Ultimately Untestable?

Contemporary physics is facing a problem—some physicists would even describe it as a crisis. And as is true for most crises, controversy erupts. Factions appear and engage in debate. Emotions bubble up. Yes, even staid physicists can become emotional, and a few of them even become impassioned.

The cause of this particular crisis is the shortcomings of what has come to be known as the “standard model” of physics. It describes the fundamental behavior of matter—which is essentially the core of physics. But the standard model, although it has been very successful in describing most of the behavior of aggregate matter, does not explain the behavior of elementary particles. The model does very well at the macro level, but is quite useless at the micro level.

Beginning about 100 years ago, a few physicists developed a new micro-matter theory that's come to be called quantum mechanics. It does a very nice job of describing the behavior of subatomic particles—such as electrons, protons, and neutrons. The problem—the crisis—lies in physicists being unable to reconcile the two theories.

What's worse, while the standard model has been verified by countless experiments, that's not true for several aspects of quantum theory. While many predictions of quantum mechanics have been verified by tests, there are some aspects of the theory that seem to be beyond experimental investigation. And that really bothers some physicists. The time-tested scientific principle is that scientific theories must be proven by experiment. So what do you do, when you can't put your theory to the test?

A rough parallel is the theory that was put forth by the Ptolemaic model for the universe—the nearly 2,000-year-old idea that placed the Earth at the center of the universe. Ptolemy's model was very cumbersome and complex, but it explained various phenomena for centuries. It was finally replaced by the far simpler Copernican (sun-centered) model in the 17^th century by Kepler, but his model's proof had to wait until science had the tools to do the experiment and irrefutably demonstrate that the new model was correct. The crucial tool that did the job: the telescope.

Quantum physics today is in a rather similar place. It could be that we may someday have the tools to run the experiments and confirm the correct theory (or correct theories). Yet some physicists are convinced we may never be able to do the experiments. If so, do we abandon the venerable rule that all theories must be testable, or just abandon those theories that can't be tested? The debate continues. Emotions are roiling.

Primordial Beach Ball

A trillionth of a trillionth of a trillionth of a second after the Big Bang that initiated our universe, all of the cosmos was about the size of a beach ball. (That fraction of a second is something like 10^-36 second after Time Zero, for those who grasp scientific notation.) What happened before that unimagineably tiny fragment in time, physicists are baffled about; but after that point in time, they have a pretty good handle on the universe’s subsequent expansion and behavior. The so-called “standard model” of cosmology does a fine job of describing that succeeding behavior.

It’s virtually impossible for us normal folks to wrap our heads around how all of the universe’s hundreds of billions of galaxies—each of which contains hundreds of billions of stars—could once have been squeezed into something like a beach ball. If nothing else, this fact is a testimony as to how empty matter really is: every atom is almost wholly empty space containing an infinitesimal amount of matter, in the form of ephemeral protons and electrons. So once upon a time (10^-36 second after the Big Bang, that is) all those countless atoms found themselves confined to the primordial Beach Ball.

At that moment, the inside of the beach ball was, in fact, more like a mush of elementary particles, than a sea of individual atoms. It was so opaque and dense that light could not escape, which is why astrophysicists are not sure what happened up to that point, since whatever transpired, did so in utter darkness. The subsequent expansion of the beach ball sort of happened after the divine command, “Let there be light,” was uttered.

The nature of the universe at this early moment is the subject of intensive ongoing research. Many PhD theses get spawned by these studies. It may soon be known how the primordial Beach Ball became inflated from an earlier baseball—or maybe even a golf ball, or...