How were Uranus, Neptune, and Pluto first discovered? Neil deGrasse Tyson explores the often un-discussed past failures in astrophysics and why “how tall are you?” is an unanswerable question. What is the Earth’s ellipticity? What is the sun’s diameter? How do you measure the edge of something that is made out of gas? Neil breaks down how measurements are inexact and the idea of scientific uncertainty. Learn about Galileo’s discovery of Jupiter’s moons, the search for Planet X, and the later discoveries of Uranus, Neptune, and Pluto. Find out about the planet, Vulcan, that scientists proposed to explain Mercury’s orbit. Plus, naturally, Neil breaks down the density of the The Hulk. Check out our second channel, @StarTalkPlus Get the NEW StarTalk book, 'To Infinity and Beyond: A Journey of Cosmic Discovery' on Amazon: https://amzn.to/3PL0NFn Support us on Patreon: https://www.patreon.com/startalkradio FOLLOW or SUBSCRIBE to StarTalk: Twitter: http://twitter.com/startalkradio Facebook: https://www.facebook.com/StarTalk Instagram: https://www.instagram.com/startalk About StarTalk: Science meets pop culture on StarTalk! Astrophysicist & Hayden Planetarium director Neil deGrasse Tyson, his comic co-hosts, guest celebrities & scientists discuss astronomy, physics, and everything else about life in the universe. Keep Looking Up! #StarTalk #neildegrassetyson 00:00 - Introduction 01:30 - Why “How Tall Are You” Has No Answer 06:57 - The Shape of Earth’s Orbit 12:28 - The Diameter of the Earth & Sun 16:15 - Discovering The Galilean Moons 21:15 - Discovering Uranus & Neptune 25:10 - The Search for Planet X 29:55 - The Birth & Death of Planet Vulcan 31:50 - Conclusions 33:07 - The Density of The Hulk