Big Bang theory and age of the universe put in new perspective

It was such a simple idea that a degree in physics was not required to the find the answer to the question: how old is the universe? Dr John Gribbin, an astrophysicist, was immensely reassured that great scientific discovery does not necessarily have to be very complicated.

Yes, there was a small matter of requiring a large telescope to orbit the Earth. But once key measurements were made of the distances to spiral galaxies far beyond the Milky Way, courtesy of the Hubble Space Telescope, it was down to basic deduction, Dr Gribbin said at the spring Irish TimesRDS Science Today lecture, which was attended by some 700 people last night. "It's very nice, the idea that science does not have to be incomprehensible."

His story was of a prolific science writer who not only returned to scientific endeavour but helped to find the answer to one of the cosmology's "big questions". Moreover, the lecture was illuminated by his ability to bring the complexities of the origin and evolution of the universe to a lay audience.

In the past, Dr Gribbin took on the Big Bang and quantum mechanics and shone strong beams of light on its dark, bewildering recesses. "This time it's personal", he said. He became an insider: doing the measurements, interpreting them, and not acting in his usual role as outsider reporting on the work of others. Not only was it establishing the age of the universe, it was confirming its very beginning: the birth of time, with the Big Bang rightly in place as its spark.

He has helped to resolve a cosmological crisis of the past 30 years centring on the relative ages of the universe and its stars. The breakthrough came in 1997, just when it seemed that scientific opinion was becoming hopelessly divergent. The split stemmed from the 1970s with "one camp arguing for a universe of less than 10 billion years, the other set nearer 13 billion years".

In reality, the story spans from the discovery that the universe is expanding and the emergence of Einstein's Theory of Relativity (which provided the first mathematical description of the universe). It continued right up to 1997. In the intervening years, the work of Alexander Friedmann and Georges Lemaitre had been egg-boxed in a not-to-be-taken-seriously category. Now, however, it is seen as having contributed to definitive measurement of the universe's age.

In 1994 measurements from Hubble seemed to support a relatively young universe, shattering hopes of a resolution. The figures, however, led to a more frenzied evaluation by astronomers, Dr Gribbin noted. With colleagues at Sussex University he developed a new technique to "measure cleanly and accurately" the Hubble Constant. It was lower than anticipated.

The age of stars is measured with quantum theory and nuclear physics; the age of the universe is measured by focusing on clusters of galaxies and using the General Theory of Relativity. Suddenly, they were giving the same answers. "This is a profound indication that physics is giving us the truth about what is going on in the world."

Dr Gribbin maintained his mastery in recounting "whodunit" science by keeping details of "how we measured the age of the universe" until the end. Using Hubble data, his team discovered that the universe is older than the stars it contains. The Big Bang explosion was at least 13 billion years ago, perhaps as much as 16 billion years ago. Other galaxies are not as near as was believed for much of the 20th century, and the Milky Way is not the biggest galaxy. "It's just an average spiral."

The significance of the stars goes far beyond the postulations of cosmologists, he said. This was despite their preoccupation with one mathematical package - "the theory of everything" - and the widespread belief that their ideas were abstract and esoteric. "Nobody has seen a quark. By contrast, though, all of us have seen the stars, and few can have failed to wonder what the stars are and how they got to be there."

Moreover, it was probably this fascination with the stars above that initiated the wonderful voyage of science itself, he said. "It probably began when our ancestors first turned their eyes to the heavens and began to wonder what the stars are and how they got to be there."

One glorious Deep Truth has emerged: "the match between stellar astrophysics and cosmology, and the discovery of the birth of time". Dr Gribbin fully acknowledged the luck he had in being able to play what he describes as a "small part" in establishing this truth about the universe. There was delight, too, in his being able to share it with the audience.

The Birth of Time by John Gribbin is published by Weidenfeld & Nicolson