Recipe for the Universe - Just Six Numbers

Cosmological ideas are no longer any more fragile and evanescent than our theories about the history of our own Earth. Geologists infer that the continents are drifting over the globe, about as fast as your fingernails grow, and that Europe and North America were joined together 200 million years ago. We believe them, even though such vast spans of time are hard to grasp. We also believe, at least in outline, the story of how our biosphere evolved and how we humans emerged.

Some key features of out cosmic environment are now underpinned by equally firm data. The empirical support for a Big Bang ten to fifteen billion years ago is as compelling as the evidence that geologists offer on our Earth's history. This is an astonishing turnaround: our ancestors could weave theories almost unencumbered by facts, and until quite recently cosmology seemed little more than speculative mathematics.

A few years ago, I already had 90% confidence that there was indeed a Big Bang - that everything in our observable Universe started as a compressed fireball, far hotter than the centre of the Sun. The case now is far stronger: dramatic advances in observations and experiments have brought the broad cosmic picture into sharp focus during the 1990s, and I would now raise my degree of certainty to 99%.