Terence Tao on how we measure the cosmos | Part 1

2025-02-08

[public] 438K views, 93.9K likes, dislikes audio only

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The Cosmic Distance Ladder, how we learned distances in the heavens.

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Artwork by Kurt Bruns

Thanks to Paul Dancstep for several animations, such as the powers of 10 zoom out and the simulations of shadows on the moon.

Corrections:

Terry has kindly cataloged many of the added nuances, including a few corrections, in this post:

https://terrytao.wordpress.com/2025/02/13/cosmic-distance-ladder-video-with-grant-sanderson-3blue1brown-commentary-and-corrections/

As an additional one, the portrait shown for Kepler, despite being somewhat widespread, actually turns out not to be Kepler. See this article by Václav Pavlík https://ui.adsabs.harvard.edu/abs/2021PhT....74i..10S/abstract

Also, although the earth is about 4 times as wide as the moon, as it happens you would not see this with the lunar eclipse composites, since the umbra of Earth's shadow from the sun is sufficiently smaller than the earth out where the moon is.

Moon composite shot by Reddit user _wanderloots: https://www.reddit.com/r/astrophotography/comments/yil0tu/partial_lunar_eclipse_composite/

https://youtube.com/@Wanderloots

Thanks to Tanya Klowden for helpful conversations about the history of the distance ladder.

Argument for why if every shadow of a convex shape is a circle, it must be a sphere: https://mathoverflow.net/questions/39127/is-the-sphere-the-only-surface-with-circular-projections-or-can-we-deduce-a-sp

Timestamps:

0:00 - About Terence Tao and the Distance Ladder

2:02 - Earth

8:07 - Moon

11:15 - Sun

15:45 - Heliocentrism in Antiquity

18:27 - Kepler’s genius

27:16 - Where this leaves us

SEV #5: https://youtu.be/uq83hprtpGE

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https://github.com/3b1b/manim

https://github.com/ManimCommunity/manim/

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https://www.vincentrubinetti.com

https://vincerubinetti.bandcamp.com/album/the-music-of-3blue1brown

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