What If? 2: Additional Serious Scientific Answers to Absurd Hypothetical Questions

by Randall Munroe

“Stand on the other side from where the physics is happening” is actually a good general rule for scientific equipment.

A mirage is a reflection of the sky; light from the sky comes down near the surface and then bends up toward your eye, so it looks like it’s coming from the ground.

Eyes first evolved about half a billion years ago, and in that time, the Permian extinction is probably the worst thing they’ve seen. A large eruption of lava in what is now Siberia injected huge amounts of CO2 into the atmosphere, causing temperatures to spike. The oceans deoxygenated and acidified. Clouds of poison gas rolled across the land. Most plant life was wiped from the continents, leaving Earth a sandy desolate wasteland. Almost everything died.

a frequency of 50 Hz. That frequency is right on the edge of the eye’s “flicker fusion threshold,” where flashes of light are too fast for your eyes to distinguish and appear to merge together into a steady glow, so the light would appear generally steady, if a little unnatural.