Thank you to Katie Mack for teaching me about this effect, and to Janelle Shane for describing redshifts as 'like galaxies sinking into a pool of dilute blood,' which is how I'll see them from now on.
Special 10th anniversary edition of WHAT IF?—revised and annotated with brand-new illustrations and answers to important questions you never thought to ask—coming from November 2024. Preorder here!
