I am deeply fascinated by any news about the creation, the structure, the size and the ultimate fate of the universe. It is not a very practical fascination but I will quite happily spend hours reading about the latest theories. For instance, I have just seen that Dr Paul Steinhardt of Princeton University has proposed that our universe was "dormant" until struck and activated by an offshoot of a hidden parallel universe. I can't wait to read more about this.

And cosmologist Alexander Vilenkin of Tufts University has recently rejected Einstein's theory that our universe is a sphere, believing instead that it is flat and infinite which he finds disturbing since, apparently, it means that eventually, somewhere, there is going to come into existence another Alexander Vilenkin, indeed an infinite number of Vilenkins, and this, says Professor Vilenkin, "I find vaguely depressing." Well, I do not. I want to know more about this theory of serial immortality.

However, of all the unfathomable questions that men have asked since men could ask questions, the one I find most deeply baffling and absolutely unanswerable is that which my young son asked me once years ago: "Dad, what was there before everything began?" It is an extension of the question that philosophers have asked for thousands of years: "Why is there not nothing?" Why, indeed? Concentrate for a while and think about it.

Trying to find an answer leads to more questions and there are always as many questions as answers. It is evading the question to reply with a take-it-or-leave-it decisiveness, "God". However, I did tell my son that most people believe that before anything was, there was God. But my son had assumed God and included Him in the "everything" of his question "No, I mean what was there before God and everything?" Was there a Super-God? But, then, what was there before super-God? and so on. He got the point. "So, Dad, what was there?"

We went outside to look up at the night sky. The weather was fine and wind was blowing the branches of the trees across the firmament packed with stars. The stars - they were so bright they seemed to hum and shiver with light like a horde of golden bees. We should sometimes stop to give thanks for our privilege. There are millions upon millions upon millions of children in smog-ridden cities who have never seen the stars - and millions upon millions upon millions more who never ask questions except to ask for food.

I pointed out some stars I knew and explained that all the stars we saw were countless millions of miles far off yet they were very near - if we measured out a thousand miles to the end of the universe, in proportion these stars we saw now would be one inch away. The universe was so vast we could not conceive its size and it was filled almost without limit with stars bigger than ten times our sun - fields upon fields of shining stars beyond the imagination.

There was wonder enough in that. But, more wondrous still, there had been a time, about 15 billion years ago wise men claimed, when all this vast universe of shining stars had been contained in a speck, something much smaller than a speck ("a micro-speck" my son, schooled in modern terms, volunteered) which, for some reason no one had yet worked out, had then exploded - though "explosion" could not begin to describe the immensity, the miraculous energy, of the event - and what we saw this fine night was the universe still exploding, but more slowly now.

This was a fine tale but it did not give the answer to three important questions: what was the universe exploding into, where had the micro-speck come from, and, finally, what had been before the speck itself was? And now I had to admit that these were questions which nobody had ever answered though many had tried and many more were still trying. They had so far decided that time itself did not exist before "the singularity," which was when the universe started, and when time does not exist then questions about before and after make no sense and should not be asked - which didn't go very far in satisfying my son's curiosity, nor indeed mine.

In the end you have to try and describe what timeless nothing is - not just empty space or anything like that - no, a void empty of emptiness itself for all eternity. I tried to describe real nothingness but try it yourself and see how impossible it is. It is impossible because in describing anything you are describing it relative to something else, so when you describe nothingness you immediately pre-suppose something and that frustrates your purpose. "Absence of anything" won't do because the mind lingers on the "anything" which exists and you're back in the solid world again.

The concept of "nothing" slips forever out of the mind's grip. The imagination comes nearest. Let it ride out to play in a non-world of all that never was and never will be until the imagination develops its own vertigo and swoons. And when it recovers it finds again only the miracle of what has somehow come to be. In complex equations the mathematicians describe how the universe began. But what breathed fire into those equations to let us see the blazing stars at night?

Gottfried Liebniz, born 1646 and died 1716, perhaps the greatest mathematician who ever lived, argued that there were only two absolutely simple concepts, God and Nothingness. From these, all other concepts can be constructed, the universe and everything in it, arising from some primordial argument between the deity and nothing whatsoever. And then, in an extraordinary leap of the imagination, Liebniz observed that what is crucial in this thought is the alternation between God and Nothingness and for this the number 1 and 0 will suffice. Thus, nearly three centuries early, as he contemplated the ultimate reality of things, did Leibniz pre-figure the world of the computer. I find this fascinating.

I stayed beneath the stars long after my son had gone to bed, to sleep and to dream not of nothingness I hope but of the limitless shining universe. The answer to his question, so far as I could tell, is that before anything was, there was nothing. However, it seems nothingness contained a potentially which waited upon its time to appear in that glorious burst of light which began it all and will never end. And that, I know, is where more questions start on some other star-filled night. And I also know the most important thing is that the questions must never stop. If questions are not asked nothing ever releases its potential. Once, an infinity ago, a question was asked and nothing ceased to be forever.