What If?: Serious Scientific Answers to Absurd Hypothetical Questions

Question: “Would dumping anti-matter into the Chernobyl reactor when it was melting down stop the meltdown?” The author offers the questioner his “‘For God’s Sake, What Were You Thinking?!’ Award” (60).

Another questioner asks: “Is it possible to cry so much you dehydrate yourself?” The author replies, “is everything ok?” (60).

Question: “If every human somehow simply disappeared from the face of the Earth, how long would it be before the last artificial light source would go out?” (61).

Without human management, fossil fuels, required by most major power grids, would go untended, and electric power would fail; outages would occur within hours, causing cascading failures until most power is off. Local diesel generators might last for months; geothermal, hydroelectric, and wind turbines would run for years until their gears broke from corrosion. Battery-powered systems could continue for two decades. Nuclear plants in low-power mode could run indefinitely, except they shut down whenever there’s a problem.

A solar-powered call box on a desert road might power its night light for 100 years. The winner, though, is nuclear waste, some of which will emit the blue light of Cherenkov radiation for two centuries.

Question: “Is it possible to build a jetpack using downward-firing machine guns?” (68).

Three hundred AK-47 machine guns with 250 rounds of ammunition each, when fired downward together at three rounds per second, could lift a person a half kilometer into the air at a speed reaching 100 meters per second.

The one-pound bullets of the US military’s GAU-8 Avenger gun would accelerate a car from a standstill to highway speed in less than three seconds. A Russian aircraft gun, the GSh-6-30, if used to lift a rider, would achieve 40 Gs of acceleration.

Question: “If you suddenly began rising steadily at 1 foot per second, how exactly would you die?” (73).

After an hour, you’d be at 3,600 feet or one kilometer. Here, it’s chilly. After seven hours, you’d be above the tallest mountains and would suffocate from lack of oxygen. After 2 million years, your frozen body would leave the solar system.

Question: “Given humanity’s current knowledge and capabilities, is it possible to build a new star?” (77). The author does not comment.

Question: “What sort of logistic anomalies would you encounter in trying to raise an army of apes?” (77). No comment.

Question: “If people had wheels and could fly, how would we differentiate them from airplanes?” (77). No comment.

Question: “How long could a nuclear submarine last in orbit?” (78).

A submarine generates oxygen from seawater; without any in space, its crew would suffocate in several days. Meanwhile, the ocean cools submarines, but in space, there’s almost conduction of heat away from the hull, and the problem for most space ships is staying cool by radiating heat. As it happens, a sub in space would lose more heat than it generates or receives from the sun.

Question: “If my printer could print out money, would it have that big an effect on the world?” (83). At four $100 bills a minute, a printer can generate $200 million in a year. This is a tiny fraction of the $100 billion in real hundreds printed each year.

Question: “What would happen if you set off a nuclear bomb in the eye of a hurricane? Would the storm cell be immediately vaporized?” (84). It won’t work; hurricanes are much too big.

Question: “If everyone put little turbine generators on the downspouts of their houses and businesses, how much power would we generate?” (84-85). In a rainy area, a house might save $1.14 in a year.

Question: “How long would names have to be to give each star in the universe a unique one-word name?” (85). Twenty-four.

Question: “How fast would I have to bike for my skin to warm up the way a spacecraft heats up during reentry?” (86). To increase skin temperature by 20 degrees, you’d have to bike at 200 meters per second, five times faster than the pros. The heat would kill you.

Question: “How much physical space does the Internet take up?” (87). Measuring by the total volume of hard drives, the internet in 2014 would fit inside an oil tanker.

Question: “What if you strapped C4 to a boomerang? Could this be an effective weapon, or would it be as stupid as it sounds?” (88). If the boomerang misses the target, there’s no advantage in having it fly back and hit you.

Lightning travels hundreds of kilometers per second and releases roughly 20,000 amps. Lightning tends to strike taller objects, but standing in their shadows doesn’t guarantee safety, as you can be touching the nearby ground through which the current passes.

A sample of the questions asked in this chapter, and their answers, follow:

Question: “How dangerous is it, really, to be in a pool during a thunderstorm?” (91). In a pool, your head sticks up; also, lightning striking the water surface within a dozen meters could be fatal. When you’re taking a shower, a bolt can get to you by traveling through the drainpipe to the water you’re standing on.

Question: “What would happen if lightning struck a bullet in midair?” (93). Not much if the bullet passed through the bolt at high speed; however, a bullet sitting still would melt.

Question: “Would it be possible to stop a volcano eruption by placing a bomb (thermobaric or nuclear) underneath the surface?” (95). No.

Question: “A friend of mine is convinced that there is sound in space. There isn’t, right?” (95). Right.

Question: “How much computing power could we achieve if the entire world population stopped whatever we are doing right now and started doing calculations?” (96).

Humans are still better than computers at understanding pictures. Shown a photo of a kid wearing a cowboy hat, holding a whip, and standing next to a broken vase being sniffed at by a cat, people quickly realize the kid broke the vase with the whip, and the cat is innocent.

A single personal computer in 1994 could do more calculations than the entire world population of humans. However, it takes about 30 transistors to perform one instruction per second, and if a human brain equals 10^15 transistors, it won’t be until the year 2036 that computers will have more computing power than all human brains combined.

Question: “If an asteroid was very small but supermassive, could you really live on it like the Little Prince?” (102).

In The Little Prince by Antoine de Saint-Exupery, a boy lives on an asteroid several feet wide. He walks on it, so it has gravity like Earth’s. To allow walking, such a small space rock would have to be as dense as all the humans on Earth put together. Standing on it, a person would feel more tug on her feet than her head, causing a stretching sensation like lying on a merry-go-round with her head near the center.

You’d have to be a professional basketball player to jump high enough to escape the rock’s gravity and float away. Otherwise, you’d go into orbit around the asteroid, moving about as fast as a jogger.

Question: “From what height would you need to drop a steak for it to be cooked when it hit the ground?” (107).

A steak the size of a hockey puck, dropped from 39 kilometers, won’t reach the speed of sound; it’s more likely to be frozen by the cold high-altitude temperatures than warmed up. Dropped from 100 kilometers—the edge of space—the steak will reach twice the speed of sound and will get slightly singed by wispy air compressed to 350 degrees. Even dropped from 250 kilometers, the steak will become charred at hypersonic speeds, but the inside will still be uncooked.

Question: “How hard would a puck have to be shot to be able to knock the goalie himself backward into the net?” (112).

A goalie is about 600 times heavier than a puck. It would take a puck flying at several times the speed of sound to knock a goalie backward. A puck launched by a hypersonic gas gun would become charred or melted but also slowed way down by the air it soars through. More likely, the end result would resemble throwing a ripe tomato at a birthday cake: messy.

Question: “If everyone on the planet stayed away from each other for a couple of weeks, wouldn’t the common cold be wiped out?” (114).

Such a quarantine would cause a major worldwide economic disruption. If everyone stood equidistant from everyone else, they’d each have an area around them of a few acres, with nearby people no closer than 77 meters. However, hundreds of millions of people would have to stand in unpleasant places like the Sahara Desert or Antarctica. Biohazard suits might work better.

Many people have poorly functioning immune systems. These and other reservoirs of cold viruses would keep reinfecting people. Munroe notes, “But if they ever come up with a rhinovirus vaccine, I’ll be first in line” (118).

Question: “What if a glass of water was, all of a sudden, literally half empty?” (119).

In a glass with a vacuum at the top, air replaces the vacuum in less than a millisecond, causing a small shock wave and a bang. The glass survives. In a glass with a vacuum in the bottom half, the water drops suddenly, and because water is incompressible, it strikes the bottom of the glass like a hammer, breaking the glass. The rest of the glass flies up and strikes the ceiling.

The author notes, “The lesson: If the optimist says the glass is half full, and the pessimist says the glass is half empty, the physicist ducks” (124).

Question: “If global warming puts us in danger through temperature rise, and super-volcanos put us into danger of global cooling, shouldn’t those two dangers balance each other out?” (125). By this logic, having the flu cancels out freezing weather.

Question: “How fast would a human have to run in order to be cut in half at the bellybutton by a cheese-cutting wire?” (125). (A cartoon stick figure screams.)

Question: “Let’s assume there’s life on the nearest habitable exoplanet and that they have technology comparable to ours. If they looked at our star right now, what would they see?” (126).

They’d see a dot of light. As for detecting life on Earth, commercial TV and radio transmissions are too weak to be received several light-years away, but high-intensity early-warning radar, used during the Cold War to search for enemy attacks, might have been detectable. Both forms of transmission have been replaced by much quieter systems—cable TV, for example—so that the Earth’s radio noise has diminished.

Aliens might still learn something about Earth by observing sunlight bounced off its atmosphere, which hints at the nature of the planet’s life forms.

Question: “If someone’s DNA suddenly vanished, how long would that person last?” (131).

Losing the body’s DNA would remove about a 1/3 pound of mass, about the same as removing a shirt or peeing. At first, aside from some nausea and diarrhea, nothing much would happen. Then the victim would die of massive organ failures and immune system collapse. Certain mushrooms, chemotherapy, and radiation poisoning also block or damage DNA and cause similar problems.

Question: “What would happen if you tried to fly a normal Earth airplane above different solar system bodies?” (137).

Planes fly through the atmosphere; most moons don’t have one. On Mars, the air is so thin that the plane wouldn’t be able to take off; dropped from on high, it might glide a bit but would probably crash. Venus’s air is thick, and the plane would take off at mere jogging speed but would quickly disintegrate in the 800-degree heat. In Jupiter’s atmosphere, the plane would descend at high speed through storm-level winds until pressures crushed it; on smaller Saturn, the same process would simply take longer. With freezing high winds, Uranus and Neptune would be fatal.

Saturn’s large moon Titan has a dense atmosphere and light gravity, making flight easy, but the extreme cold would freeze everything. An improved heating system might help.