What If? Page 5

  The outer surface of the planet would radiate heat into space and freeze. Because the moles form a literal fur coat, when frozen they would insulate the interior of the planet and slow the loss of heat to space. However, the flow of heat in the liquid interior would be dominated by convection. Plumes of hot meat and bubbles of trapped gases like methane—along with the air from the lungs of the deceased moles—would periodically rise through the mole crust and erupt volcanically from the surface, a geyser of death blasting mole bodies free of the planet.

  Eventually, after centuries or millennia of turmoil, the planet would calm and cool enough that it would begin to freeze all the way through. The deep interior would be under such high pressure that as it cooled, the water would crystallize out into exotic forms of ice such as ice III and ice V, and eventually ice II and ice IX.4

  All told, this is a pretty bleak picture. Fortunately, there’s a better approach.

  I don’t have any reliable numbers for global mole population (or small mammal biomass in general), but we’ll take a shot in the dark and estimate that there are at least a few dozen mice, rats, voles, and other small mammals for every human.

  There might be a billion habitable planets in our galaxy. If we colonized them, we’d certainly bring mice and rats with us. If just one in a hundred were populated with small mammals in numbers similar to Earth’s, after a few million years—not long, in evolutionary time—the total number that have ever lived would surpass Avogadro’s number.

  If you want a mole of moles, build a spaceship.

  1“One mole” is close to the number of atoms in a gram of hydrogen. It’s also, by chance, a decent ballpark guess for the number of grains of sand on Earth.

  2http://en.wikipedia.org/wiki/File:Condylura.jpg

  3That’s a neat coincidence I’ve never noticed before — a cubic mile happens to be almost exactly 4/3π cubic kilometers, so a sphere with a radius of X kilometers has the same volume as a cube that’s X miles on each side.

  4No relation.

  Hair Dryer

  Q. What would happen if a hair dryer with continuous power were turned on and put in an airtight 1 × 1 × 1-meter box?

  —Dry Paratroopa

  A. A typical hair dryer draws 1875 watts of power.

  All 1875 watts have to go somewhere. No matter what happens inside the box, if it’s using 1875 watts of power, eventually there will be 1875 watts of heat flowing out.

  This is true of any device that uses power, which is a handy thing to know. For example, people worry about leaving disconnected chargers plugged into the wall for fear that they’re draining power. Are they right? Heat flow analysis provides a simple rule of thumb: If an unused charger isn’t warm to the touch, it’s using less than a penny of electricity a day. For a small smartphone charger, if it’s not warm to the touch, it’s using less than a penny a year. This is true of almost any powered device.1

  But back to the box.

  Heat will flow from the hair dryer out into the box. If we assume the dryer is indestructible, the interior of the box will keep getting hotter until the outer surface reaches about 60°C (140°F). At that temperature, the box will be losing heat to the outside as fast as the hair dryer is adding it inside, and the system will be in equilibrium.

  It’s warmer than my parents! It’s my new parents.

  The equilibrium temperature will be a bit cooler if there’s a breeze, or if the box is sitting on a wet or metallic surface that conducts away heat quickly.

  If the box is made of metal, it will be hot enough to burn your hand if you touch it for more than five seconds. If it’s wood, you can probably touch it for a while, but there’s a danger that parts of the box in contact with the mouth of the hair dryer will catch fire.

  The inside of the box will be like an oven. The temperature it reaches will depend on the thickness of the box wall; the thicker and more insulating the wall, the higher the temperature. It wouldn’t take a very thick box to create temperatures high enough to burn out the hair dryer.

  But let’s assume it’s an indestructible hair dryer. And if we have something as cool as an indestructible hair dryer, it seems like a shame to limit it to 1875 watts.

  With 18,750 watts flowing out of the hair dryer, the surface of the box reaches over 200°C (475°F), as hot as a skillet on low-medium.

  I wonder how high this dial goes.

  There’s a distressing amount of space left on the dial.

  The surface of the box is now 600°C, hot enough to glow a dim red.

  If it’s made of aluminium, the inside is starting to melt. If it’s made of lead, the outside is starting to melt. If it’s on a wood floor, the house is on fire. But it doesn’t matter what’s happening around it; the hair dryer is indestructible.

  Two megawatts pumped into a laser is enough to destroy missiles.

  At 1300°C, the box is now about the temperature of lava.

  One more notch.

  This hair dryer is probably not up to code.

  Now 18 megawatts are flowing into the box.

  The surface of the box reaches 2400°C. If it were steel, it would have melted by now. If it’s made of something like tungsten, it might conceivably last a little longer.

  Just one more, then we’ll stop.

  This much power—187 megawatts—is enough to make the box glow white. Not a lot of materials can survive these conditions, so we’ll have to assume the box is indestructible.

  The floor is made of lava.

  Unfortunately, the floor isn’t.

  Before it can burn its way through the floor, someone throws a water balloon under it. The burst of steam launches the box out the front door and onto the sidewalk.2

  We’re at 1.875 gigawatts (I lied about stopping). According to Back to the Future, the hair dryer is now drawing enough power to travel back in time.

  The box is blindingly bright, and you can’t get closer than a few hundred meters due to the intense heat. It sits in the middle of a growing pool of lava. Anything within 50–100 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 18.7 gigawatts, the conditions around the box are similar to those on the pad during a space shuttle launch. The box begins to be tossed around by the powerful updrafts it’s creating.

  In 1914, H. G. Wells imagined devices like this in his book The World Set Free. He wrote of a type of bomb that, instead of exploding once, exploded continuously, a slow-burn inferno that started inextinguishable fires in the hearts of cities. 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 1.875 terawatts is like a house-sized stack of TNT going off every second.

  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 hair dryer is now, impossibly, consuming more power than every other electrical device on the planet combined.

  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.

  Let’s try something different.

  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 plum
e of steam.

  And then . . .

  In this case, that’s 11 petawatts.

  A brief story:

  The official record for the fastest manmade object is the Helios 2 probe, which reached about 70 km/s in a close swing around the Sun. But it’s possible the actual holder of that title is a two-ton metal manhole cover.

  The cover sat atop a shaft at an underground nuclear test site operated by Los Alamos as part of Operation Plumbbob. When the 1-kiloton nuke went off below, the facility effectively became a nuclear potato cannon, giving the cap a gigantic kick. A high-speed camera trained on the lid caught only one frame of it moving upward before it vanished—which means it was moving at a minimum of 66 km/s. The cap was never found.

  Now, 66 km/s is about six times escape velocity, but contrary to common speculation, it’s unlikely the cap ever reached space. Newton’s impact depth approximation suggests that it was either destroyed completely by impact with the air or slowed and fell back to Earth.

  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. The steam, heated to a plasma by the flood of radiation, accelerates the box faster and faster.

  Photo courtesy of Commander Hadfield

  Rather than slam into the atmosphere like the manhole cover, the box flies through a bubble of expanding plasma that offers little resistance. 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.

  However, a few may wish we hadn’t.

  1Though not necessarily those plugged into a second device. 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.

  2Note: If you’re ever trapped with me in a burning building, and I suggest an idea for how we could escape the situation, it’s probably best to ignore me.

  weird (and worrying) questions from the what if? INBOX, #2

  Q. Would dumping anti-matter into the Chernobyl reactor when it was melting down stop the meltdown?

  —AJ

  Q. Is it possible to cry so much you dehydrate yourself?

  —Karl Wildermuth

  The Last Human Light

  Q. 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?

  —Alan

  A. There would be a lot of contenders for the “last light” title.

  The superb 2007 book The World Without Us, by Alan Weisman, explored in great detail what would happen to Earth’s houses, roads, skyscrapers, farms, and animals if humans suddenly vanished. A 2008 TV series called Life After People investigated the same premise. However, neither of them answered this particular question.

  We’ll start with the obvious: Most lights wouldn’t last long, because the major power grids would go down relatively fast. Fossil fuel plants, which supply the vast majority of the world’s electricity, require a steady supply of fuel, and their supply chains do involve humans making decisions.

  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. The result would be a rapid series of cascade failures, leading to a blackout of all the major power grids.

  However, plenty of electricity comes from sources not tied to the major power grids. Let’s take a look at a few of those, and when each one might turn off.

  Diesel generators

  Many remote communities, like those on far-flung islands, get their power from diesel generators. These can continue to operate until they run out of fuel, which in most cases could be anywhere from days to months.

  Geothermal plants

  Generating stations that don’t need a human-provided fuel supply would be in better shape. Geothermal plants, which are powered by the Earth’s internal heat, can run for some time without human intervention.

  According to the maintenance manual for the Svartsengi Island geothermal plant in Iceland, every six months the operators must change the gearbox oil and regrease all electric motors and couplings. Without humans to perform these sorts of maintenance procedures, some plants might run for a few years, but they’d all succumb to corrosion eventually.

  Wind turbines

  People relying on wind power would be in better shape than most. Turbines are designed so that they don’t need constant maintenance, for the simple reason that there are a lot of them and they’re a pain to climb.

  Some windmills can run for a long time without human intervention. The Gedser Wind Turbine in Denmark was installed in the late 1950s, and generated power for 11 years without maintenance. Modern turbines are typically rated to run for 30,000 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.

  Eventually, most of the wind turbines would be stopped by the same thing that would destroy the geothermal plants: Their gearboxes would seize up.

  Hydroelectric dams

  Generators that convert falling water into electricity will keep working for quite a while. The History Channel show Life After People spoke with an operator at the Hoover Dam, who said that if everyone walked out, the facility would continue to run on autopilot for several years. 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.

  Batteries

  Battery-powered lights will all be off in a decade or two. 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. In the Clarendon Library at Oxford University sits a battery-powered bell that has been ringing since the year 1840. The bell “rings” so quietly it’s almost inaudible, using only a tiny amount of charge with every motion of the clapper. Nobody knows exactly what kind of batteries it uses because nobody wants to take it apart to figure it out.

  Sadly, there’s no light hooked up to it.

  Nuclear reactors

  Nuclear reactors are a little tricky. If they settle into low-power mode, they can continue running almost indefinitely; the energy density of their fuel is just that high. As a certain webcomic put it:

  Unfortunately, although there’s enough fuel, the reactors wouldn’t keep running for long. 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.

  It may seem strange that a power plant would require external power to run, but every part of a nuclear reactor’s control system is designed so that a failure causes it to rapidly shut down, or “SCRAM.”1 When outside power is lost, either because the outside power plant shuts down or the on-site backup generators run out of fuel, the reactor would SCRAM.

  Space probes

  Out of all human artifacts, our spacecraft might be the longest-lasting. Some of their orbits will last for millions of years, although their electrical power typically won’t.

  Within centuries, our Mars rovers will be buried by dust. By then, many of our satellites will have fallen back to Earth as their orbits decayed. 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. The Mars rover Curiosity, for example, is powered by the heat from a chunk of plutonium it carries in a container on the end of a stick.

  Curiosity could continue receiving electrical power from the RTG for over a century. 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. There’s one problem: no lights.

  Curiosity has lights; it uses them to illuminate samples and perform spectroscopy. However, these lights are turned on only when it’s taking measurements. With no human instructions, it will have no reason to turn them on.

  Unless they have humans on board, spacecraft don’t need a lot of lights. The Galileo probe, which explored Jupiter in the 1990s, had several LEDs in the mechanism of its flight data recorder. Since they emitted infrared rather than visible light, calling them “lights” is a stretch—and in any case, Galileo was deliberately crashed into Jupiter in 2003.2

  Other satellites carry LEDs. Some GPS satellites use, for example, UV LEDs to control charge buildup in some of their equipment, and they’re powered by solar panels; in theory they can keep running as long as the Sun is shining. Unfortunately, most won’t even last as long as Curiosity; eventually, they’ll succumb to space debris impacts.