Police bombarded with calls as ‘huge fireball’ sighted
A large meteorite may have hit southern England, after blazing a fiery trail across the UK. It was a gentle reminder of a deadly threat: a big enough asteroid could wipe out the entire human race.
‘UFO invasion?!’ exclaimed one woman in Glasgow on Saturday night, as a mysterious ball of fire flew past her window. Police across Scotland and northern England started getting anxious reports of missiles, fireworks and crashing aeroplanes, as the flaming orb streaked southwards across the sky.
Veteran sky watchers were less alarmed. What they were seeing, they knew, was one of the most spectacular asteroid impacts in years. A large rock, perhaps the size of a car, had smashed into the Earth’s atmosphere at a speed of over ten miles per second – faster than a rifle bullet. Superheated by friction with the air, the asteroid was enveloped in a halo of flame. By the time it hit the ground, all that would have been left was a charred stone the size of a man’s fist.
But although last weekend’s fireball was harmless, the threat of asteroid impacts has some scientists seriously alarmed. While most space debris simply burns up when it hits Earth’s atmosphere, the planet occasionally crosses paths with asteroids on a much bigger – and deadlier – scale.
The last time this happened was in 1908, in the remote Tunguska region of Siberia. An asteroid about 50 metres across smashed into the Earth’s atmosphere, exploding with a force 1000 times greater than the Hiroshima atomic bomb. The destruction extended over hundreds of square miles. Such an impact over a major city could kill millions of people.
And, about once every 100 million years, we encounter a real planet-killer. It was one of these, an asteroid around six miles wide, that caused the extinction of the dinosaurs – along with 75% of all species in existence at the time.
Could such a thing happen again? Yes, say astronomers. The question is when. One very threatening asteroid, in fact, has already been spotted. Called Apophis, it is scheduled to skim past Earth in 2029, although the chances of it colliding are estimated at only 250,000 to one.
Knowing too much
Even if Apophis misses, it is only a matter of time before Earth gets hit again. Many astronomers think we should be doing more to spot such threats in advance. With enough investment of time and money – enough telescopes devoted to the task – we could get years of warning before a planet-killer could strike. That might, they say, give us time to somehow dodge the cosmic bullet.
But some, more philosophical types think it might be better not to have too much warning of impending doom. After all, what if there was simply nothing we could do to escape disaster and we had to wait miserably for years for the killer blow, helpless and despairing? Would it not, in the end, just be better not to know?
- What would you do today if you discovered a huge asteroid was going to hit the Earth tomorrow?
- Is it better to see disasters coming or to be taken by surprise?
- Write a science-fiction story imagining a world where an unstoppable asteroid was due to strike in exactly five years time. How would the knowledge affect daily life?
- How would you stop an oncoming ‘planet-killer’ asteroid? Design a system that could get the job done.
Some People Say...
“No torture could be worse than seeing into the future.”
What do you think?
Q & A
- So apart from wars, financial crises, pandemics and global warming, I now have to worry about asteroids too?
- Well, a bit at least. Estimates of how likely a big asteroid is to hit us vary, but some scientists say there is a one in ten chance of impact in the next hundred years.
- And there’s nothing we can do to stop it happening?
- There are lots of ideas, but nothing that has been tested. It certainly would not be easy.
- Ideas like what?
- You could knock an asteroid off course using nuclear missiles, or simply ram it with a rocket or satellite. More subtle methods include sticking solar sails to the asteroid so it gets blown off course by solar wind, or using a ‘gravity tractor’: a heavy spacecraft that drags the asteroid off course just by using its own gravitational pull.
- The word asteroid comes from a Greek root meaning ‘something that looks like a star’. There are millions of asteroids in the solar system, mostly in the so called ‘asteroid belt’ between the planets Mars and Jupiter.
- When two things rub together, some of their kinetic energy is converted to heat. This principle allowed early humans to make fire by rubbing sticks together.
- The Japanese city of Hiroshima was the target of the world’s first atomic bomb, in 1945 at the end of World War II. The explosion had as much energy as around 13,000 tonnes of conventional explosive and killed 70,000 people instantly.
- The asteroid Apophis was named after the Egyptian god Apep, an evil serpent that tries every night to swallow the Sun.
- Skim past
- The real danger of Apophis is not that it will hit the Earth in 2029 but that it will pass through a small area of space called a ‘gravitational keyhole’. If it passes through this zone, its orbit will bend in such a way as to hit the Earth seven years later, in 2036.
- 250,000 to one
- By way of comparison, the odds of winning Britain’s national lottery are around 14,000,000 to one.