The Universe - A Biography, by John Gribbin

A Big Rip, Crunch, and Bang

We know that the universe is a big place, but we think it was once the size of a grapefruit. We believe it started with a Big Bang and could end in a Big Crunch. And we know that our place in the universe is small to the point of being insignificant both in time and in space - which, thanks to relativity, amount to much the same thing.

There are quite a few things that we know we know about the universe, and there is quite a lot more that we think we know. The line between astronomical fact and cosmological theory can often be obscure, but at least we can thank John Gribbin for leading us through the quagmire of quarks that flood the soggy bog of cosmology.

Astronomers have good reason to believe that the universe is about 13.7 billion years old. The Hubble space telescope has captured images of galaxies that formed just a billion years after the Big Bang. But it is what happened immediately after the Big Bang that has captured the imagination of cosmologists.

And when we say immediately, we mean immediately. Cosmologists think they know that a period of rapid expansion, known as inflation, occurred in the first few fractions of an instant after the universe began. We are not talking microseconds here, but unimaginably tinier fractions of time. Take, for example, the first point after the Big Bang when the strong force of gravity becomes a distinct entity - 10 ^-35 seconds after the birth of the universe. (This number has 34 zeros between the decimal point on the left and the figure one on the right.)

Quarks, the family of fundamental subatomic particles, came into their own about 10 ^-10 seconds after the universe began. For the briefest moment they existed as a plasma - a cloud - but this free-living phase ended at 10 ^-4 seconds. It was at this point that the universe entered the era of baryons, the visible matter that comprises the galaxies, stars and planets of today. Everything we see around us - including our own bodies - is composed of baryonic matter.

It is almost impossible for ordinary folk to get their minds around these minute timescales. Worrying about what happened in different parts of the first second after the Big Bang seems nonsensical, until you realise that 10 ^-35 is 10 million billion billion times bigger than 10 ^-10.

As Gribbin points out, in this sense, the era of inflation that led to the establishment of gravity was as remote from the era of quark plasma as we ourselves are from the era of quark plasma - but of course in the other direction.

Which only underlines the fact that everything in cosmology is relative.

Cosmologists think they know that quantum fluctuations affected matter during this critical period of inflation. It is these fluctuations that seeded the process that ultimately led to the creation of a "clumpy" universe of stars, galaxies, planets, and life. This belief forms one of the central tenets of the New Standard Cosmology, which attempts to explain how the universe evolved from its very beginnings to what it is today.

There is much we still don't know about the universe, of course. About 80 per cent of it, for instance, does not exist as visible, baryonic matter, but something invisible and mysterious - so-called cold dark matter. Experiments in deep underground mines - one a working salt mine at Boulby in North Yorkshire - are designed to trap the ghostly sub-atomic particles that are thought to comprise this dark matter. They have never been detected because they pass straight through ordinary matter.

And then there is something even more weird than dark matter - an immense form of hidden power called dark energy. Dark energy was revealed only a few years ago when astronomers realised that something was accelerating the rate of the universe's expansion.

Gribbin points out that dark energy actually holds the universe together today, but, paradoxically, it seems that if the acceleration of the expansion continues, then it will also be responsible for blowing it apart - a Big Rip as opposed to the Big Crunch of a universe that implodes in on itself.

Where do we fit in to this biggest of all stories? It seems that intelligent beings have emerged relatively early in the epoch of accelerated expansion and that the basic parameters of the cosmos seem ideally suited to life - a coincidence perhaps? Or is this telling us a deep truth?

"People are interesting and complicated entities, and we live in the most interesting and complicated time in the life of the universe because that is the only time when creatures like ourselves could exist," writes Gribbin.

It is intriguing that cosmologists describe the universe as "flat", meaning that it is balanced on a knife-edge between runaway expansion and precipitate collapse. They can explain our presence by the anthropic principle of cosmology, which simply states that we find ourselves living in a universe uniquely designed for life because we wouldn't be able to live in any other kind of universe.

Life on Earth has been going for about three-and-a-half billion years, and Gribbin offers fresh and important insights into how life may have been seeded from space with organic molecules carried on cometary dust.

The vital elements of carbon, nitrogen and phosphorus were forged in the nuclear furnaces of the stars, but more complicated organic molecules essential for life are known to be synthesised in interstellar clouds.

If there is one criticism of this book it is that Gribbin pursues a relentless course of detailed explication that takes no prisoners. If you really want to know about the greatest story there is without fear of it being dumbed down, then this is the book to read.