# Uncertainty principle vs destiny

I have always had a problem with the concept of "you can't know" and because of that I have always had a problem with the uncertainty principle. Because people much smarter than me have fought this issue longer than I have been alive, and I because am not really qualified to have an opinion I have a related question instead.

If the uncertainty principal is wrong and everything can be known since the big bang, doesn't that result in everything being predetermined. Is they a way to avoid this disturbing consequence without resorting to religion? Does physics give me an out, or am I left with two possibilities that I can't accept?

DaveC426913
Gold Member
Yes, you are left with two possibilities you can't accept.

Pre-QM, the universe was considered deterministic (look up Deterministic Universe).

I don't necessarily "believe" in the Heisenberg Uncertainty Principle.
When trying to measure the observables of a system with electromagnetic radiation, the radiation affects the particles in such a way as to limit our knowledge of the particle's position and momentum. However, from what I understand, the particle still existed in a definite position in space with a definite velocity at a given moment of time.

Even if particles can act as waves, and waves "cannot have a definite position", I believe (or at least really hope, for my sanity's safety) that the universe's state in one point in time is definite. We just can't measure it through spectroscopy.

I always assumed the Heisenberg Uncertainty Principle prevented the universe from being Deterministic, but, it that even true?

I just found the thread "Is everything deterministic" which covers this

DaveC426913
Gold Member
I don't necessarily "believe" in the Heisenberg Uncertainty Principle.
When trying to measure the observables of a system with electromagnetic radiation, the radiation affects the particles in such a way as to limit our knowledge of the particle's position and momentum. However, from what I understand, the particle still existed in a definite position in space with a definite velocity at a given moment of time.
No. As with you, proponents of this belief think that HUP is a limitation in measurement That we could, in principle, get better measuring devices, and in doing so, confine a system's uncertainty to an ever smaller volume/momentum.

This is not true. It is a phenomenon that holds independent of our measurement of the system.

Shouldn't this be in philosophy?

QM, IMHO, saves us from the depressing idea of superdeterminism. Regardless what interpretation you prefer, they all share the axiom that we cannot in principle know the outcome of quantum events. The future truly is unknown.

The HUP is a fundamental limitation on our ability to predict. It cannot in principle be gotten around. Imagine yourself in a computer simulation. You can see individual pixels but you will never be able to see anything smaller than a pixel because that is the basic building block of the system. Within the rules of the simulation, you can't see deeper than the simulation will allow.

Our simulation is quantized to Planck's constant, more or less. The "pixels" wander around but we can't look at them too close or else they get away.

"The more you tighten your grip, Tarkin, the more star systems will slip through your fingers."

It seems to me that this is only philosophy if we don't and can't ever know the answer. If the universe is deterministic or not seems like a fundamental property of nature that in principle should be knowable. We will never be able to predict the future (to complex) either way, but we should be able to know if it is predictable.

This is not like "what is consciousness" where we can't even define the terms of the question. This is a simple well defines question that just happens to be hard.

PS. I watched a BBC documentary about the discovery of the atom. These same arguments (this is philosophy not physics) were used to discredit Boltzmann, until Einstein proved him right. For me at least this is the question in physics that I would most like answered. I would think there must be someone working on it.

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