Book: The Tests of Time
Author: Eds Lisa Dolling, Arthur Giannelli, Glenn Statile
Price: Princeton University Press, ?25.95
There are people who think that science is a matter of opinion, a social construct that changes when society changes. This is not the case. As the Nobel prizewinner Steven Weinberg has pointed out, since the beginning of the 20th century, "no theory that has been generally accepted as valid by the world of physics has turned out simply to be a mistake." Science does progress, building incrementally and providing insight into deep truths about the nature of the world.
Lisa Dolling, Arthur Gianelli and Glenn Statile, teachers of the history and philosophy of science at St John's University in New York city, set out to demonstrate the truth of this idea of science by providing a series of readings in the five greatest developments in our physical understanding of the universe-the heliocentric theory, electromagnetic field theory, relativity theory, quantum theory and big bang theory. They do so with a judiciously selected set of writings from the great names associated with each of the subjects, and some setting of the ideas in context.
The aim of the St John's team is admirable, and on the whole they hit their target. Choosing the words of the scientists themselves humanises the subject, and gives the lie to the idea that scientists can't write. The level of the material chosen and the linking passages makes the book accessible to an interested non-scientist.
That said, there are deficiencies in the presentation, clearly linked to the inexperience of the editors in the world of physics, and the non-specialist reader should be warned against the more glaring infelicities. It is particularly unfortunate that they choose to highlight what they regard as uncertainties in the measurement of the age of the universe, which was pinned down as just under 14bn years at least a couple of years ago. This leaves them unable to note one of the great triumphs of physical science, provided by the match between this estimate and estimates of the ages of the oldest stars, which are (as they ought to be) a little bit less than the age of the universe. Since stellar ages are essentially based on our understanding of the quantum physics of atomic nuclei, while the age of the universe is calculated using the completely independent techniques of relativity theory, the match between the two is one of the clearest indications that the whole scientific enterprise is built on secure foundations.
Just as worryingly, given that the story involved is over 100 years old, they fail to give due emphasis to the importance of James Clerk Maxwell's influence on Albert Einstein. Maxwell's equations of the electromagnetic field define a speed of light that is the same for all observers, and Einstein always said that it was this prediction from those equations of the constancy of the speed of light that led him to his special theory of relativity.
The greatest sin in the book, though, is to encourage the widespread idea that Werner Heisenberg's famous uncertainty relation is something to do with our inability to make precise measurements using our clumsy instruments. Not so. Heisenberg's great discovery was that quantum uncertainty is intrinsic; that, for example, an entity such as an electron literally does not have both a precise position and a precise momentum. In everyday language, the electron itself cannot, as a matter of principle, "know" both where it is, and where it is going.
Compared with this, it is only a minor irritation that the editors fail to find room to discuss the "many worlds" interpretation of quantum theory (although they do find room for a short piece by Stephen Hawking, which seems to have been included simply to get his name in to the book).
But there are many other names who well merit their inclusion, not least the pioneering astrophysicist Arthur Eddington with his classic description of the expanding universe; William Gilbert (arguably the first true scientist); and a host of others familiar from eponymous laws, but not as people. I particularly enjoyed Eddington's critical comments, dating from the 1930s, on the early observations of the expanding universe which suggested (incorrectly, we now know) that our Milky Way galaxy was the largest.
I was part of a small team that eventually used data from the Hubble space telescope to confirm that our Milky Way galaxy is, as Eddington suspected, almost exactly middle-sized, as galaxies go. The pleasure, though, lay not so much in proving Eddington was right as in confirming the power of the scientific method of experiment and observation as a test of hypotheses.
Kepler's remark that his astronomical ideas were founded "not on fictive hypotheses, but upon physical causes" is widely known, but Galileo and Gilbert were among those who had to repeat and repeat the message that the way to understand the world is through testing hypotheses by experiments, not by philosophical considerations of the "ideal" form of nature. It was only by getting away from the notion of "perfect circles" and accepting the reality of elliptical orbits, for example, that the true nature of the solar system and the inverse square law of gravity could be discovered.
The message is crucially important when we get to quantum physics-the description of the world of the very small-where the rules we discover by experiment and observation fly in the face of common sense. The St John's team give a thorough airing to the most puzzling feature of the quantum world: the way in which two quantum entities (such as photons or electrons) that have once interacted with one another later (indeed, ever after) behave as if they were components of a single system even when far apart. Such entities have now been studied in experiments where the two components are separated by several kilometres before one of the "particles" is tweaked, provoking an instantaneous response in its partner: what Einstein referred to as "spooky action at a distance."
The technique is already being applied in the "teleportation" of information from one laser beam to another (so far, only across a distance of about a metre). Quantum physics is real, and has been tested by experiment. It flies in the face of common sense; but so too did the idea that the Earth is a spinning top hurtling through space.
This is a book that, in spite of its flaws, gives a sense of the broad sweep of scientific progress. And I mean progress; we do have a better understanding of the way the world works than the ancients, not just a different way of looking at it.
