Loneliness
After returning to Earth, Apollo 11 command module pilot Mike Collins said he did not feel at all lonely. He wrote about the experience in his book Carrying the Fire: An Astronaut’s Journeys:
Far from feeling lonely or abandoned, I feel very much a part of what is taking place on the lunar surface . . . I don’t mean to deny a feeling of solitude. It is there, reinforced by the fact that radio contact with the Earth abruptly cuts off at the instant I disappear behind the moon.
I am alone now, truly alone, and absolutely isolated from any known life. I am it. If a count were taken, the score would be three billion plus two over on the other side of the moon, and one plus God knows what on this side.
Al Worden, the Apollo 15 command module pilot, even enjoyed the experience.
There’s a thing about being alone and there’s a thing about being lonely, and they’re two different things. I was alone but I was not lonely. My background was as a fighter pilot in the air force, then as a test pilot—and that was mostly in fighter airplanes—so I was very used to being by myself. I thoroughly enjoyed it. I didn’t have to talk to Dave and Jim any more . . . On the backside of the Moon, I didn’t even have to talk to Houston and that was the best part of the flight.
Introverts understand; the loneliest human in history was just happy to have a few minutes of peace and quiet.
1Because of the curve of the Earth, you actually have to go 3619 kilometers across the surface to qualify.
2Amundsen’s expedition had left the continent by then.
Weird (and Worrying) Questions from the What If? INBOX, #11
Q. What if everyone in Great Britain went to one of the coasts and started paddling? Could they move the island at all?
—Ellen Eubanks
Q. Are fire tornadoes possible?
—Seth Wishman
Raindrop
Q. What if a rainstorm dropped all of its water in a single giant drop?
—Michael McNeill
A. It’s midsummer in kansas. The air is hot and heavy. Two old-timers sit on the porch in rocking chairs.
On the horizon to the southwest, ominous-looking clouds begin to appear. The towers build as they draw closer, the tops spreading out into an anvil shape.
They hear the tinkling of wind chimes as a gentle breeze picks up. The sky begins to darken.
Moisture
Air holds water. If you walled off a column of air, from the ground up to the top of the atmosphere, and then cooled the column of air down, the moisture it contained would condense out as rain. If you collected the rain in the bottom of the column, it would fill it to a depth of anywhere between zero and a few dozen centimeters. That depth is what we call the air’s total precipitable water (TPW).
Normally, the TPW is 1 or 2 centimeters.
Satellites measure this water vapor content for every point on the globe, producing some truly beautiful maps.
We’ll imagine our storm measures 100 kilometers on each side and has a high TPW content of 6 centimeters. This means the water in our rainstorm would have a volume of:
That water would weigh 600 million tons (which happens to be about the current weight of our species). Normally, a portion of this water would fall, scattered, as rain—at most, 6 centimeters of it.
In this storm, all that water instead condenses into one giant drop, a sphere of water over a kilometer in diameter. We’ll assume it forms a couple of kilometers above the surface, since that’s where most rain condenses.
The drop begins to fall.
For five or six seconds, nothing is visible. Then, the base of the cloud begins to bulge downward. For a moment, it looks a little like a funnel cloud is forming. Then the bulge widens, and at the ten-second mark, the bottom of the drop emerges from the cloud.
The drop is now falling at 90 meters per second (200 mph). The roaring wind whips up the surface of the water into spray. The leading edge of the droplet turns to foam as air is forced into the liquid. If it kept falling for long enough, these forces would gradually disperse the entire droplet into rain.
Before that can happen, about 20 seconds after formation, the edge of the droplet hits the ground. The water is now moving at over 200 m/s (450 mph). Right under the point of impact, the air is unable to rush out of the way fast enough, and the compression heats it so quickly that the grass would catch fire if it had time.
Fortunately for the grass, this heat lasts only a few milliseconds because it’s doused by the arrival of a lot of cold water. Unfortunately for the grass, the cold water is moving at over half the speed of sound.
If you were floating in the center of this sphere during this episode, you wouldn’t have felt anything unusual up until now. It’d be pretty dark in the middle, but if you had enough time (and lung capacity) to swim a few hundred meters out toward the edge, you’d be able to make out the dim glow of daylight.
As the raindrop approached the ground, the buildup of air resistance would lead to an increase in pressure that would make your ears pop. But seconds later, when the water contacted the surface, you’d be crushed to death—the shockwave would briefly create pressures exceeding those at the bottom of the Mariana Trench.
The water plows into the ground, but the bedrock is unyielding. The pressure forces the water sideways, creating a supersonic omnidirectional jet1 that destroys everything in its path.
The wall of water expands outward kilometer by kilometer, ripping up trees, houses, and topsoil as it goes. The house, porch, and old-timers are obliterated in an instant. Everything within a few kilometers is completely scoured away, leaving a pool of mud atop bedrock. The splash continues outward, demolishing all structures out to distances of 20 or 30 kilometers. At this distance, areas shielded by mountains or ridges are protected, and the flood begins to flow along natural valleys and waterways.
The broader region is largely protected from the effects of the storm, though areas hundreds of kilometers downstream experience flash flooding in the hours after the impact.
News trickles out into the world about the inexplicable disaster. There is widespread shock and puzzlement, and for a while, every new cloud in the sky causes mass panic. Fear reigns supreme as the world fears rain supreme, but years pass without any signs of the disaster repeating.
Atmospheric scientists try for years to piece together what happened, but no explanation is forthcoming. Eventually, they give up, and the unexplained meteorological phenomenon is simply called a “dubstep storm,” because—in the words of one researcher—“It had one hell of a drop.”
1Just about the coolest triplet of words I’ve ever seen.
SAT Guessing
Q. What if everyone who took the SAT guessed on every multiple-choice question? How many perfect scores would there be?
—Rob Balder
A. None.
The SAT is a standardized test given to American high school students. The scoring is such that under certain circumstances, guessing an answer can be a good strategy. But what if you guessed on everything?
Not all of the SAT is multiple-choice, so let’s focus on the multiple-choice questions to keep things simple. We’ll assume everyone gets the essay questions and fill-in-the-number sections correct.
In the 2014 version of the SAT, there were 44 multiple-choice questions in the math (quantitative) section, 67 in the critical reading (qualitative) section, and 47 in the newfangled1 writing section. Each question has five options, so a random guess has a 20 percent chance of being right.
The probability of getting all 158 questions right is:
That’s one in 27 quinquatrigintillion.
If all four million 17-year-olds took the SAT, and they all guessed randomly, it’s a vi
rtually certain that there would be no perfect scores on any of the three sections.
How certain is it? Well, if they each used a computer to take the test a million times each day, and continued this every day for five billion years—until the Sun expanded to a red giant and the Earth was charred to a cinder—the chance of any of them ever getting a perfect score on just the math section would be about 0.0001 percent.
How unlikely is that? Each year something like 500 Americans are struck by lightning (based on an average of 45 lightning deaths and a 9–10 percent fatality rate). This suggests that the odds of any one American being hit in a given year are about 1 in 700,000.2
This means that the odds of acing the SAT by guessing are worse than the odds of every living ex-President and every member of the main cast of Firefly all being independently struck by lightning . . . on the same day.
To everyone taking the SAT this year, good luck—but it won’t be enough.
1I took the SAT a long time ago, okay?
2See: xkcd, “Conditional Risk,” http://xkcd.com/795/.
Neutron Bullet
Q. If a bullet with the density of a neutron star were fired from a handgun (ignoring the how) at the Earth’s surface, would the Earth be destroyed?
—Charlotte Ainsworth
A. A bullet with the density of a neutron star would weigh about as much as the Empire State Building.
Whether we fired it from a gun or not, the bullet would fall straight through the ground, punching through the crust as if the rock were wet tissue paper.
We’ll look at two different questions:
What would the bullet’s passage do to the Earth?
If we kept the bullet here on the surface, what would it do to its surroundings? Could we touch it?
First, a little bit of background:
What are neutron stars?
A neutron star is what’s left over after a giant star collapses under its own gravity.
Stars exist in a balance. Their massive gravity is always trying to make them collapse inward, but that squeezing sets off several different forces that push them back apart.
In the Sun, the thing holding off collapse is heat from nuclear fusion. When a star runs out of fusion fuel, it contracts (in a complicated process involving several explosions) until the collapse is stopped by the quantum laws that keep matter from overlapping with other matter.1
If the star is heavy enough, it overcomes that quantum pressure and collapses further (with another, more massive explosion) to become a neutron star. If the remnant is even heavier, it becomes a black hole.2
Neutron stars are some of the densest objects you can find (outside of the infinite density of a black hole). They’re crushed by their own immense gravity into a compact quantum-mechanical soup that’s in some ways similar to an atomic nucleus the size of a mountain.
Is our bullet made from a neutron star?
No. Charlotte asked for a bullet as dense as a neutron star, not one made from actual neutron star material. That’s good, because you can’t make a bullet from that stuff. If you take neutron star material outside of the crushing gravity well where it’s normally found, it will re-expand into superhot normal matter with an outpouring of energy more powerful than any nuclear weapon.
That’s presumably why Charlotte suggested we make our bullet out of some magical, stable material that’s as dense as a neutron star.
What would the bullet do to the Earth?
You could imagine firing it from a gun,3 but it might be more interesting to simply drop it. In either case, the bullet would accelerate downward, punch into the ground, and burrow toward the center of the Earth.
This wouldn’t destroy the Earth, but it would be pretty strange.
As the bullet got within a few feet of the ground, the force of its gravity would yank up a huge clump of dirt, which would ripple wildly around the bullet as it fell, spraying in all directions. As it went in, you’d feel the ground shake, and it would leave a jumbled, fractured crater with no entry hole.
The bullet would fall straight through the Earth’s crust. On the surface, the vibration would quickly die down. But far below, the bullet would be crushing and vaporizing the mantle in front of it as it fell. It would blast the material out of the way with powerful shockwaves, leaving a trail of superhot plasma behind it. This would be something never before seen in the history of the universe: an underground shooting star.
Eventually, the bullet would come to rest, lodged in the nickel-iron core at the center of the Earth. The energy delivered to the Earth would be massive on a human scale, but the planet would barely notice. The bullet’s gravity would affect only the rock within a few dozen feet of it; while it’s heavy enough to fall through the crust, its gravity alone wouldn’t be strong enough to crush the rock very much.
The hole would close up, leaving the bullet forever out of anyone’s reach.4 Eventually, the Earth would be consumed by the aging, swollen Sun, and the bullet would reach its final resting place at the Sun’s core.
The Sun isn’t dense enough to become a neutron star itself. After it swallows the Earth, it will instead go through some phases of expansion and collapse, and will eventually settle down, leaving behind a small white dwarf star with the bullet still lodged in the center. Someday, far in the future—when the universe is thousands of times older than it is today—that white dwarf will cool and fade to black.
That answers the question of what would happen if the bullet were fired into the Earth. But what if we could keep it near the surface?
Set the bullet on a sturdy pedestal
First, we’d need a magical infinitely strong pedestal to put the bullet on, which would need to sit on a similarly strong platform large enough to spread the weight out. Otherwise, the whole thing would sink into the ground.
A base about the size of a city block would be strong enough to keep it above-ground for at least a few days, probably much more. After all, the Empire State Building—which weighs as much as our bullet—rests on a similar platform, and it’s more than a few days old[citation needed] and hasn’t disappeared into the ground.[citation needed]
The bullet wouldn’t vacuum up the atmosphere. It would definitely compress the air around it and warm it up a little, but surprisingly, not really enough to notice.
Can I touch it?
Let’s imagine what would happen if you tried.
The gravity from this thing is strong. But it’s not that strong.
Imagine you’re standing 10 meters away. At this distance, you feel a very slight tug in the direction of the pedestal. Your brain—not accustomed to nonuniform gravities—thinks you’re standing on a gentle slope.
Do not put on roller skates.
This perceived slope gets steeper as you walk toward the pedestal, as if the ground were tipping forward.
When you get within a few meters, you have a hard time not sliding forward. However, if you got a good grip on something—a handle or a signpost—you can get pretty close.
Los Alamos physicists might call this “tickling the dragon’s tail.”
But I wanna touch it!
To get close enough to touch it, you would need a very good grip on something. Really, you’d need to do this in a full-body support harness, or at the very least a neck brace; if you get within reach, your head will weigh as much as a small child, and your blood won’t know which way to flow. However, if you’re a fighter pilot who’s used to gee forces, you might be able to pull it off.
From this angle, the blood is rushing to your head, but you’d still be able to breathe.
As you stretch out your arm, the pull gets a lot stronger; 20 centimeters (about 8 inches) is the point of no return—as your fingertips cross that line, your arm becomes too heavy to pull back. (
If you do a lot of one-handed pull-ups, you might be able to go a little closer.)
Once you get within a few inches, the force on your fingers is overwhelming, and they’re yanked forward—with or without you—and your fingertips actually touch the bullet (probably dislocating your fingers and shoulder).
When your fingertip actually comes in contact with the bullet, the pressure in your fingertips becomes too strong, and your blood breaks through the skin.
In Firefly, River Tam famously commented that “the human body can be drained of blood in 8.6 seconds given adequate vacuuming systems.”
By touching the bullet, you’ve just created an adequate vacuuming system.
Your body is restrained by a harness, and your arm remains attached to your body—flesh is surprisingly strong—but blood pours from your fingertip much faster than ordinarily possible. River’s “8.6 seconds” might be an underestimate.
Then things get weird.
The blood wraps around the bullet, forming a growing dark red sphere whose surface hums and vibrates with ripples moving too fast to see.
But wait
There’s a fact that now becomes becomes important:
You float on blood.
As the blood sphere grows, the force on your shoulder weakens . . . because the parts of your fingertips below the surface of the blood are buoyant! Blood is denser than flesh, and half the weight on your arm was coming from the last two knuckles of your fingers. When the blood is a few centimeters deep, the load gets considerably lighter.
If you could wait for the sphere of blood to get 20 centimeters deep—and if your shoulder were intact—you might even be able to pull your arm away.
What If? Page 20