Terence Tao on the cosmic distance ladder

What people said

adolph · 2026-02 · Strong recommendation

This is so true. There is an awesome Terry Tao / 3blue1brown collaboration that explicates the epistemological basis: Terence Tao on the cosmic distance ladder Pt 1: [VIDEO] Pt 2: [LINK] Commentary and Corrections: [LINK]

Read the original HN comment ↗

GuB-42 · 2025-02 · Strong recommendation

About geocentrism vs heliocentrism, 3blue1brown has recently released a video [1] that talks about about it. It is about the cosmic distance ladder, but geocentrism is mentioned, and it makes a lot of sense in context. To summarize: heliocentrism was known to the ancient Greeks, who realized the Sun was much bigger than the Earth, so it would seem logical to have the Earth go around the sun. But the counterargument was that if the Earth goes around the Sun, the stars should move relative to each other during the year, because of parallax, and they didn't have instruments that were precise enough to see it, so they assumed that they didn't. Copernicus major contribution wasn't heliocentrism, but the orbital periods of planets. And the model wasn't complete until Kepler calculated the shapes of the orbits. For details, watch the video, it is really good. [1] [VIDEO]

Read the original HN comment ↗

epistasis · 2026-08 · Reference

They do this mostly with spectroscopy, breaking out the light by frequency. The longer the light has been travelling, the more frequency shifts into redder frequencies, because the universe is continually expanding. But those distances are all built on top of the cosmic distance ladder (Terence Tao explaining on 3blue1brown) [VIDEO] Maps like DESI add the 3d distances. [LINK]

Read the original HN comment ↗