Will Schenk

This has been rattling around my head since I was a kid lying in the yard: if the universe is that old and that full of stars, the night sky seems like it should be a wall of light. It turns out the darkness is the interesting part. (Built as a worked example of this transcript format: prompts upfront, model responses folded away, and the interactive toys inline.) Prompt copy The universe is about 14 billion years old and has something like 10²² stars. If I draw a straight line from my eye out into space in any direction, shouldn’t it eventually hit the surface of a star? Why isn’t the whole night sky as bright as the sun? The intuition in the prompt is actually right, which is what makes it a good question — in an infinite, eternal, unchanging universe every sight line does end on a star, and the sky would glow at the surface temperature of one everywhere, forever. No night. The reason ours doesn’t is the good part: