What If?

by Randall Munroe

  Sunset on the British Empire

  Q. When (if ever) did the Sun finally set on the British Empire?

  —Kurt Amundson

  A. It hasn’t. Yet. But only because of a few dozen people living in an area smaller than Disney World.

  The world’s largest empire

  The British Empire spanned the globe. This led to the saying that the Sun never set on it, since it was always daytime somewhere in the Empire.

  It’s hard to figure out exactly when this long daylight began. The whole process of claiming a colony (on land already occupied by other people) is awfully arbitrary in the first place. Essentially, the British built their empire by sailing around and sticking flags on random beaches. This makes it hard to decide when a particular spot in a country was “officially” added to the Empire.

  “What about that shadowy place over there?” “That’s France. We’ll get it one of these days.”

  The exact day when the Sun stopped setting on the Empire was probably sometime in the late 1700s or early 1800s, when the first Australian territories were added.

  The Empire largely disintegrated in the early 20th century, but—surprisingly—the Sun hasn’t technically started setting on it again.

  Fourteen territories

  Britain has 14 overseas territories, the direct remnants of the British Empire.

  Many newly independent British colonies joined the Commonwealth of Nations. Some of them, like Canada and Australia, have Queen Elizabeth as their official monarch. However, they are independent states that happen to have the same queen; they are not part of any empire.1

  The Sun never sets on all 14 British territories at once (or even 13, if you don’t count the British Antarctic Territory). However, if the UK loses one tiny territory, it will experience its first Empire-wide sunset in over two centuries.

  Every night, around midnight GMT, the Sun sets on the Cayman Islands, and doesn’t rise over the British Indian Ocean Territory until after 1:00 a.m. For that hour, the little Pitcairn Islands in the South Pacific are the only British territory in the Sun.

  The Pitcairn Islands have a population of a few dozen people, the descendants of the mutineers from the HMS Bounty. The islands became notorious in 2004 when a third of the adult male population, including the mayor, were convicted of child sexual abuse.

  As awful as the islands may be, they remain part of the British Empire, and unless they’re kicked out, the two-century-long British daylight will continue.

  Will it last forever?

  Well, maybe.

  In April of 2432, the island will experience its first total solar eclipse since the mutineers arrived.

  Luckily for the Empire, the eclipse happens at a time when the Sun is over the Cayman Islands in the Caribbean. Those areas won’t see a total eclipse; the Sun will even still be shining in London.

  In fact, no total eclipse for the next thousand years will pass over the Pitcairn Islands at the right time of day to end the streak. If the UK keeps its current territories and borders, it can stretch out the daylight for a long, long time.

  But not forever. Eventually—many millennia in the future—an eclipse will come for the island, and the Sun will finally set on the British Empire.

  1That they know of.

  Stirring Tea

  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?

  —Will Evans

  A. No.

  The basic idea makes sense. Temperature is just kinetic energy. When you stir tea, you’re adding kinetic energy to it, and that energy goes somewhere. Since the tea doesn’t do anything dramatic like rise into the air or emit light, the energy must be turning to heat.

  Am I making tea wrong?

  The reason you don’t notice the heat is that you’re not adding very much of it. It takes a huge amount of energy to heat water; by volume, it has a greater heat capacity than any other common substance.1

  If you want to heat water from room temperature to nearly boiling in two minutes, you’ll need a lot of power:2

  Our formula tells us that if we want to make a cup of hot water in two minutes, we’ll need a 700-watt power source. A typical microwave uses 700 to 1100 watts, and it takes about two minutes to heat a mug of water to make tea. It’s nice when things work out!3

  Microwaving a cup of water for two minutes at 700 watts delivers an awful lot of energy to the water. When water falls from the top of Niagara Falls, it gains kinetic energy, which is converted to heat at the bottom. But even after falling that great distance, the water heats up by only a fraction of a degree.4 To boil a cup of water, you’d have to drop it from higher than the top of the atmosphere.

  (The British Felix Baumgartner)

  How does stirring compare to microwaving?

  Based on figures from industrial mixer engineering reports, I estimate that vigorously stirring a cup of tea adds heat at a rate of about a ten-millionth of a watt. That’s completely negligible.

  The physical effect of stirring is actually a little complicated.5 Most of the heat is carried away from teacups by the air convecting over them, and so they cool from the top down. Stirring brings fresh hot water from the depths, so it can help this process. But there are other things going on—stirring disturbs the air, and it heats the walls of the mug. It’s hard to be sure what’s really going on without data.

  Fortunately, we have the Internet. Stack Exchange user drhodes measured the rate of teacup cooling from stirring vs. not stirring vs. repeatedly dipping a spoon into the cup vs. lifting it. Helpfully, drhodes posted both high-resolution graphs and the raw data itself, which is more than you can say for a lot of journal articles.

  The conclusion: It doesn’t really matter whether you stir, dip, or do nothing; the tea cools at about the same rate (although dipping the spoon in and out of the tea cooled it slightly faster).

  Which brings us back to the original question: Could you boil tea if you just stirred it hard enough?

  No.

  The first problem is power. The amount of power in question, 700 watts, is about a horsepower, so if you want to boil tea in two minutes, you’ll need at least one horse to stir it hard enough.

  You can reduce the power requirement by heating the tea over a longer period of time, but if you reduce it too far the tea will be cooling as fast as you’re heating it.

  Even if you could churn the spoon hard enough—tens of thousands of stirs per second—fluid dynamics would get in the way. At those high speeds, the tea would cavitate; a vacuum would form along the path of the spoon and stirring would become ineffective.6

  And if you stir hard enough that your tea cavitates, its surface area will increase very rapidly, and it will cool to room temperature in seconds.

  No matter how hard you stir your tea, it’s not going to get any warmer.

  1Hydrogen and helium have a higher heat capacity by mass, but they’re diffuse gasses. The only other common substance with a higher heat capacity by mass is ammonia. All three of these lose to water when measured by volume.

  2Note: Pushing almost-boiling water to boiling takes a large burst of extra energy on top of what’s required to heat it to the boiling point — this is called the enthalpy of vaporization.

  3If they didn’t, we’d just blame “inefficiency” or “vortices.”

  4

  5In some situations, mixing liquids can actually help keep them warm. Hot water rises, and when a body of water is large and still enough (like the ocean), a warm layer forms on the surface. This warm
layer radiates heat much more quickly than a cold layer would. If you disrupt this hot layer by mixing the water, the rate of heat loss decreases.

  This is why hurricanes tend to lose strength if they stop moving forward — their waves churn up cold water from the depths, cutting them off from the thin layer of hot surface water that was their main source of energy.

  6Some blenders, which are enclosed, actually do manage to warm their contents this way. But what kind of person makes tea in a blender?

  All the Lightning

  Q. If all the lightning strikes happening in the world on any given day all happened in the same place at once, what would happen to that place?

  —Trevor Jones

  A. They say lightning never strikes in the same place twice.

  “They” are wrong. From an evolutionary perspective, it’s a little surprising that this saying has survived; you’d think that people who believed it would have been gradually filtered out of the living population.

  This is how evolution works, right?

  People often wonder whether we could harvest electrical power from lightning. On the face of it, it makes sense; after all, lightning is electricity,1 and there is indeed a substantial amount of power in a lightning strike. The problem is, it’s hard to get lightning to strike where you want it.2

  A typical lightning strike delivers enough energy to power a residential house for about two days. That means that even the Empire State Building, which is struck by lightning about 100 times a year, wouldn’t be able to keep a house running on lightning power alone.

  Even in regions of the world with a lot of lightning, such as Florida and the eastern Congo, the power delivered to the ground by sunlight outweighs the power delivered by lightning by a factor of a million. Generating power from lightning is like building a wind farm whose blades are turned by a tornado: awesome impractical.3

  Trevor’s lightning

  In Trevor’s scenario, all the lightning in the world hits in one place. This would make power generation a lot more attractive!

  By “happened in the same place,” let’s assume the lightning bolts all come down in parallel, right up against each other. The main channel of a lightning bolt—the part that’s carrying current—is about a centimeter or two in diameter. Our bundle contains about a million separate bolts, which means it will be about 6 meters in diameter.

  Every science writer always compares everything to the atomic bomb dropped on Hiroshima,4 so we may as well get that out of the way: The lightning bolt would deliver about two atomic bombs’ worth of energy to the air and ground. From a more practical standpoint, this is enough electricity to power a game console and plasma TV for several million years. Or, to put it another way, it could support the US’s electricity consumption . . . for five minutes.

  The bolt itself would be only as narrow as the center circle of a basketball court, but it would leave a crater the size of the entire court.

  Within the bolt, the air would turn to high-energy plasma. The light and heat from the bolt would spontaneously ignite surfaces for miles around. The shockwave would flatten trees and demolish buildings. All in all, the Hiroshima comparison is not far off.

  Could we protect ourselves?

  Lightning rods

  The mechanism by which lightning rods work is disputed. Some people claim they actually ward off lightning strikes by “bleeding” charge from the ground to the air, lowering the cloud-to-ground voltage potential and reducing the probability of a strike. The National Fire Protection Association does not currently endorse this idea.

  I’m not sure what the NFPA would say about Trevor’s massive lightning bolt, but a lightning rod wouldn’t protect you from it. A copper cable a meter in diameter could, in theory, conduct the brief surge of current from the bolt without melting. Unfortunately, when the bolt reached the bottom end of the rod, the ground wouldn’t conduct it so well, and the explosion of molten rock would demolish your house all the same.5

  Catatumbo lightning

  Collecting all the world’s lightning into one place is obviously impossible. What about gathering all the lightning from just one area?

  No place on Earth has constant lightning, but there’s an area in Venezuela that comes close. Near the southwestern edge of Lake Maracaibo, there’s a strange phenomenon: perpetual nighttime thunderstorms. There are two spots, one over the lake and one over land to the west, where thunderstorms form almost every night. These storms can generate a flash of lightning every two seconds, making Lake Maracaibo the lightning capital of the world.

  If you somehow managed to channel all the bolts from a single night of Catatumbo thunderstorms down through a single lightning rod, and used it to charge a massive capacitor, it would store up enough power to run a game console and plasma TV for roughly a century.6

  Of course, if this happened, the old saying would need even more revision.

  1Citation: The presentation I gave to my third-grade class at Assawompset Elementary School while wearing a Ben Franklin costume.

  2And I hear it never strikes in the same place twice.

  3In case you’re curious, yes, I did run some numbers on using passing tornadoes to run wind turbines, and it’s even less practical than gathering lightning. The average location in the heart of Tornado Alley has a tornado pass over it only every 4000 years. Even if you managed to absorb all the accumulated energy of the tornado, it would still result in less than a watt of average power output in the long run. Believe it or not, something like this idea has actually been attempted. A company called AVEtec has proposed building a “vortex engine” that would produce artificial tornadoes and use them to generate power.

  4Niagara Falls has a power output equal to a Hiroshima-sized bomb going off every eight hours! The atomic bomb dropped on Nagasaki had an explosive power equal to 1.3 Hiroshima bombs! For context, the gentle breeze blowing across a prairie also carries roughly the kinetic energy of a Hiroshima bomb.

  5Your house would already be catching fire anyway, thanks to the thermal radiation from plasma in the air.

  6Since there’s no cellular data coverage on the southwest shore of Lake Maracaibo, you’ll have to buy service through a satellite provider, which generally means hundreds of milliseconds of lag.

  Loneliest Human

  Q. What is the farthest one human being has ever been from every other living person? Were they lonely?

  —Bryan J McCarter

  A. It’s hard to know for sure!

  The most likely suspects are the six Apollo command module pilots who stayed in lunar orbit during a Moon landing: Mike Collins, Dick Gordon, Stu Roosa, Al Worden, Ken Mattingly, and Ron Evans.

  Each of these astronauts stayed alone in the command module while two other astronauts landed on the Moon. At the highest point in their orbit, they were about 3585 kilometers from their fellow astronauts.

  From another point of view, this was the farthest the rest of humanity has ever managed to get from those jerk astronauts.

  You’d think astronauts would have a lock on this category, but it’s not so cut-and-dried. There are a few other candidates who come pretty close!

  Polynesians

  It’s hard to get 3585 kilometers from a permanently inhabited place.1 The Polynesians, who were the first humans to spread across the Pacific, might have managed it, but this would have required a lone sailor to travel awfully far ahead of everyone else. It may have happened—perhaps by accident, when someone was carried far from their group by a storm—but we’re unlikely to ever know for sure.

  Once the Pacific was colonized, it got a lot harder to find regions of the Earth’s surface where someone could achieve 3585-kilometer isolation. Now that the Antarctic continent has a
permanent population of researchers, it’s almost certainly impossible.

  Antarctic explorers

  During the period of Antarctic exploration, a few people have come close to beating the astronauts, and it’s possible one of them actually holds the record. One person who came very close was Robert Scott.

  Robert Falcon Scott was a British explorer who met a tragic end. Scott’s expedition reached the South Pole in 1911, only to discover that Norwegian explorer Roald Amundsen had beaten him there by several months. The dejected Scott and his companions began their trek back to the coast, but they all died while crossing the Ross Ice Shelf.

  The last surviving expedition member would have been, briefly, one of the most isolated people on Earth.2 However, he (whoever he was) was still within 3585 kilometers of a number of humans, including some other Antarctic explorer outposts as well as the Māori on Rakiura (Stewart Island) in New Zealand.

  There are plenty of other candidates. Pierre François Péron, a French sailor, says he was marooned on Île Amsterdam in the southern Indian Ocean. If so, he came close to beating the astronauts, but he wasn’t quite far enough from Mauritius, southwestern Australia, or the edge of Madagascar to qualify.

  We’ll probably never know for sure. It’s possible that some shipwrecked 18th-century sailor drifting in a lifeboat in the Southern Ocean holds the title of most isolated human. However, until some clear piece of historic evidence pops up, I think the six Apollo astronauts have a pretty good claim.

  Which brings us to the second part of Bryan’s question: Were they lonely?