Science: Fundamental Mysteries

The more the physicists learn, the less they are sure of. Last week a glittering tribe of top-rank physicists met at Princeton as part of the University’s bicentennial celebration. Conference high points: addresses by Nobel Prizewinners Paul A. M. Dirac, of Britain, and Denmark’s Niels Bohr, both of whom stressed the scientist’s extraordinary difficulty in describing the simplest things.

Dr. Dirac is the genius who sensed the existence of the positron (positive electron) by figuring how a “hole” would behave if one should appear in a field of (negative) electrons. The hole, he decided, would act like a positive electron. Though no such particle had ever been found, colleagues began to look. Sure enough, they found the holes, as tangible as anything in basic physics, and named them “positrons.”

At Princeton, 15 years later, Dr. Dirac, who had forecast a particle, theorized about what happens when one particle strikes another. He selected the two simplest: the electron and the photon (unit of electromagnetic radiation, such as light). To explain how they interact, he ploughed through relativistic bafflements, covered a blackboard with lacy mathematics. Many listeners looked as if they had been hit on the head. Dirac himself seemed unsure.

Niels Bohr, too, was unsure. Bohr’s model of the atom (nucleus and orbit electrons) won him a Nobel Prize in 1922. He escaped from Nazi-ruled Copenhagen in 1943, and brought his precious knowledge to U.S. atom-bomb builders, with whom he worked in thin incognito as “Mr. Nicholas Baker.”

In a Danish accent, Bohr spoke last week on “The Observation Problem in Atomic Physics.” It is, it seems, a tough one for the meticulous physicist. If you know where an electron is, you cannot measure its velocity; if you know its velocity, you cannot know where it is. There is also the difficulty of stopping time in its tracks while making an observation. It should be done, but it’s impossible.

But not at all unsure were the physicists who described at Princeton the gigantic and complex machines which are being designed and built as tools for atomic research. Nobelman Ernest 0. Lawrence, developer of the cyclotron, was sure that this and other “accelerators” would soon yield flying particles with energies up to one billion volts. (Present top: 100,000,000.) What the particles themselves are and how they behave, neither Lawrence nor anyone else could describe with certainty.