Every so often, when there’s a dark, clear evening, I like to stroll into the back garden to stare up into the inky night. Once you get accustomed to the light, you soon see the Milky Way stretched out across the sky above. And after a few minutes of craning upwards in wonder at the vastness of the universe my thought is always the same: “God, my neck hurts.”

It’s worse when somebody comes with me because I’m often tempted to impress them with my astronomy O-level, foolishly forgetting every time that a C grade is not in fact all that impressive.

If I keep quiet about the C grade, the conversation often goes something like this: “Amazing!” they say. “You’ll know all about the constellations, then. I’ve always wanted to know the constellations. What’s that one, for example?” That one is nearly always Cassiopeia.

It’s easy to find Cassiopeia. It’s pretty much the most obvious constellation after Orion (named after a rather dull saloon car) and the Plough (named after a pub just outside Loughborough). Cassiopeia is the one that looks like a “W” walking home from a drunken evening: the constellation that seems to have been crayoned onto the sky by a celestial three-year-old.

If you stare at the stars that make up Cassiopeia for long enough, you can just about imagine the stick-thin figure of a skier who has lost the back half of her ski. She is obviously a rather inexperienced skier too, because she is sitting much too far back (which means that, without the rear end of her ski, she will probably fall over).

Yet somebody stared up at roughly that same pattern many years ago and said with an authority that would last the next few thousand years: “Here, take a look at that strange ‘W’ shape. Doesn’t it remind you of Queen Cassiopeia, the beautiful but vain wife of King Cepheus of Ethiopia?”

Except they probably said it in classical Greek. King Cepheus is there too, next to his queen, and his picture is even more abstract: he looks like a set of antlers that have had all the fiddly bits knocked off.

If you too think about such things as you look up at the night sky, then shame on you. That’s not what you’re supposed to be thinking about. You are supposed to be considering the mysteries of the universe, the meaning of human existence and – more important – whether there could be life out there. Not just the odd lucky bacterium either, but people like us.

Could there be a carbon-based life-form on another planet right now, sitting in an armchair and complaining that there’s nothing on the television?

I mention all this because proper astronomers, people who can stare up at the night sky for hours at a time without getting the slightest crick in their necks, have discovered a solar system that appears to be very like our own. The planets in question are circling a star called Cancri 55, which is about 41 light years from here.

Astronomers are particularly excited about this discovery because, as The Sunday Times reported last week, the planets around Cancri 55 are lined up in such a way that an Earth-like planet there might support life.

The odds are against it, I know. As I understand it, we have the most amazing series of coincidences to thank for our existence. The sun is just the right size, and Earth is just the right size. We have just enough gravity, just enough nuclear force, just enough electromagnetic force, and the right kind of atmosphere.

All this and more has come together over 4½ billion years – or thereabouts – to create the sort of intelligent beings who will sit down tomorrow and enjoy I’m a Celebrity . . . Get Me Out of Here!.

Yet some people still believe the universe is so vast that there must be life out there somewhere. We cannot, they say, be alone. I do hope they’re wrong.

Consider life on Earth for a moment. There are wars in Iraq and Afghanistan. The Russians are fighting the Chechens. The Indians are fighting Kashmiris. Everybody in Africa is fighting pretty much everybody else. It’s not that long ago that we finished fighting the Germans, and they’re only next door but one. Are we really ready for the appearance of new neighbours and adversaries just a few light years away?

It’s difficult to know which would be worse: discovering life that was more intelligent, or less intelligent. If the new civilisation was much more intelligent, life here would be unbearable. They would be visiting us all the time to say how quaint we were, and how important it was that our way of life should be preserved and our customs respected.

Occasionally, famous people from the Cancri 55 system would arrive to make films in which they urged their fellow citizens to send money so that we too might have access to telepathy and other vital services.

If the Earth-like planet of Cancri 55 was underdeveloped then it would all be very different. We would be mining the planet for natural resources and would be in the middle of a fierce debate about whether immigration controls were needed to stop the flow of Cancrions into our solar system, especially since – with their eight arms – they have an unfair advantage in the building industry over native workers.

There is one consolation. Cancri 55 is 41 light years away. So if the advanced people of Cancri Earth are watching us, they have just seen England win the World Cup. It will take another 41 years for them to discover that we have discovered them. Which means there is still plenty of time to move to a less crowded part of the universe.

Jeremy Clarkson is away

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