When Theories Collide
Big Bang: The Origin of the Universe
by Simon Singh
Fourth Estate; 544 pp. $27.95
I had better declare an interest right away. Simon Singh is the British author of the 1997 book Fermat's Last Theorem, after the publication of which the phrase "math best-seller" was no longer an oxymoron. He thus opened up for lesser drudges the opportunity to actually make some money by writing popular books about mathematics, an opportunity I myself have seized upon gratefully. In spite of some minor issues I have with the Fermat book, I am therefore well-disposed towards Singh, and picked up his latest production determined to give it the benefit of any possible doubt.
In the event, I don't think there is much doubt. Big Bang is a thoroughly excellent popular history of scientific cosmology, most of it dealing with the 20th century, which is when most of the important developments in this field occurred. It is written in a plain narrative style, with a minimum of difficult math, and two neat pages of summary notes at the end of each of the five main chapters. There are lively character sketches of the principal players, and some amusing anecdotes; but the author's main aim is to tell us how we reached the present state of fair consensus (there is rarely a total consensus on large scientific theories) about the structure and history of the universe at large.
As well as the particular story he has to tell, Singh gives some fine, illuminating descriptions of what happens when theories collide. Three times in the history of this topic it has been the case that two competing theories, each of roughly equal plausibility, have contended for supremacy. In showing how, in each case, the better theory won, Singh gives the general reader a valuable lesson in the progress of scientific inquiry, in the nature of scientific method and the means by which controversies in science are resolved. A great deal of nonsense is talked and written about this, particularly by anti-evolution cranks. Singh's account shows plainly that the generality of scientists are neither passionless Mister Spocks, weighing evidence with cold, flawless objectivity, nor grim upholders of a pseudo-religious dogma determined to defend crumbling theories in the last ditch. They are human beings, equipped with the usual proportions of weaknesses and prejudices, reluctant to let go of the convictions of a lifetime, but usually willing to do so when faced with convincing evidence.
The three sets of colliding theory-pairs were:
- Our Solar System — geocentric or heliocentric? (Earliest times to ca. a.d. 1700.)
- The nebulae — inside or outside our galaxy? (Ca. 1800 to 1924.)
- Cosmic history — static or dynamic? (1949 to 1992.)
In each case there were strong arguments on both sides. Indeed, in each case there were periods when the theory that ultimately proved better was in a weaker evidentiary position.
The case of the nebulae illustrates the point. By the middle 19th century astronomers knew that all the stars we can see belonged to a single vast disk some tens of thousands of trillions of miles thick and about ten times that in diameter. But what were these faint smudges of light that could be seen everywhere? Were they inside the disk, or outside it? There was good evidence on both sides. The U.S. National Academy of Sciences hosted a great debate on the topic in 1920 between Harlow Shapley, for the "insiders," and Heber Curtis, for the "outsiders." Shapley got slightly the better of the argument. Then, just three years later, Edwin Hubble published his results on Cepheid variables, proving that the nebulae are extra-galactic. When Hubble told Shapley of his findings in a preliminary note, Shapley said: "Here is the letter that has destroyed my universe."
The resolution of the cosmic history issue was tougher sledding, partly because of the extreme difficulty of gathering decisive evidence, partly because of the strong personalities involved. Was the large-scale structure of the universe the same in the remote past as it is today? Will it be the same in the remote future? Or is the whole shebang evolving from one state to another? Albert Einstein, whose opinion carried a very great deal of weight, preferred a static universe, on conventional and esthetic grounds, and against his own mathematical instincts. (Expressed in the equations of General Relativity, a static universe is actually less mathematically elegant than a dynamic one.)
Among those on the other side of the argument was Fr. Georges Lemaître, a Roman Catholic priest from Belgium — the only man of the cloth to make major contributions to cosmology in modern times. "Your calculations are correct, but your physics is abominable," said Einstein to Lemaître at the 1927 Solvay conference. Einstein was wrong, and had to eat crow at last — and did so six years later, with the gentlemanly humility of a true scientist, saying of Lemaître's expanding-universe theory: "This is the most beautiful and satisfactory explanation of creation to which I have ever listened." So much for last-ditch dogmatism on evidentiary matters among the great men of science. Or among great men of religion, for that matter, of whom Lemaître must surely be accounted one:
Lemaître kept his physics and his religion separate, declaring that his religious beliefs certainly did not motivate his cosmology. "Hundreds of professional and amateur scientists actually believe the Bible pretends to teach science," he said. "This is a good deal like assuming there must be authentic religious dogma in the binomial theorem."
An exception to this general rule showed up after WW2 in the person of Fred Hoyle, a flamboyant and eccentric British cosmologist who, with Thomas Gold and Hermann Bondi, launched the Steady State theory of cosmic history on an unsuspecting world in 1949. Steady State was an ingenious explanation for the recession of the galaxies (an observational fact already beyond dispute) by postulating the continuous creation of matter ex nihilo at a constant rate everywhere, this matter clumping into new galaxies to keep the overall appearance of the universe constant across time.
It was a very attractive theory, conforming to the few observational facts then available. A poll of 33 astronomers in 1959 showed 11 for the Big Bang, 8 for Steady State, and 14 undecided. As observations were refined across the following decades, it became clear that Big Bang was the better theory. Hoyle, however, went to his grave (in 2001) clinging to a modified version of Steady State. Paradoxically, his most lasting impression on cosmology was his coining of the phrase "Big Bang" in a 1950 radio broadcast.
There are many more good stories in this book, which I recommend without reservation to any lay person wishing to acquaint himself with the history of cosmology, or for that matter with the history of creation. There are puzzles still to be solved and gaps yet to be filled, but the version of Big Bang currently dominant is a very good theory indeed. There is much we still do not know; but it is a testament to the power of the human intellect, and to the unquenchable curiosity of the rational mind, that we know as much as we do about this most astounding of all subjects: the structure, history, and future prospects of the universe at large.