Q. What if everyone who took the SAT guessed on every multiple-choice question? How many perfect scores would there be?

• The probability of getting all 158 questions right is: That’s one in 27 quinquatrigintillion.
• How certain is it? Well, if they each used a computer to take th...

Q. Is there enough energy to move the entire current human population off-planet?

• An absolute baseline energy requirement: 4 gigajoules per person. No matter how we do it, whether we use rockets or a cannon or a space elevator or a ladder, moving a 65-kilogram person—out of the Earth’s...

Q. This may be a bit gruesome, but . . . if someone’s DNA suddenly vanished, how long would that person last?

• If you lost your DNA, you would instantly be about a third of a pound lighter.
• Losing your DNA would most likely result in abdominal pain, nausea, dizziness, rapid immu...

Q. I read about some researchers who were trying to produce sperm from bone marrow stem cells. If a woman were to have sperm cells made from her own stem cells and impregnate herself, what would be her relationship to her daughter?

• A child from a parent who self-fertilized would be lik...

Q. I was absentmindedly stirring a cup of hot tea, when I got to thinking, “Aren’t I actually adding kinetic energy into this cup?” I know that stirring does help to cool down the tea, but what if I were to stir it faster? Would I be able to boil a cup of water by stirring?

• No.

Q. When, if ever, will Facebook contain more profiles of dead people than of living ones?

• Either the 2060s or the 2130s. There are not a lot of dead people on Facebook. The main reasons for this is that Facebook—and its users—are young. The average Facebook user has gotten older over t...

Q. If you call a random phone number and say “God bless you,” what are the chances that the person who answers just sneezed?

• It’s hard to find good numbers on this, but it’s probably about 1 in 40,000.
• Before you pick up the phone, you should also keep in mind that there’s roug...

Q. What would happen if you tried to hit a baseball pitched at 90 percent the speed of light?

• It would, however, start to eat away at the surface, blasting tiny fragments of the ball in all directions. These fragments would be going so fast that when they hit air molecules, they would ...

Q. How close would you have to be to a supernova to get a lethal dose of neutrino radiation?

• Neutrinos are ghostly particles that barely interact with the world at all. Look at your hand—there are about a trillion neutrinos from the Sun passing through it every second.
• If you o...

Q. From what height would you need to drop a steak for it to be cooked when it hit the ground?

• No matter how fast it was going when it reached the lower layers of the atmosphere, it would quickly slow down to terminal velocity. No matter the starting height, it always takes six or seve...

Q. How quickly would the oceans drain if a circular portal 10 meters in radius leading into space were created at the bottom of Challenger Deep, the deepest spot in the ocean? How would the Earth change as the water was being drained?

• It would actually take hundreds of thousands of yea...

Q. Is it possible to build a jetpack using downward-firing machine guns?

• The principle here is pretty simple. If you fire a bullet forward, the recoil pushes you back. So if you fire downward, the recoil should push you up.
• With enough machine guns, you could fly.

Q. What if a rainstorm dropped all of its water in a single giant drop?

• In this storm, all that water instead condenses into one giant drop, a sphere of water over a kilometer in diameter.
• The drop is now falling at 90 meters per second (200 mph).
• When the water contact...

Q. How fast can you hit a speed bump while driving and live?

• The two main things protecting you from bumps in the road are the tires and the suspension.
• Cars generate lift. The air flowing around a car exerts all kinds of forces on it.
• At the range of 150–300 mph, a typ...

Q. What if I took a swim in a typical spent nuclear fuel pool? Would I need to dive to actually experience a fatal amount of radiation? How long could I stay safely at the surface?

• You could probably survive treading water anywhere from 10 to 40 hours.
• Spent fuel from nuclear r...

Q. How hard would a puck have to be shot to be able to knock the goalie himself backward into the net?

• This can’t really happen.
• If you’re like me, when you first saw this question, you might’ve imagined the puck leaving a cartoon-style hockey-puck-shaped hole. But that’s becau...

Q. What would happen if lightning struck a bullet in midair?

• If it were sitting still, the current would quickly heat and melt the metal.
• But since it would be moving along so quickly, it would exit the channel before it could be warmed by more than a few degrees. It would cont...

Q. What if I jumped out of an airplane with a couple of tanks of helium and one huge, un-inflated balloon? Then, while falling, I release the helium and fill the balloon. How long of a fall would I need in order for the balloon to slow me enough that I could land safely?

• If you inflate...

Q. Assuming a zero-gravity environment with an atmosphere identical to Earth’s, how long would it take the friction of air to stop an arrow fired from a bow? Would it eventually come to a standstill and hover in midair?

• The arrow would slow down quickly. Air resistance is proportional ...

Q. If an asteroid was very small but supermassive, could you really live on it like the Little Prince?

• If the asteroid had a radius of 1.75 meters, then in order to have Earthlike gravity at the surface, it would need to have a mass of about 500 million tons. This is roughly equal to t...

Q. What would happen if everyone on Earth stood as close to each other as they could and jumped, everyone landing on the ground at the same instant?

• It doesn’t really affect the planet. Earth outweighs us by a factor of over ten trillion. On average, we humans can vertically jump maybe...

Q. If you suddenly began rising steadily at 1 foot per second, how exactly would you die? Would you freeze or suffocate first? Or something else?

• Above 8000 meters—above the tops of all but the highest mountains—the oxygen content in the air is too low to support human life. Near this ...

Q. What would happen if the Earth and all terrestrial objects suddenly stopped spinning, but the atmosphere retained its velocity?

• Nearly everyone would die.
• At the equator, the Earth’s surface is moving at about 470 meters per second—relative to its axis. If the Earth stopped ...

Q. How dangerous is it, really, to be in a pool during a thunderstorm?

• Pretty dangerous. Water is conductive, but that’s not the biggest problem—the biggest problem is that if you’re swimming, your head is poking up from a large flat surface. But lightning striking the water near you w...

Q. How much computing power could we could achieve if the entire world population stopped whatever we are doing right now and started doing calculations?How would it compare to a modern-day computer or smartphone?

• The processor in a mobile phone could do calculations about 70 times fas...