.68,"body":"is tilted by three degrees"},{"speaker":"described them thus","startTime":837.68,"endTime":839.35,"body":"with respect to the orbit of the Earth,"},{"speaker":"described them thus","startTime":839.35,"endTime":841.13,"body":"as you see in this diagram,"},{"speaker":"described them thus","startTime":841.13,"endTime":845.15,"body":"the only times when the"},{"speaker":"described them thus","startTime":841.13,"endTime":845.15,"body":"Earth and Venus alignments"},{"speaker":"described them thus","startTime":845.15,"endTime":848.473,"body":"lead to Venus actually"},{"speaker":"described them thus","startTime":845.15,"endTime":848.473,"body":"being in front of the Sun,"},{"speaker":"described them thus","startTime":848.473,"endTime":852.52,"body":"a so-called transit of Venus"},{"speaker":"described them thus","startTime":848.473,"endTime":852.52,"body":"on the face of the Sun,"},{"speaker":"described them thus","startTime":852.52,"endTime":856.62,"body":"is when the alignment"},{"speaker":"described them thus","startTime":852.52,"endTime":856.62,"body":"between the Earth and Venus"},{"speaker":"described them thus","startTime":856.62,"endTime":860.13,"body":"happens at the point of"},{"speaker":"described them thus","startTime":856.62,"endTime":860.13,"body":"intersection of the two orbits,"},{"speaker":"described them thus","startTime":860.13,"endTime":861.523,"body":"which is called a node."},{"speaker":"described them thus","startTime":862.4,"endTime":866.69,"body":"This is an extremely rare"},{"speaker":"described them thus","startTime":862.4,"endTime":866.69,"body":"astronomical phenomenon,"},{"speaker":"described them thus","startTime":866.69,"endTime":869.853,"body":"with a cycle of 243 years."},{"speaker":"described them thus","startTime":870.84,"endTime":873.3,"body":"What happens for an observer on the Earth"},{"speaker":"described them thus","startTime":873.3,"endTime":875.24,"body":"is that this transit,"},{"speaker":"described them thus","startTime":875.24,"endTime":877.88,"body":"Venus passing in front"},{"speaker":"described them thus","startTime":875.24,"endTime":877.88,"body":"of the disc of the Sun,"},{"speaker":"described them thus","startTime":877.88,"endTime":882.14,"body":"happens twice in June,"},{"speaker":"described them thus","startTime":882.14,"endTime":885.61,"body":"then nothing in the course of eight years,"},{"speaker":"described them thus","startTime":885.61,"endTime":887.93,"body":"then nothing for 105 years,"},{"speaker":"described them thus","startTime":887.93,"endTime":891.307,"body":"then another two transits"},{"speaker":"described them thus","startTime":887.93,"endTime":891.307,"body":"eight years apart in December,"},{"speaker":"described them thus","startTime":891.307,"endTime":894.513,"body":"and then nothing again"},{"speaker":"described them thus","startTime":891.307,"endTime":894.513,"body":"for the next 121 years,"},{"speaker":"described them thus","startTime":895.84,"endTime":898.093,"body":"after which the cycle recommences."},{"speaker":"described them thus","startTime":899.65,"endTime":901.86,"body":"Halley, writing in 1716,"},{"speaker":"described them thus","startTime":901.86,"endTime":905.58,"body":"predicted a pair of transits"},{"speaker":"described them thus","startTime":901.86,"endTime":905.58,"body":"happening in 1761 and 1769,"},{"speaker":"described them thus","startTime":907.99,"endTime":911.41,"body":"and he knew that by looking at Venus"},{"speaker":"described them thus","startTime":911.41,"endTime":915.76,"body":"from different vantage points"},{"speaker":"described them thus","startTime":911.41,"endTime":915.76,"body":"on the surface of the Earth,"},{"speaker":"described them thus","startTime":915.76,"endTime":919.0,"body":"and looking at the transit of"},{"speaker":"described them thus","startTime":915.76,"endTime":919.0,"body":"Venus on the face of the Sun,"},{"speaker":"described them thus","startTime":919.0,"endTime":919.97,"body":"let's say, if you were able"},{"speaker":"described them thus","startTime":919.97,"endTime":921.58,"body":"to look at Venus transiting the Sun"},{"speaker":"described them thus","startTime":921.58,"endTime":923.28,"body":"from a northerly location,"},{"speaker":"described them thus","startTime":923.28,"endTime":924.83,"body":"such as Canada,"},{"speaker":"described them thus","startTime":924.83,"endTime":926.55,"body":"and then from a southerly location,"},{"speaker":"described them thus","startTime":926.55,"endTime":929.11,"body":"such as Tahiti, in the Pacific Ocean,"},{"speaker":"described them thus","startTime":929.11,"endTime":930.1,"body":"your line of sight to the transit"},{"speaker":"described them thus","startTime":930.1,"endTime":931.71,"body":"would be slightly different,"},{"speaker":"described them thus","startTime":931.71,"endTime":933.18,"body":"and parallax would mean"},{"speaker":"described them thus","startTime":933.18,"endTime":935.58,"body":"that the transiting planet"},{"speaker":"described them thus","startTime":933.18,"endTime":935.58,"body":"on the face of the Sun,"},{"speaker":"described them thus","startTime":935.58,"endTime":938.7,"body":"which is shown by the"},{"speaker":"described them thus","startTime":935.58,"endTime":938.7,"body":"green and dashed red lines"},{"speaker":"described them thus","startTime":938.7,"endTime":940.13,"body":"on the right-hand side,"},{"speaker":"described them thus","startTime":940.13,"endTime":942.62,"body":"would cut a slightly different path."},{"speaker":"described them thus","startTime":942.62,"endTime":945.71,"body":"So by timing the transit"},{"speaker":"described them thus","startTime":945.71,"endTime":947.88,"body":"from two wildly different locations"},{"speaker":"described them thus","startTime":947.88,"endTime":949.38,"body":"on the surface of the Earth"},{"speaker":"described them thus","startTime":949.38,"endTime":951.62,"body":"and using the phenomenon of parallax,"},{"speaker":"described them thus","startTime":951.62,"endTime":954.08,"body":"one could measure the distance to Venus,"},{"speaker":"described them thus","startTime":954.08,"endTime":958.15,"body":"and therefore the AU, effectively,"},{"speaker":"described them thus","startTime":958.15,"endTime":963.15,"body":"because we know that Venus is"},{"speaker":"described them thus","startTime":958.15,"endTime":963.15,"body":"so many AUs away from the Sun."},{"speaker":"described them thus","startTime":964.76,"endTime":967.01,"body":"So this was a great opportunity,"},{"speaker":"described them thus","startTime":967.01,"endTime":968.44,"body":"and a rare opportunity,"},{"speaker":"described them thus","startTime":968.44,"endTime":970.76,"body":"to see a transit,"},{"speaker":"described them thus","startTime":970.76,"endTime":974.22,"body":"and therefore, all the"},{"speaker":"described them thus","startTime":970.76,"endTime":974.22,"body":"natural scientists of the time"},{"speaker":"described them thus","startTime":974.22,"endTime":976.82,"body":"geared up to make that observation."},{"speaker":"described them thus","startTime":976.82,"endTime":979.71,"body":"In fact, this was not the first time"},{"speaker":"described them thus","startTime":979.71,"endTime":981.57,"body":"that anybody had seen"},{"speaker":"described them thus","startTime":979.71,"endTime":981.57,"body":"the transit of Venus,"},{"speaker":"described them thus","startTime":981.57,"endTime":984.99,"body":"because the English"},{"speaker":"described them thus","startTime":981.57,"endTime":984.99,"body":"astronomer Jeremiah Horrocks"},{"speaker":"described them thus","startTime":984.99,"endTime":988.71,"body":"had been one of only two"},{"speaker":"described them thus","startTime":984.99,"endTime":988.71,"body":"people in recorded history,"},{"speaker":"described them thus","startTime":988.71,"endTime":991.53,"body":"together with his friend William Crabtree,"},{"speaker":"described them thus","startTime":991.53,"endTime":996.53,"body":"to observe the earlier"},{"speaker":"described them thus","startTime":991.53,"endTime":996.53,"body":"transit of Venus in 1639,"},{"speaker":"described them thus","startTime":998.08,"endTime":1000.95,"body":"which Horrocks himself had predicted"},{"speaker":"described them thus","startTime":1000.95,"endTime":1004.78,"body":"against Kepler's"},{"speaker":"described them thus","startTime":1000.95,"endTime":1004.78,"body":"prediction of a near-miss."},{"speaker":"described them thus","startTime":1004.78,"endTime":1006.8,"body":"In fact, there is even a memorial tablet"},{"speaker":"described them thus","startTime":1006.8,"endTime":1008.49,"body":"that commemorates him"},{"speaker":"described them thus","startTime":1008.49,"endTime":1010.42,"body":"inside Westminster Abbey, saying,"},{"speaker":"described them thus","startTime":1012.512,"endTime":1014.667,"body":"\"Having in so short a life"},{"speaker":"described them thus","startTime":1014.667,"endTime":1016.617,"body":"\"detected the long inequality"},{"speaker":"described them thus","startTime":1016.617,"endTime":1019.297,"body":"\"in the mean motion of Jupiter and Saturn,"},{"speaker":"described them thus","startTime":1019.297,"endTime":1022.017,"body":"\"discovered the orbit of"},{"speaker":"described them thus","startTime":1019.297,"endTime":1022.017,"body":"the Moon to be an ellipse,"},{"speaker":"described them thus","startTime":1022.017,"endTime":1024.257,"body":"\"determined the motion of the lunar apse,"},{"speaker":"described them thus","startTime":1024.257,"endTime":1026.917,"body":"\"suggested the physical"},{"speaker":"described them thus","startTime":1024.257,"endTime":1026.917,"body":"cause of its revolution,"},{"speaker":"described them thus","startTime":1026.917,"endTime":1029.077,"body":"\"and predicted, from his own observations,"},{"speaker":"described them thus","startTime":1029.077,"endTime":1030.377,"body":"\"the transit of Venus,"},{"speaker":"described them thus","startTime":1030.377,"endTime":1033.187,"body":"\"which was seen by himself and"},{"speaker":"described them thus","startTime":1030.377,"endTime":1033.187,"body":"his friend William Crabtree"},{"speaker":"described them thus","startTime":1033.187,"endTime":1038.187,"body":"\"on Sunday the 24th of November,"},{"speaker":"described them thus","startTime":1033.187,"endTime":1038.187,"body":"in the old calendar, 1639."},{"speaker":"described them thus","startTime":1038.457,"endTime":1040.577,"body":"\"This tablet, facing"},{"speaker":"described them thus","startTime":1038.457,"endTime":1040.577,"body":"the monument of Newton,"},{"speaker":"described them thus","startTime":1040.577,"endTime":1042.867,"body":"\"was raised after a lapse"},{"speaker":"described them thus","startTime":1040.577,"endTime":1042.867,"body":"of more than two centuries,"},{"speaker":"described them thus","startTime":1042.867,"endTime":1045.46,"body":"\"December the 9th, 1874,\""},{"speaker":"described them thus","startTime":1045.46,"endTime":1048.15,"body":"a fitting memorial to a great astronomer"},{"speaker":"described them thus","startTime":1048.15,"endTime":1052.96,"body":"whose life was tragically cut"},{"speaker":"described them thus","startTime":1048.15,"endTime":1052.96,"body":"short at the young age of 22."},{"speaker":"described them thus","startTime":1052.96,"endTime":1053.793,"body":"In fact,"},{"speaker":"described them thus","startTime":1053.793,"endTime":1055.69,"body":"when Horrocks saw the spectacle"},{"speaker":"described them thus","startTime":1053.793,"endTime":1055.69,"body":"of the transit of Venus,"},{"speaker":"described them thus","startTime":1055.69,"endTime":1059.48,"body":"he was so elated that"},{"speaker":"described them thus","startTime":1055.69,"endTime":1059.48,"body":"he wrote in his diary"},{"speaker":"this lyrical description","startTime":1063.677,"endTime":1066.797,"body":"\"Thy return, posterity shall witness,"},{"speaker":"this lyrical description","startTime":1066.797,"endTime":1068.657,"body":"\"years must roll away,"},{"speaker":"this lyrical description","startTime":1068.657,"endTime":1070.137,"body":"\"but then, at length,"},{"speaker":"this lyrical description","startTime":1070.137,"endTime":1071.647,"body":"\"the splendid sight"},{"speaker":"this lyrical description","startTime":1071.647,"endTime":1075.077,"body":"\"again shall greet our"},{"speaker":"this lyrical description","startTime":1071.647,"endTime":1075.077,"body":"distant children's eyes.\""},{"speaker":"this lyrical description","startTime":1075.92,"endTime":1078.18,"body":"Sadly, Horrocks would"},{"speaker":"this lyrical description","startTime":1075.92,"endTime":1078.18,"body":"not have any children"},{"speaker":"this lyrical description","startTime":1078.18,"endTime":1082.23,"body":"who would witness the"},{"speaker":"this lyrical description","startTime":1078.18,"endTime":1082.23,"body":"1761 or 1769 transits."},{"speaker":"this lyrical description","startTime":1087.54,"endTime":1091.36,"body":"In 1761, over 120 missions in 62 countries"},{"speaker":"this lyrical description","startTime":1091.36,"endTime":1093.66,"body":"were dispatched to observe it,"},{"speaker":"this lyrical description","startTime":1093.66,"endTime":1096.29,"body":"the grandest international"},{"speaker":"this lyrical description","startTime":1093.66,"endTime":1096.29,"body":"astronomical effort"},{"speaker":"this lyrical description","startTime":1096.29,"endTime":1098.07,"body":"ever attempted."},{"speaker":"this lyrical description","startTime":1098.07,"endTime":1101.3,"body":"In fact the Royal Astronomer,"},{"speaker":"this lyrical description","startTime":1098.07,"endTime":1101.3,"body":"Nevil Maskelyne, for example,"},{"speaker":"this lyrical description","startTime":1101.3,"endTime":1103.74,"body":"sailed all the way to St. Helena,"},{"speaker":"this lyrical description","startTime":1103.74,"endTime":1107.5,"body":"only to have his observations"},{"speaker":"this lyrical description","startTime":1103.74,"endTime":1107.5,"body":"scuppered by clouds."},{"speaker":"this lyrical description","startTime":1107.5,"endTime":1109.78,"body":"So evidently, Halley's good wishes,"},{"speaker":"this lyrical description","startTime":1109.78,"endTime":1111.693,"body":"which he expressed in 1716,"},{"speaker":"this lyrical description","startTime":1113.007,"endTime":1114.527,"body":"\"And I wish them luck,"},{"speaker":"this lyrical description","startTime":1114.527,"endTime":1115.687,"body":"\"and pray above all"},{"speaker":"this lyrical description","startTime":1115.687,"endTime":1118.777,"body":"\"that they are not robbed"},{"speaker":"this lyrical description","startTime":1115.687,"endTime":1118.777,"body":"of the hoped-for spectacle"},{"speaker":"this lyrical description","startTime":1118.777,"endTime":1122.18,"body":"\"by the untimely gloom a cloudy sky,\""},{"speaker":"this lyrical description","startTime":1122.18,"endTime":1124.73,"body":"well Halley's wishes didn't"},{"speaker":"this lyrical description","startTime":1122.18,"endTime":1124.73,"body":"work out for Maskelyne."},{"speaker":"this lyrical description","startTime":1125.58,"endTime":1126.413,"body":"In fact,"},{"speaker":"this lyrical description","startTime":1126.413,"endTime":1131.13,"body":"despite the many measurements"},{"speaker":"this lyrical description","startTime":1126.413,"endTime":1131.13,"body":"during the 1761 transit,"},{"speaker":"this lyrical description","startTime":1131.13,"endTime":1133.01,"body":"the measurements were too variable,"},{"speaker":"this lyrical description","startTime":1133.01,"endTime":1134.4,"body":"the quality wasn't sufficient"},{"speaker":"this lyrical description","startTime":1134.4,"endTime":1138.0,"body":"to pin down the AU and the parallax angle"},{"speaker":"this lyrical description","startTime":1138.0,"endTime":1139.803,"body":"in a reliable fashion."},{"speaker":"this lyrical description","startTime":1141.57,"endTime":1145.28,"body":"A second chance would"},{"speaker":"this lyrical description","startTime":1141.57,"endTime":1145.28,"body":"present itself in 1769,"},{"speaker":"this lyrical description","startTime":1145.28,"endTime":1147.01,"body":"and this time,"},{"speaker":"this lyrical description","startTime":1147.01,"endTime":1149.15,"body":"that chance could not be missed,"},{"speaker":"this lyrical description","startTime":1149.15,"endTime":1152.04,"body":"because no other chance"},{"speaker":"this lyrical description","startTime":1149.15,"endTime":1152.04,"body":"would present itself"},{"speaker":"this lyrical description","startTime":1152.04,"endTime":1154.203,"body":"for another century, or more."},{"speaker":"this lyrical description","startTime":1155.18,"endTime":1156.97,"body":"In England, the Royal Society"},{"speaker":"this lyrical description","startTime":1156.97,"endTime":1160.57,"body":"mounted an ambitious"},{"speaker":"this lyrical description","startTime":1156.97,"endTime":1160.57,"body":"scientific expedition."},{"speaker":"this lyrical description","startTime":1160.57,"endTime":1162.3,"body":"They had convinced the Admiralty"},{"speaker":"this lyrical description","startTime":1162.3,"endTime":1165.08,"body":"to buy and outfit, at great cost,"},{"speaker":"this lyrical description","startTime":1165.08,"endTime":1167.12,"body":"a sturdy merchant ship,"},{"speaker":"this lyrical description","startTime":1167.12,"endTime":1170.18,"body":"which they renamed the Endeavour,"},{"speaker":"this lyrical description","startTime":1170.18,"endTime":1172.92,"body":"and they gave its command"},{"speaker":"this lyrical description","startTime":1172.92,"endTime":1175.763,"body":"to the ablest navigator and cartographer"},{"speaker":"this lyrical description","startTime":1175.763,"endTime":1179.85,"body":"of His Majesty's fleet,"},{"speaker":"this lyrical description","startTime":1179.85,"endTime":1182.12,"body":"Lieutenant James Cook."},{"speaker":"this lyrical description","startTime":1182.12,"endTime":1184.766,"body":"They also petitioned the king, George III,"},{"speaker":"this lyrical description","startTime":1184.766,"endTime":1185.92,"body":"to bankroll the mission"},{"speaker":"this lyrical description","startTime":1185.92,"endTime":1188.79,"body":"with over a million"},{"speaker":"this lyrical description","startTime":1185.92,"endTime":1188.79,"body":"pounds, in today's money,"},{"speaker":"this lyrical description","startTime":1188.79,"endTime":1190.73,"body":"of his own money,"},{"speaker":"this lyrical description","startTime":1190.73,"endTime":1192.61,"body":"and they equipped the Endeavour"},{"speaker":"this lyrical description","startTime":1192.61,"endTime":1194.24,"body":"with the finest telescopes,"},{"speaker":"this lyrical description","startTime":1194.24,"endTime":1196.91,"body":"and the finest instruments,"},{"speaker":"this lyrical description","startTime":1194.24,"endTime":1196.91,"body":"the finest clocks"},{"speaker":"this lyrical description","startTime":1196.91,"endTime":1199.27,"body":"that money could buy at the time,"},{"speaker":"this lyrical description","startTime":1199.27,"endTime":1202.74,"body":"before sending it to the"},{"speaker":"this lyrical description","startTime":1199.27,"endTime":1202.74,"body":"other side of the world,"},{"speaker":"this lyrical description","startTime":1202.74,"endTime":1205.27,"body":"in the middle of the Pacific Ocean,"},{"speaker":"this lyrical description","startTime":1205.27,"endTime":1206.93,"body":"to the island of Tahiti,"},{"speaker":"this lyrical description","startTime":1206.93,"endTime":1209.61,"body":"that had recently been"},{"speaker":"this lyrical description","startTime":1206.93,"endTime":1209.61,"body":"conveniently discovered,"},{"speaker":"this lyrical description","startTime":1209.61,"endTime":1210.443,"body":"quote-unquote,"},{"speaker":"this lyrical description","startTime":1210.443,"endTime":1211.276,"body":"because, of course,"},{"speaker":"this lyrical description","startTime":1211.276,"endTime":1214.02,"body":"Tahiti had been inhabited"},{"speaker":"this lyrical description","startTime":1211.276,"endTime":1214.02,"body":"for centuries already"},{"speaker":"this lyrical description","startTime":1214.02,"endTime":1217.37,"body":"by Tahitians,"},{"speaker":"this lyrical 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of the artists onboard"},{"speaker":"this lyrical description","startTime":1257.67,"endTime":1262.67,"body":"James Cook's first voyage."},{"speaker":"this lyrical description","startTime":1263.01,"endTime":1265.14,"body":"This time, Cook,"},{"speaker":"this lyrical description","startTime":1265.14,"endTime":1268.07,"body":"Charles Green, who was"},{"speaker":"this lyrical description","startTime":1265.14,"endTime":1268.07,"body":"the second astronomer,"},{"speaker":"this lyrical description","startTime":1268.07,"endTime":1270.13,"body":"because Cook himself could be counted"},{"speaker":"this lyrical description","startTime":1270.13,"endTime":1271.38,"body":"as an astronomer onboard,"},{"speaker":"this lyrical description","startTime":1272.57,"endTime":1275.84,"body":"the two astronomers found"},{"speaker":"this lyrical description","startTime":1272.57,"endTime":1275.84,"body":"themselves in Tahiti"},{"speaker":"this lyrical description","startTime":1275.84,"endTime":1277.61,"body":"in perfect conditions,"},{"speaker":"this lyrical description","startTime":1277.61,"endTime":1279.447,"body":"and Cook wrote in his diary,"},{"speaker":"this lyrical description","startTime":1279.447,"endTime":1282.317,"body":"\"The day proved as"},{"speaker":"this lyrical description","startTime":1279.447,"endTime":1282.317,"body":"favorable to our purpose"},{"speaker":"this lyrical description","startTime":1282.317,"endTime":1283.717,"body":"\"as we could wish,"},{"speaker":"this lyrical description","startTime":1283.717,"endTime":1286.497,"body":"\"not a cloud was to be seen the whole day,"},{"speaker":"this lyrical description","startTime":1286.497,"endTime":1288.01,"body":"\"and the air was perfectly clear"},{"speaker":"this lyrical description","startTime":1288.01,"endTime":1291.077,"body":"\"so that we had every"},{"speaker":"this lyrical description","startTime":1288.01,"endTime":1291.077,"body":"advantage we could desire"},{"speaker":"this lyrical description","startTime":1291.077,"endTime":1294.167,"body":"\"in observing the whole of the"},{"speaker":"this lyrical description","startTime":1291.077,"endTime":1294.167,"body":"passage of the planet Venus"},{"speaker":"this lyrical description","startTime":1294.167,"endTime":1296.207,"body":"\"over the Sun's disc.\""},{"speaker":"this lyrical description","startTime":1297.24,"endTime":1300.84,"body":"The data that Cook brought back to England"},{"speaker":"this lyrical description","startTime":1300.84,"endTime":1302.28,"body":"allowed Thomas Hornsby,"},{"speaker":"this lyrical description","startTime":1302.28,"endTime":1304.72,"body":"a Savilian professor"},{"speaker":"this lyrical description","startTime":1302.28,"endTime":1304.72,"body":"of astronomy at Oxford,"},{"speaker":"this lyrical description","startTime":1304.72,"endTime":1308.91,"body":"to derive a value of the astronomical unit"},{"speaker":"this lyrical description","startTime":1308.91,"endTime":1311.06,"body":"in this paper here,"},{"speaker":"this lyrical description","startTime":1311.06,"endTime":1315.363,"body":"of 93,726,900 English miles,"},{"speaker":"this lyrical description","startTime":1318.52,"endTime":1321.36,"body":"which is an error of less than 1%"},{"speaker":"this lyrical description","startTime":1321.36,"endTime":1323.68,"body":"with respect to the actual value,"},{"speaker":"this lyrical description","startTime":1323.68,"endTime":1326.21,"body":"an absolutely brilliant measurement"},{"speaker":"this lyrical description","startTime":1326.21,"endTime":1330.53,"body":"that they performed using"},{"speaker":"this lyrical description","startTime":1326.21,"endTime":1330.53,"body":"a Gregorian telescope"},{"speaker":"this lyrical description","startTime":1330.53,"endTime":1333.08,"body":"like the one that's shown here,"},{"speaker":"this lyrical description","startTime":1333.08,"endTime":1335.47,"body":"which they stood on barrels,"},{"speaker":"this lyrical description","startTime":1335.47,"endTime":1337.6,"body":"like the one that's shown"},{"speaker":"this lyrical description","startTime":1335.47,"endTime":1337.6,"body":"in this reconstruction"},{"speaker":"this lyrical description","startTime":1337.6,"endTime":1339.7,"body":"by the Royal Observatory, Greenwich,"},{"speaker":"this lyrical description","startTime":1339.7,"endTime":1343.12,"body":"which they filled with wet"},{"speaker":"this lyrical description","startTime":1339.7,"endTime":1343.12,"body":"sand to ensure stability"},{"speaker":"this lyrical description","startTime":1343.12,"endTime":1347.637,"body":"in the scorching heat of a Tahitian June."},{"speaker":"this lyrical description","startTime":1347.637,"endTime":1349.23,"body":"And you see here at the center,"},{"speaker":"this lyrical description","startTime":1349.23,"endTime":1351.3,"body":"the observations of the transit,"},{"speaker":"this lyrical description","startTime":1351.3,"endTime":1354.72,"body":"the planet impinging onto the solar disc,"},{"speaker":"this lyrical description","startTime":1354.72,"endTime":1356.64,"body":"by the astronomer Charles Green,"},{"speaker":"this lyrical description","startTime":1356.64,"endTime":1360.25,"body":"who, tragically, would not"},{"speaker":"this lyrical description","startTime":1356.64,"endTime":1360.25,"body":"make it back to England,"},{"speaker":"this lyrical description","startTime":1360.25,"endTime":1363.71,"body":"he would die in Jakarta"},{"speaker":"this lyrical description","startTime":1363.71,"endTime":1365.753,"body":"during the second leg of the voyage."},{"speaker":"this lyrical description","startTime":1366.64,"endTime":1368.18,"body":"But thanks to the observations"},{"speaker":"this lyrical description","startTime":1368.18,"endTime":1371.76,"body":"of James Cook, Charles"},{"speaker":"this lyrical description","startTime":1368.18,"endTime":1371.76,"body":"Green, and many others,"},{"speaker":"this lyrical description","startTime":1371.76,"endTime":1374.73,"body":"the AU was finally pinpointed down"},{"speaker":"this lyrical description","startTime":1374.73,"endTime":1376.89,"body":"to 1% of its actual value,"},{"speaker":"this lyrical description","startTime":1376.89,"endTime":1379.22,"body":"and the second rung was established,"},{"speaker":"this lyrical description","startTime":1379.22,"endTime":1384.14,"body":"at 150 million kilometers' distance."},{"speaker":"this lyrical description","startTime":1384.14,"endTime":1386.25,"body":"By the end of the 18th century,"},{"speaker":"this lyrical description","startTime":1386.25,"endTime":1390.39,"body":"the size of the solar system"},{"speaker":"this lyrical description","startTime":1386.25,"endTime":1390.39,"body":"had been reliably established"},{"speaker":"this lyrical description","startTime":1390.39,"endTime":1394.863,"body":"thanks to the measurement of"},{"speaker":"this lyrical description","startTime":1390.39,"endTime":1394.863,"body":"the AU, the astronomical unit."},{"speaker":"this lyrical description","startTime":1395.93,"endTime":1398.47,"body":"Uranus, discovered in 1781,"},{"speaker":"this lyrical description","startTime":1398.47,"endTime":1400.68,"body":"stood at an average distance of the Sun"},{"speaker":"this lyrical description","startTime":1400.68,"endTime":1403.23,"body":"of 2.8 billion kilometers,"},{"speaker":"this lyrical description","startTime":1403.23,"endTime":1406.573,"body":"and Neptune, when it"},{"speaker":"this lyrical description","startTime":1403.23,"endTime":1406.573,"body":"was discovered in 1846,"},{"speaker":"this lyrical description","startTime":1408.09,"endTime":1411.43,"body":"meant that that already"},{"speaker":"this lyrical description","startTime":1408.09,"endTime":1411.43,"body":"enormous amount of empty space"},{"speaker":"this lyrical description","startTime":1411.43,"endTime":1415.7,"body":"almost doubled to almost"},{"speaker":"this lyrical description","startTime":1411.43,"endTime":1415.7,"body":"5 billion kilometers,"},{"speaker":"this lyrical description","startTime":1415.7,"endTime":1418.51,"body":"giving a really huge size"},{"speaker":"this lyrical description","startTime":1418.51,"endTime":1421.883,"body":"for the extent of the solar system."},{"speaker":"this lyrical description","startTime":1422.98,"endTime":1424.12,"body":"But what about the stars?"},{"speaker":"this lyrical description","startTime":1424.12,"endTime":1425.407,"body":"Because the stars"},{"speaker":"this lyrical description","startTime":1425.407,"endTime":1428.73,"body":"had not been pinned"},{"speaker":"this lyrical description","startTime":1425.407,"endTime":1428.73,"body":"down to a distance yet."},{"speaker":"this lyrical description","startTime":1428.73,"endTime":1430.15,"body":"Everybody agreed"},{"speaker":"this lyrical description","startTime":1430.15,"endTime":1434.34,"body":"that they had to be almost"},{"speaker":"this lyrical description","startTime":1430.15,"endTime":1434.34,"body":"unfathomably far away,"},{"speaker":"this lyrical description","startTime":1434.34,"endTime":1436.24,"body":"but how far exactly,"},{"speaker":"this lyrical description","startTime":1436.24,"endTime":1437.713,"body":"nobody could quite say."},{"speaker":"this lyrical description","startTime":1439.27,"endTime":1440.75,"body":"Parallax could, in principle,"},{"speaker":"this lyrical description","startTime":1440.75,"endTime":1442.52,"body":"be used to establish their distance"},{"speaker":"this lyrical description","startTime":1442.52,"endTime":1444.63,"body":"by exploiting the fact"},{"speaker":"this lyrical description","startTime":1444.63,"endTime":1448.33,"body":"that our vantage point with"},{"speaker":"this lyrical description","startTime":1444.63,"endTime":1448.33,"body":"respect to the universe"},{"speaker":"this lyrical description","startTime":1448.33,"endTime":1451.087,"body":"changes as we go around the Sun,"},{"speaker":"this lyrical description","startTime":1451.087,"endTime":1452.83,"body":"and so if we measure the position"},{"speaker":"this lyrical description","startTime":1452.83,"endTime":1456.67,"body":"of a relatively nearby"},{"speaker":"this lyrical description","startTime":1452.83,"endTime":1456.67,"body":"star six months apart,"},{"speaker":"this lyrical description","startTime":1456.67,"endTime":1459.29,"body":"as we go around the Sun,"},{"speaker":"this lyrical description","startTime":1459.29,"endTime":1462.21,"body":"its apparent location"},{"speaker":"this lyrical description","startTime":1462.21,"endTime":1465.77,"body":"on the background of"},{"speaker":"this lyrical description","startTime":1462.21,"endTime":1465.77,"body":"even more distant stars"},{"speaker":"this lyrical description","startTime":1465.77,"endTime":1468.25,"body":"will change by a certain angle."},{"speaker":"this lyrical description","startTime":1468.25,"endTime":1469.78,"body":"If we can only measure this angle,"},{"speaker":"this lyrical description","startTime":1469.78,"endTime":1474.313,"body":"the parallax formula will"},{"speaker":"this lyrical description","startTime":1469.78,"endTime":1474.313,"body":"give us the distance,"},{"speaker":"this lyrical description","startTime":1475.29,"endTime":1478.09,"body":"but those angles are incredibly small,"},{"speaker":"this lyrical description","startTime":1478.09,"endTime":1480.73,"body":"even though the distance"},{"speaker":"this lyrical description","startTime":1478.09,"endTime":1480.73,"body":"from one end to the other"},{"speaker":"this lyrical description","startTime":1480.73,"endTime":1482.45,"body":"of our change of vantage point"},{"speaker":"this lyrical description","startTime":1482.45,"endTime":1486.533,"body":"is a mighty 300 million kilometers."},{"speaker":"this lyrical description","startTime":1488.23,"endTime":1490.45,"body":"Let's get a sense for those angles."},{"speaker":"this lyrical description","startTime":1490.45,"endTime":1491.44,"body":"Remember, the Moon in the sky,"},{"speaker":"this lyrical description","startTime":1491.44,"endTime":1496.433,"body":"the Moon in the sky subtends"},{"speaker":"this lyrical description","startTime":1491.44,"endTime":1496.433,"body":"an angle of about 1/2 a degree."},{"speaker":"this lyrical description","startTime":1497.67,"endTime":1501.07,"body":"Each degree is further"},{"speaker":"this lyrical description","startTime":1497.67,"endTime":1501.07,"body":"subdivided in 60 parts,"},{"speaker":"this lyrical description","startTime":1501.07,"endTime":1504.51,"body":"which we call minutes"},{"speaker":"this lyrical description","startTime":1501.07,"endTime":1504.51,"body":"of arc, or arc minutes,"},{"speaker":"this lyrical description","startTime":1504.51,"endTime":1505.66,"body":"and each arc minute"},{"speaker":"this lyrical description","startTime":1505.66,"endTime":1510.38,"body":"is further subdivided in 60"},{"speaker":"this lyrical description","startTime":1505.66,"endTime":1510.38,"body":"arc seconds, equal parts."},{"speaker":"this lyrical description","startTime":1510.38,"endTime":1512.13,"body":"And the reason why we"},{"speaker":"this lyrical description","startTime":1510.38,"endTime":1512.13,"body":"use this factor of 60"},{"speaker":"this lyrical description","startTime":1512.13,"endTime":1514.07,"body":"goes back all the way to 5,000 years ago,"},{"speaker":"this lyrical description","startTime":1514.07,"endTime":1515.68,"body":"to Babylonian time,"},{"speaker":"this lyrical description","startTime":1515.68,"endTime":1516.72,"body":"it's a fascinating story,"},{"speaker":"this lyrical description","startTime":1516.72,"endTime":1519.573,"body":"but not one that we can tell today."},{"speaker":"this lyrical description","startTime":1521.79,"endTime":1523.92,"body":"The unaided human eye"},{"speaker":"this lyrical description","startTime":1523.92,"endTime":1527.33,"body":"can discern angles as"},{"speaker":"this lyrical description","startTime":1523.92,"endTime":1527.33,"body":"small as one arc minute,"},{"speaker":"this lyrical description","startTime":1527.33,"endTime":1529.563,"body":"so 1/60 of a degree."},{"speaker":"this lyrical description","startTime":1530.56,"endTime":1532.05,"body":"This is the same angular size"},{"speaker":"this lyrical description","startTime":1532.05,"endTime":1536.053,"body":"as a one pound coin seen"},{"speaker":"this lyrical description","startTime":1532.05,"endTime":1536.053,"body":"from 80 meters away."},{"speaker":"this lyrical description","startTime":1537.14,"endTime":1538.11,"body":"An arc second, remember,"},{"speaker":"this lyrical description","startTime":1538.11,"endTime":1539.5,"body":"is 60 times smaller,"},{"speaker":"this lyrical description","startTime":1539.5,"endTime":1541.41,"body":"so this is the angular size"},{"speaker":"this lyrical description","startTime":1541.41,"endTime":1546.41,"body":"of a pound coin seen"},{"speaker":"this lyrical description","startTime":1541.41,"endTime":1546.41,"body":"from 4.8 kilometers away."},{"speaker":"this lyrical description","startTime":1547.89,"endTime":1549.98,"body":"Today, we have space-based observatories"},{"speaker":"this lyrical description","startTime":1549.98,"endTime":1552.77,"body":"that can measure tiny, tiny angles,"},{"speaker":"this lyrical description","startTime":1552.77,"endTime":1554.44,"body":"and therefore measure the distance"},{"speaker":"this lyrical description","startTime":1554.44,"endTime":1557.35,"body":"to stars in the Milky Way very reliably."},{"speaker":"this lyrical description","startTime":1557.35,"endTime":1559.473,"body":"The best observatories we have"},{"speaker":"this lyrical description","startTime":1559.473,"endTime":1564.26,"body":"have achieved accuracy of one"},{"speaker":"this lyrical description","startTime":1559.473,"endTime":1564.26,"body":"millionth of an arc second."},{"speaker":"this lyrical description","startTime":1564.26,"endTime":1565.33,"body":"This is equivalent"},{"speaker":"this lyrical description","startTime":1565.33,"endTime":1569.76,"body":"to the angle subtended"},{"speaker":"this lyrical description","startTime":1565.33,"endTime":1569.76,"body":"by a coin on Neptune"},{"speaker":"this lyrical description","startTime":1569.76,"endTime":1571.093,"body":"seen from the Earth."},{"speaker":"this lyrical description","startTime":1572.19,"endTime":1573.88,"body":"The parallax is, in fact, so fundamental"},{"speaker":"this lyrical description","startTime":1573.88,"endTime":1575.77,"body":"that it led astronomers to use it"},{"speaker":"this lyrical description","startTime":1575.77,"endTime":1580.77,"body":"to define another unit of measure"},{"speaker":"this lyrical description","startTime":1575.77,"endTime":1580.77,"body":"for distances, the parsec,"},{"speaker":"this lyrical description","startTime":1581.884,"endTime":1583.55,"body":"a word that's a contraction"},{"speaker":"this lyrical description","startTime":1583.55,"endTime":1586.953,"body":"of the words parallax and second."},{"speaker":"this lyrical description","startTime":1586.953,"endTime":1589.51,"body":"A parsec is the distance"},{"speaker":"this lyrical description","startTime":1589.51,"endTime":1594.51,"body":"at which a star would exhibit"},{"speaker":"this lyrical description","startTime":1589.51,"endTime":1594.51,"body":"a parallax of one arc second,"},{"speaker":"this lyrical description","startTime":1595.4,"endTime":1599.24,"body":"and that corresponds to 3.26 light years,"},{"speaker":"this lyrical description","startTime":1599.24,"endTime":1601.36,"body":"and given how big a light year is,"},{"speaker":"this lyrical description","startTime":1601.36,"endTime":1604.473,"body":"that amounts to 30,000 billion kilometers."},{"speaker":"this lyrical description","startTime":1606.22,"endTime":1608.66,"body":"In order to measure the"},{"speaker":"this lyrical description","startTime":1606.22,"endTime":1608.66,"body":"distance to the stars, then,"},{"speaker":"this lyrical description","startTime":1608.66,"endTime":1609.77,"body":"we needed to be able"},{"speaker":"this lyrical description","startTime":1609.77,"endTime":1612.67,"body":"to measure tiny, tiny angles of parallax."},{"speaker":"this lyrical description","startTime":1612.67,"endTime":1614.55,"body":"Nobody had been able"},{"speaker":"this lyrical description","startTime":1614.55,"endTime":1619.5,"body":"to build an instrument capable"},{"speaker":"this lyrical description","startTime":1614.55,"endTime":1619.5,"body":"of doing that until 1838,"},{"speaker":"this lyrical description","startTime":1619.5,"endTime":1622.91,"body":"when the mathematician and"},{"speaker":"this lyrical description","startTime":1619.5,"endTime":1622.91,"body":"astronomer Friedrich Bessel,"},{"speaker":"this lyrical description","startTime":1622.91,"endTime":1625.06,"body":"the director of Konigsberg Observatory,"},{"speaker":"this lyrical description","startTime":1625.06,"endTime":1627.63,"body":"in today's Kaliningrad,"},{"speaker":"this lyrical description","startTime":1625.06,"endTime":1627.63,"body":"on the Russian Baltic,"},{"speaker":"this lyrical description","startTime":1627.63,"endTime":1628.463,"body":"did it."},{"speaker":"this lyrical description","startTime":1629.6,"endTime":1632.811,"body":"What Bessel did was to use a heliometer,"},{"speaker":"this lyrical description","startTime":1632.811,"endTime":1635.06,"body":"an instrument that had"},{"speaker":"this lyrical description","startTime":1632.811,"endTime":1635.06,"body":"been originally conceived"},{"speaker":"this lyrical description","startTime":1635.06,"endTime":1636.87,"body":"to measure the diameter of the Sun,"},{"speaker":"this lyrical description","startTime":1636.87,"endTime":1637.9,"body":"but then perfected."},{"speaker":"this lyrical description","startTime":1637.9,"endTime":1640.63,"body":"A Heliometer is a telescope"},{"speaker":"this lyrical description","startTime":1640.63,"endTime":1643.0,"body":"with a lens that's sliced in half,"},{"speaker":"this lyrical description","startTime":1643.0,"endTime":1645.14,"body":"like you can see here,"},{"speaker":"this lyrical description","startTime":1645.14,"endTime":1648.04,"body":"and the two relative halves of the lens"},{"speaker":"this lyrical description","startTime":1648.04,"endTime":1649.78,"body":"can be adjusted horizontally"},{"speaker":"this lyrical description","startTime":1649.78,"endTime":1653.7,"body":"by moving a micrometer screw."},{"speaker":"this lyrical description","startTime":1653.7,"endTime":1656.403,"body":"And so if you have two stars in the sky,"},{"speaker":"this lyrical description","startTime":1657.256,"endTime":1659.05,"body":"and you see them through a telescope"},{"speaker":"this lyrical description","startTime":1659.05,"endTime":1660.89,"body":"with this kind of sliced lens,"},{"speaker":"this lyrical description","startTime":1660.89,"endTime":1665.89,"body":"that will give you four"},{"speaker":"this lyrical description","startTime":1660.89,"endTime":1665.89,"body":"different images, here,"},{"speaker":"this lyrical description","startTime":1666.17,"endTime":1670.07,"body":"and by moving the micrometer thumbscrew,"},{"speaker":"this lyrical description","startTime":1670.07,"endTime":1675.07,"body":"you can make those double"},{"speaker":"this lyrical description","startTime":1670.07,"endTime":1675.07,"body":"images of the stars align,"},{"speaker":"this lyrical description","startTime":1675.16,"endTime":1678.05,"body":"and if you are able to do so"},{"speaker":"this lyrical description","startTime":1678.05,"endTime":1679.0,"body":"by reading off"},{"speaker":"this lyrical description","startTime":1679.0,"endTime":1681.67,"body":"by how much you've moved the"},{"speaker":"this lyrical description","startTime":1679.0,"endTime":1681.67,"body":"relative position of the lenses"},{"speaker":"this lyrical description","startTime":1681.67,"endTime":1683.8,"body":"with respect to each"},{"speaker":"this lyrical description","startTime":1681.67,"endTime":1683.8,"body":"other from the micrometer,"},{"speaker":"this lyrical description","startTime":1683.8,"endTime":1685.28,"body":"in this scale up here,"},{"speaker":"this lyrical description","startTime":1685.28,"endTime":1688.62,"body":"you can establish very,"},{"speaker":"this lyrical description","startTime":1685.28,"endTime":1688.62,"body":"very small angle differences"},{"speaker":"this lyrical description","startTime":1688.62,"endTime":1689.743,"body":"between the stars."},{"speaker":"this lyrical description","startTime":1691.367,"endTime":1693.147,"body":"Bessel carefully monitored the position"},{"speaker":"this lyrical description","startTime":1693.147,"endTime":1698.147,"body":"of the star 61 Cygni"},{"speaker":"this lyrical description","startTime":1693.147,"endTime":1698.147,"body":"over the course of a year"},{"speaker":"this lyrical description","startTime":1698.22,"endTime":1699.84,"body":"with respect to the background stars"},{"speaker":"this lyrical description","startTime":1699.84,"endTime":1701.5,"body":"using his heliometer,"},{"speaker":"this lyrical description","startTime":1701.5,"endTime":1706.5,"body":"finally announcing a parallax"},{"speaker":"this lyrical description","startTime":1701.5,"endTime":1706.5,"body":"of 0.314 arc seconds."},{"speaker":"this lyrical description","startTime":1706.78,"endTime":1710.89,"body":"He pinned this star to being"},{"speaker":"this lyrical description","startTime":1706.78,"endTime":1710.89,"body":"about three parsecs away,"},{"speaker":"which meant 10 light years","startTime":1713.93,"endTime":1718.93,"body":"a new rung had been added to"},{"speaker":"which meant 10 light years","startTime":1713.93,"endTime":1718.93,"body":"the cosmic distance ladder,"},{"speaker":"which meant 10 light years","startTime":1719.53,"endTime":1721.34,"body":"one that was described"},{"speaker":"which meant 10 light years","startTime":1721.34,"endTime":1724.83,"body":"by the Royal Astronomical"},{"speaker":"which meant 10 light years","startTime":1721.34,"endTime":1724.83,"body":"Society President John Herschel"},{"speaker":"which meant 10 light years","startTime":1724.83,"endTime":1728.27,"body":"as the greatest and most glorious triumph"},{"speaker":"which meant 10 light years","startTime":1728.27,"endTime":1730.91,"body":"which practical astronomy"},{"speaker":"which meant 10 light years","startTime":1728.27,"endTime":1730.91,"body":"has ever witnessed,"},{"speaker":"which meant 10 light years","startTime":1730.91,"endTime":1732.25,"body":"when he conferred"},{"speaker":"which meant 10 light years","startTime":1732.25,"endTime":1734.99,"body":"the Gold Medal of the"},{"speaker":"which meant 10 light years","startTime":1732.25,"endTime":1734.99,"body":"Royal Astronomical Society"},{"speaker":"which meant 10 light years","startTime":1734.99,"endTime":1737.74,"body":"to Bessel in 1841."},{"speaker":"which meant 10 light years","startTime":1737.74,"endTime":1741.19,"body":"61 Cygni is not the"},{"speaker":"which meant 10 light years","startTime":1737.74,"endTime":1741.19,"body":"nearest star to the Earth,"},{"speaker":"which meant 10 light years","startTime":1741.19,"endTime":1744.06,"body":"Alpha Centauri and Proxima"},{"speaker":"which meant 10 light years","startTime":1741.19,"endTime":1744.06,"body":"Centauri actually are,"},{"speaker":"which meant 10 light years","startTime":1744.06,"endTime":1746.33,"body":"they stand at about four light years,"},{"speaker":"which meant 10 light years","startTime":1746.33,"endTime":1748.52,"body":"or just over a parsec way,"},{"speaker":"which meant 10 light years","startTime":1748.52,"endTime":1751.92,"body":"but still, this is the new distance scale,"},{"speaker":"which meant 10 light years","startTime":1751.92,"endTime":1755.28,"body":"which puts stars, generally,"},{"speaker":"which meant 10 light years","startTime":1755.28,"endTime":1760.083,"body":"tens, hundreds, thousands"},{"speaker":"which meant 10 light years","startTime":1755.28,"endTime":1760.083,"body":"of light years away from us."},{"speaker":"which meant 10 light years","startTime":1762.67,"endTime":1764.67,"body":"John Herschel also said"},{"speaker":"which meant 10 light years","startTime":1764.67,"endTime":1765.64,"body":"that thanks to this measurement,"},{"speaker":"which meant 10 light years","startTime":1765.64,"endTime":1770.3,"body":"finally, the sounding line"},{"speaker":"which meant 10 light years","startTime":1765.64,"endTime":1770.3,"body":"of distances in the universe"},{"speaker":"which meant 10 light years","startTime":1770.3,"endTime":1771.7,"body":"had touched bottom"},{"speaker":"which meant 10 light years","startTime":1771.7,"endTime":1773.81,"body":"by measuring, finally,"},{"speaker":"which meant 10 light years","startTime":1771.7,"endTime":1773.81,"body":"the distance to the stars,"},{"speaker":"which meant 10 light years","startTime":1773.81,"endTime":1775.84,"body":"but of course, that wasn't true,"},{"speaker":"which meant 10 light years","startTime":1775.84,"endTime":1779.83,"body":"because further and further"},{"speaker":"which meant 10 light years","startTime":1775.84,"endTime":1779.83,"body":"realms of discovery beckoned"},{"speaker":"which meant 10 light years","startTime":1779.83,"endTime":1781.77,"body":"immediately afterwards,"},{"speaker":"which meant 10 light years","startTime":1781.77,"endTime":1783.23,"body":"the question was merely displaced"},{"speaker":"which meant 10 light years","startTime":1783.23,"endTime":1785.24,"body":"from the province of the stars,"},{"speaker":"which meant 10 light years","startTime":1785.24,"endTime":1787.43,"body":"whose distances now could"},{"speaker":"which meant 10 light years","startTime":1785.24,"endTime":1787.43,"body":"routinely be measured"},{"speaker":"which meant 10 light years","startTime":1787.43,"endTime":1789.66,"body":"to thousands of light years away,"},{"speaker":"which meant 10 light years","startTime":1789.66,"endTime":1793.31,"body":"to the mysterious realm of the nebulae."},{"speaker":"which meant 10 light years","startTime":1793.31,"endTime":1796.17,"body":"Those were those faint puffs of haze,"},{"speaker":"which meant 10 light years","startTime":1796.17,"endTime":1797.57,"body":"sometimes showing a hint"},{"speaker":"which meant 10 light years","startTime":1797.57,"endTime":1799.53,"body":"of some twirling and spiral structure"},{"speaker":"which meant 10 light years","startTime":1799.53,"endTime":1802.763,"body":"that nobody could quite"},{"speaker":"which meant 10 light years","startTime":1799.53,"endTime":1802.763,"body":"understand what they were."},{"speaker":"which meant 10 light years","startTime":1803.81,"endTime":1808.37,"body":"Were those just puffs of"},{"speaker":"which meant 10 light years","startTime":1803.81,"endTime":1808.37,"body":"gas nearby the Milky Way,"},{"speaker":"which meant 10 light years","startTime":1808.37,"endTime":1809.96,"body":"but they're quite small,"},{"speaker":"which meant 10 light years","startTime":1809.96,"endTime":1813.36,"body":"or were they mighty"},{"speaker":"which meant 10 light years","startTime":1809.96,"endTime":1813.36,"body":"galaxies in their own right,"},{"speaker":"which meant 10 light years","startTime":1813.36,"endTime":1815.48,"body":"which were reduced to faintness"},{"speaker":"which meant 10 light years","startTime":1815.48,"endTime":1818.86,"body":"merely by virtue of their great distances?"},{"speaker":"which meant 10 light years","startTime":1818.86,"endTime":1819.953,"body":"Nobody could tell."},{"speaker":"which meant 10 light years","startTime":1820.94,"endTime":1823.14,"body":"Maybe, if you could"},{"speaker":"which meant 10 light years","startTime":1820.94,"endTime":1823.14,"body":"measure distances to us,"},{"speaker":"which meant 10 light years","startTime":1823.14,"endTime":1826.143,"body":"that could give us a hint"},{"speaker":"which meant 10 light years","startTime":1823.14,"endTime":1826.143,"body":"about their true nature."},{"speaker":"which meant 10 light years","startTime":1827.77,"endTime":1829.33,"body":"With the turn of the 20th century,"},{"speaker":"which meant 10 light years","startTime":1829.33,"endTime":1833.04,"body":"a new, powerful tool came"},{"speaker":"which meant 10 light years","startTime":1829.33,"endTime":1833.04,"body":"in aid to the astronomers,"},{"speaker":"which meant 10 light years","startTime":1833.04,"endTime":1835.55,"body":"the photographic plate."},{"speaker":"which meant 10 light years","startTime":1835.55,"endTime":1837.96,"body":"One of the pioneers of the technique"},{"speaker":"which meant 10 light years","startTime":1837.96,"endTime":1841.74,"body":"had been the amateur astronomer,"},{"speaker":"which meant 10 light years","startTime":1837.96,"endTime":1841.74,"body":"and medic by profession,"},{"speaker":"which meant 10 light years","startTime":1841.74,"endTime":1843.57,"body":"Henry Draper,"},{"speaker":"which meant 10 light years","startTime":1843.57,"endTime":1846.96,"body":"who, together with his"},{"speaker":"which meant 10 light years","startTime":1843.57,"endTime":1846.96,"body":"wife Mary Anna Draper,"},{"speaker":"which meant 10 light years","startTime":1846.96,"endTime":1849.89,"body":"was among the first to"},{"speaker":"which meant 10 light years","startTime":1846.96,"endTime":1849.89,"body":"use photographic plates"},{"speaker":"which meant 10 light years","startTime":1849.89,"endTime":1852.66,"body":"to capture stars and nebulae,"},{"speaker":"which meant 10 light years","startTime":1852.66,"endTime":1856.1,"body":"and spectra, even, of those objects."},{"speaker":"which meant 10 light years","startTime":1856.1,"endTime":1859.7,"body":"His untimely death in 1882"},{"speaker":"which meant 10 light years","startTime":1859.7,"endTime":1861.69,"body":"spurred his widowed wife"},{"speaker":"which meant 10 light years","startTime":1861.69,"endTime":1866.69,"body":"to generously support the"},{"speaker":"which meant 10 light years","startTime":1861.69,"endTime":1866.69,"body":"efforts of Harvard Observatory"},{"speaker":"which meant 10 light years","startTime":1866.81,"endTime":1869.3,"body":"to continue her husband's work"},{"speaker":"which meant 10 light years","startTime":1869.3,"endTime":1871.17,"body":"and map out the stars,"},{"speaker":"which meant 10 light years","startTime":1871.17,"endTime":1872.28,"body":"and for several decades,"},{"speaker":"which meant 10 light years","startTime":1872.28,"endTime":1875.54,"body":"she generously funded the establishment"},{"speaker":"which meant 10 light years","startTime":1875.54,"endTime":1877.32,"body":"of the Henry Draper Catalogue"},{"speaker":"which meant 10 light years","startTime":1877.32,"endTime":1878.77,"body":"that would eventually consist of"},{"speaker":"which meant 10 light years","startTime":1878.77,"endTime":1881.173,"body":"over half a million photographic plates."},{"speaker":"which meant 10 light years","startTime":1882.2,"endTime":1886.1,"body":"As the observatory kept on"},{"speaker":"which meant 10 light years","startTime":1882.2,"endTime":1886.1,"body":"measuring and photographing"},{"speaker":"which meant 10 light years","startTime":1886.1,"endTime":1888.123,"body":"all parts of the sky,"},{"speaker":"which meant 10 light years","startTime":1888.123,"endTime":1891.7,"body":"a great deal of effort was"},{"speaker":"which meant 10 light years","startTime":1888.123,"endTime":1891.7,"body":"needed to look at the plates,"},{"speaker":"which meant 10 light years","startTime":1891.7,"endTime":1893.69,"body":"measure the position and brightness"},{"speaker":"which meant 10 light years","startTime":1893.69,"endTime":1896.54,"body":"of the ever-increasing number of stars"},{"speaker":"which meant 10 light years","startTime":1896.54,"endTime":1899.54,"body":"that the photographic"},{"speaker":"which meant 10 light years","startTime":1896.54,"endTime":1899.54,"body":"plates were revealing,"},{"speaker":"which meant 10 light years","startTime":1899.54,"endTime":1903.32,"body":"and that's where the Harvard"},{"speaker":"which meant 10 light years","startTime":1899.54,"endTime":1903.32,"body":"Observatory computers come in,"},{"speaker":"which meant 10 light years","startTime":1903.32,"endTime":1907.68,"body":"a team made exclusively of women"},{"speaker":"which meant 10 light years","startTime":1907.68,"endTime":1911.11,"body":"who were entrusted the"},{"speaker":"which meant 10 light years","startTime":1907.68,"endTime":1911.11,"body":"difficult and painstaking job"},{"speaker":"which meant 10 light years","startTime":1911.11,"endTime":1912.63,"body":"of going through the plates,"},{"speaker":"which meant 10 light years","startTime":1912.63,"endTime":1917.61,"body":"measuring position and"},{"speaker":"which meant 10 light years","startTime":1912.63,"endTime":1917.61,"body":"brightness of the stars."},{"speaker":"which meant 10 light years","startTime":1917.61,"endTime":1919.193,"body":"You can see some of them here,"},{"speaker":"which meant 10 light years","startTime":1920.09,"endTime":1924.763,"body":"the lady sat in the middle"},{"speaker":"which meant 10 light years","startTime":1920.09,"endTime":1924.763,"body":"is Mary Anna Draper herself."},{"speaker":"which meant 10 light years","startTime":1926.03,"endTime":1930.22,"body":"The most gifted and prolific"},{"speaker":"which meant 10 light years","startTime":1926.03,"endTime":1930.22,"body":"of the lady astronomers"},{"speaker":"which meant 10 light years","startTime":1930.22,"endTime":1933.37,"body":"was undoubtedly Ms. Annie Jump Cannon,"},{"speaker":"which meant 10 light years","startTime":1933.37,"endTime":1935.89,"body":"who worked for 40 years"},{"speaker":"which meant 10 light years","startTime":1933.37,"endTime":1935.89,"body":"at the observatory,"},{"speaker":"which meant 10 light years","startTime":1935.89,"endTime":1940.89,"body":"and she personally classified"},{"speaker":"which meant 10 light years","startTime":1935.89,"endTime":1940.89,"body":"over 200,000 stars,"},{"speaker":"which meant 10 light years","startTime":1941.22,"endTime":1943.17,"body":"and she not only classified them"},{"speaker":"which meant 10 light years","startTime":1943.17,"endTime":1947.41,"body":"according to their spectrum"},{"speaker":"which meant 10 light years","startTime":1943.17,"endTime":1947.41,"body":"and measured their brightness,"},{"speaker":"which meant 10 light years","startTime":1947.41,"endTime":1952.41,"body":"she did so using an instrument"},{"speaker":"which meant 10 light years","startTime":1947.41,"endTime":1952.41,"body":"which appears quite strange,"},{"speaker":"which meant 10 light years","startTime":1953.36,"endTime":1955.15,"body":"but was very, very useful,"},{"speaker":"which meant 10 light years","startTime":1955.15,"endTime":1957.76,"body":"the so-called fly spanker."},{"speaker":"which meant 10 light years","startTime":1957.76,"endTime":1960.64,"body":"It's nothing else but a glass"},{"speaker":"which meant 10 light years","startTime":1957.76,"endTime":1960.64,"body":"plate with a little handle,"},{"speaker":"which meant 10 light years","startTime":1960.64,"endTime":1961.56,"body":"and on the glass plate,"},{"speaker":"which meant 10 light years","startTime":1961.56,"endTime":1966.16,"body":"you see marked in ink calibration stars,"},{"speaker":"which meant 10 light years","startTime":1966.16,"endTime":1968.96,"body":"little stars that were used as comparators"},{"speaker":"which meant 10 light years","startTime":1968.96,"endTime":1970.75,"body":"to establish the magnitude, the brightness"},{"speaker":"which meant 10 light years","startTime":1970.75,"endTime":1972.63,"body":"of the stars of interest."},{"speaker":"which meant 10 light years","startTime":1972.63,"endTime":1974.55,"body":"It was called the fly spanker"},{"speaker":"which meant 10 light years","startTime":1974.55,"endTime":1978.773,"body":"because it was too small"},{"speaker":"which meant 10 light years","startTime":1974.55,"endTime":1978.773,"body":"to be a fly swatter."},{"speaker":"which meant 10 light years","startTime":1980.462,"endTime":1984.3,"body":"A contemporary of Ms. Cannon"},{"speaker":"which meant 10 light years","startTime":1980.462,"endTime":1984.3,"body":"was Ms. Henrietta Swan Leavitt,"},{"speaker":"which meant 10 light years","startTime":1984.3,"endTime":1987.6,"body":"who had excelled in her"},{"speaker":"which meant 10 light years","startTime":1984.3,"endTime":1987.6,"body":"studies at Radcliffe College,"},{"speaker":"which meant 10 light years","startTime":1987.6,"endTime":1990.403,"body":"one of the few women's"},{"speaker":"which meant 10 light years","startTime":1987.6,"endTime":1990.403,"body":"colleges at the time,"},{"speaker":"which meant 10 light years","startTime":1990.403,"endTime":1992.98,"body":"and she was a particularly"},{"speaker":"which meant 10 light years","startTime":1990.403,"endTime":1992.98,"body":"gifted in mathematics,"},{"speaker":"which meant 10 light years","startTime":1992.98,"endTime":1993.99,"body":"algebra and calculus,"},{"speaker":"which meant 10 light years","startTime":1993.99,"endTime":1996.53,"body":"and she therefore landed, initially,"},{"speaker":"which meant 10 light years","startTime":1996.53,"endTime":2001.53,"body":"an unpaid assistantship at the"},{"speaker":"which meant 10 light years","startTime":1996.53,"endTime":2001.53,"body":"Harvard Observatory in 1895,"},{"speaker":"which meant 10 light years","startTime":2001.62,"endTime":2002.71,"body":"and at that point,"},{"speaker":"which meant 10 light years","startTime":2002.71,"endTime":2004.58,"body":"Edward Pickering, the"},{"speaker":"which meant 10 light years","startTime":2002.71,"endTime":2004.58,"body":"director of the observatory,"},{"speaker":"which meant 10 light years","startTime":2004.58,"endTime":2008.08,"body":"charged her with assessing the brightness,"},{"speaker":"which meant 10 light years","startTime":2008.08,"endTime":2010.22,"body":"and therefore the magnitude, of stars,"},{"speaker":"which meant 10 light years","startTime":2010.22,"endTime":2011.52,"body":"from photographic plates,"},{"speaker":"which meant 10 light years","startTime":2011.52,"endTime":2013.833,"body":"and she used the fly"},{"speaker":"which meant 10 light years","startTime":2011.52,"endTime":2013.833,"body":"spanker to do the job."},{"speaker":"which meant 10 light years","startTime":2014.99,"endTime":2017.33,"body":"She later left the observatory"},{"speaker":"which meant 10 light years","startTime":2014.99,"endTime":2017.33,"body":"for a stint in Europe,"},{"speaker":"which meant 10 light years","startTime":2017.33,"endTime":2018.177,"body":"and then in Wisconsin,"},{"speaker":"which meant 10 light years","startTime":2018.177,"endTime":2020.76,"body":"and she returned in 1903,"},{"speaker":"which meant 10 light years","startTime":2020.76,"endTime":2024.84,"body":"when she was paid 30 cents an hour"},{"speaker":"which meant 10 light years","startTime":2024.84,"endTime":2027.11,"body":"to first identify variable stars,"},{"speaker":"which meant 10 light years","startTime":2027.11,"endTime":2030.09,"body":"stars whose brightness changes over time,"},{"speaker":"which meant 10 light years","startTime":2030.09,"endTime":2033.15,"body":"in the Magellanic Clouds,"},{"speaker":"which meant 10 light years","startTime":2030.09,"endTime":2033.15,"body":"in the Southern Hemisphere,"},{"speaker":"which meant 10 light years","startTime":2033.15,"endTime":2036.3,"body":"and then measure the changes"},{"speaker":"which meant 10 light years","startTime":2033.15,"endTime":2036.3,"body":"in the brightness over time,"},{"speaker":"which meant 10 light years","startTime":2036.3,"endTime":2038.403,"body":"a painstakingly difficult job."},{"speaker":"which meant 10 light years","startTime":2039.28,"endTime":2044.28,"body":"By 1908, she had amassed"},{"speaker":"which meant 10 light years","startTime":2039.28,"endTime":2044.28,"body":"777 variable stars,"},{"speaker":"which meant 10 light years","startTime":2045.69,"endTime":2049.69,"body":"and she noticed a strange"},{"speaker":"which meant 10 light years","startTime":2045.69,"endTime":2049.69,"body":"pattern among 16 of them"},{"speaker":"which meant 10 light 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found"},{"speaker":"which meant 10 light years","startTime":2067.64,"endTime":2070.733,"body":"another nine variables"},{"speaker":"which meant 10 light years","startTime":2070.733,"endTime":2073.38,"body":"exhibiting the same pattern."},{"speaker":"which meant 10 light years","startTime":2073.38,"endTime":2076.47,"body":"The period of variability"},{"speaker":"which meant 10 light years","startTime":2073.38,"endTime":2076.47,"body":"of those remarkable stars"},{"speaker":"which meant 10 light years","startTime":2076.47,"endTime":2078.64,"body":"appeared to reflect their brightness."},{"speaker":"which meant 10 light years","startTime":2078.64,"endTime":2081.65,"body":"You see here a sketch"},{"speaker":"which meant 10 light years","startTime":2081.65,"endTime":2085.58,"body":"of what the brightness over"},{"speaker":"which meant 10 light years","startTime":2081.65,"endTime":2085.58,"body":"time of those stars would do,"},{"speaker":"which meant 10 light years","startTime":2085.58,"endTime":2089.88,"body":"it would grow, and then"},{"speaker":"which meant 10 light years","startTime":2085.58,"endTime":2089.88,"body":"it would rapidly decline,"},{"speaker":"which meant 10 light years","startTime":2089.88,"endTime":2091.25,"body":"and then grow rapidly again"},{"speaker":"which meant 10 light years","startTime":2091.25,"endTime":2092.52,"body":"in this characteristic pattern."},{"speaker":"which meant 10 light years","startTime":2092.52,"endTime":2094.29,"body":"We now know that those stars,"},{"speaker":"which meant 10 light years","startTime":2094.29,"endTime":2096.193,"body":"which we call Cepheid variables,"},{"speaker":"which meant 10 light years","startTime":2097.66,"endTime":2098.493,"body":"because of the name"},{"speaker":"which meant 10 light years","startTime":2098.493,"endTime":2101.53,"body":"of the prototypical"},{"speaker":"which meant 10 light years","startTime":2098.493,"endTime":2101.53,"body":"example of those stars,"},{"speaker":"which meant 10 light years","startTime":2101.53,"endTime":2106.53,"body":"which is a star found in the"},{"speaker":"which meant 10 light years","startTime":2101.53,"endTime":2106.53,"body":"constellation of Cepheus,"},{"speaker":"which meant 10 light years","startTime":2106.86,"endTime":2109.0,"body":"those stars are actually pulsating stars,"},{"speaker":"which meant 10 light years","startTime":2109.0,"endTime":2110.36,"body":"they blow up,"},{"speaker":"which meant 10 light years","startTime":2110.36,"endTime":2113.5,"body":"and they trap their light"},{"speaker":"which meant 10 light years","startTime":2110.36,"endTime":2113.5,"body":"inside them as they blow up,"},{"speaker":"which meant 10 light years","startTime":2113.5,"endTime":2115.61,"body":"and then their opacity drops,"},{"speaker":"which meant 10 light years","startTime":2115.61,"endTime":2117.34,"body":"and therefore the star contracts,"},{"speaker":"which meant 10 light years","startTime":2117.34,"endTime":2118.55,"body":"they release the light,"},{"speaker":"which meant 10 light years","startTime":2118.55,"endTime":2122.21,"body":"and they dim again in a periodic fashion."},{"speaker":"which meant 10 light years","startTime":2122.21,"endTime":2124.25,"body":"Effectively, those stars"},{"speaker":"which meant 10 light years","startTime":2124.25,"endTime":2128.53,"body":"are stars that breathe light in and out."},{"speaker":"which meant 10 light years","startTime":2128.53,"endTime":2130.41,"body":"But what Henrietta Leavitt discovered"},{"speaker":"which meant 10 light years","startTime":2130.41,"endTime":2133.88,"body":"was that the period of a pulsation,"},{"speaker":"which meant 10 light years","startTime":2133.88,"endTime":2136.48,"body":"for the period of variation in brightness,"},{"speaker":"which meant 10 light years","startTime":2136.48,"endTime":2141.48,"body":"seemed to be related to"},{"speaker":"which meant 10 light years","startTime":2136.48,"endTime":2141.48,"body":"their intrinsic brightness."},{"speaker":"which meant 10 light years","startTime":2141.8,"endTime":2145.27,"body":"So by establishing the"},{"speaker":"which meant 10 light years","startTime":2141.8,"endTime":2145.27,"body":"existence of 25 such stars"},{"speaker":"which meant 10 light years","startTime":2145.27,"endTime":2147.43,"body":"in the Magellanic Cloud,"},{"speaker":"which meant 10 light years","startTime":2147.43,"endTime":2149.68,"body":"and because they were"},{"speaker":"which meant 10 light years","startTime":2147.43,"endTime":2149.68,"body":"all in the same cloud,"},{"speaker":"which meant 10 light years","startTime":2149.68,"endTime":2153.53,"body":"so presumably at the"},{"speaker":"which meant 10 light years","startTime":2149.68,"endTime":2153.53,"body":"same distance from Earth,"},{"speaker":"which meant 10 light years","startTime":2153.53,"endTime":2155.79,"body":"she could arguably say"},{"speaker":"which meant 10 light years","startTime":2155.79,"endTime":2158.07,"body":"that their apparent brightness"},{"speaker":"which meant 10 light years","startTime":2158.07,"endTime":2160.78,"body":"was a function of their period,"},{"speaker":"which meant 10 light years","startTime":2160.78,"endTime":2164.493,"body":"and it wasn't due to"},{"speaker":"which meant 10 light years","startTime":2160.78,"endTime":2164.493,"body":"their different distance,"},{"speaker":"which meant 10 light years","startTime":2164.493,"endTime":2166.27,"body":"they were all at the same distance."},{"speaker":"which meant 10 light years","startTime":2166.27,"endTime":2168.87,"body":"And when she plotted the brightness here,"},{"speaker":"which meant 10 light years","startTime":2168.87,"endTime":2171.59,"body":"the logarithm of the brightness,"},{"speaker":"which meant 10 light years","startTime":2171.59,"endTime":2173.94,"body":"as a function of the"},{"speaker":"which meant 10 light years","startTime":2171.59,"endTime":2173.94,"body":"logarithm of the period,"},{"speaker":"which meant 10 light years","startTime":2173.94,"endTime":2177.403,"body":"all 25 stars snapped on a line."},{"speaker":"which meant 10 light years","startTime":2178.31,"endTime":2179.26,"body":"That meant"},{"speaker":"which meant 10 light years","startTime":2179.26,"endTime":2182.31,"body":"that if you could measure"},{"speaker":"which meant 10 light years","startTime":2179.26,"endTime":2182.31,"body":"the period of the stars,"},{"speaker":"which meant 10 light years","startTime":2182.31,"endTime":2183.48,"body":"by looking at this line,"},{"speaker":"which meant 10 light years","startTime":2183.48,"endTime":2187.6,"body":"you would be able to work"},{"speaker":"which meant 10 light years","startTime":2183.48,"endTime":2187.6,"body":"the brightness of the stars,"},{"speaker":"which meant 10 light years","startTime":2187.6,"endTime":2189.943,"body":"and from that, you"},{"speaker":"which meant 10 light years","startTime":2187.6,"endTime":2189.943,"body":"could work out distance."},{"speaker":"which meant 10 light years","startTime":2191.04,"endTime":2195.89,"body":"Leavitt's Law gave us a new"},{"speaker":"which meant 10 light years","startTime":2191.04,"endTime":2195.89,"body":"way of measuring distances"},{"speaker":"which meant 10 light years","startTime":2195.89,"endTime":2197.313,"body":"to the universe."},{"speaker":"which meant 10 light years","startTime":2198.44,"endTime":2201.1,"body":"And guided by this very law,"},{"speaker":"which meant 10 light years","startTime":2201.1,"endTime":2202.41,"body":"Edwin Hubble,"},{"speaker":"which meant 10 light years","startTime":2202.41,"endTime":2204.17,"body":"working hundreds of nights"},{"speaker":"which meant 10 light years","startTime":2204.17,"endTime":2205.83,"body":"at the 100-inch Hooker telescope"},{"speaker":"which meant 10 light years","startTime":2205.83,"endTime":2208.43,"body":"at Mount Wilson Observatory in California,"},{"speaker":"which meant 10 light years","startTime":2208.43,"endTime":2213.348,"body":"started to hunt for Cepheid"},{"speaker":"which meant 10 light years","startTime":2208.43,"endTime":2213.348,"body":"variables in nebulae,"},{"speaker":"which meant 10 light years","startTime":2213.348,"endTime":2215.42,"body":"and no other nebula"},{"speaker":"which meant 10 light years","startTime":2215.42,"endTime":2219.61,"body":"was as prominent as the Andromeda Nebula,"},{"speaker":"which meant 10 light years","startTime":2219.61,"endTime":2221.993,"body":"which we now know as the Andromeda Galaxy."},{"speaker":"which meant 10 light years","startTime":2222.86,"endTime":2227.4,"body":"In this historic plate,"},{"speaker":"which meant 10 light years","startTime":2227.4,"endTime":2229.74,"body":"that's preserved at the"},{"speaker":"which meant 10 light years","startTime":2227.4,"endTime":2229.74,"body":"Carnegie Observatories,"},{"speaker":"which meant 10 light years","startTime":2229.74,"endTime":2234.74,"body":"he put down his exclamation of joy"},{"speaker":"which meant 10 light years","startTime":2234.87,"endTime":2236.28,"body":"when he identified,"},{"speaker":"which meant 10 light years","startTime":2236.28,"endTime":2238.21,"body":"with red ink, in the top-right,"},{"speaker":"which meant 10 light years","startTime":2238.21,"endTime":2239.93,"body":"a new variable star"},{"speaker":"which meant 10 light years","startTime":2239.93,"endTime":2244.45,"body":"that he later understood was"},{"speaker":"which meant 10 light years","startTime":2239.93,"endTime":2244.45,"body":"precisely a Cepheid variable"},{"speaker":"which meant 10 light years","startTime":2244.45,"endTime":2247.38,"body":"of the kind identified"},{"speaker":"which meant 10 light years","startTime":2244.45,"endTime":2247.38,"body":"by Henrietta Leavitt,"},{"speaker":"which meant 10 light years","startTime":2247.38,"endTime":2250.65,"body":"and therefore, by observing"},{"speaker":"which meant 10 light years","startTime":2247.38,"endTime":2250.65,"body":"the period of that star,"},{"speaker":"which meant 10 light years","startTime":2250.65,"endTime":2254.5,"body":"he was able to measure the"},{"speaker":"which meant 10 light years","startTime":2250.65,"endTime":2254.5,"body":"distance to the Andromeda Nebula,"},{"speaker":"which meant 10 light years","startTime":2254.5,"endTime":2258.93,"body":"which we see here."},{"speaker":"which meant 10 light years","startTime":2258.93,"endTime":2259.92,"body":"At this point in time,"},{"speaker":"which meant 10 light years","startTime":2259.92,"endTime":2263.49,"body":"nobody knew how distant"},{"speaker":"which meant 10 light years","startTime":2259.92,"endTime":2263.49,"body":"the Andromeda Nebula was."},{"speaker":"which meant 10 light years","startTime":2263.49,"endTime":2266.95,"body":"Some, including the Harvard"},{"speaker":"which meant 10 light years","startTime":2263.49,"endTime":2266.95,"body":"Observatory director"},{"speaker":"which meant 10 light years","startTime":2266.95,"endTime":2268.64,"body":"Harlow Shapley,"},{"speaker":"which meant 10 light years","startTime":2268.64,"endTime":2272.09,"body":"thought that the Andromeda"},{"speaker":"which meant 10 light years","startTime":2268.64,"endTime":2272.09,"body":"Nebula was just a mass of gas,"},{"speaker":"which meant 10 light years","startTime":2272.09,"endTime":2274.517,"body":"relatively nearby our own Milky Way,"},{"speaker":"which meant 10 light years","startTime":2274.517,"endTime":2277.6,"body":"and that there were no other"},{"speaker":"which meant 10 light years","startTime":2274.517,"endTime":2277.6,"body":"galaxies in the universe."},{"speaker":"which meant 10 light years","startTime":2277.6,"endTime":2280.29,"body":"Others stated"},{"speaker":"which meant 10 light years","startTime":2280.29,"endTime":2283.55,"body":"that Andromeda was actually"},{"speaker":"which meant 10 light years","startTime":2280.29,"endTime":2283.55,"body":"a galaxy in itself,"},{"speaker":"which meant 10 light years","startTime":2283.55,"endTime":2286.28,"body":"but deciding the matter"},{"speaker":"which meant 10 light years","startTime":2283.55,"endTime":2286.28,"body":"was crucially dependent"},{"speaker":"which meant 10 light years","startTime":2286.28,"endTime":2289.26,"body":"on how far away the nebula was,"},{"speaker":"which meant 10 light years","startTime":2289.26,"endTime":2292.54,"body":"and Hubble, by measuring this light curve,"},{"speaker":"which meant 10 light years","startTime":2292.54,"endTime":2297.54,"body":"which is a characteristic"},{"speaker":"which meant 10 light years","startTime":2292.54,"endTime":2297.54,"body":"pattern of Cepheid variables"},{"speaker":"which meant 10 light years","startTime":2297.82,"endTime":2301.09,"body":"exactly of the kind discovered"},{"speaker":"which meant 10 light years","startTime":2297.82,"endTime":2301.09,"body":"by Henrietta Leavitt,"},{"speaker":"which meant 10 light years","startTime":2301.09,"endTime":2305.92,"body":"was able to put the actual"},{"speaker":"which meant 10 light years","startTime":2301.09,"endTime":2305.92,"body":"distance to Andromeda"},{"speaker":"which meant 10 light years","startTime":2305.92,"endTime":2307.66,"body":"to 1 million light years,"},{"speaker":"which meant 10 light years","startTime":2307.66,"endTime":2310.53,"body":"that's half the right"},{"speaker":"which meant 10 light years","startTime":2307.66,"endTime":2310.53,"body":"value that we know today,"},{"speaker":"which meant 10 light years","startTime":2310.53,"endTime":2311.46,"body":"less than half,"},{"speaker":"which meant 10 light years","startTime":2311.46,"endTime":2312.85,"body":"but still substantial enough"},{"speaker":"which meant 10 light years","startTime":2312.85,"endTime":2316.98,"body":"to firmly place Andromeda"},{"speaker":"which meant 10 light years","startTime":2312.85,"endTime":2316.98,"body":"outside the Milky Way,"},{"speaker":"which meant 10 light years","startTime":2316.98,"endTime":2321.83,"body":"and therefore put it into"},{"speaker":"which meant 10 light years","startTime":2316.98,"endTime":2321.83,"body":"the realm of the galaxies,"},{"speaker":"which meant 10 light years","startTime":2321.83,"endTime":2325.08,"body":"and determine its nature as a galaxy."},{"speaker":"which meant 10 light years","startTime":2325.08,"endTime":2327.85,"body":"So it was only fitting, then,"},{"speaker":"which meant 10 light years","startTime":2327.85,"endTime":2331.81,"body":"that when Hubble sent this"},{"speaker":"which meant 10 light years","startTime":2327.85,"endTime":2331.81,"body":"letter, including this diagram,"},{"speaker":"which meant 10 light years","startTime":2331.81,"endTime":2336.197,"body":"to Harlow Shapley at Harvard, writing,"},{"speaker":"which meant 10 light years","startTime":2336.197,"endTime":2337.097,"body":"\"Dear Shapley,"},{"speaker":"which meant 10 light years","startTime":2337.097,"endTime":2338.647,"body":"\"you will be interested to hear"},{"speaker":"which meant 10 light years","startTime":2338.647,"endTime":2339.917,"body":"\"that I have found a Cepheid variable"},{"speaker":"which meant 10 light years","startTime":2339.917,"endTime":2341.51,"body":"\"in the Andromeda Nebula,\""},{"speaker":"which meant 10 light years","startTime":2341.51,"endTime":2343.55,"body":"this was in 1924,"},{"speaker":"which meant 10 light years","startTime":2343.55,"endTime":2344.55,"body":"it was only fitting"},{"speaker":"which meant 10 light years","startTime":2344.55,"endTime":2347.11,"body":"that when Shapley happened"},{"speaker":"which meant 10 light years","startTime":2344.55,"endTime":2347.11,"body":"to open Hubble's letter,"},{"speaker":"which meant 10 light years","startTime":2347.11,"endTime":2352.09,"body":"which he knew would deal"},{"speaker":"which meant 10 light years","startTime":2347.11,"endTime":2352.09,"body":"a fatal blow to his theory"},{"speaker":"which meant 10 light years","startTime":2352.09,"endTime":2356.27,"body":"of the Andromeda Nebula"},{"speaker":"which meant 10 light years","startTime":2352.09,"endTime":2356.27,"body":"being part of our own galaxy,"},{"speaker":"which meant 10 light years","startTime":2356.27,"endTime":2359.18,"body":"the person who witnessed"},{"speaker":"which meant 10 light years","startTime":2356.27,"endTime":2359.18,"body":"Shapley's reaction"},{"speaker":"which meant 10 light years","startTime":2359.18,"endTime":2360.89,"body":"was Cecilia Payne,"},{"speaker":"which meant 10 light years","startTime":2360.89,"endTime":2362.04,"body":"a Cambridge graduate"},{"speaker":"which meant 10 light years","startTime":2362.04,"endTime":2365.04,"body":"who had taken over Ms. Leavitt's"},{"speaker":"which meant 10 light years","startTime":2362.04,"endTime":2365.04,"body":"old desk in the observatory"},{"speaker":"which meant 10 light years","startTime":2365.04,"endTime":2368.03,"body":"as a computer herself,"},{"speaker":"which meant 10 light years","startTime":2368.03,"endTime":2370.34,"body":"and Ms. Payne later said"},{"speaker":"which meant 10 light years","startTime":2370.34,"endTime":2373.58,"body":"that when Shapley read Hubble's letter,"},{"speaker":"which meant 10 light years","startTime":2373.58,"endTime":2378.58,"body":"said, \"This is the letter that"},{"speaker":"which meant 10 light years","startTime":2373.58,"endTime":2378.58,"body":"has destroyed my universe.\""},{"speaker":"which meant 10 light years","startTime":2379.49,"endTime":2381.06,"body":"Hubble's discovery, then,"},{"speaker":"which meant 10 light years","startTime":2381.06,"endTime":2383.28,"body":"thanks to Ms. Leavitt's Law,"},{"speaker":"which meant 10 light years","startTime":2383.28,"endTime":2386.8,"body":"added a fourth rung to our"},{"speaker":"which meant 10 light years","startTime":2383.28,"endTime":2386.8,"body":"cosmic distance ladder,"},{"speaker":"which meant 10 light years","startTime":2386.8,"endTime":2388.01,"body":"its top end"},{"speaker":"which meant 10 light years","startTime":2388.01,"endTime":2392.253,"body":"now reaching firmly into"},{"speaker":"which meant 10 light years","startTime":2388.01,"endTime":2392.253,"body":"the millions of light years,"},{"speaker":"which meant 10 light years","startTime":2393.14,"endTime":2395.51,"body":"thus the distance ladder"},{"speaker":"which meant 10 light years","startTime":2395.51,"endTime":2400.003,"body":"started to seriously stretch"},{"speaker":"which meant 10 light years","startTime":2395.51,"endTime":2400.003,"body":"far into the distance."},{"speaker":"which meant 10 light years","startTime":2402.025,"endTime":2404.81,"body":"Cepheid variables gave us the"},{"speaker":"which meant 10 light years","startTime":2402.025,"endTime":2404.81,"body":"means of measuring distances"},{"speaker":"which meant 10 light years","startTime":2404.81,"endTime":2407.47,"body":"to galaxies millions of light years away,"},{"speaker":"which meant 10 light years","startTime":2407.47,"endTime":2412.47,"body":"but as telescopes became bigger,"},{"speaker":"which meant 10 light years","startTime":2413.0,"endTime":2415.75,"body":"and fainter and fainter"},{"speaker":"which meant 10 light years","startTime":2413.0,"endTime":2415.75,"body":"galaxies came into view,"},{"speaker":"which meant 10 light years","startTime":2415.75,"endTime":2418.96,"body":"even Cepheid variables"},{"speaker":"which meant 10 light years","startTime":2415.75,"endTime":2418.96,"body":"became unobservable."},{"speaker":"which meant 10 light years","startTime":2418.96,"endTime":2423.01,"body":"Those new galaxies were simply"},{"speaker":"which meant 10 light years","startTime":2418.96,"endTime":2423.01,"body":"too far away, too distant"},{"speaker":"which meant 10 light years","startTime":2423.01,"endTime":2426.97,"body":"for Cepheid variables to be observable,"},{"speaker":"which meant 10 light years","startTime":2426.97,"endTime":2431.49,"body":"and so a new, even more"},{"speaker":"which meant 10 light years","startTime":2426.97,"endTime":2431.49,"body":"distant rung was needed"},{"speaker":"which meant 10 light years","startTime":2431.49,"endTime":2433.9,"body":"if we were to extend our ladder"},{"speaker":"which meant 10 light years","startTime":2433.9,"endTime":2437.423,"body":"all the way to the end"},{"speaker":"which meant 10 light years","startTime":2433.9,"endTime":2437.423,"body":"of the visible universe."},{"speaker":"which meant 10 light years","startTime":2438.97,"endTime":2440.96,"body":"Another thing that came"},{"speaker":"which meant 10 light years","startTime":2438.97,"endTime":2440.96,"body":"into view in the 1920s"},{"speaker":"which meant 10 light years","startTime":2440.96,"endTime":2445.96,"body":"is that the distance between"},{"speaker":"which meant 10 light years","startTime":2440.96,"endTime":2445.96,"body":"us and galaxies is growing"},{"speaker":"which meant 10 light years","startTime":2447.06,"endTime":2449.13,"body":"due to the expansion of the universe,"},{"speaker":"which meant 10 light years","startTime":2449.13,"endTime":2451.07,"body":"as predicted and described"},{"speaker":"which meant 10 light years","startTime":2451.07,"endTime":2453.63,"body":"by Einstein's general"},{"speaker":"which meant 10 light years","startTime":2451.07,"endTime":2453.63,"body":"theory of relativity,"},{"speaker":"which meant 10 light years","startTime":2453.63,"endTime":2455.47,"body":"a topic that I describe in more detail"},{"speaker":"which meant 10 light years","startTime":2455.47,"endTime":2458.347,"body":"in my other Gresham lecture"},{"speaker":"which meant 10 light years","startTime":2455.47,"endTime":2458.347,"body":"\"Einstein's Blunder.\""},{"speaker":"which meant 10 light years","startTime":2459.33,"endTime":2461.06,"body":"The discovery of the"},{"speaker":"which meant 10 light years","startTime":2459.33,"endTime":2461.06,"body":"expansion of the universe"},{"speaker":"which meant 10 light years","startTime":2461.06,"endTime":2463.67,"body":"is usually attributed to Edwin Hubble,"},{"speaker":"which meant 10 light years","startTime":2463.67,"endTime":2465.13,"body":"but that's an historical mistake"},{"speaker":"which meant 10 light years","startTime":2465.13,"endTime":2465.963,"body":"because, in fact,"},{"speaker":"which meant 10 light years","startTime":2465.963,"endTime":2468.21,"body":"the Belgian priest Georges Lemaitre"},{"speaker":"which meant 10 light years","startTime":2468.21,"endTime":2471.17,"body":"had made that discovery two years earlier,"},{"speaker":"which meant 10 light years","startTime":2471.17,"endTime":2474.03,"body":"in a paper that was only"},{"speaker":"which meant 10 light years","startTime":2471.17,"endTime":2474.03,"body":"published in 1931 in English,"},{"speaker":"which meant 10 light years","startTime":2474.03,"endTime":2476.61,"body":"therefore the credit went to Hubble,"},{"speaker":"which meant 10 light years","startTime":2476.61,"endTime":2478.71,"body":"but really belongs, equally at least,"},{"speaker":"which meant 10 light years","startTime":2478.71,"endTime":2480.123,"body":"to Lemaitre and Hubble."},{"speaker":"which meant 10 light years","startTime":2481.29,"endTime":2482.97,"body":"As the universe expands,"},{"speaker":"which meant 10 light years","startTime":2482.97,"endTime":2485.01,"body":"the light coming to us"},{"speaker":"which meant 10 light years","startTime":2482.97,"endTime":2485.01,"body":"from distant galaxies"},{"speaker":"which meant 10 light years","startTime":2485.01,"endTime":2489.81,"body":"is uniformly shifted towards"},{"speaker":"which meant 10 light years","startTime":2485.01,"endTime":2489.81,"body":"the red end of the spectrum,"},{"speaker":"which meant 10 light years","startTime":2489.81,"endTime":2492.293,"body":"a phenomenon we call redshift."},{"speaker":"which meant 10 light years","startTime":2493.19,"endTime":2495.81,"body":"Redshift tells us how much"},{"speaker":"which meant 10 light years","startTime":2493.19,"endTime":2495.81,"body":"the universe has expanded"},{"speaker":"which meant 10 light years","startTime":2495.81,"endTime":2498.32,"body":"since the light left the galaxy,"},{"speaker":"which meant 10 light years","startTime":2498.32,"endTime":2503.03,"body":"but says nothing about the"},{"speaker":"which meant 10 light years","startTime":2498.32,"endTime":2503.03,"body":"distance that the galaxy is at"},{"speaker":"which meant 10 light years","startTime":2503.03,"endTime":2505.22,"body":"that has emitted it."},{"speaker":"which meant 10 light years","startTime":2505.22,"endTime":2509.35,"body":"In fact, if we multiply"},{"speaker":"which meant 10 light years","startTime":2505.22,"endTime":2509.35,"body":"redshift by the speed of light,"},{"speaker":"which meant 10 light years","startTime":2509.35,"endTime":2510.34,"body":"we get the velocity,"},{"speaker":"which meant 10 light years","startTime":2510.34,"endTime":2511.8,"body":"and that velocity can be interpreted"},{"speaker":"which meant 10 light years","startTime":2511.8,"endTime":2514.2,"body":"as the recession velocity of the galaxy,"},{"speaker":"which meant 10 light years","startTime":2514.2,"endTime":2517.01,"body":"the velocity at which the"},{"speaker":"which meant 10 light years","startTime":2514.2,"endTime":2517.01,"body":"galaxy is flying away from us,"},{"speaker":"which meant 10 light years","startTime":2517.01,"endTime":2519.05,"body":"and as an aside,"},{"speaker":"which meant 10 light years","startTime":2519.05,"endTime":2521.99,"body":"that velocity can and does"},{"speaker":"which meant 10 light years","startTime":2519.05,"endTime":2521.99,"body":"exceed the speed of light"},{"speaker":"which meant 10 light years","startTime":2521.99,"endTime":2523.33,"body":"for distant galaxies."},{"speaker":"which meant 10 light years","startTime":2523.33,"endTime":2524.81,"body":"That is an apparent contradiction"},{"speaker":"which meant 10 light years","startTime":2524.81,"endTime":2526.78,"body":"with the special theory of relativity,"},{"speaker":"which meant 10 light years","startTime":2526.78,"endTime":2528.38,"body":"but it's actually allowed"},{"speaker":"which meant 10 light years","startTime":2528.38,"endTime":2530.18,"body":"under the general theory of relativity"},{"speaker":"which meant 10 light years","startTime":2530.18,"endTime":2534.31,"body":"because those galaxies are not"},{"speaker":"which meant 10 light years","startTime":2530.18,"endTime":2534.31,"body":"moving away from us in space,"},{"speaker":"which meant 10 light years","startTime":2534.31,"endTime":2535.61,"body":"it is space itself"},{"speaker":"which meant 10 light years","startTime":2535.61,"endTime":2537.88,"body":"that's stretching faster"},{"speaker":"which meant 10 light years","startTime":2535.61,"endTime":2537.88,"body":"than the speed of light"},{"speaker":"which meant 10 light years","startTime":2537.88,"endTime":2540.183,"body":"between us and the distant galaxies."},{"speaker":"which meant 10 light years","startTime":2543.362,"endTime":2545.6,"body":"Einstein's theory of general"},{"speaker":"which meant 10 light years","startTime":2543.362,"endTime":2545.6,"body":"relativity, like I say,"},{"speaker":"which meant 10 light years","startTime":2545.6,"endTime":2547.15,"body":"predicted this relationship,"},{"speaker":"which meant 10 light years","startTime":2547.15,"endTime":2548.83,"body":"and in fact,"},{"speaker":"which meant 10 light years","startTime":2548.83,"endTime":2550.57,"body":"for relatively small distances,"},{"speaker":"which meant 10 light years","startTime":2550.57,"endTime":2552.66,"body":"still measured in millions of light years,"},{"speaker":"which meant 10 light years","startTime":2552.66,"endTime":2555.26,"body":"that relationship is a line,"},{"speaker":"which meant 10 light years","startTime":2555.26,"endTime":2560.217,"body":"and this is the so-called"},{"speaker":"which meant 10 light years","startTime":2555.26,"endTime":2560.217,"body":"Discovery Plot by Hubble in 1929"},{"speaker":"which meant 10 light years","startTime":2560.217,"endTime":2562.22,"body":"that shows that, indeed,"},{"speaker":"which meant 10 light years","startTime":2562.22,"endTime":2565.71,"body":"further galaxies appear in this plot"},{"speaker":"which meant 10 light years","startTime":2565.71,"endTime":2566.94,"body":"fly away from us"},{"speaker":"which meant 10 light years","startTime":2566.94,"endTime":2570.61,"body":"at a faster and faster"},{"speaker":"which meant 10 light years","startTime":2566.94,"endTime":2570.61,"body":"speed than nearby ones."},{"speaker":"which meant 10 light years","startTime":2570.61,"endTime":2572.04,"body":"The slope of this line,"},{"speaker":"which meant 10 light years","startTime":2572.04,"endTime":2575.25,"body":"the relationship between"},{"speaker":"which meant 10 light years","startTime":2572.04,"endTime":2575.25,"body":"distance and recession velocity"},{"speaker":"which meant 10 light years","startTime":2575.25,"endTime":2578.64,"body":"is today called the"},{"speaker":"which meant 10 light years","startTime":2575.25,"endTime":2578.64,"body":"Hubble-Lemaitre constant,"},{"speaker":"which meant 10 light years","startTime":2578.64,"endTime":2581.127,"body":"and it's denoted by this symbol here, H0."},{"speaker":"which meant 10 light years","startTime":2582.69,"endTime":2584.65,"body":"It used to be called the Hubble constant,"},{"speaker":"which meant 10 light years","startTime":2584.65,"endTime":2587.25,"body":"and in 2018, rightly,"},{"speaker":"which meant 10 light years","startTime":2587.25,"endTime":2588.82,"body":"the International Astronomical Union"},{"speaker":"which meant 10 light years","startTime":2588.82,"endTime":2591.36,"body":"decided to call it"},{"speaker":"which meant 10 light years","startTime":2588.82,"endTime":2591.36,"body":"Hubble-Lemaitre constant"},{"speaker":"which meant 10 light years","startTime":2591.36,"endTime":2592.39,"body":"in recognition"},{"speaker":"which meant 10 light years","startTime":2592.39,"endTime":2596.63,"body":"of Georges Lemaitre's fundamental"},{"speaker":"which meant 10 light years","startTime":2592.39,"endTime":2596.63,"body":"contributions to cosmology"},{"speaker":"which meant 10 light years","startTime":2596.63,"endTime":2598.453,"body":"early on in its history."},{"speaker":"which meant 10 light years","startTime":2599.315,"endTime":2601.44,"body":"We need to dwell a second on this constant"},{"speaker":"which meant 10 light years","startTime":2601.44,"endTime":2604.26,"body":"because it's one of the"},{"speaker":"which meant 10 light years","startTime":2601.44,"endTime":2604.26,"body":"fundamental quantities"},{"speaker":"which meant 10 light years","startTime":2604.26,"endTime":2605.97,"body":"in cosmology today."},{"speaker":"which meant 10 light years","startTime":2605.97,"endTime":2608.75,"body":"Its physical interpretation"},{"speaker":"which meant 10 light years","startTime":2605.97,"endTime":2608.75,"body":"is that it tells us"},{"speaker":"which meant 10 light years","startTime":2608.75,"endTime":2612.68,"body":"the expansion speed of the universe today."},{"speaker":"which meant 10 light years","startTime":2612.68,"endTime":2615.16,"body":"It's expressed in funny units,"},{"speaker":"which meant 10 light years","startTime":2615.16,"endTime":2618.53,"body":"the units are kilometers"},{"speaker":"which meant 10 light years","startTime":2615.16,"endTime":2618.53,"body":"per second, per megaparsec,"},{"speaker":"which meant 10 light years","startTime":2618.53,"endTime":2622.6,"body":"which means that if the"},{"speaker":"which meant 10 light years","startTime":2618.53,"endTime":2622.6,"body":"Hubble-Lemaitre constant is,"},{"speaker":"which meant 10 light years","startTime":2622.6,"endTime":2626.37,"body":"let's say, 70 kilometers"},{"speaker":"which meant 10 light years","startTime":2622.6,"endTime":2626.37,"body":"per second, per megaparsec,"},{"speaker":"which meant 10 light years","startTime":2626.37,"endTime":2629.96,"body":"it means that for every"},{"speaker":"which meant 10 light years","startTime":2626.37,"endTime":2629.96,"body":"megaparsec of distance,"},{"speaker":"which meant 10 light years","startTime":2629.96,"endTime":2634.96,"body":"that's to say every 3.26"},{"speaker":"which meant 10 light years","startTime":2629.96,"endTime":2634.96,"body":"million light years of distance,"},{"speaker":"which meant 10 light years","startTime":2635.41,"endTime":2639.84,"body":"galaxies speed away 70"},{"speaker":"which meant 10 light years","startTime":2635.41,"endTime":2639.84,"body":"kilometers per second faster."},{"speaker":"which meant 10 light years","startTime":2639.84,"endTime":2641.04,"body":"So for example,"},{"speaker":"which meant 10 light years","startTime":2641.04,"endTime":2643.24,"body":"if you have a galaxy 100"},{"speaker":"which meant 10 light years","startTime":2641.04,"endTime":2643.24,"body":"million light years away,"},{"speaker":"which meant 10 light years","startTime":2643.24,"endTime":2645.41,"body":"which is about 30 megaparsecs,"},{"speaker":"which meant 10 light years","startTime":2645.41,"endTime":2646.78,"body":"it would be moving away from us"},{"speaker":"which meant 10 light years","startTime":2646.78,"endTime":2650.303,"body":"at a speed of 2,100 kilometers per second."},{"speaker":"which meant 10 light years","startTime":2652.15,"endTime":2653.65,"body":"Measuring this constant is, therefore,"},{"speaker":"which meant 10 light years","startTime":2653.65,"endTime":2656.09,"body":"one of the key endeavors of cosmology,"},{"speaker":"which meant 10 light years","startTime":2656.09,"endTime":2656.99,"body":"and Hubble and Lemaitre,"},{"speaker":"which meant 10 light years","startTime":2656.99,"endTime":2658.61,"body":"early on in the '20s and '30s,"},{"speaker":"which meant 10 light years","startTime":2658.61,"endTime":2661.36,"body":"had only sketchy data to go by,"},{"speaker":"which meant 10 light years","startTime":2661.36,"endTime":2663.04,"body":"and that put the value of H0"},{"speaker":"which meant 10 light years","startTime":2663.04,"endTime":2664.1,"body":"to somewhere in the region"},{"speaker":"which meant 10 light years","startTime":2664.1,"endTime":2668.66,"body":"to 500 or 600 kilometers"},{"speaker":"which meant 10 light years","startTime":2664.1,"endTime":2668.66,"body":"per second, per megaparsec."},{"speaker":"which meant 10 light years","startTime":2668.66,"endTime":2669.493,"body":"As we shall see,"},{"speaker":"which meant 10 light years","startTime":2669.493,"endTime":2672.1,"body":"this number has steadily gone down,"},{"speaker":"which meant 10 light years","startTime":2672.1,"endTime":2673.64,"body":"but we also realized"},{"speaker":"which meant 10 light years","startTime":2673.64,"endTime":2678.51,"body":"that the relationship between"},{"speaker":"which meant 10 light years","startTime":2673.64,"endTime":2678.51,"body":"distance, on this axis,"},{"speaker":"which meant 10 light years","startTime":2678.51,"endTime":2681.93,"body":"and recession speed, or"},{"speaker":"which meant 10 light years","startTime":2678.51,"endTime":2681.93,"body":"redshift, on this axis,"},{"speaker":"which meant 10 light years","startTime":2681.93,"endTime":2685.58,"body":"is linear only for nearby objects,"},{"speaker":"which meant 10 light years","startTime":2685.58,"endTime":2688.75,"body":"millions or hundreds of"},{"speaker":"which meant 10 light years","startTime":2685.58,"endTime":2688.75,"body":"millions of light years away,"},{"speaker":"which meant 10 light years","startTime":2688.75,"endTime":2691.72,"body":"those are the first four"},{"speaker":"which meant 10 light years","startTime":2688.75,"endTime":2691.72,"body":"rungs of our ladder."},{"speaker":"which meant 10 light years","startTime":2691.72,"endTime":2693.73,"body":"If you go to even further distances,"},{"speaker":"which meant 10 light years","startTime":2693.73,"endTime":2697.697,"body":"this relationship begins to"},{"speaker":"which meant 10 light years","startTime":2693.73,"endTime":2697.697,"body":"deviate from a straight line,"},{"speaker":"which meant 10 light years","startTime":2697.697,"endTime":2698.94,"body":"and it deviates in a way"},{"speaker":"which meant 10 light years","startTime":2698.94,"endTime":2702.42,"body":"that depends on the matter-energy"},{"speaker":"which meant 10 light years","startTime":2698.94,"endTime":2702.42,"body":"content of the universe,"},{"speaker":"which meant 10 light years","startTime":2702.42,"endTime":2703.81,"body":"how much dark matter,"},{"speaker":"which meant 10 light years","startTime":2703.81,"endTime":2706.77,"body":"how much cosmological constant"},{"speaker":"which meant 10 light years","startTime":2703.81,"endTime":2706.77,"body":"you have in the universe."},{"speaker":"which meant 10 light years","startTime":2706.77,"endTime":2711.073,"body":"And so by measuring recession"},{"speaker":"which meant 10 light years","startTime":2706.77,"endTime":2711.073,"body":"speeds, therefore redshifts,"},{"speaker":"which meant 10 light years","startTime":2712.234,"endTime":2714.5,"body":"and distances for very distant objects,"},{"speaker":"which meant 10 light years","startTime":2714.5,"endTime":2717.19,"body":"one can pinpoint down the cosmic recipe,"},{"speaker":"which meant 10 light years","startTime":2717.19,"endTime":2718.54,"body":"and more about this"},{"speaker":"which meant 10 light years","startTime":2718.54,"endTime":2722.103,"body":"is described in my \"Einstein's"},{"speaker":"which meant 10 light years","startTime":2718.54,"endTime":2722.103,"body":"Blunder\" Gresham lecture."},{"speaker":"which meant 10 light years","startTime":2723.68,"endTime":2725.02,"body":"But the point is that"},{"speaker":"which meant 10 light years","startTime":2725.02,"endTime":2726.783,"body":"to peer even further out in space"},{"speaker":"which meant 10 light years","startTime":2726.783,"endTime":2728.58,"body":"than the four measured distances,"},{"speaker":"which meant 10 light years","startTime":2728.58,"endTime":2732.81,"body":"to even greater separation from us,"},{"speaker":"which meant 10 light years","startTime":2732.81,"endTime":2734.93,"body":"Cepheid variables could not be used,"},{"speaker":"which meant 10 light years","startTime":2734.93,"endTime":2736.46,"body":"they were simply too faint,"},{"speaker":"which meant 10 light years","startTime":2736.46,"endTime":2740.92,"body":"we needed a much more"},{"speaker":"which meant 10 light years","startTime":2736.46,"endTime":2740.92,"body":"powerful light beacon,"},{"speaker":"which meant 10 light years","startTime":2740.92,"endTime":2743.61,"body":"and one came to us"},{"speaker":"which meant 10 light years","startTime":2743.61,"endTime":2747.5,"body":"in the form of powerful"},{"speaker":"which meant 10 light years","startTime":2743.61,"endTime":2747.5,"body":"explosions of stars"},{"speaker":"which meant 10 light years","startTime":2747.5,"endTime":2748.72,"body":"at the end of their lives"},{"speaker":"which meant 10 light years","startTime":2748.72,"endTime":2750.633,"body":"called supernovae, type Ia."},{"speaker":"which meant 10 light years","startTime":2751.61,"endTime":2754.5,"body":"Here is a Hubble Space Telescope picture"},{"speaker":"which meant 10 light years","startTime":2754.5,"endTime":2757.15,"body":"of one such explosion."},{"speaker":"which meant 10 light years","startTime":2757.15,"endTime":2760.63,"body":"You will see here the supernova exploding"},{"speaker":"which meant 10 light years","startTime":2760.63,"endTime":2762.81,"body":"and then dimming away over time."},{"speaker":"which meant 10 light years","startTime":2762.81,"endTime":2766.69,"body":"This is a star that is"},{"speaker":"which meant 10 light years","startTime":2762.81,"endTime":2766.69,"body":"made of carbon, and oxygen,"},{"speaker":"which meant 10 light years","startTime":2766.69,"endTime":2770.8,"body":"a very compact, dense star,"},{"speaker":"which meant 10 light years","startTime":2770.8,"endTime":2774.17,"body":"a white dwarf at the end of its life,"},{"speaker":"which meant 10 light years","startTime":2774.17,"endTime":2776.34,"body":"accreting mass from a companion star,"},{"speaker":"which meant 10 light years","startTime":2776.34,"endTime":2779.36,"body":"and the gravitational pressure"},{"speaker":"which meant 10 light years","startTime":2779.36,"endTime":2781.97,"body":"increases the temperature"},{"speaker":"which meant 10 light years","startTime":2779.36,"endTime":2781.97,"body":"in the core of the star,"},{"speaker":"which meant 10 light years","startTime":2781.97,"endTime":2785.64,"body":"and that creates a"},{"speaker":"which meant 10 light years","startTime":2781.97,"endTime":2785.64,"body":"thermonuclear runaway reaction,"},{"speaker":"which meant 10 light years","startTime":2785.64,"endTime":2787.46,"body":"which unbinds the star,"},{"speaker":"which meant 10 light years","startTime":2787.46,"endTime":2790.48,"body":"makes it explode in a"},{"speaker":"which meant 10 light years","startTime":2787.46,"endTime":2790.48,"body":"fraction of a second,"},{"speaker":"which meant 10 light years","startTime":2790.48,"endTime":2792.54,"body":"and then the afterglow of the star,"},{"speaker":"which meant 10 light years","startTime":2792.54,"endTime":2794.61,"body":"powered by radioactive elements,"},{"speaker":"which meant 10 light years","startTime":2794.61,"endTime":2798.27,"body":"lasts for a few weeks"},{"speaker":"which meant 10 light years","startTime":2794.61,"endTime":2798.27,"body":"in a very bright phase,"},{"speaker":"which meant 10 light years","startTime":2798.27,"endTime":2803.27,"body":"during which the star can be"},{"speaker":"which meant 10 light years","startTime":2798.27,"endTime":2803.27,"body":"as bright as 10 billion suns."},{"speaker":"which meant 10 light years","startTime":2804.3,"endTime":2807.03,"body":"Such bright explosions are"},{"speaker":"which meant 10 light years","startTime":2804.3,"endTime":2807.03,"body":"very, very useful for us"},{"speaker":"which meant 10 light years","startTime":2807.03,"endTime":2809.13,"body":"because they can be"},{"speaker":"which meant 10 light years","startTime":2807.03,"endTime":2809.13,"body":"seen from very far away,"},{"speaker":"which meant 10 light years","startTime":2809.13,"endTime":2810.69,"body":"in very distant galaxies,"},{"speaker":"which meant 10 light years","startTime":2810.69,"endTime":2812.88,"body":"and they're all uniform"},{"speaker":"which meant 10 light years","startTime":2812.88,"endTime":2817.06,"body":"because of the threshold mass"},{"speaker":"which meant 10 light years","startTime":2812.88,"endTime":2817.06,"body":"at which the star explodes,"},{"speaker":"which meant 10 light years","startTime":2817.06,"endTime":2818.92,"body":"the light emitted by the star"},{"speaker":"which meant 10 light years","startTime":2818.92,"endTime":2821.63,"body":"is not exactly identical for all of them,"},{"speaker":"which meant 10 light years","startTime":2821.63,"endTime":2823.64,"body":"but can be made uniform"},{"speaker":"which meant 10 light years","startTime":2823.64,"endTime":2827.97,"body":"by looking at the shape of"},{"speaker":"which meant 10 light years","startTime":2823.64,"endTime":2827.97,"body":"the light curve of the star."},{"speaker":"which meant 10 light years","startTime":2827.97,"endTime":2831.573,"body":"So by using a similar"},{"speaker":"which meant 10 light years","startTime":2827.97,"endTime":2831.573,"body":"trick as Leavitt's Law,"},{"speaker":"which meant 10 light years","startTime":2832.946,"endTime":2835.48,"body":"we can not only"},{"speaker":"which meant 10 light years","startTime":2832.946,"endTime":2835.48,"body":"standardize the supernovae,"},{"speaker":"which meant 10 light years","startTime":2835.48,"endTime":2838.81,"body":"make them all look equal to each other,"},{"speaker":"which meant 10 light years","startTime":2838.81,"endTime":2843.19,"body":"but also tell how much distance"},{"speaker":"which meant 10 light years","startTime":2838.81,"endTime":2843.19,"body":"there is between us and them"},{"speaker":"which meant 10 light years","startTime":2843.19,"endTime":2845.09,"body":"simply by the fact that if they all emit"},{"speaker":"which meant 10 light years","startTime":2845.09,"endTime":2847.64,"body":"the same amount of light intrinsically,"},{"speaker":"which meant 10 light years","startTime":2847.64,"endTime":2849.92,"body":"the amount of light that"},{"speaker":"which meant 10 light years","startTime":2847.64,"endTime":2849.92,"body":"we receive and observe"},{"speaker":"which meant 10 light years","startTime":2849.92,"endTime":2851.83,"body":"must be diluted by distance,"},{"speaker":"which meant 10 light years","startTime":2851.83,"endTime":2854.69,"body":"and therefore we can work out the distance"},{"speaker":"which meant 10 light years","startTime":2854.69,"endTime":2858.43,"body":"to very faraway objects in the universe."},{"speaker":"which meant 10 light years","startTime":2858.43,"endTime":2861.94,"body":"And that has been done over"},{"speaker":"which meant 10 light years","startTime":2858.43,"endTime":2861.94,"body":"the past 20 or 30 years,"},{"speaker":"which meant 10 light 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the original Hubble"},{"speaker":"which meant 10 light years","startTime":2877.74,"endTime":2881.27,"body":"range of observations"},{"speaker":"which meant 10 light years","startTime":2881.27,"endTime":2885.09,"body":"is the tiny, little red"},{"speaker":"which meant 10 light years","startTime":2881.27,"endTime":2885.09,"body":"square in the bottom-left."},{"speaker":"which meant 10 light years","startTime":2885.09,"endTime":2886.43,"body":"So the distance ladder,"},{"speaker":"which meant 10 light years","startTime":2886.43,"endTime":2888.86,"body":"thanks to the supernovae, type Ia,"},{"speaker":"which meant 10 light years","startTime":2888.86,"endTime":2893.86,"body":"has been increased to achieve a new rung,"},{"speaker":"which meant 10 light years","startTime":2894.55,"endTime":2898.23,"body":"a rung that now firmly puts"},{"speaker":"which meant 10 light years","startTime":2894.55,"endTime":2898.23,"body":"the top end of the ladder"},{"speaker":"which meant 10 light years","startTime":2898.23,"endTime":2901.64,"body":"to 2 billion light years,"},{"speaker":"which meant 10 light years","startTime":2901.64,"endTime":2903.93,"body":"so really a big ladder"},{"speaker":"which meant 10 light years","startTime":2903.93,"endTime":2907.61,"body":"reaching very, very far into the universe."},{"speaker":"which meant 10 light years","startTime":2907.61,"endTime":2909.75,"body":"In December, 2021,"},{"speaker":"which meant 10 light years","startTime":2909.75,"endTime":2914.7,"body":"the SHOES program reported"},{"speaker":"which meant 10 light years","startTime":2909.75,"endTime":2914.7,"body":"their new results."},{"speaker":"which meant 10 light years","startTime":2914.7,"endTime":2918.54,"body":"This program had been"},{"speaker":"which meant 10 light years","startTime":2914.7,"endTime":2918.54,"body":"going on for over 15 years"},{"speaker":"which meant 10 light years","startTime":2918.54,"endTime":2922.27,"body":"using 1,000 orbits of the"},{"speaker":"which meant 10 light years","startTime":2918.54,"endTime":2922.27,"body":"Hubble Space Telescope"},{"speaker":"which meant 10 light years","startTime":2922.27,"endTime":2927.08,"body":"in order to observe the"},{"speaker":"which meant 10 light years","startTime":2922.27,"endTime":2927.08,"body":"three distance ladder rungs"},{"speaker":"which meant 10 light years","startTime":2927.08,"endTime":2928.2,"body":"in sequence,"},{"speaker":"which meant 10 light years","startTime":2928.2,"endTime":2931.86,"body":"and with overlapping distance indicators."},{"speaker":"which meant 10 light years","startTime":2931.86,"endTime":2933.91,"body":"They spent a great deal of effort"},{"speaker":"which meant 10 light years","startTime":2933.91,"endTime":2935.78,"body":"in improving the distance ladder"},{"speaker":"which meant 10 light years","startTime":2935.78,"endTime":2938.57,"body":"by looking at parallax measurements,"},{"speaker":"which meant 10 light 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offsets"},{"speaker":"which meant 10 light years","startTime":2951.91,"endTime":2954.98,"body":"would be introduced"},{"speaker":"which meant 10 light years","startTime":2954.98,"endTime":2957.26,"body":"between one rung and the other."},{"speaker":"which meant 10 light years","startTime":2957.26,"endTime":2959.4,"body":"They also used the Hubble Space Telescope"},{"speaker":"which meant 10 light years","startTime":2959.4,"endTime":2961.61,"body":"because of its unique stability"},{"speaker":"which meant 10 light years","startTime":2961.61,"endTime":2964.22,"body":"and unique capability of seeing clearly"},{"speaker":"which meant 10 light years","startTime":2964.22,"endTime":2967.82,"body":"and measuring brightness very,"},{"speaker":"which meant 10 light years","startTime":2964.22,"endTime":2967.82,"body":"very precisely from orbit,"},{"speaker":"which meant 10 light years","startTime":2967.82,"endTime":2972.4,"body":"where conditions are stable"},{"speaker":"which meant 10 light 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variables,"},{"speaker":"which meant 10 light years","startTime":3002.16,"endTime":3005.297,"body":"and the top-right, the"},{"speaker":"which meant 10 light years","startTime":3002.16,"endTime":3005.297,"body":"supernovae stellar explosions,"},{"speaker":"which meant 10 light years","startTime":3005.297,"endTime":3008.6,"body":"and you can see they"},{"speaker":"which meant 10 light years","startTime":3005.297,"endTime":3008.6,"body":"all line up beautifully."},{"speaker":"which meant 10 light years","startTime":3008.6,"endTime":3011.11,"body":"And from this very precise data,"},{"speaker":"which meant 10 light years","startTime":3011.11,"endTime":3014.35,"body":"they could derive a value"},{"speaker":"which meant 10 light years","startTime":3011.11,"endTime":3014.35,"body":"for the Hubble constant,"},{"speaker":"which meant 10 light years","startTime":3014.35,"endTime":3015.6,"body":"which comes out to"},{"speaker":"which meant 10 light 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wonderful,"},{"speaker":"which meant 10 light years","startTime":3033.85,"endTime":3036.32,"body":"except while the astronomers"},{"speaker":"which meant 10 light years","startTime":3036.32,"endTime":3040.85,"body":"were busy building and"},{"speaker":"which meant 10 light years","startTime":3036.32,"endTime":3040.85,"body":"improving their distance ladder"},{"speaker":"which meant 10 light years","startTime":3040.85,"endTime":3042.74,"body":"from the ground up,"},{"speaker":"which meant 10 light years","startTime":3042.74,"endTime":3045.48,"body":"cosmologists, such as myself,"},{"speaker":"which meant 10 light years","startTime":3045.48,"endTime":3047.973,"body":"were actually doing it in the other way,"},{"speaker":"which meant 10 light years","startTime":3048.86,"endTime":3051.13,"body":"building a distance ladder"},{"speaker":"which meant 10 light years","startTime":3051.13,"endTime":3054.07,"body":"from the opposite end of the universe"},{"speaker":"which meant 10 light 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old,"},{"speaker":"which meant 10 light years","startTime":3072.03,"endTime":3075.64,"body":"and that has been traveling"},{"speaker":"which meant 10 light years","startTime":3072.03,"endTime":3075.64,"body":"through the cosmos ever since,"},{"speaker":"which meant 10 light years","startTime":3075.64,"endTime":3078.86,"body":"until it ends up in our"},{"speaker":"which meant 10 light years","startTime":3075.64,"endTime":3078.86,"body":"telescopes and observatories"},{"speaker":"which meant 10 light years","startTime":3078.86,"endTime":3082.43,"body":"13.8 billion years later."},{"speaker":"which meant 10 light years","startTime":3082.43,"endTime":3086.4,"body":"This map shows a snapshot"},{"speaker":"which meant 10 light years","startTime":3082.43,"endTime":3086.4,"body":"of the baby universe,"},{"speaker":"which meant 10 light years","startTime":3086.4,"endTime":3089.21,"body":"and the distribution of that cosmic light"},{"speaker":"which meant 10 light 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of"},{"speaker":"which meant 10 light years","startTime":3106.06,"endTime":3110.09,"body":"the Hubble-Lemaitre constant,"},{"speaker":"which meant 10 light years","startTime":3110.09,"endTime":3114.19,"body":"while not measured directly"},{"speaker":"which meant 10 light years","startTime":3110.09,"endTime":3114.19,"body":"by the relic radiation,"},{"speaker":"which meant 10 light years","startTime":3114.19,"endTime":3118.25,"body":"is important because"},{"speaker":"which meant 10 light years","startTime":3114.19,"endTime":3118.25,"body":"dialing the value of H0"},{"speaker":"which meant 10 light years","startTime":3118.25,"endTime":3121.78,"body":"puts this data in and"},{"speaker":"which meant 10 light years","startTime":3118.25,"endTime":3121.78,"body":"out of focus as well,"},{"speaker":"which meant 10 light years","startTime":3121.78,"endTime":3124.01,"body":"so by choosing a specific value"},{"speaker":"which meant 10 light years","startTime":3124.01,"endTime":3126.7,"body":"for the Hubble-Lemaitre constant,"},{"speaker":"which meant 10 light years","startTime":3126.7,"endTime":3130.27,"body":"the data from the relic"},{"speaker":"which meant 10 light years","startTime":3126.7,"endTime":3130.27,"body":"radiation snap into focus,"},{"speaker":"which meant 10 light years","startTime":3130.27,"endTime":3132.89,"body":"and that is an indirect method"},{"speaker":"which meant 10 light years","startTime":3132.89,"endTime":3135.953,"body":"of measuring the value of H0."},{"speaker":"which meant 10 light years","startTime":3137.88,"endTime":3140.383,"body":"The cosmologists had another means,"},{"speaker":"which meant 10 light years","startTime":3140.383,"endTime":3142.95,"body":"a very distant means, in fact,"},{"speaker":"which meant 10 light years","startTime":3142.95,"endTime":3145.81,"body":"of measuring the current"},{"speaker":"which meant 10 light years","startTime":3142.95,"endTime":3145.81,"body":"expansion of the universe,"},{"speaker":"which meant 10 light 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as it were,"},{"speaker":"which meant 10 light years","startTime":3162.49,"endTime":3164.07,"body":"from the end of the universe,"},{"speaker":"which meant 10 light years","startTime":3164.07,"endTime":3166.0,"body":"that the two ladders would meet"},{"speaker":"which meant 10 light years","startTime":3166.0,"endTime":3168.983,"body":"and give us the same value of"},{"speaker":"which meant 10 light years","startTime":3166.0,"endTime":3168.983,"body":"the Hubble-Lemaitre constant."},{"speaker":"which meant 10 light years","startTime":3170.09,"endTime":3172.79,"body":"But the fact is they don't."},{"speaker":"which meant 10 light years","startTime":3172.79,"endTime":3175.33,"body":"And you can see that the"},{"speaker":"which meant 10 light years","startTime":3172.79,"endTime":3175.33,"body":"relic light measurement"},{"speaker":"which meant 10 light years","startTime":3175.33,"endTime":3177.95,"body":"of the Hubble-Lemaitre constant"},{"speaker":"which meant 10 light 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friends?"},{"speaker":"which meant 10 light years","startTime":3195.91,"endTime":3197.47,"body":"Well that's true,"},{"speaker":"which meant 10 light years","startTime":3197.47,"endTime":3200.06,"body":"but the margin of error is important,"},{"speaker":"which meant 10 light years","startTime":3200.06,"endTime":3200.97,"body":"the margin of error"},{"speaker":"which meant 10 light years","startTime":3200.97,"endTime":3203.83,"body":"is now only one kilometer"},{"speaker":"which meant 10 light years","startTime":3200.97,"endTime":3203.83,"body":"per second, per megaparsec"},{"speaker":"which meant 10 light years","startTime":3204.74,"endTime":3206.7,"body":"according to the SHOES program,"},{"speaker":"which meant 10 light years","startTime":3206.7,"endTime":3208.13,"body":"and this margin of error"},{"speaker":"which meant 10 light years","startTime":3208.13,"endTime":3211.54,"body":"has been really very"},{"speaker":"which meant 10 light years","startTime":3208.13,"endTime":3211.54,"body":"precisely established,"},{"speaker":"which meant 10 light years","startTime":3211.54,"endTime":3216.39,"body":"and the way those margins of error work"},{"speaker":"which meant 10 light years","startTime":3216.39,"endTime":3219.77,"body":"is that a margin of one kilometer"},{"speaker":"which meant 10 light years","startTime":3216.39,"endTime":3219.77,"body":"per second, per megaparsec"},{"speaker":"which meant 10 light years","startTime":3219.77,"endTime":3222.85,"body":"means that there is a"},{"speaker":"which meant 10 light years","startTime":3219.77,"endTime":3222.85,"body":"probability of about 68%"},{"speaker":"which meant 10 light years","startTime":3224.06,"endTime":3229.06,"body":"that the true value of"},{"speaker":"which meant 10 light years","startTime":3224.06,"endTime":3229.06,"body":"H0 is between 72 and 74,"},{"speaker":"which meant 10 light years","startTime":3229.06,"endTime":3231.69,"body":"there is a probability of about 95%"},{"speaker":"which meant 10 light years","startTime":3231.69,"endTime":3236.69,"body":"that it is between 71 and 75, and so on,"},{"speaker":"which meant 10 light years","startTime":3236.81,"endTime":3237.77,"body":"and actually,"},{"speaker":"which meant 10 light years","startTime":3237.77,"endTime":3242.42,"body":"there is a probability of"},{"speaker":"which meant 10 light years","startTime":3237.77,"endTime":3242.42,"body":"less than one in a million"},{"speaker":"which meant 10 light years","startTime":3242.42,"endTime":3245.94,"body":"that the true value of the"},{"speaker":"which meant 10 light years","startTime":3242.42,"endTime":3245.94,"body":"Hubble-Lemaitre constant"},{"speaker":"which meant 10 light years","startTime":3245.94,"endTime":3248.58,"body":"is between five times the error,"},{"speaker":"which meant 10 light years","startTime":3248.58,"endTime":3253.533,"body":"which is a range between 68 and 78,"},{"speaker":"which meant 10 light years","startTime":3255.34,"endTime":3256.35,"body":"and therefore,"},{"speaker":"which meant 10 light years","startTime":3256.35,"endTime":3259.24,"body":"the fact that the margin"},{"speaker":"which meant 10 light years","startTime":3256.35,"endTime":3259.24,"body":"of error is so tight"},{"speaker":"which meant 10 light years","startTime":3259.24,"endTime":3264.13,"body":"means that the value measured"},{"speaker":"which meant 10 light years","startTime":3259.24,"endTime":3264.13,"body":"by the relic radiation, of 67,"},{"speaker":"which meant 10 light years","startTime":3264.13,"endTime":3266.49,"body":"is really, really improbably,"},{"speaker":"which meant 10 light years","startTime":3266.49,"endTime":3268.36,"body":"it's really, really improbable"},{"speaker":"which meant 10 light years","startTime":3268.36,"endTime":3270.66,"body":"that the two measurements"},{"speaker":"which meant 10 light years","startTime":3268.36,"endTime":3270.66,"body":"are both correct,"},{"speaker":"which meant 10 light years","startTime":3270.66,"endTime":3272.78,"body":"and they differ only by random noise,"},{"speaker":"which meant 10 light years","startTime":3272.78,"endTime":3275.1,"body":"by measurement uncertainty,"},{"speaker":"which meant 10 light years","startTime":3275.1,"endTime":3278.65,"body":"something is up in the universe."},{"speaker":"which meant 10 light years","startTime":3278.65,"endTime":3280.92,"body":"The fact that these two measurements,"},{"speaker":"which meant 10 light years","startTime":3280.92,"endTime":3282.53,"body":"with very tight errors,"},{"speaker":"which meant 10 light years","startTime":3282.53,"endTime":3285.86,"body":"nevertheless are far away from each other"},{"speaker":"which meant 10 light years","startTime":3285.86,"endTime":3287.57,"body":"in terms of theirs margins of error,"},{"speaker":"which meant 10 light years","startTime":3287.57,"endTime":3290.96,"body":"means that there is"},{"speaker":"which meant 10 light years","startTime":3287.57,"endTime":3290.96,"body":"something we don't understand"},{"speaker":"which meant 10 light years","startTime":3290.96,"endTime":3292.333,"body":"in the distance scale."},{"speaker":"which meant 10 light years","startTime":3293.33,"endTime":3294.87,"body":"What could it be?"},{"speaker":"which meant 10 light years","startTime":3294.87,"endTime":3298.74,"body":"There are three possible"},{"speaker":"which meant 10 light years","startTime":3294.87,"endTime":3298.74,"body":"solutions to this conundrum."},{"speaker":"which meant 10 light years","startTime":3298.74,"endTime":3303.16,"body":"One, the SHOES distance"},{"speaker":"which meant 10 light years","startTime":3298.74,"endTime":3303.16,"body":"ladder is somehow in error."},{"speaker":"which meant 10 light years","startTime":3303.16,"endTime":3304.61,"body":"That's possible,"},{"speaker":"which meant 10 light years","startTime":3304.61,"endTime":3307.35,"body":"because it's made up of"},{"speaker":"which meant 10 light years","startTime":3304.61,"endTime":3307.35,"body":"many different measurements"},{"speaker":"which meant 10 light years","startTime":3307.35,"endTime":3309.5,"body":"from geometry and parallax,"},{"speaker":"which meant 10 light years","startTime":3309.5,"endTime":3312.69,"body":"Cepheid variables, supernova explosions,"},{"speaker":"which meant 10 light years","startTime":3312.69,"endTime":3315.84,"body":"and all of them are"},{"speaker":"which meant 10 light years","startTime":3312.69,"endTime":3315.84,"body":"very difficult to make,"},{"speaker":"which meant 10 light years","startTime":3315.84,"endTime":3318.44,"body":"and they rely on certain assumptions,"},{"speaker":"which meant 10 light years","startTime":3318.44,"endTime":3321.57,"body":"they rely on the physics of the objects,"},{"speaker":"which meant 10 light years","startTime":3321.57,"endTime":3326.42,"body":"some observational error"},{"speaker":"which meant 10 light years","startTime":3321.57,"endTime":3326.42,"body":"could have crept in somehow."},{"speaker":"which meant 10 light years","startTime":3326.42,"endTime":3329.73,"body":"But the SHOES team has"},{"speaker":"which meant 10 light years","startTime":3326.42,"endTime":3329.73,"body":"been incredibly careful"},{"speaker":"which meant 10 light years","startTime":3329.73,"endTime":3332.48,"body":"in trying different"},{"speaker":"which meant 10 light years","startTime":3329.73,"endTime":3332.48,"body":"variants of the analysis,"},{"speaker":"which meant 10 light years","startTime":3332.48,"endTime":3335.9,"body":"in making sure they have"},{"speaker":"which meant 10 light years","startTime":3332.48,"endTime":3335.9,"body":"checked for all possible errors"},{"speaker":"which meant 10 light years","startTime":3335.9,"endTime":3338.15,"body":"in their distance rung measurements,"},{"speaker":"which meant 10 light years","startTime":3338.15,"endTime":3339.59,"body":"it's really, really difficult"},{"speaker":"which meant 10 light years","startTime":3339.59,"endTime":3341.873,"body":"to see how their analysis"},{"speaker":"which meant 10 light years","startTime":3339.59,"endTime":3341.873,"body":"could be improved."},{"speaker":"which meant 10 light years","startTime":3342.94,"endTime":3345.22,"body":"What about the distant end of the ladder,"},{"speaker":"which meant 10 light years","startTime":3345.22,"endTime":3346.87,"body":"maybe that is in error?"},{"speaker":"which meant 10 light years","startTime":3346.87,"endTime":3348.28,"body":"That's possible too,"},{"speaker":"which meant 10 light years","startTime":3348.28,"endTime":3352.67,"body":"but really, the relic radiation"},{"speaker":"which meant 10 light years","startTime":3348.28,"endTime":3352.67,"body":"from the early universe"},{"speaker":"which meant 10 light years","startTime":3352.67,"endTime":3354.36,"body":"is very well understood,"},{"speaker":"which meant 10 light years","startTime":3354.36,"endTime":3356.25,"body":"and it's in exceedingly good agreement"},{"speaker":"which meant 10 light years","startTime":3356.25,"endTime":3358.67,"body":"with many, many predictions"},{"speaker":"which meant 10 light years","startTime":3356.25,"endTime":3358.67,"body":"of general relativity,"},{"speaker":"which meant 10 light years","startTime":3358.67,"endTime":3361.67,"body":"we think we really"},{"speaker":"which meant 10 light years","startTime":3358.67,"endTime":3361.67,"body":"understand the baby universe"},{"speaker":"which meant 10 light years","startTime":3361.67,"endTime":3363.23,"body":"almost better, in fact,"},{"speaker":"which meant 10 light years","startTime":3363.23,"endTime":3365.85,"body":"than we understand the"},{"speaker":"which meant 10 light years","startTime":3363.23,"endTime":3365.85,"body":"present-day universe,"},{"speaker":"which meant 10 light years","startTime":3365.85,"endTime":3367.41,"body":"so it's really hard to see how"},{"speaker":"which meant 10 light years","startTime":3367.41,"endTime":3371.14,"body":"this 67 kilometers per second,"},{"speaker":"which meant 10 light years","startTime":3367.41,"endTime":3371.14,"body":"per megaparsec measurement"},{"speaker":"which meant 10 light years","startTime":3371.14,"endTime":3372.163,"body":"could be in error."},{"speaker":"which meant 10 light years","startTime":3373.03,"endTime":3376.15,"body":"And so if both measurements are right,"},{"speaker":"which meant 10 light years","startTime":3376.15,"endTime":3380.59,"body":"then the third option is that"},{"speaker":"which meant 10 light years","startTime":3376.15,"endTime":3380.59,"body":"our model for the universe"},{"speaker":"which meant 10 light years","startTime":3380.59,"endTime":3381.49,"body":"might be wrong,"},{"speaker":"which meant 10 light years","startTime":3381.49,"endTime":3384.44,"body":"or at least missing a piece."},{"speaker":"which meant 10 light years","startTime":3384.44,"endTime":3385.59,"body":"It could be, for example,"},{"speaker":"which meant 10 light years","startTime":3385.59,"endTime":3388.35,"body":"that in the early universe,"},{"speaker":"which meant 10 light years","startTime":3385.59,"endTime":3388.35,"body":"right after the Big Bang,"},{"speaker":"which meant 10 light years","startTime":3388.35,"endTime":3389.96,"body":"something else is going on,"},{"speaker":"which meant 10 light years","startTime":3389.96,"endTime":3392.11,"body":"some new physics is at work"},{"speaker":"which meant 10 light years","startTime":3392.11,"endTime":3395.09,"body":"that makes it so that"},{"speaker":"which meant 10 light years","startTime":3392.11,"endTime":3395.09,"body":"the data that we receive"},{"speaker":"which meant 10 light years","startTime":3395.09,"endTime":3398.04,"body":"from the relic light from the Big Bang"},{"speaker":"which meant 10 light years","startTime":3398.04,"endTime":3399.8,"body":"are somehow in a different focus,"},{"speaker":"which meant 10 light years","startTime":3399.8,"endTime":3403.99,"body":"and therefore they lead"},{"speaker":"which meant 10 light years","startTime":3399.8,"endTime":3403.99,"body":"to the wrong value of H0"},{"speaker":"which meant 10 light years","startTime":3403.99,"endTime":3406.45,"body":"simply because we're"},{"speaker":"which meant 10 light years","startTime":3403.99,"endTime":3406.45,"body":"missing a piece of physics"},{"speaker":"which meant 10 light years","startTime":3406.45,"endTime":3409.58,"body":"that goes on very early"},{"speaker":"which meant 10 light years","startTime":3406.45,"endTime":3409.58,"body":"on after the Big Bang,"},{"speaker":"which meant 10 light years","startTime":3409.58,"endTime":3411.11,"body":"that we don't know about."},{"speaker":"which meant 10 light years","startTime":3411.11,"endTime":3413.29,"body":"So it could well be that this discrepancy"},{"speaker":"which meant 10 light years","startTime":3413.29,"endTime":3416.49,"body":"is pointing at some"},{"speaker":"which meant 10 light years","startTime":3413.29,"endTime":3416.49,"body":"fundamental new component"},{"speaker":"which meant 10 light years","startTime":3416.49,"endTime":3418.28,"body":"in the makeup of the universe"},{"speaker":"which meant 10 light years","startTime":3418.28,"endTime":3420.63,"body":"and our understanding of the physics"},{"speaker":"which meant 10 light years","startTime":3420.63,"endTime":3422.64,"body":"right after the Big Bang,"},{"speaker":"which meant 10 light years","startTime":3422.64,"endTime":3424.423,"body":"we simply don't know."},{"speaker":"which meant 10 light years","startTime":3425.27,"endTime":3427.23,"body":"Many, many theoretical explanations"},{"speaker":"which meant 10 light years","startTime":3427.23,"endTime":3429.21,"body":"have been put forward by the community,"},{"speaker":"which meant 10 light years","startTime":3429.21,"endTime":3430.63,"body":"none of them, so far,"},{"speaker":"which meant 10 light years","startTime":3430.63,"endTime":3432.05,"body":"is clearly in the lead,"},{"speaker":"which meant 10 light years","startTime":3432.05,"endTime":3435.91,"body":"and so I think that the"},{"speaker":"which meant 10 light years","startTime":3432.05,"endTime":3435.91,"body":"resolution of this big conundrum,"},{"speaker":"which meant 10 light years","startTime":3435.91,"endTime":3439.43,"body":"the bringing together of"},{"speaker":"which meant 10 light years","startTime":3435.91,"endTime":3439.43,"body":"the two distance ladders,"},{"speaker":"which meant 10 light years","startTime":3439.43,"endTime":3441.05,"body":"will have to await,"},{"speaker":"which meant 10 light years","startTime":3441.05,"endTime":3443.017,"body":"unless we find a mistake in"},{"speaker":"which meant 10 light years","startTime":3441.05,"endTime":3443.017,"body":"the current measurements,"},{"speaker":"which meant 10 light years","startTime":3443.017,"endTime":3447.22,"body":"will have to await new,"},{"speaker":"which meant 10 light years","startTime":3443.017,"endTime":3447.22,"body":"independent measurements of H0"},{"speaker":"which meant 10 light years","startTime":3447.22,"endTime":3449.51,"body":"that do not rely on the distance ladder"},{"speaker":"which meant 10 light years","startTime":3449.51,"endTime":3450.97,"body":"as we've known it so far,"},{"speaker":"which meant 10 light years","startTime":3450.97,"endTime":3453.3,"body":"that do not rely on the relic radiation,"},{"speaker":"which meant 10 light years","startTime":3453.3,"endTime":3454.89,"body":"if we do get a third measurement,"},{"speaker":"which meant 10 light years","startTime":3454.89,"endTime":3457.113,"body":"for example using gravitational waves,"},{"speaker":"which meant 10 light years","startTime":3458.41,"endTime":3460.73,"body":"then that could be the way"},{"speaker":"which meant 10 light years","startTime":3460.73,"endTime":3465.02,"body":"to establish which one of"},{"speaker":"which meant 10 light years","startTime":3460.73,"endTime":3465.02,"body":"the two, 67 or 73, is right,"},{"speaker":"which meant 10 light years","startTime":3465.02,"endTime":3466.85,"body":"and that could give us a hint"},{"speaker":"which meant 10 light years","startTime":3466.85,"endTime":3469.163,"body":"as to what the universe is up to."},{"speaker":"which meant 10 light years","startTime":3470.09,"endTime":3473.07,"body":"It is a fascinating mystery,"},{"speaker":"which meant 10 light years","startTime":3473.07,"endTime":3476.83,"body":"and one that will keep"},{"speaker":"which meant 10 light years","startTime":3473.07,"endTime":3476.83,"body":"cosmologists and astronomers busy"},{"speaker":"which meant 10 light years","startTime":3476.83,"endTime":3478.54,"body":"for the next few years,"},{"speaker":"which meant 10 light years","startTime":3478.54,"endTime":3479.5,"body":"and finally,"},{"speaker":"which meant 10 light years","startTime":3479.5,"endTime":3482.03,"body":"we hope to be able, one day,"},{"speaker":"which meant 10 light years","startTime":3482.03,"endTime":3486.12,"body":"to extend our cosmic distance"},{"speaker":"which meant 10 light years","startTime":3482.03,"endTime":3486.12,"body":"ladder, uninterrupted,"},{"speaker":"which meant 10 light years","startTime":3486.12,"endTime":3490.35,"body":"all the way to the end"},{"speaker":"which meant 10 light years","startTime":3486.12,"endTime":3490.35,"body":"of the visible universe."},{"speaker":"which meant 10 light years","startTime":3490.35,"endTime":3491.183,"body":"Thank you."}]}