Armageddon Science (25 page)

Just as the effects of Krakatoa were felt around the world, so the much bigger supervolcano eruptions would not be limited in impact to their immediate surroundings, however large. It’s 630,000 years since the Yellowstone supervolcano erupted, but there have been more recent supervolcano eruptions, including Toba in Sumatra some 74,000 years ago, where the distribution of ash in the atmosphere cut back sunlight to such an extent that there was, in effect, a six-year-long winter. Such a change in the Earth’s climate would totally devastate agriculture, and billions could die.

Luckily for us, supervolcano eruptions are not common. If they were, the chances are that life on Earth would never have reached the complexity it has. However, we can’t be totally complacent. It is impossible to predict when a supervolcano will next erupt, but we do know the rough frequency with which their eruptions occur. The Yellowstone supervolcano seems to blow its top around every 600,000 years. The next eruption is due any day now—though geological “any day now” can easily be give or take a few tens of thousands of years.

The possibility of a supervolcano eruption is terrifying, but the odds are fairly long against it happening in our lifetimes. Besides, there’s nothing we can do to prevent it, and little we can do to prepare for an event of this scale. Each year, though, there are other devastating natural events, phenomena of wind and wave, that we should be better prepared for: hurricanes and tsunamis.

There is a certain amount of confusion over just what a hurricane is. It is a powerful storm that arises out at sea, forming huge, slowly spinning spirals that are often as much as 30 or 50 kilometers (twenty or thirty miles) across, and have been known to be three hundred miles wide. The spin is usually counter-clockwise in the Northern Hemisphere and clockwise in the Southern. Hurricanes can drift for days or even weeks before finally dispersing, usually after they make landfall.

Although hurricanes are very obvious on weather-satellite images, their paths of destruction are hard to predict, as they can suddenly veer, or even double back on themselves. Part of the confusion that surrounds them arises from the way that the same phenomenon is given different names in different parts of the world. Though they’re hurricanes in the North Atlantic, Caribbean, and parts of the Pacific, they are also known as cyclones around the Indian Ocean and as typhoons in the rest of the Pacific and the China Sea. There is no distinction—they’re all the same phenomenon.

Hurricanes can be massive killers—in fact, they kill more people on a regular basis than any other natural phenomenon. In 2005, Hurricane Katrina brought home just how much devastation could be produced even in a highly developed country like the United States, when that storm left behind such a trail of misery and destruction in New Orleans, laying waste around 80 percent of the city, leaving 1,500 dead and many, many thousands homeless—and this was with enough warning to evacuate most of the residents.

But for the true power to devastate we have to look back a little further, to 1970, when in November a cyclone hit what is now Bangladesh and was then East Pakistan. Blasted by 150-mile-an-hour winds, the vast, low-lying coastal areas were inundated with a surge of water six meters (twenty feet) high, covering over 20 percent of the country’s land area during the night, catching many people unawares. With no way to spread a warning and little opportunity to escape, nearly half a million people perished.

Hurricanes are easy enough to spot, especially with modern weather radar and satellite monitoring. The difficulty is being sure of their route, getting a warning out in time, and enabling people to reach safety. Much of the time a hurricane’s path is predictable, but because of the sudden swerves one can make, constant monitoring and updates are necessary. In areas like Bangladesh, communications have been improved by the use of cell phones and other modern technology, while concrete shelters have now been built, recognizing the impracticality of mass evacuation on the scale needed to survive a major cyclone—and these have helped save lives in more recent storms.

Often, much of the devastation from a hurricane is caused by the storm surge, where the high-speed winds force the sea to rise and breach the usual defenses. Another, different kind of sea surge is a tsunami or tidal wave. This is usually triggered by underwater seismic activity—an earthquake, or eruption—or it could even result from a meteorite impact on the sea. Unlike waves whipped up by the wind, the tsunami is a solitary wave front, a vast wall of water that moves ahead implacably and destroys buildings like toys.

December 26, 2004, saw the worst tsunami in modern times take shape in Southeast Asia. Around 200,000 people were killed in a sweep of countries bordering on the Indian Ocean. On a smaller scale, but still with devastating effects for the inhabitants, another tsunami struck Samoa at the end of September 2009. Some countries have done what they can to minimize the impact of tsunamis. Japan, for example, has built special coastal walls, while other at-risk areas have planted trees on the shoreline to try to reduce the impact of a solitary wave.

There are also warning systems in place in a few countries—Japan, again, and the United States—that monitor the likely origins of tsunamis and issue alerts to try to get people moved away from the coast in time. There are even a few examples where specific warning signs have been spotted on the beach before a tsunami hit, enabling individuals to run to safety. The water may bubble or take on a strange smell, while the seas recede prior to the arrival of the wave. Such auguries may not provide much of a warning, but they’re better than nothing. For now, though, in the often very poor areas most at risk from tsunamis, there is still little chance of receiving a good enough warning to safely evacuate the coast.

Such extreme weather and seismological events may produce tragedies, but at least they are understandable as an extreme form of everyday experiences. Even a meteor or comet, despite its extraterrestrial origins, is, in the end, a collision with a lump of rock or ice, as straightforward as a car crash. But space is also home to some more insidious natural threats.

Perhaps the most obvious worry, when we look out into space, is that our Sun will go nova. “Nova” just means “new” in Latin, referring to a time when a nova was seen as a new star (
stella nova
) in the sky. Early astronomers would occasionally be surprised to discover a star where none had been seen before. Often these got brighter over a period of time before eventually fading away.

We now know that a nova is a star that has exploded, flashing into unparalleled brightness so that it suddenly becomes visible from Earth whereas before it was far too faint to see. In the process it will have totally destroyed any planets around it. If the Sun went nova, the Earth could not survive. Nothing can travel faster than light, so we would not be aware for the first eight minutes after the explosion, the time light takes to reach us from the Sun, but after that, in a matter of moments, all life would be extinguished.

To be precise, if the Sun exploded it would be a supernova, not a nova. This is because the terminology of novas has changed over the years. Although “nova” originally just meant a new star—any star that’s suddenly bright—it now applies to a particular way this can happen, when a certain type of a star, a white dwarf, pulls material from a second star that is its binary companion, the two stars orbiting each other like the Earth and the Moon. The new matter, primarily hydrogen, sucked onto the white dwarf from its neighbor forms a thin, high-pressure layer, which undergoes a thermonuclear explosion, like a vast hydrogen bomb.

Only the outer layer is blown away in the explosion, and the nova can then re-form, as the white dwarf sucks more material from the companion star, on a regular basis. This clearly isn’t going to happen to the Sun, which isn’t a white dwarf and doesn’t have a companion star. But no companion is required for the more devastating explosion that is a supernova.

Here, an aging star begins to collapse as the gravitational pull of its mass overwhelms the outward pressure from the nuclear reaction that keeps it alight. As pressure increases, extra nuclear fusion processes that had not previously been possible, such as carbon fusion, may take place. While up to this only a tiny portion of the material in the star has experienced the right conditions to undergo the fusion process, now a good proportion of the material in the star undergoes fusion all at once. The result is a massive stellar explosion that would inevitably take out the whole solar system if the Sun underwent it.

Luckily for us, only certain kinds of stars, at particular points in their life cycle, are able to go supernova. The Sun doesn’t fit the bill. To become a supernova it would need either to be much older or much heavier. The Sun is likely to be around for several billion years before it gives us any trouble. But this doesn’t mean that we are entirely safe from attack from the depths of space.

This sounds like the plot of a B movie, but it’s not a matter of alien invasions (something we’ll consider in a moment). Instead, we are at risk from the sinister-sounding gamma ray bursts.

These may be one of the side effects of a star that collapses without going supernova, though we are not certain exactly why they happen, and there are a number of theories battling it out to be accepted as their cause. Everything from collapsing stars to evaporating black holes has been blamed for the production of the bursts. We just know for certain that they’re out there and they’re very, very dangerous.

A gamma ray burst is an incredibly powerful blast of the most potent rays in the electromagnetic spectrum, which can last anywhere from a fraction of a second to an hour. This doesn’t sound too scary, but gamma rays are so energetic that they can cause massive disruption to living things—it’s gamma rays that cause most of the damage in nuclear radiation. Simply put, they’re killers.

The scale of a gamma ray burst is awesome—in that concentrated blast, the burst will carry as much energy as the Sun is going to give out in its whole lifetime. The good news is that they seem to be rare phenomena. We see only a few hundred a year, and they are so bright that we would expect to see most of the bursts that are occurring throughout the visible universe. This being the case, a burst that threatened the Earth would probably occur only once every few million years.

If we did experience a gamma ray burst close enough to cause damage—which would mean within a few thousand light-years—there would be considerable immediate genetic damage to life on Earth, but more disastrous would be the destruction of the ozone layer. The energy of the gamma rays, slamming into the atmosphere, would cause nitrogen to react with oxygen, forming nitric oxide, which is highly reactive with ozone. Without the protection of the ozone layer, much more ultraviolet light would get through, and it would be this lower-energy but still dangerous light from the Sun that over a number of years would cause the cellular damage that could result in the loss of practically all life on Earth.

Of course, some science-fiction authors would have us believe that dangerous rays are more likely to emanate from the weapons of spaceships belonging to visiting aliens. As weapons of mass destruction go, the ray gun had a surprisingly early conception. To see its first origins, we need to go back to ancient Greece.

Here in Syracuse, on the island of Sicily, Archimedes was born in 287 BC. He is most remembered for his mechanical inventions and for carrying on Euclid’s mathematical work. Archimedes certainly had an obsessive enthusiasm for geometry. Plutarch, writing 350 years later, wryly observed that Archimedes’ servants had to drag him from his work to get him to the baths to wash him, and when he was there, Archimedes would still be drawing diagrams using the embers of the fires, and even marking out lines on his naked body as he was being washed and anointed.

Archimedes lived in an unsettled time for Greece. The Romans, whom the Greeks had contemptuously dismissed as insignificant barbarians, were sweeping across Greek territories. The once great Hellenic civilization was on the verge of collapse. And Archimedes, for all his genius, ended up in the wrong place at the wrong time. He had designed engines of war that were used to bombard invading ships, but despite these, the Romans seemed unstoppable.

It was 212 BC. With the enemy closing in on Syracuse, Archimedes had the inspiration of using light itself as a weapon. He knew that small, curved mirrors could concentrate the rays of the Sun enough to set kindling alight. This ability to focus energy at a distance seemed an ideal way to attack the Romans’ vulnerably flammable wooden ships before they were even in range of the projectile weapons Archimedes had arrayed along the quayside.

Archimedes drew up plans for great curved metal sheets to be fixed in frames on the harbor walls. These dazzling constructions were intended to capture the Sun’s rays, focusing them to a point until the undiluted heat of the day became a miniature furnace. But the mirrors were never made. Perhaps the craftsmen, more used to blacksmithing than to precision engineering, found their construction too much of a challenge. Perhaps the stricken city had lost so much to the war effort that it could not find time and money to construct the mirrors. Perhaps even the great Archimedes was laughed at when he claimed it was possible to destroy their Roman enemies without even touching them.

It may have been the mirrors that Archimedes was still working on in his last minutes. According to some legends, he was drawing and redrawing diagrams when one of the invading Roman soldiers found him. Without looking up, Archimedes cursed the interruption: “Do not disturb my diagrams.” They are said to be his last words. The soldier who found the seventy-five-year-old man was in no mood to tolerate such disrespect from a member of a defeated nation. Archimedes was slaughtered without compassion.

The concept of destructive energy rays, whether heat or light, resurfaced regularly in fiction from the nineteenth century onward. A typical example was the devastating energy source called “vril,” dreamed up by Victorian author Edward Bulwer-Lytton in a book called
The Coming Race
. Vril was a power source that could do anything from drive vehicles to emit a destructive beam that would disintegrate an enemy.