Armageddon Science (24 page)

Although we have used enhancements for thousands of years, the more dire possibilities for our destruction by enhancement are attributed to technologies we have yet to fully develop. The possibility that normal, unenhanced humans will become outdated, made obsolete by cyborgs or artificial intelligence, is still remote. As we look into the future, this is not the only threat we face, either from technology or from the natural world.

When we consider the disasters that could befall us in the future over and above the areas we have already explored, there are two possible culprits: natural disaster and the outcomes of our own interaction with the planet. Sometimes the two are hard to separate. Although it’s unlikely we would be responsible for an asteroid collision with the Earth, it is entirely possible that our interference could trigger seismic activity. But whether or not we do mess things up, we know from history that there are a whole range of natural phenomena just waiting to give life on Earth a pounding in the future.

The first distinct possibility for widespread human destruction has a clear precursor in a mass extermination that has been subject to some subtle crime-scene investigation, an ancient genocide solved thanks to our knowledge of the element iridium. The concentration of iridium in meteorites is considerably higher than it is in rocks on the Earth, as most of the Earth’s iridium is in the planet’s molten core. One class of meteorite particularly, called chondritic (meaning it has a granular structure), still has the original levels of iridium that were present when the solar system was formed.

In 1980, a team led by physicist Luis Alvarez was investigating the layer of sedimentary clay that was laid down around 65 million years ago, a time of particular interest because this so-called K/T boundary between the Cretaceous and Tertiary periods marks the point at which the majority of dinosaurs became extinct. (“Cretaceous” is represented by K because C was already allocated. “Tertiary” is now a largely disused term, and it should more properly be the K/Pg or Cretaceous-Paleogene event.) This layer contains considerably more iridium than would normally be expected, suggesting that there may have been a large meteor or asteroid strike on the Earth at this time.

There is so much iridium present that the asteroid would have to have been over six miles across—large enough to devastate global weather patterns, bringing about changes in climate that could have wiped out the dinosaurs. This was neither the first nor the last strike by an asteroid or comet that the Earth has faced. It is a constant threat, and one that we are only now starting to wake up to.

The most recent sizable impact was the Tunguska event in Siberia in 1908. Although some still try to cloak this occurrence in mystery because there is no impact crater, it is generally accepted in the scientific community that an extraterrestrial body, probably a comet, exploded above the Tunguska plain, flattening trees for miles around and leaving a shattered terrain. If this impact had taken place in a city rather than in the wilderness, it would have had an effect similar to that of a nuclear explosion in terms of blast, if not of radioactive fallout.

There’s a one in five hundred chance of an event on the scale of Tunguska or bigger happening each year—not hugely probable, but distinctly possible. It has been estimated that the odds are only one in four that the strike would kill anyone, and one in seventeen that it would result in mass-scale mortality with ten thousand or more dying. This surprisingly low risk reflects how much of the planet’s surface is either under water or not highly populated. Even so, the risk is there, and if a large enough body did hit an ocean, it could generate a vast tsunami, which could cause almost as much devastation as would a direct impact.

Although there are asteroid surveys under way that should give us a few days’ warning of an incoming piece of space debris on a collision course, these are limited in scope, both in their coverage of the skies and when they can operate. There are plans for future observatories that would give us much better coverage, but for the moment it is entirely possible that an asteroid strike will occur without warning.

The nightmare scenario for Armageddon is that such a strike will be interpreted as a human attack and will result in retaliatory launches of missiles leading to a nuclear holocaust before it can be established what caused the first impact.

Some movies would have us believe that collisions with asteroids don’t really present a problem. All we need to do, they suggest, is to blast any incoming asteroids to dust with nuclear weapons. This was also the approach favored by H-bomb enthusiast Edward Teller. However, there are some real problems any would-be asteroid blaster would face. First, we’d need plenty of warning. At the moment it is only in a few rare cases that we would have the years of preparation needed to construct and fire off the appropriate device. It’s not enough to take any old nuclear warhead and fire it into space, as neither the bomb nor the delivery rocket was designed for this task.

To make matters worse, many scientists think that a nuclear bomb would just shatter an asteroid into an array of chunks, still big enough to cause devastation, but now spread over a wider area of Earth’s surface, rather than arriving at a single point of impact. There’s also the minor matter that there is a treaty preventing the use of nuclear weapons in space—though this could probably be got around if the survival of the world depended on it.

In practice, our best hope is not deflection, but to build a better warning network so that we can give those who are likely to be anywhere near the impact zone days of warning to evacuate. This still won’t help us if we were faced with the kind of impact that wiped out the dinosaurs. That would have planetwide effects. But for any likely impact in the next few hundred years, a good warning system should deliver the results. Until then—we’d better all hold our breaths.

One of the inevitable outcomes of a collision with a body from outer space would be seismic disturbance, but we don’t need a space invader to get the Earth moving beneath our feet. The natural processes of the planet are perfectly capable of producing devastating results. Although to the casual observer the Earth’s solid surface is immobile and rigid, seen on a large scale with a longer time frame than year-by-year human observation, it is anything but.

The outer skin of the Earth floats on the hot, fluid material beneath. You’ve probably seen film from the International Space Station, where globules of liquid float in space. Imagine an immense drop of such a liquid that forms a crust on the outside. The crust is split into a number of segments, and convection flows in the liquid are constantly trying to move those segments. Where these plates are forced against each other, or one segment of crust is pushed under another, vast forces come into play. This is the how the Earth is built. And the outcome of such a collision of plates is an earthquake.

Earthquakes can have a double impact on human beings. First there is the direct damage, most often caused by falling buildings. But also an earthquake in the sea can cause a tsunami, which we will return to a little later. Many earthquakes have relatively little impact—the vast majority are so low in power that they are not noticed by casual observers—but a few have catastrophic effects. At least two earthquakes in China have killed hundreds of thousands of people each, while the earthquake that struck Haiti on January 12, 2010, is thought to have killed over 200,000 people.

Although earthquakes have been recorded since ancient times, it is only very recently that we have begun to understand what is happening. At one time they would have been considered a ground-based relative of thunder and blamed on the action of gods. It was only in the eighteenth century that any real attempt was made to explain these strange forces, with an idea dreamed up by a man who lived in one of the countries least affected by earthquakes, England.

In the 1760s, the astronomer and geologist John Michell, whom we’ve already met dreaming up the black hole, put forward the idea that earthquakes were caused by underground steam. The timing of this deduction was not accidental. The power of steam was just beginning to be realized in Britain’s Industrial Revolution, with steam-pumping engines replacing manual pumps in mines. Steam was capable of delivering a power that went far beyond any human or animal capability. Michell believed that buildups of steam underground were responsible for the tremors and shifts in the Earth that occur in earthquakes.

He might have been wrong about the cause, but Michell did work out the way that shock waves pass through the Earth’s surface to produce quaking. Others would blame earthquakes on the influence of the Moon, but it was only with the twentieth-century concept of continental drift, later developed into plate tectonics, that a convincing explanation for the forces behind the earthquake, based on those vast shifting plates colliding and passing over each other, was developed.

If we are to avoid significant devastation caused by earthquakes we need to know where they are likely to take place, to build structures in such areas that can withstand earthquakes, and to be able to forecast an earthquake’s arrival to be able to evacuate as many people as possible from the danger zone.

It’s fair to say that we are getting better at this. We have good information on areas that are at risk, and of the probability of future quakes in the general sense. And in some earthquake-prone areas, like Japan, a huge amount of effort has been put into constructing buildings that can withstand high levels of seismic activity without collapsing and crushing those within. But in poorer countries there are still many buildings that cannot stand up to expected shock levels, let alone the less frequent quake of really major proportions.

Although we have to continue building more sensibly in earthquake-prone regions, we still need warning of a quake coming. Like weather forecasting, this is never likely to be possible beyond a certain time frame—and for the same reason. The Earth’s weather system is chaotic in the mathematical sense. Very small changes in initial conditions can make huge differences a few days down the line. In the last few years, meteorologists have made giant steps forward in the accuracy of short-term prediction, but we will never be able to forecast accurately several weeks out.

Similarly, although it may be possible in time to predict an earthquake with reasonable accuracy a few hours before it occurs, we will never have an ideal warning, weeks in advance. Rather like heart attacks (which also have chaotic features), some earthquakes do have warnings in the form of preshocks, but others don’t. Predictions have been made already that have saved lives; but predicted earthquakes have often not come about, and if forecasts are repeatedly inaccurate they will soon be ignored. A lot of work is going into earthquake prediction, but the jury is still out on what’s possible.

The other significant geological threat to human life comes from volcanoes. These are formed when magma, molten rock, rises under pressure and bursts through the crust. An eruption can be a relatively gradual process, or an explosive one, usually becoming explosive when an underground volume of water is flash-boiled by the magma, blowing out a section of the Earth’s surface (surprisingly similar to Michell’s mechanism for earthquakes).

Volcanoes are always with us—there are estimated to be around 1,500 volcanoes at the moment that present a potential danger. Often it is possible to escape an eruption where the only hazard is a lava flow, but communities can suddenly be engulfed by tons of ash, as happened at Pompeii and Herculaneum in Italy when Mount Vesuvius erupted in AD 79, leaving amazingly well-preserved remains.

Even relatively small eruptions in the present day can cause death and disruption. The Mount St. Helens eruption in Washington State that took place in 1980 killed fifty-seven people, though there was enough warning to give everyone the chance to get to safety. At the other extreme, the Krakatoa eruption in 1883 killed around thirty-five thousand people, and the less well-known Indonesian eruption on Sumbawa in 1815 had a death toll that reached fifty thousand.

Unlike earthquakes, because a volcano is a known, specific target to watch, it is possible to get much better warnings of potential eruptions. A whole gamut of monitoring technology is now used in high-risk locations. Small explosions are used to generate shock waves, which are tracked to map the progress of the magma within the Earth, while variations in both electrical conductivity and magnetic fields can show the increasing nearness of an event, as can subtle bulging movements in the outer layers of the volcano itself, as if the mountain were a cartoon figure, puffing up ready to vent its wrath.

The newest possibility for monitoring volcanoes comes from scientists in Japan, a country with more than its fair share of volcanic activity, who are using short-lived particles called muons to keep an eye on what’s going on under the ground. Muons are produced in the atmosphere when cosmic rays—high-energy particles from the depths of space—crash into the upper atmosphere.

Muons have a very short lifetime and few should make it to ground level, but they travel so fast that special relativity plays its part. Because of their relative speed, the time the muons experience is significantly slowed down, by about a factor of five. The result is enough muons penetrating volcanoes to be able to use them to monitor the amount of magma inside a volcano, as the percentage of muons that gets through depends on the mass of the material inside.

But for all the disruption that a regular volcano can cause, it is trivial compared to a supervolcano. Supervolcanoes are on a totally different scale—and one of them could erupt at any time in Wyoming’s best-known natural attraction, the Yellowstone National Park.

The remains of this supervolcano were discovered by Bob Christiansen of the U.S. Geological Survey in the 1960s, and they provide the classic example of something so big it’s difficult to spot. All the geothermal activity in Yellowstone, producing those famous geysers, implies there’s a volcano around somewhere. But where, Christiansen wondered, was the crater? It was only by coincidence that he saw some NASA high-altitude photographs of the park and realized that the caldera of the Yellowstone volcano—the pit left after its most recent volcanic explosion—was so big that it hadn’t been spotted: fifty-five by seventy kilometers (thirty-five by forty-five miles) across.

The scale of eruption of a supervolcano like Yellowstone—and around half a dozen others have since been found around the world—is truly tremendous. If it were to explode again, it would devastate hundreds of miles around it. In its most recent truly large eruption, nearly 640,000 years ago, the Yellowstone volcano produced enough ash to cover the whole of California six meters (twenty feet) deep. In practice the ash spread over what would now be nineteen states, the vast majority of the United States west of the Mississippi river. Leaving aside the immediate deadly impact, if such an eruption were to happen today it would leave those nineteen states with a vast amount of debris to clear before they could even vaguely return to normal.