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

by Randall Munroe

black holes don’t have any distinguishing traits or defining characteristics. Other than a handful of simple variables like mass, spin, and electric charge, all black holes are identical.

You can feel this “cold radiation” by looking up at the stars on a summer night. Your face will feel cold since your body heat is pouring away into space. If you hold up an umbrella to block your view of the sky, you’ll feel warmer—almost as if the umbrella is “blocking the cold” from the sky. This “cold sky” effect can cool things down to below the ambient air temperature. If you leave out a tray of water under a clear sky, it can turn to ice overnight even if the air temperature stays well above freezing.

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.

The question of why moths and other insects fly toward lamps is something of an open question in entomology,

you weigh almost a pound less at the equator than you do at the poles.

Air pressure doubles with every six kilometers you descend, so at a depth of 10 kilometers, it would be nearly four times higher than what you’re used to.

Humans can survive acceleration best if they’re accelerated forward, in the direction of their chest, like a driver accelerating forward. The body is least capable of being accelerated downward toward the feet, which causes blood to pile up in the head.

Transistors and vacuum tubes use different mechanisms to do the same basic task: If they receive an electrical signal, they flip a switch one way, and if they don’t, they flip it the other way.

A fluffy cumulous cloud the size of a house contains about a liter of liquid water, or 2 or 3 large glasses, which is about the volume a human stomach can hold at one time.

In addition to later sunsets, taller people also experience earlier sunrises, which means that days last longer for them in general.

using electricity to directly produce heat is generally less efficient than using that power to warm up outside air using a heat pump,

You can’t use lenses and mirrors to make something hotter than the surface of the light source itself. In other words, you can’t use sunlight to make something hotter than the surface of the Sun.

Laws give people power. If a law is complicated, it empowers people who can afford lawyers to interpret it. “Laws that are complicated, arbitrary, and unintuitive empower the state,” says Jonathan Zittrain, professor of international law and the Harvard Law Library’s director, “since prosecutorial discretion means they can pick whom to enforce against and be selective in discriminatory ways.”