The Dancing Universe: From Creation Myths to the Big Bang

7 | Of Things Fast

❍ 7 OF THINGS FAST The most beautiful experience we can have is the mysterious. —Albert Einstein earning modern physics can be an emotional experience. As students are first introduced to the ideas of relativity and quantum mechanics, initial perplexity is almost invariably followed by peevish disbelief. There is something outrageous about these theories , which seem to contradict our common sense. Among other things, the new physics tells us that a moving object contracts in the direction of its motion. A moving clock runs slower than a stationary one. Mass and energy may be interchangeable. The basic constituents of matter have the characteristics of both particles and waves, the socalled “wave-particle duality.” The act of observing a physical system influences its behavior. The presence of matter can bend the geometry of space and alter the flow of time. We can’t even say with certainty if something is here or there—only express the probability that it is here or there. That is, we must abandon a strictly deterministic description of natural phenomena, at least at the scales of molecules and atoms, and rely on probabilities. And there is more. Much more. Common sense does not accord with these strange phenomena, and that’s unfortunate, since we tend to rely on our common sense in the world around us. Webster’s Dictionary defines common sense as “the unreflective opinions of ordinary people,” or “sound and L prudent but often unsophisticated judgment.” Alternatively, we could say that common sense results from repetitive contact with certain situations, be they emotional or physical. Classical physics, to a large extent, deals with situations that are well within our direct sensorial experience. Even though certain basic results from classical physics, such as Galileo’s observations of free fall and the law of inertia (Newton’s first law), are somewhat counterintuitive (after all, even Aristotle was fooled), they deal with tangible situations; with some thought, it is not hard to realize that they make sense. Not so with modern physics. Relativistic or quantum phenomena appear at first bizarre because they are far removed from our immediate sensorial reality; they are not part of the phenomena to which we can apply our “common sense.” Indeed, the shrinking of moving objects or the slowing of time is manifest only at speeds close to the speed of light. The wave-particle duality of matter is relevant only for objects at the atomic scale. The effects of ordinary matter on the geometry of space and the flow of time are negligible for objects less massive than stars. Since we ordinarily deal with slow (compared to the speed of light), large (compared to an atom), and light (compared to a star) objects, our perception of the physical world is quite limited. Modern physics makes it clear that we should not have our expectations projected onto a realm that is alien to our everyday experiences. As Einstein has said: “Common sense is the set of all prejudices acquired by the age of eighteen.” Once we look at relativistic and quantum phenomena with an open mind, what seemed nonsensical becomes fascinating. Of course, it is easy for me to say this now, comfortably typing away on my computer, long after the dramatic discoveries of the first three decades of this century have been digested by several generations of physicists. But to the actual players in this drama, those thirty years were full of angst and despair. On several occasions, physicists were forced to put forward ideas or accept experimental results with which they felt very uncomfortable. Thus, Max Planck, the first man to propose that energy is emitted in discrete amounts (quanta), wrote of his discovery in an unpublished letter: Briefly put, I can describe the whole effort as an act of desperation, for by nature I am peaceful and against dubious adventures. But I 192 MODERN TIMES had been fighting already for six years, from 1894 on, with the problem of equilibrium between radiation and matter without having any success; I knew that this problem is of fundamental significance for physics . . . a theoretical explanation, therefore, had to be found at all cost, whatever the price. Classical physics was not sufficient , that was clear to me. . . . No matter what the circumstances, may it cost what it will, I had to bring about a positive result. [My italics] In other words, Planck’s quantum hypothesis was...