The Birth of Time: How We Measured the Age of the Universe by John Gribbin, Weidenfeld & Nicolson, 216pp, £20 in UK
We draw a great many conclusions about a person on the basis of their age. We decide, almost on a notion, that one is too old/too young to see a film or go roller-blading or get married. Generally, we need to get a fix on a person's critical little number before we conclude whether they are acting their age.
This inclination to establish age and a point of origin in time extends outwards into other spheres and humankind does it compulsively. How old is that song, when was that cathedral built, when did dinosaurs stalk the land? The ultimate question behind all of this searching, however, must be when time itself began. When did the pendulum first swing and for how long has it traced time since?
John Gribbin tackles this problem in his latest, outstanding contribution to the public under standing of science, in which he explains how one of the great scientific puzzles - determining when everything began - was finally solved. He is well qualified for such a challenge as a working astrophysicist who actually played a part in the international effort to establish an age for the universe.
Gribbin draws together all the many scientific strands, from the pre-Christian Greeks to the latest images captured by the Hubble Space Telescope which currently orbits the Earth. Like a scientist's who-dunnit - better described as a when-dunnit - he travels stepwise through centuries of cosmological discoveries, waiting until the end of his book to finally explain that the universe began with the Big Bang explosion at least 13 billion years ago and perhaps as much as 16 billion years ago. The readers get more than that, however. We also learn how the physicists were able to put an age on the oldest known objects in the universe, the globular clusters. These are reckoned to have formed between 10 and 13 billion years ago with a current best value of 11.5 billion years.
Thanks for nothing, you might say - the numbers are incomprehensible and there is also the small matter that these answers are only whittled down to give or take a few billion years. But as Gribbin points out, it is quite a big deal. For the first time in scientific history, astronomers are now able to prove the universe is actually older than the stars which populate it. Things were not always so. People have been trying to figure these things out for generations either using the Bible or by observing the stars. Dublin's own Bishop James Ussher calculated in the 1650s that God created the earth, sun, stars and the space they occupy on Sunday, October 26th, 4004 B.C. at 9 a.m. - Mesopotamian time. Ussher's and other early attempts to set the point of creation came to grief, as Gribbin explains, when scientists realised that Earth was a good bit older than 4,004 years.
Gribbin brings the reader through the gradual learning process as scientists delved backwards in time towards the origins of the universe. He has a remarkable skill for expressing the most complex theories and concepts as if they were no more difficult than descriptions of the weekly shopping list. For example, he waltzes happily through the intricacies of Einstein's General Relativity, leaving the reader wondering what all the fuss is about - sure, everyone understands space-time and curved space. He also manages to convey the very human side of many of the giants of astronomy and astrophysics along the way. He describes how Milton Humason, who with Edwin Hubble helped to define the expanding universe, started out not as a scientist but as a mule-driver carting building materials up to a new observatory atop California's Mount Wilson.
Too many well-received popular-science writers make heavy demands on their audience, requiring that they first learn to manipulate obscure terms and concepts if they want to understand. Gribbin manages to achieve this level of audience familiarity with the subject in so painless a fashion that you are discussing parsecs and spectroscopes and red-shifts long before you realise they have comfortably slipped into your vocabulary.
He also employs a disarmingly familiar style when he chooses, as he coaxes the reader along. Much of what we know of the universe and its age comes from measuring distances to stars and much of the book is dedicated to the techniques for doing this. He begins to describe one such method thus: "I'm almost ashamed to tell you about the other crucial technique for measuring distances to stars, because it sounds so silly. But it does work, after a fashion."
And so Gribbin guides the reader to the breakthrough findings published only last year that showed that the universe is actually older than the stars it contains. "It is hard to overstate the importance of this discovery," he concludes. "Unless we are the victims of the most cruel coincidence, it means both that we really do understand the way stars behave, and that the universe really did begin at a finite moment in time - or rather, that there was a beginning to time itself."
John Gribbin will deliver the spring Irish Times/RDS Science Today lecture next Wednesday evening, March 10th at the RDS. Tickets for the event are sold out.