And Then You're Dead
Page 7
Unfortunately, every other organism was doing just fine in the old atmosphere. For them oxygen was toxic, so nearly all of them went extinct in Earth’s first great pollution event.
But what was bad for them is good for you. Unfortunately, the atmosphere is only 4 percent oxygen, and unless you are a Himalayan Sherpa you are used to 21 percent. Breathing 4 percent oxygen is like breathing at 30,000 feet, which is possible but requires training. So spend some time in the Himalayas before your trip.*
If you can manage the oxygen issue there is fresh water in rivers to drink, but no animals to eat and no plants bigger than algae. On top of which, if the algae is like its modern progeny (hard to know for sure), it has cyanotoxins, which are some of nature’s most powerful neurotoxins. If you ate them they would paralyze your intestines and diaphragm and you would suffocate.
In other words, visiting Earth 1.4 billion years ago means death by starvation if you avoid the local cuisine, and suffocation if you don’t.
500 million years ago: Your chances of survival depend on where you pop up, and beachfront property is the way to go. Nothing has crawled out of the oceans yet, so land is totally barren, but the oceans are thriving. If you appeared somewhere along the coast you would have a chance.
There’s enough oxygen in the air now that you could breathe for more than a few minutes, and there are shelled organisms to eat. But be careful in the water: There are bigger fish out there, and without a shell you would look like a nice pork roast. Supersize leeches are also around, able to drill into your side and suck out your innards.
The ozone layer is still in development, so you would need to bring some industrial-strength sunscreen (something on the order of SPF 250) and a good pair of sunglasses (the UV will burn your corneas in fifteen minutes if you go without), but, all in all, you would finally have a chance at survival.
450 million years ago: The ozone layer is complete, so you would be able to venture out without getting a lethal sunburn. Sea life is booming and the rivers have fish, so you could survive. Still, there’s nothing taller than a shrub, so shade is hard to come by, and finding food on land would be difficult.
370 million years ago: This is the late Devonian period—and for a time traveler interested in staying alive this might be the sweet spot. There’s life on land, and there are trees to sit under, potentially edible plants, and no animals big enough to eat you. Insects are still 70 million years from showing up too, so that’s nice.
You would have to get the timing just right, though, because it’s starting to get a bit chilly. While trees are plentiful, there aren’t yet any organisms that cause dead trees to rot, so they never return their CO2 to the atmosphere. A good CO2 balance is important for Earth’s temperature—less of it reduces our atmosphere’s greenhouse effect and produces the opposite of global warming: an ice age.* Lucky for you, the next one is still a few hundred thousand years off.
This era is our pick: air to breathe, food to eat, trees to sit under, and no mosquitoes.
300 million years ago: A huge pulse of oxygen in the atmosphere (up to 35 percent, compared to today’s 21 percent) results in enormous insects.* We’re talking predatory dragonflies the size of seagulls, eight-foot-long centipedes, three-foot-long scorpions, and huge cockroaches.
Bad time to visit if you’re not into bugs.
250 million years ago: You have really poor timing. Fifty million years before or after this would be perfect, but at this moment 96 percent of all sea life and 70 percent of all animals are dying in the greatest extinction event on record. Earth will take 10 million years to recover its biodiversity.
Scientists aren’t exactly sure what caused the die-off. One possible explanation is that many enormous volcanic eruptions—called a flood basalt—covered an area the size of India in lava and released enough CO2 to change the composition of the atmosphere.
Whatever the reason for the die-off, mass extinctions always hit the top of the food chain hardest, and that’s where you sit. There would be nothing to eat, and if the volcano theory is correct there might be something funny going on with the air.
Death by giant volcanoes. Sorry.
215 million years ago: The first dinosaurs have arrived and will wander the globe for the next 150 million years. This is a dangerous time to be a relatively unathletic human.
The Tyrannosaurus rex won’t evolve for another 148 million years, but that doesn’t mean you’re out of the woods. Giant crocodiles, called Postosuchus, roam about and would be more than happy to eat you, as would an oversize hyena-type dinosaur called a Coelophysis.
Fortunately, nearly all the predators you need to worry about would be focused on prey living on the ground. The pterosaurs and pteranodons flying around are more interested in smaller animals, so if you spend as much time as possible in trees you would have a shot.
There are vegetation and fauna in this time period, but it’s a little different from the present day. Flowers are still a few million years from showing up, for instance, so everything would look a little dreary.
For food you would be able to catch fish, spear small animals, and steal eggs for protein—just keep a sharp eye out for the parents.
There are some plants to eat, but that comes with a few caveats. Namely, some of them are poisonous. So when in doubt, follow the universal edibility test, which can be summarized as follows: Eat only one part of any plant at a time. Do not eat too much of it, and if you don’t feel well, start throwing up as fast as you can.
Bottom line: If you are quick on your toes, cautious with the local food, and build a really nice tree fort, you have a chance.
65 million years ago: Avoid the Yucatán—there is a large space rock headed for that corner of Mexico. (For more details on death by meteorite, see p. 27.) In fact, you should avoid this period altogether, because the meteorite fallout will eventually kill you even if you are on the far side of Earth.
3.2 million years ago: This is the time of Lucy, the world’s most famous predecessor to Homo sapiens. We know that by now our ancestors have begun to come out of the trees. That’s both good and bad for you. It’s good because we know man could survive in this environment; it’s bad because early man could very well be the one to kill you. Lucy was shorter than you but considerably stronger—you would be a heavy underdog in a one-on-one fight.
Not to mention that you would still be in the middle of the food chain, thanks to large predators like the saber-toothed tiger roaming about. Lucy and her ilk were able to survive by grouping up, but that probably won’t be an option for you.
So be nice to your fellow humanoids. Their help is probably your only hope.
• • •
If your time machine goes forward as well as back, perhaps you would like to take your chances on distant future scenarios. Despite what you always hear, we actually do have a good idea of what the future will hold. It’s not good. Here’s what would happen if you traveled forward to . . .
1 billion years from now: The sun is very slowly getting hotter. Why? As the sun burns all the hydrogen fuel at its core, the nuclear reactions start moving to the surface, where there’s less pressure on the explosions, and the sun expands. Even though the surface is slightly cooler, there’s a lot more surface area and so more heat blasting Earth.
This is hard to notice on a day-to-day basis, but over the course of 100 million years it does make a difference. In 1 billion years, the average temperature on Earth will be 115 degrees (right now it’s 61 degrees), and so hot the oceans will have boiled off.
If it were dry heat you would last hours at 115 degrees, but because all of Earth’s water has boiled off, it will be extremely humid.
In other words, Earth would be a giant humidifier and you would last only a few minutes on it.
5 billion plus years from now: The sun has grown so large it has gobbled up Mercury, so the sunsets are extraordinary. Unfortun
ately, you would have only a few seconds to experience one.
Right now if you hold your hand at arm’s length you can cover the sun with the tip of your pinkie. In 3 billion years you would need to hold up a watermelon at arm’s length to block the sun. In 5 billion years it would fill the sky, which wouldn’t bode well for you.
7.5 billion plus years from now: Perhaps the prettiest images in the universe are planetary nebula, which happen when a dying star throws out shells of gas that burn in gorgeous, fiery displays.
But just like fireworks, planetary nebula are best enjoyed from a distance, and if you were on Earth when the sun had its final call, you would be far too close.
Beautiful, but deadly.
What Would Happen If . . .
You Were Caught in a Human Stampede?
ISAAC ASIMOV CALCULATED that if the human population continues its exponential growth, in a few thousand years we will be part of a packed ball of human flesh expanding into space at the speed of light. Exciting, but there is a problem with that theory, and it is the same problem that might come up at your next rock concert: human stampede.
If you hear the words “human stampede” you probably imagine herds of people running around like a bunch of wildebeests charging across the African savanna, but it turns out this isn’t at all how human stampedes look or what makes them dangerous. In fact, the really dangerous stampedes are not when people are running—it’s when they can’t move at all.
Stampedes—more aptly named crushes—are typically crazes and not panics, which means a crowd of people is moving toward something they want, and not away from something they don’t. If you are stuck in one you will face a couple of problems. Your first? A lack of pheromones.
In dense crowds things start to get dangerous because we, as a species, have an issue with crowd movement. Unlike ants, we’re not designed for it. When ants go marching, an ant at the front of the pack can release pheromones to communicate with the ants in the back. If the way is blocked, these pheromones tell those in the back to go another way.
You don’t have these pheromones. If someone trips, you can’t tell the back of the pack to stop like the ants can.
In large, dense groups this lack of crowd communication becomes a serious problem. What makes a crowd large and dense? When it comes to size, if the crowd is even large enough to be called a crowd, it’s large enough to kill you—but we’ll get to that later. The more important factor is density. Crowd density is measured by people per ten square feet.
Ten square feet is about the same area of the chalk outline the police draw around a murder victim. The number of people stuffed inside each imaginary chalk outline, averaged throughout the crowd, is its density.
If there’s an average of two people, that’s a solid crowd, but walking is easy and there’s little bumping. If it’s double that it’s called a thick crowd—there’s a lot of bumping and shuffling, but people can still move.
Six people per every ten square feet is getting dangerous—you’re always touching the people next to you and moving is nearly impossible.
Seven people per ten square feet is like stuffing twenty-one people into an average-size elevator—this is rush-hour-on-the-Tokyo-subway dense. In deadly crushes crowd density is typically in this zone.
At this density a crowd’s movements stop resembling people and start looking like a fluid. Powerful waves that originate with people pushing in the back and gain momentum as more people are swept up pass through crowds—waves capable of sweeping you off your feet and depositing you wherever they happen to be going. If the person next to you falls, there won’t be anything to hold you up and you would fall too, leading to a domino pileup of people on top of you.
If you happen to find yourself in one of these crowds—typically a religious festival, sporting event, or concert—the transition from friendly bumping to crushing can happen quickly. Suddenly you would realize you cannot raise your arms, cannot escape, and are at the mercy of the crowd.
Falling is of course dangerous, but you don’t necessarily need to fall to be in trouble. Even if you’re on your feet, opposing waves can pass through the crowd and pin you in place, squeezing you between the two forces in the crowd. Because of how force scales in crowds this gets dangerous quickly.
The average person can typically push with a maximum of fifty pounds of force. If there are only four or five people pushing on you, like in an overcrowded elevator, that’s uncomfortable but not dangerous. In crushes people are usually not pushing with maximum effort, usually with only five or ten pounds of force each, but in a crowd of thousands, this force scales and can put a lethal strain on your diaphragm.
You need to expand your chest a few inches to breathe. Fortunately, your diaphragm is strong. A healthy person can breathe with four hundred pounds on their chest for two days before tiring.* Unfortunately, in crushes the diaphragm can be overpowered. In the aftermath of crushes investigators have found steel barriers designed to withstand thousands of pounds bent in half.
We said crowds of seven people per ten square feet can become lethal, but that is an average number for the entire crowd. At the crush point, where you’re likely to be killed, there will probably be at least ten people per ten square feet. Getting that many people to squeeze that tightly is not possible without extraordinary force. It’s like squeezing twenty-eight people into an average-size elevator—not possible with only a couple of unwanted passengers pushing. You would need either thousands of people pressing from behind or a bulldozer.
If you’re caught between two opposing waves in the crowd, or if you fall and six or more people domino on top you, it would be like being a passenger in that overcrowded elevator with a bulldozer pushing from the back. A thousand or more pounds would press on your diaphragm and you would not be able to breathe even once.
You can replicate a thousand pounds on your chest by going three feet under water and trying to breathe through a straw. But we’ll save you the trouble: It’s not possible. In the crush, or under water, with a thousand pounds on your chest you would pass out in fifteen seconds. If it’s applied for longer than four minutes you would suffer permanent brain damage and then death.
So Isaac Asimov was wrong. We know from crushes that no one can survive with six or more people lying on top of them, so Earth’s population will never have the chance to be a ball of people thousands deep expanding into space at the speed of light.
The stack of people would never get deeper than six.
What Would Happen If . . .
You Jumped into a Black Hole?
ASTROPHYSICIST NEIL DEGRASSE Tyson believes that jumping into a black hole is the most spectacular way to die in outer space. Considering that there are quite a few ways to die in space (actually, there are only ways to die in space, the truly spectacular thing would be to find someplace where you would not), this is saying something.
So what exactly is a black hole? In a nutshell, here’s how one is created:
A black hole begins as a star ten times bigger than our sun.
Eventually the star burns all its fuel. This takes a while.
Without any nuclear reactions happening in the star’s center, the star can no longer resist its own gravity and the outer shell collapses at a quarter the speed of light.
If you happen to observe this collapse, you need to run. It takes a couple of hours for the shock wave from the shell hitting the iron core to reverberate back to the surface. Once that happens the star explodes, and in that instant emits as much energy as an entire galaxy of 100 billion stars.
After the explosion what remains of the star collapses under its own gravity and you’re left with something very small (about the size of San Francisco) but with an enormous mass (five times more massive than the sun). Its gravitational pull is so strong, its escape velocity is faster than the speed of light. This is a black hole.
S
o what would happen if you jumped into it?
First of all, you should know that your decision to jump is final. To exit a black hole you would have to cross the event horizon, and to do that you would have to go faster than the speed of light, which is impossible.
So far the fastest thing we have ever built is the unmanned Helios spaceship. It reached 157,078 miles per hour when it did a slingshot around the sun, which is fast, but only 0.0002 the speed of light. Unless you can figure out a way to go faster than Einstein says is possible, your death in a black hole is inevitable.
How you die, however, will depend upon the type of black hole you jump into. Your first option is diving into a small stellar mass black hole.
Here’s what would happen: Once your feet left the spaceship you would begin free-falling into the hole. This would not be your typical free-fall, however. By the time you reached the event horizon of this stellar mass black hole you would be falling just short of the speed of light, or roughly 186,000 miles per second.
Interestingly, you would be fine. Normally, traveling through space at the speed of light is not recommended. It’s not the speed or acceleration that’s dangerous, though; the issue is hitting stuff. Even teeny particles pose a big problem when you’re going that fast—and space is not a perfect vacuum. It is littered with bits of hydrogen that hit like atom-destroying bullets when you’re traveling near the speed of light. The hydrogen would smash through your body and destroy the nuclei of your atoms, which would be fatal.
Most black holes are surrounded by a pure vacuum, so you shouldn’t hit enough hydrogen to kill you—just make sure you don’t jump into a messy black hole that’s surrounded by orbiting gases.
If you chose correctly, your acceleration to near light speed should pass smoothly. As you got closer to the black hole, though, you would feel your body beginning to stretch as the strength of the gravity increased so dramatically the pull at your head (assuming you have maintained pike position) would be stronger than the tug at your feet, stretching your head away from your toes.