All cultures and all civilisations known to us have a few things in common. For instance, all of them have tried to answer the question of how large the Universe is, what it is made of, how old it is and how (or if) it will end. In short, every culture and civilisation has its own cosmology. And a concern that is central to mythology, philosophy, astrology and indeed modern cosmology is the question about the extent of the Universe in space as well as time. Is the Universe finite or infinite? Is it eternal, or temporally finite?
David Weintraub's book is an exploration of the attempts by humans since Aristotle (who incidentally believed the Universe to be eternal) to answer this question, although he restricts himself to Christian theology and Western science.
The challenge to Aristotle's hegemony in Western science came with the publication in 1543 of the Polish astronomer Nicolaus Copernicus' revolutionary book, De Revolutionibus Orbium Coelestium, in which he proposed the heliocentric theory. Subsequently, the work of Johannes Kepler, Isaac Newton and Galileo set the stage for asking the question about the age of the Universe (implicitly thus acknowledging that it may not be eternal, but would have a beginning and an end).
Christian theology, of course, had a ready answer: the world (in other words, the Universe) was created five days before God created Adam. And depending on your interpretation of the scriptures, this turned out to be around 4,000BC. However, the growth of palaeontology in the early 19th century made it clear to all but the most doctrinaire that the Earth must be much older.
And thus started the process of estimating the age of the Universe, as Weintraub recounts. The Earth was found to be at least 4 billion years old by using the methods of radiometric dating of rocks. Of course the Earth has to be younger than the Universe it is a part of, and hence the Universe must be at least as old. Then meteorites were discovered and their age estimated to be somewhat greater than 4.5 billion years, which is essentially how old the solar system (including the Sun) is thought to be.
Weintraub goes on to describe how astronomers continued to find older and older objects in the Universe as their instruments were able to probe further into space. His account is an interesting mix of the history of astronomy (mostly in the 20th century) and the science. From white dwarfs to globular clusters, from supernovae to dark matter and energy, the book covers essentially all the attempts made by astronomers to answer the question in its title.
Weintraub's ambition to cover everything is both the strength and weakness of the book. It is a wonderfully comprehensive survey, and it is to the author's credit that he does not trivialise complicated science. Instead, he tries to simplify it with analogies and simple, non-mathematical explanations - presumably taking seriously Stephen Hawking's wry comment that every equation in a popular science book halves its sales.
However, this ambitious scope is also the book's shortcoming - the conceptual and experimental toolkit used by astronomers is so vast that to explain it all without being superficial is a tall order. And here the book disappoints: just as one thinks one is getting to the crux of something, Weintraub shifts gears to the next development.
Cosmologists can now confidently assert that the Universe is 13.7 billion years old, give or take a few hundred million years. Although this is much longer than the Biblical 6,000 years, the present scientific estimate of the age of the Universe is not even an instant compared with some timelines proposed in non-Western cultures. Modern cosmologists are still not confident whether the Universe will be destroyed in the future, but the Hindu scriptures are unequivocal - the Universe (creation) will end in 155 trillion years' time. A truly longue durée if ever there were one!
How Old is the Universe?
By David A. Weintraub
Princeton University Press
Published 5 January 2011