About a week ago a large piece of rock flew past the earth. It was further away than the moon but near enough for people to see with telescopes. It was also near enough for journalists to write 'What if?' articles about the end of all life on earth. Of course, there is nothing to stop an asteroid hitting our planet so it is only a matter of time before one does. Very small pieces break through the atmosphere every day but every once in a while they cause enormous damage.

In the early twentieth century Siberia received a direct hit. Over two thousand square kilometres of forest were knocked flat as if there has been a small atomic bomb. In fact this asteroid didn't even reach the ground. It exploded in midair. We don't have photographs of the actual explosion but some artists have managed to draw what it probably looked like from eyewitness accounts.

If something that big hit a city, there would be thousands or millions of deaths. The good news is that, because cities are so small compared with the size of the planet, the chances of an asteroid hitting one are very small. The main problem is if the asteroid is larger. Something only a few kilometres wide is enough to change the weather on earth by blocking out the sun with the dust it throws into the air. Landing in the sea would cause tidal waves and landing anywhere would cause earthquakes. If one is big enough (and there are some massive asteroids out there), it could end all life on earth just through the heat of the explosion.

So is there anything we can do about it? Fortunately all the largest ones have already been spotted and we know where they are going. If something is coming towards us, we have a few tricks up our sleeve. Something the size of a small Fiat could knock an asteroid off its course if it was launched early enough and if it was going fast enough. Painting one side of the rock would make the sunlight deflect it. A robotic drill and some atomic bombs might work, depending on the type of rock it is made of. At the moment we probably won't need a team of oil drillers led by Bruce Willis, although I think ESA and NASA have his number just in case.

Glossary

a direct hit celny strzał

to knock something flat rozbić coś na placek

midair powietrzny

an eyewitness naoczny świadek

dust kurz

a tidal wave = a tsunami

an earthquake trzęsienie ziemi

to spot something dostrzec

I have a trick up my sleeve. = I have a plan.

to deflect something odchylić

a drill wiertarka

Here are four words that have something to do with rocks.

Countable:

1 down

A stone about the size of your hand or smaller.

2 across

A large stone that is big enough to block a path and would be too heavy to lift by one person

Uncountable:

3 down

Small stones on a beach.

3 across

Almost microscopically small pieces of sand that can block up harbours and canals. They need to be taken away with special ships called dredgers.

KEY

pebble

boulder

shingle

silt

Did you know?

As well as all the small pieces of rock, there are about 110,000 pieces of 'space junk' more than a centimetre wide going round the earth at the moment. These include nuts and bolts, cables, pieces of paint and other parts of satellites and probes. Each one is travelling fast enough to damage something in orbit and they spend a long time up there until they fall back to earth and burn up in the atmosphere.

Asteroids and comets get their names from the people who discover them. Hurricanes on the other hand get their names from prepared lists which are repeated every six years. There are six alphabetical lists for Atlantic hurricanes and another six for Pacific ones. A name is replaced if a lot of damage is caused by the hurricane.

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