In a book called 'Brief Letters to the Times', published last year, a correspondent quoted Sir Fred Hoyle (one-time Astronomer Royal) as saying: "The idea that life was put together by a random shuffling of constituent molecules can be shown as ridiculous and improbable as the proposition that a tornado blowing through a junk-yard might assemble a Boeing 747 from the materials therein."

Which brings me to this beautiful blue jewel in space that so captivated the astronauts who first saw it from the moon, our planet Earth.

On any assessment it has to be an amazing place and, quite possibly, among the trillion stars, galaxies and planets, unique.

Robotic probes are now boring through the dry dust of Mars to search for signs of life. There is evidence that there was water on the red planet in some previous age and some space explorers have assumed that this provided a vital building block for life. To date, none has been discovered. Moreover, we have sent radio messages to the outer limits of space and we are still met with a cosmic silence.

Other planets in the Solar System (eg Mercury, too hot at 600 degrees, and Pluto, too cold at 300 degrees below freezing) have been all ruled out as inimical to life.

But planet Earth teems with life, from microscopic organisms to homo sapiens: earth, sea and air are vibrant with life; indeed the earth is like an incubation chamber where life manifests itself in irrepressible variety and beauty and vigour and abundance. As the Astronomer Royal inferred, earth shows every sign of being specifically designed to initiate and sustain life.

Why this should be has beguiled and troubled the mind and heart of man since the beginning of recorded time.

Consider a few astonishing facts. The earth is 93,000,000 miles from the sun. That, in itself, may seem of little consequence, but if the earth was a little closer (like Mercury) or a little farther off (like Pluto) life would be insupportable. Earth's finely-tuned distance from the sun is sustained by its speed through space (66,000 miles an hour) and the gravitational pull of the sun. And this harmonious relationship is timed to a milli-second through endless ages.

Moreover, its 24-hour rotation through light and heat and darkness and cold keeps it rhythmically and viably temperate. And its tilt (in relation to the sun) of 23.5 degrees ensures our change of seasons is nicely adjusted for the sowing and harvesting of our crops. And all the various forces impacting on the dance of the seasons are as stable and reliable as sunrise and sunset.

Just as remarkable is our atmosphere. 21pc of the air we breathe is oxygen. Without it, all living things on earth would perish. 78pc of the atmosphere is nitrogen which falls to the earth in rain and is essential for plant life. Man and animals breathe in oxygen and exhale carbon dioxide (1pc of the atmosphere) which is a basic ingredient of the life of plants: and plants take in carbon dioxide and exhale oxygen. It is difficult to conceive of a more beneficent exchange.

If it wasn't for our atmosphere, this protective garment of blue around us, thousands of meteors that hurtle down from space daily and burn themselves out would otherwise leave our planet home as battered, cratered and pock-marked as the moon. By night, of course, incandescent meteors are seen as shooting stars.

And in addition to all this is the miracle of water. I try never to complain of rain. Water is life. But water is also a very odd substance. It exists as a gas in water vapour, as a solid as ice and as a liquid. And it has another useful quality. As it cools, it becomes heavy and sinks. But when freezing point is neared, it rises to the surface, sometimes as sheet ice, and acts as an insulator to protect marine life.

It is hardly a scientific observation, but I am always beguiled at the sensible size of raindrops. If they were like golf-balls, we would have something to complain about (so would the snowdrops), and more to complain about if hail was the same. It is just one of those fine adjustments that seem so satisfying.

I have only hinted at a few things about this amazing space-ship, Earth. There is clearly a balance, harmony, symmetry, pattern, shape and plan in its construction that must be, to the unencumbered mind, nothing short of awesome.

As the correspondent in the Tiime's letter concluded "...this extraordinary dance of life we all enjoy calls for a choreographer."

And perhaps the nature of the choreographer is the greatest question of all.

Updated: 11:13 Wednesday, April 21, 2004