Astronomers are ringing out the bells. Two new 'Goldilocks' planets have just been discovered: Kepler-438b and Kepler-442b.

Well, it's a gloomy time of the year. Earth-bound news is depressing. Maybe we need a celestial pick-me-up.

But I don't share the astro-scientists' enthusiasm. They always strike me as space-age boy-racers - with access to the ultimate playground in the sky.

Take the search for these 'Goldilocks' planets - so-called because they are not too cold and not too hot, not too big and not too small. A bit like our own Earth, in fact.

The scientists say we need to search because our own world has a limited life span. Seven billion years max. Then, the sun will expand into a red giant and vaporise us.

However, some scientists think the expanding sun will raise temperatures on Earth so much that life will be unsustainable in 500 million years.

Stephen Hawking gives us even less time. He thinks we'll be lucky to get through the next few thousand years. Nuclear catastrophe, global warming, a stray asteroid. Take your pick.

For the astro-doom merchants, Earth is too fragile a basket to put all of humankind's eggs in. We need to spread our risks around the universe. Colonize space in order to survive. Migrate to planets like Kepler-438b and Kepler-442b. The ultimate Great Escape.

Even better, as we boldly go where no human has gone before, we might meet a friendly Extra-Terrestrial to give us a helping hand.

All of this enthusiasm for space travel is surely a few stars short of a galaxy.

Take the hope for Close Encounters.

You might remember the Pioneer spacecraft of the 1970s - sent beyond our Solar System, complete with directions how to find our Earth. By now it's far away in deep space - waiting for someone or something to find those directions.

This is a very, very bad idea. A bit like the Aztecs and Incas training carrier pigeons to fly to Spain. Here we are.

If there is life out there, it's more likely to be an Alien-type monster than E.T. Or, worse still, an entity resembling our own violent, species-destroying humanity - armed with technology millions of years in advance of ours.

And these so-called 'Goldilocks' planets. They only fulfil the most basic criteria. From the other end of the universe, Mars and Venus would probably qualify. Being a lot closer, we know differently.

Never mind. There are billions of galaxies in the universe. There must be earth-like planets and intelligent life somewhere. I saw one estimate of 11 billion 'Goldilocks' planets orbiting sun-like stars.

I'm not sure big numbers prove anything. It's like the theorem that an infinite number of monkeys banging away on an infinite number of typewriters will eventually produce 'Hamlet'.

Using 'infinite' is cheating. Let's use a real number. Say, a billion monkeys typing for a billion years. Forget about a whole text. I'd bet my life savings that not one monkey would manage "To be or not to be."

I suspect the universe is like that. An awfully big place with an awfully big number of stars and planets. But the odds against the various factors required for life coming together in the right way must be colossal. The monkeys with the typewriters are probably a better bet.

The universe is a very, very hostile place as far as life, any kind of life, is concerned. Our Earth may be a freak of nature, utterly unique in the cosmos.

Even if there is a lifeboat planet or a saviour out there in the great beyond, there's still a problem. Distance.

For example, Kepler-438b is 470 light-years away and Kepler-442b is 1,100 light years away.

A light year is six trillion miles. So if 438b or 442b are paradises, we're not going to enjoy them anytime soon. You can forget about Star Trek 'warp' speeds. There's one big obstacle in the way. The laws of physics.

You might think that such distances would dampen the enthusiasm for colonizing space. But no. Some scientists even contemplate spaceships which take generations to reach their destination.

Well, I have to take my hat off to someone who's prepared to spend their whole life in a rocket in the hope that his/her great, great, great, great etc. grandchild might get to land on a planet with water and air - hopefully not populated by monsters with acid for blood or by Pizarros with ray guns.

These distances mean that, for the foreseeable future, we are on our own. That's no bad thing. We have enough on our hands sorting out our Earth. We should forget about cosmic boys' toys. Leave all that to science fiction.

We need to focus on solving the problems of global warming, pollution, war, disease and poverty. Not dreaming up ways to run away from them.

Humans have only been around for 200,000 years. We should spend the next 200,000 sorting out the Earth. And evolving into something nicer.

Maybe then, but only then, should we start thinking the Final Frontier. We'd still have at least 499 million years before the Earth pops it.