Peas, plates and croissants

It is very hard for the human mind to comprehend the concept of the age of the universe. Our lives are absurdly brief and we are comically tiny compared to the time and space in which we are immersed. But one aspect of us is truly cosmic: the fact that our minds can make sense of things that are far too large, small, quick, old, slow or fast for us to observe directly.

These three books explore the way in which the human race has taken its understanding of the cosmos to new heights in recent centuries.

One author, Leila Belkora, takes the "great man" route, looking at the people behind our knowledge of our own and other galaxies from the 18th century onwards. Another, John Charap, takes a textbook approach in which we start with our knowledge of the physical world in 1900 and run through everything discovered since. The third, Robert Kirshner, concentrates on contemporary developments and makes the most of his position at Harvard University at the centre of some topical scientific research.

Belkora's, the most eccentric of the three, comes with drawings that resemble the kind of rough sketches an author might hand to an illustrator. It starts with an elementary chapter on the sky visible to the naked eye that shows the confusion at the heart of the book. Minding the Heavens is too simple for the serious reader of cosmology, at whom its forbidding design is clearly aimed. There will also be arguments about the seven astronomers Belkora chooses as exemplars (this reviewer would also vote for John Herschel), although other important figures enter the narrative without a chapter of their own.

The tale starts with Thomas Wright (1711-86). He described the layout of the heavens as the "slab of stars", and for this reason, Belkora points out, he is sometimes regarded wrongly as the originator of the concept of our galaxy. In fact, his tale is intriguing as he was a "society scientist" who was a lecturer, publisher and surveyor, as well as a cultivator of powerful allies. But he spread his energies thinly (writing about earthquakes and Ireland) and his claim to an appearance in these pages is a slender one.

The pace picks up when we meet William Herschel, perhaps the greatest astronomer who ever lived. Apart from becoming the first person to discover a planet (Uranus, in 1782), he made the first attempts to measure distances to stars and showed that the Earth receives invisible energy from the sky.

His attempts to find out how far away the stars are, foundered on the inaccuracy of his measurements, but he did produce the first map of the galaxy. His vocabulary of stellar "strata" owed much to the contemporary revolution in geology.

Later the book lights upon Wilhelm Struve, the first of the sample to spend a large part of his career as a science administrator (largely working for Tsar Nicholas I) and probably the first to work out the distance to a star. After this we meet Thomas Huggins, developer of the technology for determining stellar composition and the last amateur astronomer to figure in these pages. In the 20th century, the story becomes one of "big science", in which professionals such as Harlow Shapley (originally a journalist) and Edwin Hubble (first trained as a lawyer) work out the shape of the galaxy and, by discovering the recession of galaxies, that of the universe itself.

There is not much to object to in the book and nor is there much to like. Minding the Heavens is likely to prove too detailed for some readers and too shallow for the rest.

John Charap poses fewer such problems in Explaining the Universe , which should be a hit with lecturers wanting a text that is thorough but wears its knowledge lightly. He sets out to prove that even the wilder reaches of particle physics and cosmology are consistent with common sense. His canvas is the whole of physics at the start of the 21st century, including the structure of the universe, the bizarre objects it contains - from black holes to superclusters of galaxies - and the deep level at which it contains order. For those who are mystified by "attractors" in mathematics, Charap offers a neat analogy with folding a croissant.

He explains spacetime and the theories of everything that claim to unite all the forces and particles in the universe. So do many popularisers. But unlike most of them, he also teaches the reader a lot of statistical mechanics in an unassuming way. He writes better than Belkora and his book is certainly more attractive. And with sections on topics such as gravity waves and M-theory, cosmology's current fashion, Charap has an eye on the future as well as on current knowledge. He shows there is a direct link between apparently obscure science and everyday life. From quantum theory come lasers, for example, with impacts on everything from entertainment (CDs) and shopping (bar codes) to surgery, in which lasers make cuts that no surgeon's scalpel could manage.

Though Charap is a cheery fellow, at least in print, he and Robert Kirshner could probably never be friends. For Kirshner, author of The Extravagant Universe , is an astronomer. His tribe would rather risk dining with Hannibal Lecter than with a physicist such as Charap. Astronomers, says Kirshner, use bizarre physical units and terms to put physicists off the scent and shun the Astrophysical Journal in favour of the Astronomical Journal to make their disdain for physics clear. Particularly distasteful to astronomers are physicists who turn to matters celestial when their careers are well advanced, a condition Kirshner dismisses as "late-onset astrophysics".

Kirshner's book represents a high point in popular science publishing. It works at several levels, especially the personal, in which he offers a well-written, even classic, account of the life of a working scientist - complete with its personality clashes, struggles for jobs and money, competition with rivals around the world, fights over priority and attribution, and its sheer difficulty and necessary ingenuity. He sees the big picture of why this activity is an essential part of human life, and aims a sideswipe at those who see research only as part of the hunt for economic success. He also tells an anecdote well, whether it be about himself being beaten up in Arizona or the first demonstration of the Doppler effect, in which Christian Doppler had musicians play from a railway truck driven at speed past musically acute listeners.

The connection between Kirshner's research field and our new knowledge of the universe is direct. His work on using supernovae to determine the distances of early galaxies is at the edge of contemporary astronomy and cosmology, especially the question of whether the universe will expand forever or will eventually collapse. He also has a good sense of history. His account of the 1920 debate on the possibility of galaxies beyond our own is far better than Belkora's much longer version of the same event.

As a scientist, Kirshner believes in data, and lots of it. He regards debate about a scientific theory as a sure sign that more facts are needed. Astronomers argue long and hard for access to big telescopes. For many years, he says, the California Institute of Technology kept ahead of the game by having the biggest telescope, a position it is now regaining. But his supernova investigations at Harvard are in a category of their own for difficulty, as supernovae arise instantly and must be observed without delay, preferably with busy instruments such as the Hubble Space Telescope. Kirshner's dealings with the Hubble planners make fascinating reading and there is no doubt that their decision to back him and his colleagues has yielded scientific dividends. Here is a handy hint: discover your supernovae on Saturday to guarantee the briefest delay before Hubble is turned on them.

In Kirshner's world, established beliefs must often be abandoned - for example, the long-held view that all supernovae of type 1a are identical in brightness. The reward is astounding insights into the "missing mass" of the universe, for example, and more recently the "dark energy" whose push counteracts the gravitational pull of dark matter.

The Extravagant Universe is a book that will be read for pleasure. Who could resist an author who points out that Mars is like "Tucson before the developers arrived"? Kirshner has a real gift for visualising the shape and structure of the universe. He points out that stars are far apart but galaxies are close. If our Sun were a pea, the next star would be 100 miles away, but if our galaxy were a dinner plate, then the Andromeda nebula, its nearest major neighbour, would be just 10ft off. These authoritative analogies genuinely help to bring the cosmos to life.

Martin Ince is contributing editor, The THES , and writes regularly on astronomy.