20 Ways the World Could End // canavarlar

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20 Ways the World Could End
Swept away
By Corey S. Powell

DISCOVER Vol. 21 No. 10 | October 2000

We've had a good run of it. In the 500,000 years Homo sapiens has
roamed the land we've built cities, created complex languages, and sent
robotic scouts to other planets. It's difficult to imagine it all coming to an
end. Yet 99 percent of all species that ever lived have gone extinct,
including every one of our hominid ancestors. In 1983, British cosmologist
Brandon Carter framed the "Doomsday argument," a statistical way to
judge when we might join them. If humans were to survive a long time and
spread through the galaxy, then the total number of people who will ever
live might number in the trillions. By pure odds, it's unlikely that we would
be among the very first hundredth of a percent of all those people. Or turn
the argument around: How likely is it that this generation will be the one
unlucky one? Something like one fifth of all the people who have ever lived
are alive today. The odds of being one of the people to witness doomsday
are highest when there is the largest number of witnesses around— so
now is not such an improbable time.

Human activity is severely disrupting almost all life on the planet, which
surely doesn't help matters. The current rate of extinctions is, by some
estimates, 10,000 times the average in the fossil record. At present, we
may worry about snail darters and red squirrels in abstract terms. But the
next statistic on the list could be us.

Natural Disasters

1 Asteroid impact Once a disaster scenario gets the cheesy Hollywood
treatment, it's hard to take it seriously. But there is no question that a
cosmic interloper will hit Earth, and we won't have to wait millions of years
for it to happen. In 1908 a 200-foot-wide comet fragment slammed into the
atmosphere and exploded over the Tunguska region in Siberia, Russia,
with nearly 1,000 times the energy of the atomic bomb dropped on
Hiroshima. Astronomers estimate similar-sized events occur every one to
three centuries. Benny Peiser, an anthropologist-cum-pessimist at
Liverpool John Moores University in England, claims that impacts have
repeatedly disrupted human civilization. As an example, he says one killed
10,000 people in the Chinese city of Chi'ing-yang in 1490. Many scientists
question his interpretations: Impacts are most likely to occur over the
ocean, and small ones that happen over land are most likely to affect
unpopulated areas. But with big asteroids, it doesn't matter much where
they land. Objects more than a half-mile wide— which strike Earth every
250,000 years or so— would touch off firestorms followed by global cooling
from dust kicked up by the impact. Humans would likely survive, but
civilization might not. An asteroid five miles wide would cause major
extinctions, like the one that may have marked the end of the age of
dinosaurs. For a real chill, look to the Kuiper belt, a zone just beyond
Neptune that contains roughly 100,000 ice-balls more than 50 miles in
diameter. The Kuiper belt sends a steady rain of small comets earthward. If
one of the big ones headed right for us, that would be it for pretty much all
higher forms of life, even cockroaches.

2 Gamma-ray burst If you could watch the sky with gamma-ray vision, you
might think you were being stalked by cosmic paparazzi. Once a day or so,
you would see a bright flash appear, briefly outshine everything else, then
vanish. These gamma-ray bursts, astrophysicists recently learned,
originate in distant galaxies and are unfathomably powerful— as much as
10 quadrillion (a one followed by 16 zeros) times as energetic as the sun.
The bursts probably result from the merging of two collapsed stars. Before
the cataclysmal event, such a double star might be almost completely
undetectable, so we'd likely have no advance notice if one is lurking
nearby. Once the burst begins, however, there would be no missing its
fury. At a distance of 1,000 light-years— farther than most of the stars you
can see on a clear night— it would appear about as bright as the sun.
Earth's atmosphere would initially protect us from most of the burst's
deadly X rays and gamma rays, but at a cost. The potent radiation would
cook the atmosphere, creating nitrogen oxides that would destroy the
ozone layer. Without the ozone layer, ultraviolet rays from the sun would
reach the surface at nearly full force, causing skin cancer and, more
seriously, killing off the tiny photosynthetic plankton in the ocean that
provide oxygen to the atmosphere and bolster the bottom of the food
chain. All the gamma-ray bursts observed so far have been extremely
distant, which implies the events are rare. Scientists understand so little
about these explosions, however, that it's difficult to estimate the
likelihood of one detonating in our galactic neighborhood.

3 Collapse of the vacuum In the book Cat's Cradle, Kurt Vonnegut
popularized the idea of "ice-nine," a form of water that is far more stable
than the ordinary kind, so it is solid at room temperature. Unleash a bit of
it, and suddenly all water on Earth transforms to ice-nine and freezes solid.
Ice-nine was a satirical invention, but an abrupt, disastrous phase
transition is a possibility. Very early in the history of the universe,
according to a leading cosmological model, empty space was full of energy.
This state of affairs, called a false vacuum, was highly precarious. A new,
more stable kind of vacuum appeared and, like ice-nine, it quickly took
over. This transition unleashed a tremendous amount of energy and
caused a brief runaway expansion of the cosmos. It is possible that
another, even more stable kind of vacuum exists, however. As the universe
expands and cools, tiny bubbles of this new kind of vacuum might appear
and spread at nearly the speed of light. The laws of physics would change
in their wake, and a blast of energy would dash everything to bits. "It
makes for a beautiful story, but it's not very likely," says Piet Hut of the
Institute for Advanced Studies in Princeton, New Jersey. He says he
worries more about threats that scientists are more certain of— such as
rogue black holes.

4 Rogue black holes Our galaxy is full of black holes, collapsed stellar
corpses just a dozen miles wide. How full? Tough question. After all,
they're called black holes for a reason. Their gravity is so strong they
swallow everything, even the light that might betray their presence. David
Bennett of Notre Dame University in Indiana managed to spot two black
holes recently by the way they distorted and amplified the light of ordinary,
more distant stars. Based on such observations, and even more on
theoretical arguments, researchers guesstimate there are about 10 million
black holes in the Milky Way. These objects orbit just like other stars,
meaning that it is not terribly likely that one is headed our way. But if a
normal star were moving toward us, we'd know it. With a black hole there
is little warning. A few decades before a close encounter, at most,
astronomers would observe a strange perturbation in the orbits of the
outer planets. As the effect grew larger, it would be possible to make
increasingly precise estimates of the location and mass of the interloper.
The black hole wouldn't have to come all that close to Earth to bring ruin;
just passing through the solar system would distort all of the planets'
orbits. Earth might get drawn into an elliptical path that would cause
extreme climate swings, or it might be ejected from the solar system and
go hurtling to a frigid fate in deep space.

5 Giant solar flares Solar flares— more properly known as coronal mass
ejections— are enormous magnetic outbursts on the sun that bombard
Earth with a torrent of high-speed subatomic particles. Earth's atmosphere
and magnetic field negate the potentially lethal effects of ordinary flares.
But while looking through old astronomical records, Bradley Schaefer of
Yale University found evidence that some perfectly normal-looking, sunlike
stars can brighten briefly by up to a factor of 20. Schaefer believes these
stellar flickers are caused by superflares, millions of times more powerful
than their common cousins. Within a few hours, a superflare on the sun
could fry Earth and begin disintegrating the ozone layer (see #2). Although
there is persuasive evidence that our sun doesn't engage in such excess,
scientists don't know why superflares happen at all, or whether our sun
could exhibit milder but still disruptive behavior. And while too much solar
activity could be deadly, too little of it is problematic as well. Sallie Baliunas
at the Harvard-Smithsonian Center for Astrophysics says many solar-type
stars pass through extended quiescent periods, during which they become
nearly 1 percent dimmer. That might not sound like much, but a similar
downturn in the sun could send us into another ice age. Baliunas cites
evidence that decreased solar activity contributed to 17 of the 19 major
cold episodes on Earth in the last 10,000 years.

6 Reversal of Earth's magnetic field Every few hundred thousand years
Earth's magnetic field dwindles almost to nothing for perhaps a century,
then gradually reappears with the north and south poles flipped. The last
such reversal was 780,000 years ago, so we may be overdue. Worse, the
strength of our magnetic field has decreased about 5 percent in the past
century. Why worry in an age when GPS has made compasses obsolete?
Well, the magnetic field deflects particle storms and cosmic rays from the
sun, as well as even more energetic subatomic particles from deep space.
Without magnetic protection, these particles would strike Earth's
atmosphere, eroding the already beleaguered ozone layer (see #5). Also,
many creatures navigate by magnetic reckoning. A magnetic reversal might
cause serious ecological mischief. One big caveat: "There are no
identifiable fossil effects from previous flips," says Sten Odenwald of the
NASA Goddard Space Flight Center. "This is most curious." Still, a disaster
that kills a quarter of the population, like the Black Plague in Europe, would
hardly register as a blip in fossil records.

7 Flood-basalt volcanism In 1783, the Laki volcano in Iceland erupted,
spitting out three cubic miles of lava. Floods, ash, and fumes wiped out
9,000 people and 80 percent of the livestock. The ensuing starvation killed
a quarter of Iceland's population. Atmospheric dust caused winter
temperatures to plunge by 9 degrees in the newly independent United
States. And that was just a baby's burp compared with what the Earth can
do. Sixty-five million years ago, a plume of hot rock from the mantle burst
through the crust in what is now India. Eruptions raged century after
century, ultimately unleashing a quarter-million cubic miles of lava— the
Laki eruption 100,000 times over. Some scientists still blame the Indian
outburst, not an asteroid, for the death of the dinosaurs. An earlier, even
larger event in Siberia occurred just about the time of the Permian-Triassic
extinction, the most thorough extermination known to paleontology. At
that time 95 percent of all species were wiped out.

Sulfurous volcanic gases produce acid rains. Chlorine-bearing compounds
present yet another threat to the fragile ozone layer— a noxious brew all
around. While they are causing short-term destruction, volcanoes also
release carbon dioxide that yields long-term greenhouse-effect
warming.The last big pulse of flood-basalt volcanism built the Columbia
River plateau about 17 million years ago. We're ripe for another.

8 Global epidemics If Earth doesn't do us in, our fellow organisms might be
up to the task. Germs and people have always coexisted, but occasionally
the balance gets out of whack. The Black Plague killed one European in
four during the 14th century; influenza took at least 20 million lives
between 1918 and 1919; the AIDS epidemic has produced a similar death
toll and is still going strong. From 1980 to 1992, reports the Centers for
Disease Control and Prevention, mortality from infectious disease in the
United States rose 58 percent. Old diseases such as cholera and measles
have developed new resistance to antibiotics. Intensive agriculture and
land development is bringing humans closer to animal pathogens.
International travel means diseases can spread faster than ever. Michael
Osterholm, an infectious disease expert who recently left the Minnesota
Department of Health, described the situation as "like trying to swim
against the current of a raging river." The grimmest possibility would be
the emergence of a strain that spreads so fast we are caught off guard or
that resists all chemical means of control, perhaps as a result of our stirring
of the ecological pot. About 12,000 years ago, a sudden wave of mammal
extinctions swept through the Americas. Ross MacPhee of the American
Museum of Natural History argues the culprit was extremely virulent
disease, which humans helped transport as they migrated into the New
World.

Human-Triggered Disasters

9 Global warming The Earth is getting warmer, and scientists mostly agree
that humans bear some blame. It's easy to see how global warming could
flood cities and ruin harvests. More recently, researchers like Paul Epstein
of Harvard Medical School have raised the alarm that a balmier planet could
also assist the spread of infectious disease by providing a more suitable
climate for parasites and spreading the range of tropical pathogens (see
#8). That could include crop diseases which, combined with substantial
climate shifts, might cause famine. Effects could be even more dramatic. At
present, atmospheric gases trap enough heat close to the surface to keep
things comfortable. Increase the global temperature a bit, however, and
there could be a bad feedback effect, with water evaporating faster,
freeing water vapor (a potent greenhouse gas), which traps more heat,
which drives carbon dioxide from the rocks, which drives temperatures still
higher. Earth could end up much like Venus, where the high on a typical
day is 900 degrees Fahrenheit. It would probably take a lot of warming to
initiate such a runaway greenhouse effect, but scientists have no clue
where exactly the tipping point lies.

10 Ecosystem collapse Images of slaughtered elephants and burning rain
forests capture people's attention, but the big problem— the overall loss of
biodiversity— is a lot less visible and a lot more serious. Billions of years of
evolution have produced a world in which every organism's welfare is
intertwined with that of countless other species. A recent study of Isle
Royale National Park in Lake Superior offers an example. Snowy winters
encourage wolves to hunt in larger packs, so they kill more moose. The
decline in moose population allows more balsam fir saplings to live. The fir
trees pull carbon dioxide out of the atmosphere, which in turn influences
the climate. It's all connected. To meet the demands of the growing
population, we are clearing land for housing and agriculture, replacing
diverse wild plants with just a few varieties of crops, transporting plants
and animals, and introducing new chemicals into the environment. At least
30,000 species vanish every year from human activity, which means we are
living in the midst of one of the greatest mass extinctions in Earth's history.
Stephen Kellert, a social ecologist at Yale University, sees a number of
ways people might upset the delicate checks and balances in the global
ecology. New patterns of disease might emerge (see #8), he says, or
pollinating insects might become extinct, leading to widespread crop
failure. Or as with the wolves of Isle Royale, the consequences might be
something we'd never think of, until it's too late.

11 Biotech disaster While we are extinguishing natural species, we're also
creating new ones through genetic engineering. Genetically modified crops
can be hardier, tastier, and more nutritious. Engineered microbes might
ease our health problems. And gene therapy offers an elusive promise of
fixing fundamental defects in our DNA. Then there are the possible
downsides. Although there is no evidence indicating genetically modified
foods are unsafe, there are signs that the genes from modified plants can
leak out and find their way into other species. Engineered crops might also
foster insecticide resistance. Longtime skeptics like Jeremy Rifkin worry that
the resulting superweeds and superpests could further destabilize the
stressed global ecosystem (see #9). Altered microbes might prove to be
unexpectedly difficult to control. Scariest of all is the possibility of the
deliberate misuse of biotechnology. A terrorist group or rogue nation might
decide that anthrax isn't nasty enough and then try to put together, say,
an airborne version of the Ebola virus. Now there's a showstopper.

12 Particle accelerator mishap Theodore Kaczynski, better known as the
Unabomber, raved that a particle accelerator experiment could set off a
chain reaction that would destroy the world. Surprisingly, many sober-
minded physicists have had the same thought. Normally their anxieties
come up during private meetings, amidst much scribbling on the backs of
used envelopes. Recently the question went public when London's Sunday
Times reported that the Relativistic Heavy Ion Collider (RHIC) on Long
Island, New York, might create a subatomic black hole that would slowly
nibble away our planet. Alternately, it might create exotic bits of altered
matter, called strangelets, that would obliterate whatever ordinary matter
they met. To assuage RHIC's jittery neighbors, the lab's director convened
a panel that rejected both scenarios as pretty much impossible. Just for
good measure, the panel also dismissed the possibility that RHIC would
trigger a phase transition in the cosmic vacuum energy (see #3). These
kinds of reassurances follow the tradition of the 1942 "LA-602" report, a
once-classified document that explained why the detonation of the first
atomic bomb almost surely would not set the atmosphere on fire. The RHIC
physicists did not, however, reject the fundamental possibility of the
disasters. They argued that their machine isn't nearly powerful enough to
make a black hole or destabilize the vacuum. Oh, well. We can always build
a bigger accelerator.

13 Nanotechnology disaster Before you've even gotten the keyboard dirty,
your home computer is obsolete, largely because of incredibly rapid
progress in miniaturizing circuits on silicon chips. Engineers are using the
same technology to build crude, atomic-scale machines, inventing a new
field as they go called nanotechnology. Within a few decades, maybe
sooner, it should be possible to build microscopic robots that can assemble
and replicate themselves. They might perform surgery from inside a
patient, build any desired product from simple raw materials, or explore
other worlds. All well and good if the technology works as intended. Then
again, consider what K. Eric Drexler of the Foresight Institute calls
the "grey goo problem" in his book Engines of Creation, a cult favorite
among the nanotech set. After an industrial accident, he writes, bacteria-
sized machines, "could spread like blowing pollen, replicate swiftly, and
reduce the biosphere to dust in a matter of days." And Drexler is actually a
strong proponent of the technology. More pessimistic souls, such as Bill
Joy, a cofounder of Sun Microsystems, envision nano-machines as the
perfect precision military or terrorist tools.

14 Environmental toxins From Donora, Pennsylvania, to Bhopal, India,
modern history abounds with frightening examples of the dangers of
industrial pollutants. But the poisoning continues. In major cities around
the world, the air is thick with diesel particulates, which the National
Institutes of Health now considers a carcinogen. Heavy metals from
industrial smokestacks circle the globe, even settling in the pristine snows
of Antarctica. Intensive use of pesticides in farming guarantees runoff into
rivers and lakes. In high doses, dioxins can disrupt fetal development and
impair reproductive function— and dioxins are everywhere. Your house may
contain polyvinyl chloride pipes, wallpaper, and siding, which belch dioxins
if they catch fire or are incinerated. There are also the unknown risks to
think about. Every year NIH adds to its list of cancer-causing substances—
the number is up to 218. Theo Colburn of the World Wildlife Fund argues
that dioxins and other, similar chlorine-bearing compounds mimic the
effects of human hormones well enough that they could seriously reduce
fertility. Many other scientists dispute her evidence, but if she's right, our
chemical garbage could ultimately threaten our survival.

Willful Self-Destruction

15 Global war Together, the United States and Russia still have almost
19,000 active nuclear warheads. Nuclear war seems unlikely today, but a
dozen years ago the demise of the Soviet Union also seemed rather
unlikely. Political situations evolve; the bombs remain deadly. There is also
the possibility of an accidental nuclear exchange. And a ballistic missile
defense system, given current technology, will catch only a handful of stray
missiles— assuming it works at all. Other types of weaponry could have
global effects as well. Japan began experimenting with biological weapons
after World War I, and both the United States and the Soviet Union
experimented with killer germs during the cold war. Compared with atomic
bombs, bioweapons are cheap, simple to produce, and easy to conceal.
They are also hard to control, although that unpredictability could appeal
to a terrorist organization. John Leslie, a philosopher at the University of
Guelph in Ontario, points out that genetic engineering might permit the
creation of "ethnic" biological weapons that are tailored to attack primarily
one ethnic group (see #11).

16 Robots take over People create smart robots, which turn against us and
take over the world. Yawn. We've seen this in movies, TV, and comic books
for decades. After all these years, look around and still— no smart robots.
Yet Hans Moravec, one of the founders of the robotics department of
Carnegie Mellon University, remains a believer. By 2040, he predicts,
machines will match human intelligence, and perhaps human
consciousness. Then they'll get even better. He envisions an eventual
symbiotic relationship between human and machine, with the two merging
into "postbiologicals" capable of vastly expanding their intellectual power.
Marvin Minsky, an artificial-intelligence expert at MIT, foresees a similar
future: People will download their brains into computer-enhanced
mechanical surrogates and log into nearly boundless files of information
and experience. Whether this counts as the end of humanity or the next
stage in evolution depends on your point of view. Minsky's vision might
sound vaguely familiar. After the first virtual-reality machines hit the
marketplace around 1989, feverish journalists hailed them as electronic
LSD, trippy illusion machines that might entice the user in and then never
let him out. Sociologists fretted that our culture, maybe even our species,
would whither away. When the actual experience of virtual reality turned
out to be more like trying to play Pac-Man with a bowling ball taped to your
head, the talk died down. To his credit, Minsky recognizes that the merger
of human and machine lies quite a few years away.

17 Mass insanity While physical health has improved in most parts of the
world over the past century, mental health is getting worse. The World
Health Organization estimates that 500 million people around the world
suffer from a psychological disorder. By 2020, depression will likely be the
second leading cause of death and lost productivity, right behind
cardiovascular disease. Increasing human life spans may actually intensify
the problem, because people have more years to experience the loneliness
and infirmity of old age. Americans over 65 already are disproportionately
likely to commit suicide. Gregory Stock, a biophysicist at the University of
California at Los Angeles, believes medical science will soon allow people
to live to be 200 or older. If such an extended life span becomes common,
it will pose unfathomable social and psychological challenges. Perhaps 200
years of accumulated sensations will overload the human brain, leading to
a new kind of insanity or fostering the spread of doomsday cults,
determined to reclaim life's endpoint. Perhaps the current trends of
depression and suicide among the elderly will continue. One possible
solution— promoting a certain kind of mental well-being with psychoactive
drugs such as Prozac— heads into uncharted waters. Researchers have no
good data on the long-term effects of taking these medicines.

A Greater Force Is Directed Against Us

18 Alien invasion At the SETI Institute in Mountain View, California, a cadre
of dedicated scientists sifts through radio static in search of a telltale signal
from an alien civilization. So far, nothing. Now suppose the long-sought
message arrives. Not only do the aliens exist, they are about to stop by for
a visit. And then . . . any science-fiction devotee can tell you what could go
wrong. But the history of human exploration and exploitation suggests the
most likely danger is not direct conflict. Aliens might want resources from
our solar system (Earth's oceans, perhaps, full of hydrogen for refilling a
fusion-powered spacecraft) and swat us aside if we get in the way, as we
might dismiss mosquitoes or beetles stirred up by the logging of a rain
forest. Aliens might unwittingly import pests with a taste for human flesh,
much as Dutch colonists reaching Mauritius brought cats, rats, and pigs
that quickly did away with the dodo. Or aliens might accidentally upset our
planet or solar system while carrying out some grandiose interstellar
construction project. The late physicist Gerard O'Neill speculated that
contact with extraterrestrial visitors could also be socially
disastrous. "Advanced western civilization has had a destructive effect on
all primitive civilizations it has come in contact with, even in those cases
where every attempt was made to protect and guard the primitive
civilization," he said in a 1979 interview. "I don't see any reason why the
same thing would not happen to us."

19 Divine intervention Judaism has the Book of Daniel; Christianity has the
Book of Revelation; Islam has the coming of the Mahdi; Zoroastrianism has
the countdown to the arrival of the third son of Zoroaster. The stories and
their interpretations vary widely, but the underlying concept is similar: God
intervenes in the world, bringing history to an end and ushering in a new
moral order. Apocalyptic thinking runs at least back to Egyptian mythology
and right up to Heaven's Gate and Y2K mania. More worrisome, to the
nonbelievers at least, are the doomsday cults that prefer to take holy
retribution into their own hands. In 1995, members of the Aum Shinri Kyo
sect unleashed sarin nerve gas in a Tokyo subway station, killing 12
people and injuring more than 5,000. Had things gone as intended, the
death toll would have been hundreds of times greater. A more determined
group armed with a more lethal weapon— nuclear, biological,
nanotechnological even— could have done far more damage.

20 Someone wakes up and realizes it was all a dream Are we living a
shadow existence that only fools us into thinking it is real? This age-old
philosophical question still reverberates through cultural thought, from the
writings of William S. Burrows to the cinematic mind games of The Matrix.
Hut of the Institute of Advanced Studies sees an analogy to the danger of
the collapse of the vacuum. Just as our empty space might not be the true,
most stable form of the vacuum, what we call reality might not be the true,
most stable form of existence. In the fourth century B.C., Taoist
philosopher Chuang Tzu framed the question in more poetic terms. He
described a vivid dream. In it, he was a butterfly who had no awareness of
his existence as a person. When he awoke, he asked: "Was I before
Chuang Tzu who dreamt about being a butterfly, or am I now a butterfly
who dreams about being Chuang Tzu?"
— with additional research by Diane Martindale