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Randall Munroe-What If__ Serious Scientific Answers to Absurd Hypothetical Questions-Houghton Mifflin Harcourt ().pdf - Ebook download as PDF File. Randall Munroe's blog/comic What If uses open access scholarly and homeranking.info%homeranking.info>. author of What If? and the creator of the webcomic xkcd uses line drawings and common words to provide simple explanations for how things.


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RANDALL MUNROE what if? GLOBAL WINDSTORM Q. What would happen if the Earth and all terrestrial objects suddenly stopped spinning, but the. [PDF] What If?: Serious Scientific Answers to Absurd Hypothetical Questions From Millions of people visit xkcd: I'm a Car each week to read Randall Munroe's. RANDALL MUNROE. HOUGHTON from the What If? Inbox, #8. If you're going to wait it out, one of the best places to do it might be Helsinki,. Finland.

I mean, as she lived for the last few hours. But forget the Earth—what would happen to the Moon? The first row is simple, if boring: Reprinted by permission of Tim Minchin. However, if it lands in the water, mud, or leaves, it will probably be fine.

Anything within 50— meters bursts into flame. A column of heat and smoke rise high into the air. Periodic explosions of gas beneath the box launch it into the air, and it starts fires and forms a new lava pool where it lands.

We keep turning the dial. At In , H. Wells imagined devices like this in his book The World Set Free. The story eerily foreshadowed the development, 30 years later, of nuclear weapons.

The box is now soaring through the air. Each time it nears the ground, it superheats the surface, and the plume of expanding air hurls it back into the sky. The outpouring of 1. A trail of firestorms —massive conflagrations that sustain themselves by creating their own wind systems —winds its way across the landscape.

A new milestone: The box, soaring high above the surface, is putting out energy equivalent to three Trinity tests every second. At this point, the pattern is obvious. This thing is going to skip around the atmosphere until it destroys the planet. We turn the dial to zero as the box is passing over northern Canada. Rapidly cooling, it plummets to Earth, landing in Great Bear Lake with a plume of steam. And then. A brief story: When the 1- kiloton nuke went off below, the facility effectively became a nuclear potato cannon, giving the cap a gigantic kick.

The cap was never found. When we turn it back on, our reactivated hair dryer box, bobbing in lake water, undergoes a similar process. The heated steam below it expands outward, and as the box rises into the air, the entire surface of the lake turns to steam.

It exits the atmosphere and continues away, slowly fading from second sun to dim star. Much of the Northwest Territories is burning, but the Earth has survived. If a charger is connected to something, like a smartphone or laptop, power can be flowing from the wall through the charger into the device. However, neither of them answered this particular question.

Without people, there would be less demand for power, but our thermostats would still be running. As coal and oil plants started shutting down in the first few hours, other plants would need to take up the slack. This kind of situation is difficult to handle even with human guidance.

However, plenty of electricity comes from sources not tied to the major power grids. These can continue to operate until they run out of fuel, which in most cases could be anywhere from days to months.

Wind turbines People relying on wind power would be in better shape than most. Some windmills can run for a long time without human intervention. Modern turbines are typically rated to run for 30, hours three years without servicing, and there are no doubt some that would run for decades. One of them would no doubt have at least a status LED in it somewhere. Their gearboxes would seize up. Hydroelectric dams Generators that convert falling water into electricity will keep working for quite a while.

The dam would probably succumb to either clogged intakes or the same kind of mechanical failure that would hit the wind turbines and geothermal plants. Even without anything using their power, batteries gradually self-discharge.

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.

There are a few exceptions. Nobody knows exactly what kind of batteries it uses because nobody wants to take it apart to figure it out. Nuclear reactors Nuclear reactors are a little tricky. As a certain webcomic put it: As soon as something went wrong, the core would go into automatic shutdown. This would happen quickly; many things can trigger it, but the most likely culprit would be a loss of external power.

Space probes Out of all human artifacts, our spacecraft might be the longest-lasting. Within centuries, our Mars rovers will be buried by dust. GPS satellites, in distant orbits, will last longer, but in time, even the most stable orbits will be disrupted by the Moon and Sun. Many spacecraft are powered by solar panels, and others by radioactive decay.

Eventually the voltage will drop too low to keep the rover operating, but other parts will probably wear out before that happens. So Curiosity looks promising.

With no human instructions, it will have no reason to turn them on. Solar power Emergency call boxes, often found along the side of the road in remote locations, are frequently solar-powered. They usually have lights on them, which provide illumination every night. If we follow a strict definition of lighting, solar- powered lights in remote locations could conceivably be the last surviving human light source. Watch dials used to be coated in radium, which made them glow. Over the years, the paint has broken down.

Although the watch dials are still radioactive, they no longer glow. Watch dials, however, are not our only radioactive light source. In the dark, these glass blocks glow blue. And thus, we arrive at our answer: Centuries from now, deep in concrete vaults, the light from our most toxic waste will still be shining. In case something went wrong, next to the railing was stationed a distinguished physicist with an axe.

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. The Saturn V had a takeoff thrust-to-weight ratio of about 1. As it turns out, the AK has a thrust-to-weight ratio of around 2. This means if you stood it on end and somehow taped down the trigger, it would rise into the air while firing.

Thrust is the product of these two amounts: If an AK fires ten 8- gram bullets per second at meters per second, its thrust is: Since the AK weighs only In practice, the actual thrust would turn out to be up to around 30 percent higher.

The amount of extra force this adds varies by gun and cartridge. The overall efficiency also depends on whether you eject the shell casings out of the vehicle or carry them with you. I asked my Texan acquaintances if they could weigh some shell casings for my calculations.

We can try using multiple guns. If you fire two guns at the ground, it creates twice the thrust. If each gun can lift 5 pounds more than its own weight, two can lift You will not go to space today. An AK magazine holds 30 rounds. We can improve this with a larger magazine—but only up to a point.

The reason for this is a fundamental and central problem in rocket science: Fuel makes you heavier. If we added more than about rounds, the AK would be too heavy to take off. The largest versions of this craft could accelerate upward to vertical speeds approaching meters per second, climbing over half a kilometer into the air.

With enough machine guns, you could fly. Can we do better? My Texas friends suggested a series of machine guns, and I ran the numbers on each one. Some did pretty well; the MG, a heavier machine gun, had a marginally higher thrust-to-weight ratio than the AK Then we went bigger. To put it another way: If I mounted a GAU-8 on my car, put the car in neutral, and started firing backward from a standstill, I would be breaking the interstate speed limit in less than three seconds.

Its thrust-to- weight ratio approaches 40, which means if you pointed one at the ground and fired, not only would it take off in a rapidly expanding spray of deadly metal fragments, but you would experience 40 gees of acceleration. This is way too much. Landing lights almost always broke after firing. Or something else? Fortunately, your body handles air pressure changes like that all the time.

Air pressure changes quickly with height. If your phone has a barometer in it, as a lot of modern phones do, you can download an app and actually see the pressure difference between your head and your feet. At about two hours and two kilometers, the temperature would drop below freezing. The wind would also, most likely, be picking up.

If you have any exposed skin, this is where frostbite would start to become a concern. However, unless you had a warm coat, the temperature would be a bigger problem. Over the next two hours, the air would drop to below- zero temperatures. But when? The scholarly authorities on freezing to death seem to be, unsurprisingly, Canadians. According to their model, the main factor in the cause of death would be your clothes. Above 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 zone, you would experience a range of symptoms, possibly including confusion, dizziness, clumsiness, impaired vision, and nausea. Your veins are supposed to bring low-oxygen blood back to your lungs to be refilled with oxygen. This would happen around the seven-hour mark; the chances are very slim that you would make it to eight. She died as she lived—rising at a foot per second. I mean, as she lived for the last few hours. And two million years later, your frozen body, still moving along steadily at a foot per second, would pass through the heliopause into interstellar space.

Clyde Tombaugh, the astronomer who discovered Pluto, died in It can, of course, vary quite a bit. The hull would likely be airtight. There may be a few specialized one- way valves that would let air out, but in all likelihood, the submarine would remain sealed. The big problem the crew would face would be the obvious one: Everyone knows that space is very cold. The ocean is colder than space. Interstellar space is very cold, but space near the Sun —and near Earth—is actually incredibly hot!

When I was a kid, my dad had a machine shop in our basement, and I remember watching him use a metal grinder. Without a warm environment around you radiating heat back to you, you lose heat by radiation much faster than normal. Without rockets, it has no way to do this.

Okay—technically, a submarine does have rockets. Unfortunately, the rockets are pointing the wrong way to give the submarine a push. Rockets are self-propelling, which means they have very little recoil. With a rocket, you just light it and let go. But not launching them could. Remember to disable the detonators on the missiles. It means the warmth of sunlight in winter. Since there are 7. Your extra two million bills a year would barely be enough to notice.

Would the storm cell be immediately vaporized? It turns out the National Oceanic and Atmospheric Administration—the agency that runs the National Hurricane Center—gets it a lot, too. I recommend you read the whole thing,1 but I think the last sentence of the first paragraph says it all: Water turbines can be pretty efficient. For those 42 minutes, our hypothetical house could generate up to watts of electricity, which might be enough to power everything inside it.

The stars are named Joe Biden. It works, but it feels so wrong. I bike to class sometimes. To increase the temperature of the air layer in front of your body by 20 degrees Celsius enough to go from freezing to room temperature , you would need to be biking at meters per second. Since drag increases with the square of the speed, this limit would be pretty hard to push any further.

How much physical space does the Internet take up?

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The storage industry produces in the neighborhood of million hard drives per year. If most of them are 3.

So, by that measure, the Internet is smaller than an oil tanker. I am not an authority on lightning safety. I am a guy who draws pictures on the Internet. With that out of the way. To answer the questions that follow, we need to get an idea of where lightning is likely to go.

Roll an imaginary meter sphere across the landscape and look at where it touches. They say lightning strikes the tallest thing around.

I mean, not all lightning hits Mount Everest. But does it find the tallest person in a crowd?

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The tallest person I know is probably Ryan North. What about other reasons? So how does lightning pick its targets? The leader carries comparatively little current —on the order of amps. This is the blinding flash you see. It races back up the channel at a significant fraction of the speed of light, covering the distance in under a millisecond.

This is where the meter sphere comes in. To figure out where lightning is likely to hit, you roll the imaginary meter sphere across the landscape. Places the surface makes contact —treetops, fence posts, and golfers in fields—are potential lightning targets. The shadow is the area where the leader is likely to hit the tall object instead of the ground around it: After the current hits the tall object, it flows out into the ground. Of the 28 people killed by lightning in the US in , 13 were standing under or near trees.

But lightning striking the water near you would still be bad. The 20, amps spread outward—mostly over the surface—but how much of a jolt it will give you at what distance is hard to calculate. What would happen if you were taking a shower when you were struck by lightning?

Or standing under a waterfall? Or a submarine?

A boat with a closed cabin and a lightning protection system is about as safe as a car. Or what if you were doing a backflip? Or looking straight up at the bolt? The core of a lightning bolt is a few centimeters in diameter. A bullet fired from an AK is about 26 mm long and moves at about millimeters every millisecond.

Copper is a fantastically good conductor of electricity, and much of the 20, amps could easily take a shortcut through the bullet. Surprisingly, the bullet would handle it pretty well. If it were sitting still, the current would quickly heat and melt the metal. It would continue on to its target relatively unaffected.

This effect is similar to how when a traffic light turns green, the cars in front start moving, then the cars in back, so the movement appears to spread backward. On the other hand, apples are better. Humans, for example, are probably still far better at looking at a picture of a scene and guessing what just happened: To test this theory, I sent this picture to my mother and asked her what she thought had happened. The cat knocked over the vase.

The cat jumped out of the vase at the kid. The cat was mummified in the vase, but arose when the kid touched it with a magic rope.

The vase exploded, attracting a child and a cat. The child put on the hat for protection from future explosions. The kid and cat are running around trying to catch a snake. According to computer scientist Hans Moravec, a human running through computer chip benchmark calculations by hand, using pencil and paper, can carry out the equivalent of one full instruction every minute and a half.

A new high-end desktop PC chip would increase that ratio to So, what year did a single typical desktop computer surpass the combined processing power of humanity? After all, these comparisons are one computer against all humans. How do all humans stack up against all computers? This is tough to calculate. It turns out that processors from the s and processors from today have a roughly similar ratio of transistors to MIPS —about 30 transistors per instruction per second, give or take an order of magnitude.

It looks something like this: This tells us that a typical modern laptop, which has a benchmark score in the tens of thousands of MIPS, has more computing power than existed in the entire world in The complexity of neurons Again, making people do pencil-and-paper CPU benchmarks is a phenomenally silly way to measure human computing power. There are projects that attempt to use supercomputers to fully simulate a brain at the level of individual synapses. The numbers from a run of the Japanese K supercomputer suggest a figure of transistors per human brain.

One, the pencil-and-paper Dhrystone benchmark, asks humans to manually simulate individual operations on a computer chip, and finds humans perform about 0. A slightly better approach might be to combine the two estimates. This actually makes a strange sort of sense. If we assume our computer programs are about as inefficient at simulating human brain activity as human brains are at simulating computer chip activity, then maybe a more fair brain power rating would be the geometric mean of the two numbers.

Wilson, there are to ants in the world. By comparison, in there were about transistors in the world, or tens of thousands of transistors per ant. Mere Machine to Transcendent Mind. Biology is tricky. I hope things are better in the future.

Please figure out a way to come get us. It was written in Even in our best telescopes, the largest asteroids were visible only as points of light. The Little Prince took this a step further, imagining an asteroid as a tiny planet with gravity, air, and a rose. If there really were a superdense asteroid with enough surface gravity to walk around on, it would have some pretty remarkable properties.

If the asteroid had a radius of 1. This is roughly equal to the combined mass of every human on Earth. It would feel like you were stretched out on a curved rubber ball, or were lying on a merry-go-round with your head near the center.

The escape velocity at the surface would be about 5 meters per second. That means you might be able to leave our asteroid by running horizontally and jumping off the end of a ramp. Your orbital speed would be roughly 3 meters per second, which is a typical jogging speed. But this would be a weird orbit. Tidal forces would act on you in several ways. If you stretched your arm down toward the planet, it would be pulled much harder than the rest of you.

And when you reach down with one arm, the rest of you gets pushed upward, which means other parts of your body feel even less gravity. A large orbiting object under these kinds of tidal forces—say, a moon—will generally break apart into rings. However, your orbit would become chaotic and unstable.

Rugescu and Daniele Mortari. Their simulations showed that large, elongated objects follow strange paths around their central bodies. This type of analysis could actually have practical applications. There have been various proposals over the years to use long, whirling tethers to move cargo in and out of gravity wells—a sort of free-floating space elevator.

The inherent instability of many tether orbits poses a challenge for such a project. Mallory Ortberg, writing on the-toast. And you may need to defrost it after you pick it up. Things get really hot when they come back from space. When skydiver Felix Baumgartner jumped from 39 kilometers, he hit Mach 1 at around 30 kilometers. There was no clear conclusion. To try to get a better answer, I decided to run a series of simulations of a steak falling from various heights.

Apparently, the US government was shoveling tons of money at anything even loosely related to weapons research. It took me a while to realize there was a much easier way to learn what combinations of time and temperature will effectively heat the various layers of a steak: Check a cookbook.

No matter how fast it was going when it reached the lower layers of the atmosphere, it would quickly slow down to terminal velocity. For much of those 25 kilometers, the air temperature is below freezing —which means the steak will spend six or seven minutes subjected to a relentless blast of subzero, hurricane-force winds.

When the steak does finally hit the ground, it will be traveling at terminal velocity —about 30 meters per second. To get an idea of what this means, imagine a steak flung at the ground by a major-league pitcher. If the steak is even partially frozen, it could easily shatter. However, if it lands in the water, mud, or leaves, it will probably be fine. Steaks can probably survive breaking the sound barrier.

In addition to Felix, pilots have ejected at supersonic speeds and lived to tell about it. We need to go higher. At supersonic and hypersonic speeds, a shockwave forms around the steak that helps protect it from the faster and faster winds. I searched the literature, but was unable to find any research on this. However, this is little more than a wild guess. If anyone puts a steak in a hypersonic wind tunnel to get better data on this, please, send me the video. In this scenario, the steak reaches a top speed of Mach 6, and the outer surface may even get pleasantly seared.

The inside, unfortunately, is still uncooked. From higher altitudes, the heat starts to get really substantial. That is, it becomes charred. Charring is a normal consequence of dropping meat in a fire. If the heat is high enough, it will simply blast the surface layer off as it flash-cooks it.

If most of the steak makes it to the ground, the inside will still be raw. Which is why we should drop the steak over Pittsburgh. And the Andromeda Strain. Not necessarily fine to eat. The problem, in a nutshell, is that hockey players are heavy and pucks are not. A goalie in full gear outweighs a puck by a factor of about Even the fastest slap shot has less momentum than a ten- year-old skating along at a mile per hour.

It also suggests that if you started to slowly rotate a hockey rink, it could tilt up to 50 degrees before the players would all slide to one end.

Clearly, experiments are needed to confirm this. Firing an object at Mach 8 is not, in itself, very hard.

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One of the best methods for doing so is the aforementioned hypersonic gas gun, which is—at its core —the same mechanism a BB gun uses to fire BBs. Imagine throwing a ripe tomato—as hard as you can—at a cake. After a few days, your immune system notices and destroys it,3 but not before you infect, on average, one other person. Could our immune systems then wipe out every copy of the virus? A global quarantine brings us to another question: How far apart can we actually get from one another? A lot of us would be stuck standing in the Sahara Desert,5 or central Antarctica.

That way, we could walk around and interact, even allowing some normal economic activity to continue: Would it work? To help figure out the answer, I talked to Professor Ian M. He said that rhinoviruses—and other RNA respiratory viruses —are completely eliminated from the body by the immune system; they do not linger after infection. The remote islands of St. Kilda, far to the northwest of Scotland, for centuries hosted a population of about people.

The exact cause of the outbreaks is unknown,8 but rhinoviruses were probably responsible for many of them. Every time a boat visited, it would introduce new strains of virus. These strains would sweep the islands, infecting virtually everyone.

After several weeks, all the residents would have fresh immunity to those strains, and with nowhere to go, the viruses would die out. If all humans were isolated from one another, the St. After a week or two, our colds would run their course, and healthy immune systems would have plenty of time to clear the viruses. The story is different for those with severely weakened immune systems.

In transplant patients, for example, whose immune systems have been artificially suppressed, common infections —including rhinoviruses —can linger for weeks, months, or conceivably years. This small group of immunocompromised people would serve as safe havens for rhinoviruses.

The hope of eradicating them is slim; they would need to survive in only a few hosts in order to sweep out and retake the world. While colds are no fun, their absence might be worse. On the other hand, colds suck. And in addition to being unpleasant, some research says infections by these viruses also weaken our immune systems directly and can open us up to further infections. If the average were less than one, the virus would die out.

If it were more than one, eventually everyone would have a cold all the time. Kilda correctly identified the boats as the trigger for the outbreaks. But what if the empty half of the glass were actually empty—a vacuum?

Which half is empty? For the first handful of microseconds, nothing happens. On this timescale, even the air molecules are nearly stationary. For the most part, air molecules jiggle around at speeds of a few hundred meters per second.

But at any given time, some happen to be moving faster than others. The fastest few are moving at over meters per second. These are the first to drift into the vacuum in the glass on the right. However, in the vacuum of the glasses, it does start to boil, slowly shedding water vapor into the empty space. While the water on the surface in both glasses starts to boil away, in the glass on the right, the air rushing in stops it before it really gets going.

The sides of the glass bulge slightly, but they contain the pressure and do not break. A shockwave reverberates through the water and back into the air, joining the turbulence already there. The shockwave from the vacuum collapse takes about a millisecond to spread out through the other two glasses. The glass and water both flex slightly as the wave passes through them. Around this time, the glass on the left starts to visibly lift into the air.

This is the force we think of as suction. The boiling water has filled the vacuum with a very small amount of water vapor. However, the glass and water are now moving too fast for the vapor buildup to matter.

Without a cushion of air between them —only a few wisps of vapor —the water smacks into the bottom of the glass like a hammer. The momentary force on the glass is immense, and it breaks. In our situation, the forces would be more than enough to destroy even the heaviest drinking glasses. The bottom is carried downward by the water and thunks against the table. The water splashes around it, spraying droplets and glass shards in all directions.

Meanwhile, the detached upper portion of the glass continues to rise. After half a second, the observers, hearing a pop, have begun to flinch. Their heads lift involuntarily to follow the rising movement of the glass. The glass has just enough speed to bang against the ceiling, breaking into fragments. The lesson: If the optimist says the glass is half full, and the pessimist says the glass is half empty, the physicist ducks. Radio transmissions Contact popularized the idea of aliens listening in on our broadcast media.

Sadly, the odds are against it. Space is really big. The full picture is more complicated, but the bottom line is that as our technology has gotten better, less of our radio traffic has been leaking out into space.

Even in the late 20th century, when we were using TV and radio to scream into the void at the top of our lungs, the signal probably faded to undetectability after a few light-years. They were outshone by the beams from early- warning radar. But the same march of technological progress that made the TV broadcast towers obsolete has had the same effect on early- warning radar.

This massive dish in Puerto Rico can function as a radar transmitter, bouncing a signal off nearby targets like Mercury and the asteroid belt. However, it transmits only occasionally, and in a narrow beam. If an exoplanet happened to be caught in the beam, and they were lucky enough to be pointing a receiving antenna at our corner of the sky at the time, all they would pick up would be a brief pulse of radio energy, then silence.

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Visible light This is more promising. The Sun is really bright, [citation needed ] and its light illuminates the Earth. Both of these effects could potentially be detected from an exoplanet. You could probably figure out what our water cycle looked like, and our oxygen-rich atmosphere would give you a hint that something weird was going on.

So in the end, the clearest signal from Earth might not be from us at all. Heeeey, look at the time. Gotta run. A radio transmission has the problem that they have to be paying attention when it arrives. Instead, we could make them pay attention. If we can figure out how to make a guidance system that survives the trip which would be tough , we could use it to steer toward any inhabited planet. But slowing down takes even more fuel. So maybe if those aliens looked toward our solar system, this is what they would see: There are easier ways to lose a third of a pound, including: This happens for two reasons: One, the Earth is shaped like this: When you stand, your muscles are constantly working to keep you upright.

For a while. Amanita bisporigera is a species of mushroom found in eastern North America. Destroying angel is a small, white, inoccuous-looking mushroom. Amanita is the reason why. Then you start to feel better. Amanita mushrooms contain amatoxin, which binds to an enzyme that is used to read information from DNA.

Since most of your body is made of cells,4 this is bad. Death is generally caused by liver or kidney failure, since those are the first sensitive organs in which the toxin accumulates.

The picture is even more vividly illustrated by two other examples of DNA damage: Some are more precisely targeted than others, but many simply interrupt cell division in general. The reason that this selectively kills cancer cells, instead of harming the patient and the cancer equally, is that cancer cells are dividing all the time, whereas most normal cells divide only occasionally.

Some human cells do divide constantly. The most rapidly dividing cells are found in the bone marrow, the factory that produces blood. Without it, we lose the ability to produce white blood cells, and our immune system collapses. Chemotherapy causes damage to the immune system, which makes cancer patients vulnerable to stray infections. Doxorubicin, one of the most common and potent chemotherapy drugs, works by linking random segments of DNA to one another to tangle them.

A loss of DNA would cause similar cell death, and probably similar symptoms. This is the period where the body is still working, but no new proteins can be synthesized and the immune system is collapsing. On the other hand, there would be at least one silver lining. If we ever end up in a dystopian future where Orwellian governments collect our genetic information and use it to track and control us. I got one of your friends to sneak into your room with a microscope while you were sleeping and check.

They stimulate white blood cell production by, in effect, tricking the body into thinking that it has a massive E. Instead, they physically dissolve the blood-brain barrier, resulting in rapid death from cerebral hemorrhage brain bleeding.

Plants undo this by stripping the oxygen back out and pumping it into the air. Engines need oxygen in the air to run. The Sun: To see what would happen to our aircraft on Mars, we turn to X-Plane. X-Plane is the most advanced flight simulator in the world. This makes it a valuable research tool, since it can accurately simulate entirely new aircraft designs —and new environments.

X-Plane tells us that flight on Mars is difficult, but not impossible. NASA knows this, and has considered surveying Mars by airplane. The tricky thing is that with so little atmosphere, to get any lift, you have to go fast. The X-Plane author compared piloting Martian aircraft to flying a supersonic ocean liner.

If dropped from 4 or 5 kilometers, it could gain enough speed to pull up into a glide—at over half the speed of sound. The landing would not be survivable.

But physics calculations give us an idea of what flight there would be like. The upshot is: Your plane would fly pretty well, except it would be on fire the whole time, and then it would stop flying, and then stop being a plane. Unfortunately, that air is hot enough to melt lead.

A much better bet would be to fly above the clouds. You would need the wetsuit, though, to protect you from the sulfuric acid. Venus is a terrible place. The picture here is a little friendlier than on Jupiter. Uranus is a strange, uniform bluish orb. It at least has some clouds to look at before you freeze to death or break apart from the turbulence. Its gravity—lower than that of the Moon—means that flying is easy.

Our Cessna could get into the air under pedal power. A human in a hang glider could comfortably take off and cruise around powered by oversized swim-flipper boots —or even take off by flapping artificial wings. The power requirements are minimal—it would probably take no more effort than walking. Judging from some numbers on heating requirements for light aircraft, I estimate that the cabin of a Cessna on Titan would probably cool by about 2 degrees per minute. The Huygens probe, which descended with batteries nearly drained, taking fascinating pictures as it fell, succumbed to the cold after only a few hours on the surface.

If humans put on artificial wings to fly, we might become Titanian versions of the Icarus story—our wings could freeze, fall apart, and send us tumbling to our deaths.

The cold of Titan is just an engineering problem. With the right refitting, and the right heat sources, a Cessna could fly on Titan —and so could we. What is the total nutritional value calories, fat, vitamins, minerals, etc. How much Force power can Yoda output? First we need to know how heavy the ship was. Next, we need to know how fast it was rising.

The front landing strut rises out of the water in about three and a half seconds, and I estimated the strut to be 1. Lastly, we need to know the strength of gravity on Dagobah. Wookieepeedia has just such a catalog, and informs us that the surface gravity on Dagobah is 0. Combining this with the X- wing mass and lift rate gives us our peak power output: But telekinesis is just one type of Force power.

What about that lightning the Emperor used to zap Luke? Those Tesla coils typically use lots of very short pulses.

If the Emperor is sustaining a continuous arc, as in an arc welder, the power could easily be in the megawatts. What about Luke? I examined the scene where he used his nascent Force powers to yank his lightsaber out of the snow. The numbers are harder to estimate here, but I went through frame-by-frame and came up with an estimate of watts for his peak output. So Yoda sounds like our best bet as an energy source. But with world electricity consumption pushing 2 terawatts, it would take a hundred million Yodas to meet our demands.

But what state do the largest number of planes actually fly over? There are a lot of flights up and down the East Coast; it would be easy to imagine that people fly over New York more often than Wyoming. To figure out what the real flyover states are, I looked at over 10, air traffic routes, determining which states each flight passed over.

Surprisingly, the state with the most planes flying over it —without taking off or landing—is. This result surprised me. These states have substantially more daily flyovers than any other. So why Virginia? There are a number of factors, but one of the biggest is Hartsfield-Jackson Atlanta International Airport. By this measure, the flyover states are, for the most part, simply the least dense states. The state with the highest ratio of flights-over-to- flights-to, however, is a surprise: A little digging turned up the very straightforward reason: Delaware has no airports.

This came as a surprise to me, since California is long and skinny, and it seems like a lot of flights over the Pacific would need to pass over it. What is the most flown-under state? The answer turns out to be Hawaii. The reason such a tiny state wins in this category is that most of the US is opposite the Indian Ocean, which has very few commercial flights over it. Falling from great heights is dangerous. A balloon will act as a parachute, slowing your fall to nonfatal speeds.

As one medical paper put it. It is, of course, obvious that speed, or height of fall, is not in itself injurious. A powerful fan could be used to fill it with ambient air, but at that point, you may as well just use a parachute. In , Larry Walters flew across Los Angeles in a lawn chair lifted by weather balloons, eventually reaching several miles in altitude. On landing, Walters was arrested, although the authorities had some trouble figuring out what to charge him with.

Compressed helium cylinders are smooth and often quite heavy, which means they have a high terminal velocity. This is true of everything from small meteors1 to Felix Baumgartner.

The ban- appeal form asked me to explain what task I was performing that necessitated so many queries. One poster compared a fall from height to being hit by a bus.

Another user, a medical examiner, replied that this was a bad comparison: The lower legs break, sending them into the air.

If pdf what munroe

They then go over the top of the car. They die when they hit the ground. They die from head injury. But lifting people into space is hard. Barring a massive reduction in the population, is launching the whole human race into space physically possible?

To figure out if this is plausible, we can start with an absolute baseline energy requirement: How much is 4 gigajoules? A lot, but not physically implausible.

However, 4 gigajoules is just a minimum. In practice, everything would depend on our means of transportation. This is because of a fundamental problem with rockets: They have to lift their own fuel. We load that fuel on board—and now our spaceship weighs kilograms.

A kilogram spaceship requires kilograms of fuel, so we load another kilograms on board. We burn it as we go, so we get lighter and lighter, which means we need less and less fuel. But we do have to lift the fuel partway. The formula for how much propellant we need to burn to get moving at a given speed is given by the Tsiolkovsky Rocket equation: If that ratio is x, then to launch a kilogram of ship, we need ex kilograms of fuel.

As x grows, this amount gets very large. Launching all of humanity total weight: As crazy as it sounds, we might be better off trying to 1 literally climb into space on a rope, or 2 blow ourselves off the planet with nuclear weapons. These are actually serious—if audacious —ideas for launch systems, both of which have been bouncing around since the start of the Space Age. The idea is that we connect a tether to a satellite orbiting far enough out that the tether is held taut by centrifugal force.

The biggest engineering hurdle is that the tether would have to be several times stronger than anything we can currently build. The basic idea is that you toss a nuclear bomb behind you and ride the shockwave.

If it could be made reliable enough, this system would in theory be capable of lifting entire city blocks into orbit, and could—potentially —accomplish our goal. The engineering principles behind this were thought to be solid enough that in the s, under the guidance of Freeman Dyson, the US government actually tried to build one of these spaceships. Advocates for nuclear pulse propulsion are still disappointed that the project was cancelled before any prototypes were built.

So the answer is that while sending one person into space is easy, getting all of us there would tax our resources to the limit and possibly destroy the planet. Would this be possible in real life? More on how that randomization works in a moment.

In humans, these cells are from two different people. Stem cells, which can form any type of tissue, could in principle be used to produce sperm or eggs. So far, nobody has been able to produce complete sperm from stem cells. In , a group of researchers succeeded in turning bone marrow stem cells into spermatogonial stem cells. These cells are the predecessors to sperm.

There were two problems. They said they produced sperm-like cells, but the media generally glossed over this. It turns out the authors had plagiarized two paragraphs of their article from another paper. He likes candlelight dinners and long walks on the beach--very long walks.

Lots of people say they like long walks on the beach, but then they get out on the beach, and after just an hour or two, they say they're getting tired. Bring a tent. He lives in Massachusetts. Enter your mobile number or email address below and we'll send you a link to download the free Kindle App. Then you can start reading Kindle books on your smartphone, tablet, or computer - no Kindle device required.

Would you like to tell us about a lower price? If you are a seller for this product, would you like to suggest updates through seller support? Read more Read less. Save Extra with 3 offers. Customers who viewed this item also viewed. Page 1 of 1 Start over Page 1 of 1. How Not to be Wrong. Jordan Ellenberg. Thing Explainer: Complicated Stuff in Simple Words. Randall Munroe. We Have No Idea: A Guide to the Unknown Universe. The Magic of Reality: Richard Dawkins.

How To Lie With Statistics. Darrell Huff. Hyperbole and a Half: Customers who bought this item also bought.

A Short History of Nearly Everything. Bill Bryson. Stuff Matters: Mark Miodownik. About the Author Randall Munroe is the author of the popular webcomic xkcd and the science question-and-answer blog What If?

To get the free app, enter mobile phone number. See all free Kindle reading apps. Start reading What If? Don't have a Kindle? Product details Audio CD: Blackstone Pub; Unabridged edition 2 September Language: English ISBN What other items do customers buy after viewing this item? A Brief History of Humankind.

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Top Reviews Most recent Top Reviews. There was a problem filtering reviews right now. Please try again later. Paperback Verified Purchase. This book opens with the best disclaimer I have ever seen: The author of this book is an Internet cartoonist, not a health or safety expert.

He likes it when things catch fire or explode, which means he does not have your best interests in mind. The publisher and the author disclaim responsibility for any adverse effects resulting, directly or indirectly, from information contained in this book. Dangerous ideas ahead, folks! Don't get too close -- these things could kill ya! On his website, he takes "absurd hypothetical questions" from readers and tries to answer some of them.

Here are some of my favorite questions in this book: 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? 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?