Michael Drieschner Abstract

Present and Future in Quantum Mechanics

We are used to thinking of time as something that „flows“ or „goes“. But if that were true, flowing or going would have to happen in time. Apparently something is wrong with that idea. Its basis might be the “classical” picture of time as a real parameter t one could imagine as the position of the hand of a clock. This could support the idea of time being something that is there like a coordinate of space. We are used to this image from Special Relativity; but it is misleading! Aristotle already states that time actually is not. Because the past is not any more, the future is not yet, and the present (now) is nothing but the separation between past and future; thus neither of those modes of time is. Augustine, in his famous essay on time in confessiones XI, suggests to treat instead the presence of the future and the presence of the past: The past is present in my memory, the future in my expectations, hopes, and fears.

Considerations like these seem rather subjective in view of the classical “ontology” of physics. That ontology is beautifully represented in Laplace’s image of the superhuman intelligence who knows all about the present state of the world and sees, by this knowledge, past and future before him in one view of the world at all times at once. According to that view, our impression of the time modes can only be a subjective feeling.

This image of time fails already in classical thermodynamics. As soon as probability comes in, we have to take into consideration the modes of time. We attempt in vain to understand probability or thermodynamics without considering the fact that they regard the future.

This is true all the more for quantum mechanics since probability lies at its foundation. In classical thermodynamics we could still imagine that probability serves only to deal with our lack of knowledge; “in reality” all states of the world are there “objectively”. In quantum mechanics that is no way out: quantum mechanics is fundamentally indeterminist (pace David Bohm: This is a story of its own!). Thus it fundamentally relies on the difference between past, present, and future.

But how can time be something "objective"? What is the role of "timeless" concepts? of eternal truth? of logic, mathematics? - The solution to all those questions is the fact that time is actually more fundamental than concepts, logic, or objectivity. Thus it is philosophically indispensible to deal with the structure of time. This is also the key to understanding quantum mechanics.