How were Uranus, Neptune, and Pluto first discovered? Neil deGrasse Tyson explores the often undiscussed 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.

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About StarTalk:
Science meets pop culture on StarTalk! Astrophysicist & Hayden Planetarium director Neil deGrasse Tyson, his comic cohosts, guest celebrities & scientists discuss astronomy, physics, and everything else about life in the universe. Keep Looking Up!

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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