The End of Civilisation: When Is It Nigh? an Asteroid Is More Likely to Kill You Than an Air Crash. but Your Government Does Not Seem to Care. (Space)
Steel, Duncan, New Statesman (1996)
Space research delivers benefits in contrasting ways. One is through education, and inspiration to the young. The astronomy and space technology courses I teach are simply physics in disguise, the sugar that makes the pill palatable.
Another advantage comes through the stimulation of national economies. The US investment in space leads to high prestige for American science and technology in general, and so aids all the country's business dealings.
But direct benefits are what taxpayers mostly look for: satellites that give better weather forecasts, or scan for natural resources, or allow you to watch more television channels. These are the positives of space.
A double negative also results in a positive. Forensic science produces a positive by reducing crime. Medical research does likewise, through curing disease. How about space?
Twenty years ago, we had little idea about the environment in which our planet orbits the sun. We had thought that all was benign, apart from when the sun hiccups, affecting our radio communications for a few days. Now we know that space is a cosmic shooting gallery, with huge lumps of rock zipping past our planet at unimaginable speed.
It's not a matter of whether one of them will strike us; it's just a question of when. Stopping the one that is heading our way is clearly a double negative, producing a positive of immense importance. It could save civilisation. It could save the human race. The dinosaurs, almost certainly, died because they did not have a space programme.
A lump of space detritus a mile across, hitting Earth at around 15 miles per second, would release energy equivalent to a million megatons of TNT, or a hundred million Hiroshima bombs. Computations of the effect of such a blast suggest global catastrophe. No matter where ground zero was located, we'd all be in deep trouble.
You may think this is just theory, but astronomers have seen such a cataclysm, on another planet. Inmid-1994, the 20-odd pieces of a broken-up comet called Shoemaker-Levy 9 slammed into Jupiter. The black eyes that the planet received had areas ranging up to four times the surface area of Earth. And the largest of the comet fragments responsible were only a third of a mile in size.
We know also that such things have occurred on our deceptively docile planet. Geologists have so far identified more than 250 impact craters spread over the continents. On Earth, unlike on the dead, pock-marked moon, active geology and atmospheric weathering erode craters relatively quickly. In any case, 70 per cent of the globe is ocean.
But geologists have estimated how often Earth suffers a cataclysmic impact energetic enough to disrupt the climate globally. Astronomers like myself have made similar estimates from studying asteroids and comets in space.
Our answers agree. Once every 100,000 to 500,000 years, we can expect a major impact, sufficiently powerful to cause the deaths of perhaps half of humankind. That may seem like a comforting answer, but it implies, say, 2.5 billion deaths every 250,000 years, or ten thousand deaths per year, taken as a global long-term average.
Smaller events occur more often. The last really significant one was in 1908, when an asteroid 50 or 60 yards across blew up in the atmosphere above Siberia. This is what usually happens, deceiving us in several ways. For one, it leaves no crater. For another, by exploding at an altitude of a few miles (when the shock of its hypervelocity plummet into the atmosphere causes the rock to shatter into pieces) the object actually causes maximum damage across a wide area. In the Siberian case, it was over a largely uninhabited region. But the flash from the 15 megaton explosion ignited the forest instantaneously, and the following blast (taking 20 to 30 seconds to reach the ground) then blew out the fire and blasted flat the trees over an area of a thousand square miles. …