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

Question: “I noticed recently that the number of people in a family tree increases exponentially with each generation: I have 2 parents, 4 grandparents, 8 great-grandparents, and so on. Which got me thinking—are most people descended from the majority of Homo sapiens who have ever lived? If not, what fraction of all the people that have ever lived am I descended from?” (172).

You are probably descended from approximately 10% of all the humans who ever lived. Experts theorize that at an “identical ancestors point,” approximately 7,000 to 4,000 years ago, every person’s lineage either incudes every living human or has since died out. From that point backwards, everyone has an identical set of ancestors, but in the millennia since then, family trees have diverged.

Question: “I’m a lowly college student stuck in a car without AC. As such, the windows are down most of the time when I’m driving, and I started thinking: If a bird happens to match my speed and direction perfectly, and I swerve to catch the bird in my car… what happens next, other than an angry bird? Does the bird stay right where it was? Fly into the windshield? Drop into the seat? My roommate and I disagree. Any help settling this would really make all our lives easier” (176).

The car would engulf the bird, and without lift or drag from the headwind the bird would drop down onto the passenger seat. The bird would then react to its new circumstances, either flying out of the open window, or into the windshield, or embracing its position as a passenger.

Question: “If you stripped away all the rules of car racing and had a contest that was simply to get a human being around a track 200 times as fast as possible, what strategy would win? Let’s say the racer has to survive” (180).

The fastest possible strategy would be to strap a human into a swiveling pod on a variable velocity completing the Daytona Sands track in approximately 90 minutes. The main restriction would come from survivable limits of G forces due to acceleration. Disregarding the constraint of a surviving passenger, a particle accelerator could see the track completed by an atomic or subatomic particle in a tiny fraction of a second.

This chapter lists several submitted questions that the author does not answer but instead responds to via small comics or doodles.

Question: “What would happen if you put the end of a vacuum hose up to your eye and turned on the vacuum?” (185).

A stylized caution sign warns against such an act.

Question: “Is it possible to hold your arm straight out of a car window and punch a mailbox clean off its pole? Could you do it without breaking your hand?” (185).

A mailbox states that it would be less harmed than the person punching it.

Question: “If people’s teeth kept growing, but when they were fully grown they came off and are swallowed, how long would it take before it causes any problems?” (185).

The author, aghast, notes that the question itself has already caused a problem for him.

Question: “In a defensive situation, how much epinephrine (in an EpiPen) would it take to subdue a possible attacker?” (185).

A man wielding a sword confronts two stick figures, one claiming that an EpiPen is the mightier weapon.

Question: “What if my phone was based on vacuum tubes? How big would it be?” (186).

The modern iPhone 12 has 11.8 billion transistors in an 80ml case, whereas the early UNIVAC computer had 5,000 vacuum tubes in a 25m³ case. An iPhone using solely UNIVAC hardware would be the size of five city blocks, and an iPhone using vacuum tubes alongside modern technology would be the size of one city block. The components would have to be coordinated so that processing was not inhibited by the limits of the speed of light, and the phone would require 10¹¹ watts of power, reaching approximately 1,780 degrees Celsius.

Question: “Stopping rain from falling on something with an umbrella or a tent is boring. What if you tried to stop rain with a laser that targeted and vaporized each incoming droplet before it could come within ten feet of the ground?” (193).

This would be imminently impractical, requiring a huge amount of energy and vaporizing the rain into a steam cloud. Targeting would require specialized and sophisticated equipment, but just firing in random directions would see the laser travel hundreds of feet.

Question: “Could a person eat a whole cloud?” (195).

If a person could squeeze the air out of a cloud, they could then drink the cloud as water. A house-sized cloud holds approximately a liter of liquid and given its low density is probably the largest single object a human could consume in one sitting.

Question: “Let’s say that two people of different heights (159 cm and 206 cm) stand beside each other while looking at the sunset. How much longer will the taller person be able to see the Sun than the shorter one?” (199).

The taller person would see the sun for more than one second longer. Taller people see later sunsets and earlier sunrises, and the difference is slightly larger at the equator and smaller nearer the poles.

Question: “What if I made a lava lamp out of real lava? What could I use as a clear medium? How close could I stand to watch it?” (202).

This is relatively feasible, although the lava’s heat would cause the elements of the lamp to glow, obscuring the lava lamp effect. The transparent casing could be made out of fused quartz glass or sapphire, since both have a higher melting point than lava, and the clear medium could be made of melted glass, though it would likely be clouded by impurities in the lava. The lamp would require a huge amount of energy to prevent the lava from quickly cooling and solidifying.

Question: “Suppose everyone with a fridge or a freezer opened them at the same time, outdoors. Would that amount of cooling be able to noticeably change the temperature? If not, how many fridges would it take to lower the temperature, say, 5 degrees F? What about even lower?” (206).

Fridges heat their surroundings by pumping heat from their interior to the exterior, so opening any number of fridge doors would cause no net cooling effect. In fact, open refrigerators would continue to consume electricity—thereby heating Earth by a miniscule amount as the electrical energy was inevitably converted into heat energy and likely also contributing to raising Earth’s temperature through the increased combustion of fossil fuels.

Question: “Could you get drunk from drinking a drunk person’s blood?” (210).

A blood alcohol content of 0.4% is the median lethal dose. If you drank all five liters of someone’s blood at 0.4% alcohol content, you would imbibe as much alcohol as is in a single pint of beer. You would likely vomit, but that would be because of the blood rather than the alcohol, and you might also contract bloodborne diseases.

Question: “You know how when you spin a basketball on your finger you hit the side to make it go faster and balance it? If a meteor passes close enough to Earth, can it make the Earth spin faster like your hand does the basketball?” (214).

Yes, provided that the meteor at least makes contact with Earth’s atmosphere. Depending on the angle of the meteor, the impact would either slow down or speed up Earth’s rotation by a tiny amount. The Chicxulub meteor impact changed the day’s length by several milliseconds at most.

Question: “Which has a greater gravitational pull on me: the Sun or spiders? Granted, the Sun is much bigger, but it is also much farther away, and as I have learned in high school physics, the gravitational force is proportional to the square of the distance.” (217).

No individual spider could exert enough gravitational pull to rival the sun. If all of the world’s spiders were equally distributed across Earth’s surface, their collective gravitational pull on any individual would be approximately 13 orders of magnitude weaker than that of the sun. Even if a huge number of spiders were concentrated in your immediate vicinity, their gravitational pull on you would still be far less than that of the sun.

Question: “If house dust comprises up to 80 percent dead skin, how many people worth of skin does a person consume/inhale in a lifetime?” (220).

Household dust is only partly—rather than mostly—skin, and the dust has different components in different proportions depending on its location. Humans do shed a huge number of skin flakes, but they mostly concentrate on clothes and pillows or are washed away. Even if the air were mechanically pumped full of skin flakes, a person could only inhale a maximum of 3kg of skin throughout their lifetime.

Question: “How many Wint-O-Green Life Savers would it take to create a life-size lightning bolt if you crushed them?” (223).

Sugar emits light when crushed due to triboluminescence, which is the same phenomenon that causes lightning. Although the light of crushed sugar is usually ultraviolet, the flavoring additive methyl silicate in the Wint-O-Green flavor of Life Savers causes the candy to emit a distinctive bright blue flash when crushed. Crushed sugar does not cause a spark, however, and it would take 5-10 billion crushed Life Savers to equal the average energy output of a lightning strike.

In this chapter, the author answers several user-submitted questions via a brief written answer, a short comic, or both.

Question: “Can humans safely eat rabid creatures?” (226).

No.

Question: “What if the Earth’s core suddenly stopped producing heat?” (227).

The short-term impact would be minimal since most of our heat comes from the sun. Eventually, however, plate tectonics would stop, disrupting the long-term carbon cycle that regulates Earth’s temperature.

Question: “Could humanity, with our current technology destroy the moon?” (228).

No.

Question: “Can global warming cause the Earth’s magnetic fields to weaken?” (228).

No.

Question: “If you used a laser, would you be able to bake something?” (228).

Yes.

Question: “What if the Earth was sliced in half, like an apple? Where should you be such that you have the best chance of survival?” (229).

You should be holding the knife.

Question: “What would happen if a person dropped into a pool full of jellyfish?” (229).

It would depend on the species of jellyfish. For instance, a person encountering moon jellies could befriend them.

Question: “Would it be possible to make a house floor into a massive air hockey table, so you could move heavy furniture across the room?” (230).

Yes, and the author is enthusiastic about the concept.

Question: “My 7-year-old son asked us over dinner recently at which point potatoes melt (I assume in a vacuum). Please advise” (230).

Potatoes don’t really melt (and Munroe mocks the idea of adding “in a vacuum” to the question).

Question: “Would a pigeon be able to make it to space if it was not affected by gravity?” (231).

No, there would be too little oxygen in the upper atmosphere, and it would be too cold.

Question: “If you were flying blind through the Milky Way, what would be the odds of hitting a star or planet?” (231).

The odds of hitting a star would be one in 10 billion, which is still a thousand times more likely than hitting a planet.

Question: “On various bodies in our solar system (feel free to group any that are equivalent), roughly how long could you typically survive on the surface […] with nothing but an infinite air supply and warm winter clothing? […]” (232).

On Earth, you could survive a lifetime; on Venus, months; anywhere else, hours at most.

Question: “What would happen if someone dropped an anvil on you from space?” (233).

The anvil would slow to terminal velocity, approximately 500 miles per hour, and kill you.

Question: “What if I want to heat my house using toasters. How many do I need?” (234).

Due to the laws of thermodynamics, every appliance transfers electrical energy into heat energy at the same rate it consumes electricity. The average toaster uses 1,200 watts per hour, so it would take 20 toasters to heat a typical American house.