3 See “Leap Seconds,” rasasoflaser.ga, for an explanation of why this happens. RELATIVISTIC BASEBALL Q. What would happen if you tried to hit a. sonic wind zone, but the winds there would still be twice as strong as those in the most powerful tornadoes. Buildings, from sheds to skyscrapers, would be. From the creator of the wildly popular webcomic xkcd, hilarious and informative answers to important questions you probably never thought to ask. Millions of people visit xkcd: I'm a Car each week to read Randall Munroe’s iconic webcomic. Fans of xkcd ask Munroe a lot of strange.

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What If?: Serious Scientific Answers to Absurd Hypothetical Questions is a collection of many of the blog's most popular answers, along with brand new weird. A Mole of Moles. July 24, Robot Apocalypse. July 31, Glass Half Empty. August 7, Everybody Out. August 14, Everybody Jump. Q. What would happen if you made a periodic table out of cube-shaped bricks, where each brick was made of the corresponding element?—Andy Connolly.

World-record pole climbers[4]Of course there's a world record for pole climbing. On the Moon, gravity is much weaker, so it will probably be easier to climb. On the other hand, you'll have to wear a spacesuit, so that will probably slow you down a little.

If you climb up the pole far enough, Earth's gravity will take over and start pulling you down. When you're hanging onto the pole, there are three forces pulling on you: The Earth's gravity pulling you toward Earth, the Moon's gravity pulling you away from Earth, and centrifugal force[6]As usual, anyone arguing about "centrifugal" versus "centripetal" force will be put in a centrifuge.

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At first, the combination of the Moon's gravity and centrifugal force are stronger, pulling you toward the Moon, but as you get closer to the Earth, Earth's gravity takes over. The Earth is pretty big, so you reach this point—which is known as the L1 Lagrange point—while you're still pretty close to the Moon.

Unfortunately for you, space is big, so "pretty close" is still a long way. Even if you climb at better-than-world-record speed, it will still take you several years to get to the L1 crossover point. As you approach the L1 point, you'll start to be able to switch from climbing to pushing-and-gliding: You can push once and then coast a long distance up the pole. You don't have to wait to stop, either—you can grab the pole again and give yourself a push to move even faster, like a skateboarder kicking several times to speed up.

Eventually, as you reach the vicinity of the L1 point and are no longer fighting gravity, the only limit on your speed will be how quickly you can grab the pole and "throw" it past you. The best baseball pitchers can move their hands at about mph while flinging objects past them, so you probably can't expect to move much faster than that. Note: While you're flinging yourself along, be careful not to drift out of reach of the pole.

Hopefully you brought some kind of safety line so you can recover if that happens. After another few weeks of gliding along the pole, you'll start to feel gravity take over, speeding you up faster than you can go by pushing yourself.

When this happens, be careful—soon, you'll need to start worrying about going too fast. As you approach the Earth and the pull of its gravity increases, you'll start to speed up quite a bit. Even if an object is moving slowly when it's drifting through space, when it gets close to the Earth it gets accelerated up to at least escape velocity by that final segment of the trip down into the Earth's gravity well.

Spacecraft deal with this problem by including heat shields, which are capable of absorbing and dissipating this heat without burning up the spacecraft behind it.

Thanks to heat shields, slowing down is much easier than speeding up—which requires the aforementioned giant fuel tank.

A Conversation With Randall Munroe, the Creator of XKCD

For more on this, see this What If question. Heat shields only work for slowing down; if there were a way to use the same heat shield mechanism to speed up, space travel would get a lot easier. Sadly, no one's figured out a practical way to build a "reverse heat shield" rocket. However, while the idea seems silly, in a sense it's sort of the principle behind both Project Orion and laser ablation propulsion.

Since you have this handy metal pole, you can control your descent by clamping onto it and controlling your rate of descent through friction. Make sure to keep your speed low during the whole approach and descent—and, if necessary, pausing to let your hands or brakepads cool down—rather than waiting until the end to try to slow down. If you get up to escape velocity, then at the last minute remember that you need to slow down, you'll be in for an unpleasant surprise as you try to grab on to the pole.

At best, you'll be flung away and plummet to your death.

At worst, your hands and the surface of the pole will both be converted into exciting new forms of matter, and then you'll be flung away and plummet to your death. Assuming you descend slowly and enter the atmosphere in a controlled manner, you'll soon encounter your next problem: Your pole isn't moving at the same speed as the Earth. Not even close. The land and atmosphere below you are moving very fast relative to you.

You're about to drop into some extremely strong winds. The Moon orbits around the Earth at a speed of roughly one kilometer per second, making a wide circle[10]Yes, I know, orbits are conic sections which in the case of the Moon is technically not exactly a circle.

It's actually a pentagon. That's how fast the top end of our hypothetical fire pole will be traveling. The bottom end of the pole makes a much smaller circle in the same amount of time, moving at an average speed of only about 35 mph relative to the center of the Moon's orbit: 35 miles per hour doesn't sound bad.

Unfortunately for you, the Earth is also spinning,[11]I mean, unfortunately in this specific context. In general, the fact that the Earth spins is very fortunate for you, and for the planet's overall habitability.

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 Mt. 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 Mt. Through all of this, I carried my precious ARC around, waiting for the time when I'd be able to spare the brainpower to read it.

I even took it on tour with me.

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Honestly, this book has more frequent flier miles than any three of you put together. It wasn't until I got back home that I started it. I wanted something to read before I went to bed, and I picked What If because I was worried if I picked up another book I'd be reading half the night and it would screw up my already dysfunctional sleep schedule.

Despite my best intentions, I read half the book that night. It cost me precious sleep I couldn't afford to lose. But I don't regret it. Not a bit. It's clever, but if you know anything about Randall Munroe, that won't come as a surprise to you.

And it's funny, and witty which are two different things, by the way. But again to readers of XKCD this won't come as any sort of surprise. There's some decent science in there, but it wasn't anywhere nearly as brain-taxing as I'd expected. Munroe does a brilliant job of explaining very complex concepts simply.

That's a rare gift. The other surprise is how much it pulled me in. I expected to read the book in dribs and drabs over a couple weeks.

xkcd: Volume 0

Instead, I tore through it. That's not usually the case for me with non-fiction books.Things get really hot when they come back from space. Maybe more of them should, but it feels a little condescending to assume I know who those people are. Astatine is the bad one. This is true of everything from small meteors1 to Felix Baumgartner. Reprinted by permission of Tim Minchin.

From higher altitudes, the heat starts to get really substantial. Many details of this history remain uncertain; the world of a billion years ago is difficult to reconstruct. Often, I start by just thinking about them for a while, or doing some calculations, before I start on the research at all.

Some types last longer than others, but even batteries advertised as having long shelf lives typically hold their charge only for a decade or two.