Terence Tao continuing history’s cleverest cosmological measurements

this animation is zooming out by a factor of 10 every 2 seconds maybe you've seen things like this before conveying the mindboggling scale of our universe but here in this video you and I are going to continue the Saga through the many moments of delightful Ingenuity throughout human history that led us to First discover how far away objects in the cosmos really are appreciating how we know these distances is to me more amazing than the distances themselves this is part two of a collaboration with teren TOA and it's okay if you haven't yet seen part one each video should be relatively self-contained but for context we left off with Kepler's ingenious method for deducing the shapes of all of the orbits of the planets around the Sun so people knew what the solar system looked like but they still didn't have an exact sense of scale and this left astronomers hungry to measure any distance that they could in this system like maybe how far away a given planet is from Earth at a given moment since that would be enough to lock everything else into place now I'll admit while I had vaguely learned about how this was done before I definitely had not appreciated the cleverness of the details you could measure distances to the planets like Venus take two measurements on different sides of the Earth around the time of Captain Cook when when they were traveling to discover Australia and so forth part of the reason for this was the scientific Mission I mean they wanted to know the distance to Venus and Mars and so forth they wanted people to take precise measurements they W in Greenwich in the UK and one somewhere in southern hemisphere at exactly the same time of the same object the key idea here is that as you sail down to the Sou Southern Hemisphere and You observe a given object up in the sky its position in the sky say relative to the background constellations will appear to shift up as the angle of your line of sight slowly changes with your position we call this Parallax it is the same Parallax that we use with binocular vision our eyes are a certain distance apart and so we can determine depth or any distance that's not too much larger than the distance between our ...