What If? Read online

  Suppose you’re watching from a hilltop outside the city. The first thing you would see would be a blinding light, far outshining the sun. This would gradually fade over the course of a few seconds, and a growing fireball would rise into a mushroom cloud. Then, with a great roar, the blast wave would arrive, tearing up trees and shredding houses.

  Everything within roughly a mile of the park would be leveled, and a firestorm would engulf the surrounding city. The baseball diamond, now a sizable crater, would be centered a few hundred feet behind the former location of the backstop.

  Major League Baseball Rule 6.08(b) suggests that in this situation, the batter would be considered “hit by pitch,” and would be eligible to advance to first base.

  1After I initially published this article, MIT physicist Hans Rinderknecht contacted me to say that he’d simulated this scenario on their lab’s computers. He found that early in the ball’s flight, most of the air molecules were actually moving too quickly to cause fusion, and would pass right through the ball, heating it more slowly and uniformly than my original article described.

  Spent Fuel Pool

  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?

  —Jonathan Bastien-Filiatrault

  A. Assuming you’re a reasonably good swimmer, you could probably survive treading water anywhere from 10 to 40 hours. At that point, you would black out from fatigue and drown. This is also true for a pool without nuclear fuel in the bottom.

  Spent fuel from nuclear reactors is highly radioactive. Water is good for both radiation shielding and cooling, so fuel is stored at the bottom of pools for a couple of decades until it’s inert enough to be moved into dry casks. We haven’t really agreed on where to put those dry casks yet. One of these days we should probably figure that out.

  Here’s the geometry of a typical fuel storage pool:

  The heat wouldn’t be a big problem. The water temperature in a fuel pool can in theory go as high as 50°C, but in practice it’s generally between 25°C and 35°C—warmer than most pools but cooler than a hot tub.

  The most highly radioactive fuel rods are those recently removed from a reactor. For the kinds of radiation coming off spent nuclear fuel, every 7 centimeters of water cuts the amount of radiation in half. Based on the activity levels provided by Ontario Hydro in this report, this would be the region of danger for fresh fuel rods:

  Swimming to the bottom, touching your elbows to a fresh fuel canister, and immediately swimming back up would probably be enough to kill you.

  Yet outside the outer boundary, you could swim around as long as you wanted—the dose from the core would be less than the normal background dose you get walking around. In fact, as long as you were underwater, you would be shielded from most of that normal background dose. You may actually receive a lower dose of radiation treading water in a spent fuel pool than walking around on the street.

  Remember: I am a cartoonist. If you follow my advice on safety around nuclear materials, you probably deserve whatever happens to you.

  That’s if everything goes as planned. If there’s corrosion in the spent fuel rod casings, there may be some fission products in the water. They do a pretty good job of keeping the water clean, and it wouldn’t hurt you to swim in it, but it’s radioactive enough that it wouldn’t be legal to sell it as bottled water.1

  We know spent fuel pools can be safe to swim in because they’re routinely serviced by human divers.

  However, these divers have to be careful.

  On August 31, 2010, a diver was servicing the spent fuel pool at the Leibstadt nuclear reactor in Switzerland. He spotted an unidentified length of tubing on the bottom of the pool and radioed his supervisor to ask what to do. He was told to put it in his tool basket, which he did. Due to bubble noise in the pool, he didn’t hear his radiation alarm.

  When the tool basket was lifted from the water, the room’s radiation alarms went off. The basket was dropped back in the water and the diver left the pool. The diver’s dosimeter badges showed that he’d received a higher-than-normal whole-body dose, and the dose in his right hand was extremely high.

  The object turned out to be protective tubing from a radiation monitor in the reactor core, made highly radioactive by neutron flux. It had been accidentally sheared off while a capsule was being closed in 2006. It sank to a remote corner of the pool, where it sat unnoticed for four years.

  The tubing was so radioactive that if he’d tucked it into a tool belt or shoulder bag, where it sat close to his body, he could’ve been killed. As it was, the water protected him, and only his hand—a body part more resistant to radiation than the delicate internal organs—received a heavy dose.

  So, as far as swimming safety goes, the bottom line is that you’d probably be OK, as long as you didn’t dive to the bottom or pick up anything strange.

  But just to be sure, I got in touch with a friend of mine who works at a research reactor, and asked him what he thought would happen to someone who tried to swim in their radiation containment pool.

  “In our reactor?” He thought about it for a moment. “You’d die pretty quickly, before reaching the water, from gunshot wounds.”

  1Which is too bad — it’d make a hell of an energy drink.

  weird (and worrying) questions from the what if? INBOX, #1

  Q. Would it be possible to get your teeth to such a cold temperature that they would shatter upon drinking a hot cup of coffee?

  —Shelby Hebert

  Q. How many houses are burned down in the United States every year? What would be the easiest way to increase that number by a significant amount (say, at least 15%)?

  —Anonymous

  New York–Style Time Machine

  Q. I assume when you travel back in time you end up at the same spot on the Earth’s surface. At least, that’s how it worked in the Back to the Future movies. If so, what would it be like if you traveled back in time, starting in Times Square, New York, 1000 years? 10,000 years? 100,000 years? 1,000,000 years? 1,000,000,000 years? What about forward in time 1,000,000 years?

  —Mark Dettling

  1000 years back

  Manhattan has been continuously inhabited for the past 3000 years, and was first settled by humans perhaps 9000 years ago.

  In the 1600s, when Europeans arrived, the area was inhabited by the Lenape people.1 The Lenape were a loose confederation of tribes who lived in what is now Connecticut, New York, New Jersey, and Delaware.

  A thousand years ago, the area was probably inhabited by a similar collection of tribes, but those inhabitants lived half a millennium before European contact. They were as far removed from the Lenape of the 1600s as the Lenape of the 1600s are from the modern day.

  To see what Times Square looked like before a city was there, we turn to a remarkable project called Welikia, which grew out of a smaller project called Mannahatta. The Welikia project has produced a detailed ecological map of the landscape in New York City at the time of the arrival of Europeans.

  The interactive map, available online at welikia.org, is a fantastic snapshot of a different New York. In 1609, the island of Manhattan was part of a landscape of rolling hills, marshes, woodlands, lakes, and rivers.

  The Times Square of 1000 years ago may have looked ecologically similar to the Times Square described by Welikia. Superficially, it probably resembled the old-growth forests that are still found in a few locations in the northeastern US. However, there would be some notable differences.

  There would be more large animals 1000 years ago. Today’s disconnected patchwork of northeastern old-growth forests is nearly free of large predators; we have some bears, few wolves and coyotes, and virtually no mountain li
ons. (Our deer populations, on the other hand, have exploded, thanks in part to the removal of large predators.)

  The forests of New York 1000 years ago would be full of chestnut trees. Before a blight passed through in the early twentieth century, the hardwood forests of eastern North America were about 25 percent chestnut. Now, only their stumps survive.

  You can still come across these stumps in New England forests today. They periodically sprout new shoots, only to see them wither as the blight takes hold. Someday, before too long, the last of the stumps will die.

  Wolves would be common in the forests, especially as you moved inland. You might also encounter mountain lions2,3,4,5,6 and passenger pigeons.7

  There’s one thing you would not see: earthworms. There were no earthworms in New England when the European colonists arrived. To see the reason for the worms’ absence, let’s take our next step into the past.

  10,000 years back

  The Earth of 10,000 years ago was just emerging from a deep cold period.

  The great ice sheets that covered New England had departed. As of 22,000 years ago, the southern edge of the ice was near Staten Island, but by 18,000 years ago it had retreated north past Yonkers.8 By the time of our arrival, 10,000 years ago, the ice had largely withdrawn across the present-day Canadian border.

  The ice sheets scoured the landscape down to bedrock. Over the next 10,000 years, life crept slowly back northward. Some species moved north faster than others; when Europeans arrived in New England, earthworms had not yet returned.

  As the ice sheets withdrew, large chunks of ice broke off and were left behind.

  When these chunks melted, they left behind water-filled depressions in the ground called kettlehole ponds. Oakland Lake, near the north end of Springfield Boulevard in Queens, is one of these kettlehole ponds. The ice sheets also dropped boulders they’d picked up on their journey; some of these rocks, called glacial erratics, can be found in Central Park today.

  Below the ice, rivers of meltwater flowed at high pressure, depositing sand and gravel as they went. These deposits, which remain as ridges called eskers, crisscross the landscape in the woods outside my home in Boston. They are responsible for a variety of odd landforms, including the world’s only vertical U-shaped riverbeds.

  100,000 years back

  The world of 100,000 years ago might have looked a lot like our own.9 We live in an era of rapid, pulsating glaciations, but for 10,000 years our climate has been stable10 and warm.

  A hundred thousand years ago, Earth was near the end of a similar period of climate stability. It was called the Sangamon interglacial, and it probably supported a developed ecology that would look familiar to us.

  The coastal geography would be totally different; Staten Island, Long Island, Nantucket, and Martha’s Vineyard were all berms pushed up by the most recent bulldozer-like advance of the ice. A hundred millennia ago, different islands dotted the coast.

  Many of today’s animals would be found in those woods—birds, squirrels, deer, wolves, black bears—but there would be a few dramatic additions. To learn about those, we turn to the mystery of the pronghorn.

  The modern pronghorn (American antelope) presents a puzzle. It’s a fast runner—in fact, it’s much faster than it needs to be. It can run at 55 mph, and sustain that speed over long distances. Yet its fastest predators, wolves and coyotes, barely break 35 mph in a sprint. Why did the pronghorn evolve such speed?

  The answer is that the world in which the pronghorn evolved was a much more dangerous place than ours. A hundred thousand years ago, North American woods were home to Canis dirus (the dire wolf), Arctodus (the short-faced bear), and Smilodon fatalis (sabre-toothed cat), each of which may have been faster and deadlier than modern predators. All died out in the Quaternary extinction event, which occured shortly after the first humans colonized the continent.11

  If we go back a little further, we will meet another frightening predator.

  1,000,000 years back

  A million years ago, before the most recent great episode of glaciations, the world was fairly warm. It was the middle of the Quaternary period; the great modern ice ages had begun several million years earlier, but there had been a lull in the advance and retreat of the glaciers, and the climate was relatively stable.

  The predators we met earlier, the fleet-footed creatures who may have preyed on the pronghorn, were joined by another terrifying carnivore, a long-limbed hyena that resembled a modern wolf. Hyenas were mainly found in Africa and Asia, but when the sea level fell, one species crossed the Bering Strait into North America. Because it was the only hyena to do so, it was given the name Chasmaporthetes, which means “the one who saw the canyon.”

  Next, Mark’s question takes us on a great leap backward in time.

  1,000,000,000 years back

  A billion years ago, the continental plates were pushed together into one great supercontinent. This was not the well-known supercontinent Pangea—it was Pangea’s predecessor, Rodinia. The geologic record is spotty, but our best guess is that it looked something like this:

  In the time of Rodinia, the bedrock that now lies under Manhattan had yet to form, but the deep rocks of North America were already old. The part of the continent that is now Manhattan was probably an inland region connected to what is now Angola and South Africa.

  In this ancient world, there were no plants and no animals. The oceans were full of life, but it was simple single-cellular life. On the surface of the water were mats of blue-green algae.

  These unassuming critters are the deadliest killers in the history of life.

  Blue-green algae, or cyanobacteria, were the first photosynthesizers. They breathed in carbon dioxide and breathed out oxygen. Oxygen is a volatile gas; it causes iron to rust (oxidation) and wood to burn (vigorous oxidation). When cyanobacteria first appeared, the oxygen they breathed out was toxic to nearly all other forms of life. The resulting extinction is called the oxygen catastrophe.

  After the cyanobacteria pumped Earth’s atmosphere and water full of toxic oxygen, creatures evolved that took advantage of the gas’s volatile nature to enable new biological processes. We are the descendants of those first oxygen-breathers.

  Many details of this history remain uncertain; the world of a billion years ago is difficult to reconstruct. But Mark’s question now takes us into an even more uncertain domain: the future.

  1,000,000 years forward

  Eventually, humans will die out. Nobody knows when,12 but nothing lives forever. Maybe we’ll spread to the stars and last for billions or trillions of years. Maybe civilization will collapse, we’ll all succumb to disease and famine, and the last of us will be eaten by cats. Maybe we’ll all be killed by nanobots hours after you read this sentence. There’s no way to know.

  A million years is a long time. It’s several times longer than Homo sapiens has existed, and a hundred times longer than we’ve had written language. It seems reasonable to assume that however the human story plays out, in a million years it will have exited its current stage.

  Without us, Earth’s geology will grind on. Winds and rain and blowing sand will dissolve and bury the artifacts of our civilization. Human-caused climate change will probably delay the start of the next glaciation, but we haven’t ended the cycle of ice ages. Eventually, the glaciers will advance again. A million years from now, few human artifacts will remain.

  Our most lasting relic will probably be the layer of plastic we’ve deposited across the planet. By digging up oil, processing it into durable and long-lasting polymers, and spreading it across the Earth’s surface, we’ve left a fingerprint that could outlast everything else we do.

  Our plastic will become shredded and buried, and perhaps some microbes will learn to digest it, but in all likelihood, a million years from now, an out-of-place layer of processed hydrocarbons—transfo
rmed fragments of our shampoo bottles and shopping bags—will serve as a chemical monument to civilization.

  The far future

  The Sun is gradually brightening. For three billion years, a complex system of feedback loops has kept the Earth’s temperature relatively stable as the Sun has grown steadily warmer.

  In a billion years, these feedback loops will have given out. Our oceans, which nourished life and kept it cool, will have turned into its worst enemy. They will have boiled away in the hot Sun, surrounding the planet with a thick blanket of water vapor and causing a runaway greenhouse effect. In a billion years, Earth will become a second Venus.

  As the planet heats up, we may lose our water entirely and acquire a rock vapor atmosphere, as the crust itself begins to boil. Eventually, after several billion more years, we will be consumed by the expanding Sun.

  The Earth will be incinerated, and many of the molecules that made up Times Square will be blasted outward by the dying Sun. These dust clouds will drift through space, perhaps collapsing to form new stars and planets.

  If humans escape the solar system and outlive the Sun, our descendants may someday live on one of these planets. Atoms from Times Square, cycled through the heart of the Sun, will form our new bodies.

  One day, either we will all be dead, or we will all be New Yorkers.

  1Also known as the Delaware.

  2Also known as cougars.

  3Also known as pumas.