The Indeterminate Universe

The Indeterminate Universe

As this whirlwind overview may suggest, the new physics, quantum physics, differs from classical physics in nearly every way imaginable-from its elements and laws to the kind of knowledge it provides. It is in this last respect that the implications of the quantum revolution are most profound.

Classical physics yields precise information about the properties and behavior of individual, independent systems. It holds out to the scientist the promise that, in principle at least, he can know everything. Quantum physics says that this is just not so, that nature imposes fundamental limitations on knowledge, constraints such as the Heisenberg Uncertainty Principle.

These limitations derive from the probabilistic nature of quantum mechanics. The new physics yields only statistical information about aggregates of identical systems. It is mute about the behavior of individual systems. Moreover, the statistical information provided by quantum theory is limited to the results of measurements. That is, quantum physicists are not allowed to infer facts about a system unless these facts could be verified by experiment. This is a severe limitation-for example, it prohibits us from ascribing an orbit (a path) to a particle, because measurements of position are necessarily performed at discrete times. Even if we measure the position of a particle at two very nearby times, t1 and t2, we cannot even make the simple inference that it traveled from r(tt} to r(t2) via a path in geometric space; we can only say that we found it at r(t1) at tl and then at r(t2) at t2.

This limitation, that physics describes only observed phenomena, forces us to think about reality in a strange, new way. At its most fundamental level, reality seems to be discontinuous. Here is Erwin Schrodinger, the father of quantum mechanics, on this most non-classical feature of his theory:

it is better to regard a particle not as a permanent entity but as an instantaneous event. Sometimes these events form chains that give the illusion of permanent beings-but only in particular circumstance and only for an extremely short period of time in every single case.

In closing, I should note that alI this has not set welI with many physicists. Even today, some find the world view implied by quantum mechanics-a subjective universe, acausal and indeterminate, where the knowledge accessible to man is limited-to be intolerably offensive. And the battle over the interpretation of quantum mechanics goes on. But all agree on the usefulness of the theory for predicting and understanding the physics of matter. It is, after all, the only game in town.

The source:

Michael A. Morrison - Understanding Quantum Physics.

By. Fady Tarek