Steering a path through a cloud of confusion

<i>Stardust </i>by John Gribbin (Allen Lane, &pound;18.99)

Open a popular physics book these days, and the chances are that you will find the word "mind-boggling" in the first few pages. The more exotic the raw material, the more extreme the examples of gee-whizzery. Superstrings, wormholes, and other esoterica may sell books, but these are fringe topics and popular descriptions often grossly misrepresent their status in the canon of scientific knowledge. They also contribute to a popular suspicion that science is dominated by untested speculation.

Open a popular physics book these days, and the chances are that you will find the word "mind-boggling" in the first few pages. The more exotic the raw material, the more extreme the examples of gee-whizzery. Superstrings, wormholes, and other esoterica may sell books, but these are fringe topics and popular descriptions often grossly misrepresent their status in the canon of scientific knowledge. They also contribute to a popular suspicion that science is dominated by untested speculation.

In Stardust, John Gribbin bucks this trend by taking us on a astronomical journey rooted in well-known science. It tells the story of how, in the last 80 years or so, scientists have gradually put together a complete picture of the origin of the chemical stuff from which we are made.

All familiar material is made of atoms, and all atoms possess a nucleus made of a mixture of particles called neutrons and protons. The complexity of a nucleus depends on how many neutrons or protons it has. The simplest atom of all is hydrogen, with one proton and no neutrons. Helium has two neutrons and two protons. More complex atoms can have dozens of nuclear particles, and their complexity leads to the subject called chemistry. Among these elements are carbon, nitrogen and oxygen, which, together with hydrogen, play a crucial part in the chemistry of living things.

The story proper begins in the 1920s, when it became generally accepted by astronomers that stars are basically made of hydrogen and helium, the simplest nuclei. Stars produce energy using nuclear reactions that merge hydrogen nuclei together to form helium, but it took 30 years before the details of this process were worked out.

Meanwhile, cosmologists were developing the Big Bang theory. In this picture, the entire universe is created in a primordial fireball in which nuclear fusion occurs. According to detailed calculations of the fallout from this cosmic furnace, about 25 per cent of atoms were already in the form of helium before any stars were born.

Elements heavier than helium were not made in significant quantities in the Big Bang. So the stuff from which we are made (particularly carbon, nitrogen and oxygen) was cooked in stars that formed relatively recently in the history of the universe. At this point the story gets complicated.

Stars such as the Sun burn hydrogen, but different stars burn at different rates and temperatures, like a diverse collection of cookers. These cook the basic stuff of the universe into various flavours containing combinations of heavier elements. Some stars, the supernovae, end their active life in an explosion that not only creates more heavy elements but also sprays them around in a cloud of dust and ash.

This material is the "stardust" from which living things are made. We are the product of recycling on a cosmic scale. This is the story in a nutshell, but there are many twists, making Stardust an absorbing read.

We also meet some of the 20th century's greatest scientists, warts and all. One is George Gamow, the tragically neglected genius of nuclear physics who could be called the father of the modern Big Bang theory (his Mr Tompkins books belong to the finest popular science writing). The brooding presence of Sir Fred Hoyle also looms large. Though best known for his criticism of the Big Bang theory, Hoyle's greatest work was in nuclear-fusion theory - for which he conspicuously did not win a Nobel prize.

Gribbin is an expert science writer, and this book is as good as any he has written. Beautifully conceived and highly readable, Stardust covers a range of interconnected topics with great clarity and technical accuracy. Above all, it demonstrates the interconnectedness of science through the overlaps between physics, biology, chemistry and astronomy. I hope books like this will serve as an antidote to the creeping compartmentalisation that is the bane of the present education system.

The reviewer is professor of astrophysics at Nottingham University