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

by Randall Munroe

But if you ask me how much all the electrons in a bottlenose dolphin weigh, that’s a different situation. No one knows that number off the top of their head—unless they have an extremely cool job—which means it’s okay to feel confused and a little silly and take some time to look stuff up. (The answer, in case anyone ever asks you, is about half a pound.)

Physicists don’t have a good general theory for why some materials shed electrons from their surfaces on contact while other materials pick them up. This phenomenon, called triboelectric charging, is an area of cutting-edge research.

If the rotor kept accelerating at its normal rate, and you somehow stayed attached, then after another full rotation you’d be swinging almost straight outward, with your hands trying to support many times your own body weight. If you hung on for 20 seconds, the rotor would be making one revolution per second, putting several tons of force on your hands. After 30 seconds, you’d have lost your grip on the helicopter one way or another. If your hands stay attached to the rotor, they won’t stay attached to your body.

Adding just a few ounces of weight to the base of a blade can cause (or cancel out) uncomfortably strong vibrations. Adding a human-size weight to the end of a blade would cause the helicopter to flip itself over and tear itself apart long before it got up to speed.

Cold things and hot things are different. [citation needed] Standing near a hot object can kill you very fast—for more on this, flip to basically any other random page of this book—but standing near a cold thing won’t freeze you instantly. Hot objects emit thermal radiation that heats up things around them, but cold objects don’t emit cold radiation. They just sit there.

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.

Engineers working with cold industrial equipment have to watch out for this oxygen buildup, since liquid oxygen is pretty dangerous stuff. It’s highly reactive and tends to cause flammable things to spontaneously ignite. A really cold object can set your house on fire.

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

In 1988, oceanographer John Martin famously claimed—in his best supervillain voice—“Give me half a tanker of iron, and I will give you an ice age.”

Based on US crash rates, the odds of a driver traveling 46 billion light-years without a crash would be about 1 in 101015. That’s roughly the same as the probability of a monkey with a typewriter typing out the entire Library of Congress, with no typos, fifty times in a row. You’ll want a self-driving car, or at least one with one of those alarms that warns you if you drift out of your lane.

if you’re ever faced with some kind of frightening illusory phantom, just remember this handy optics rule: If you can see it, you can shoot it with a laser.

No, although in my personal opinion, if you could get them to stay there, it would make the other side of the Earth a nicer place to live.

Based on the textbook definition of temperature, space is hot, at least here in the Solar System. The molecules in space are individually moving very fast, which means that each one has a lot of energy, and temperature is usually defined as the average kinetic energy of the molecules in a substance. But there are so few molecules in space that even though each one has a lot of energy, the total amount of heat energy is small, which means it doesn’t warm things up very much. It may be warm in theory, but it feels cold in practice. Space may be hot, but it’s the hottest place you can freeze to death.

“Soil liquefaction” is a boring-sounding phrase for a terrifying thing. Under certain conditions, such as earthquakes, soil can flow like a liquid, which is extremely alarming for anyone who lives on the ground.

A gram of pure plutonium, for example, would cost about $5,000. [*] As a bonus, plutonium is even denser than gold, which means you could fit almost 300 kilograms of it in a shoebox. Before you spend $2 billion on plutonium, take note: Plutonium’s critical mass is about 10 kilograms. You could technically fit 300 kilograms of it in a shoebox, but you could only do so briefly.

High-quality diamonds are expensive, but it’s hard to get a handle on their exact price because the entire industry is a scam the gemstone market is complicated.

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.”

making laws simpler and vaguer doesn’t necessarily move that power from the state to the people. You could get rid of a lot of laws and replace them with “everyone just needs to behave properly.” But that leaves it up to law enforcement to decide the meaning of “properly.”

There’s a number in engineering that measures how long a dangling piece of a material can get before snapping under its own weight. It’s called the “free-hanging length,” and it’s a ratio between a material’s tensile strength, density, and gravity.

It’s common knowledge that Mount Everest is the tallest mountain on Earth, measured from sea level. A somewhat more obscure piece of trivia is that the point on the Earth’s surface farthest from its center is the summit of Mount Chimborazo in Ecuador, due to the fact that the planet bulges out at the equator. Even more obscure is the question of which point on the Earth’s surface moves the fastest as the Earth spins, which is the same as asking which point is farthest from the Earth’s axis. The answer isn’t Chimborazo or Everest. The fastest point turns out to be the peak of Mount Cayambe,‡ a volcano north of Chimborazo. You just learned that. ‡ Mt. Cayambe’s southern slope also happens to be the highest point on Earth’s surface directly on the equator. I have a lot of mountain facts.