How did the universe come to exist? Paul Davies looks at those asking the questions

For thousands of years, humans have gazed in wonder at the world about them and asked the big questions: How did the universe come to exist? What is it made of? Where do humans fit into the great cosmic scheme? Is there some sort of meaning to it all?

Throughout history, such questions have mostly been restricted to religion and philosophy. Now scientists are starting to address them too. Propelled by spectacular discoveries in cosmology and the subatomic world, physicists have begun formulating "theories of everything" - attempting to meld the many disparate branches of physics into a single all-embracing mathematical scheme.

The tantalising glimpse of a final unified theory has re-ignited ancient debates about the very nature of the physical universe and the place of mankind within it.

One issue in particular has served to split the scientific community above all others. It revolves around the question of why the universe can be observed at all. Observers (at least of the human variety) are living organisms, and exist only because the universe is fit for life in the first place.

This glaringly obvious fact conceals a gigantic subtlety, however. Unless the laws of physics had more or less the form they do, life as we know it would be impossible. Take the masses of the familiar subatomic particles such as electrons, protons and neutrons. Altering their values, even by a tiny amount, would have lethal consequences. Eliminating any of these building blocks of matter would certainly scupper any hope of life emerging. Similar conclusions can be inferred about the strengths of the fundamental forces of nature and the distribution of matter in the universe. Like Goldilocks' porridge, lots of basic features of nature are uncannily "just right" for life. What is going on?

The Cambridge astronomer Fred Hoyle hit the mark when he described the universe as "a put-up job," its felicitous properties appearing "as if a super-intellect has been monkeying with the laws of physics." Needless to say, most scientists recoil from such talk as being uncomfortably theological, but they can't agree on what to put in its place.

On the one hand are those who are fixated on string theory, a fashionable research field which seeks to explain everything in the universe entirely in terms of little loops of string that wiggle in various ways to produce all the particles and forces of nature. String theory holds the promise of predicting a unique physical world with laws completely determined by the mathematical structure of the theory, including the values of all those bio-friendly Goldilocks numbers.

But other researchers reject this claim, as little more than wishful thinking, citing evidence that string theory seems instead to predict a stupendous number of different universes. It is then a small step to believe that all such universes exist within a gigantic multiverse - a patchwork of cosmic regions of which our universe is part of but one atypical patch. It would then be no surprise that our universe is peculiarly bio-friendly, because the more common bio-hostile regions are sterile and go unobserved.

Meanwhile, a small band of theorists have been toying with an even more radical notion: that a deep principle of nature links the laws of the cosmos to the emergence of life and consciousness, perhaps through some form of backward causation. In this manner, beings such as ourselves, who can come to understand, at least in part, the hidden mathematical rules on which the universe runs, play a small but nevertheless significant part in the great cosmic scheme.

Want to find out more? Come along to The Goldilocks Enigma at The Oxford Playhouse (see right for more details).

The Oxford Trust co-ordinates the Science Matters Page.