Terence Tao explains the cosmic distance ladder
3Blue1Brown · Explainer · YouTube title: Terence Tao on the cosmic distance ladder
Why it's here
HN recommends it as an excellent explanation of how we know cosmic distances.
What it covers
Terence Tao and Grant Sanderson of 3Blue1Brown walk through the cosmic distance ladder, showing how humans measured distances from the Earth to the Moon, Sun, planets and beyond. It includes animations and the history behind each step.