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Is the universe deterministic or probabilistic?

In: Physics

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It’s both.

The Universe is deterministic, albeit it’s not commonly possible to measure the necessary parameters.

The Universe is probabilistic, in that it’s quantum and these quantum measurements reflect probabilistic formulae.

That is a big debate. We do not actually know. However it looks like it is probabilistic given our understanding of quantum physics. On the other hand we once thought that the movement of the planets were probabilistic. So it could be that our understanding of quantum physics is wrong and that it is actually possible to determine the exact outcome of each experiment.

It sure seems to be probabilistic, but there’s really no good way to know for sure: how do you tell the difference between a random event, and a random-looking event whose outcome was determined at some kind of cosmic scale?

For all practical purposes though, it’s essentially probabilistic.

weird answers. It cannot be deterministic at least for any definition of deterministic I’ve ever encountered.

Quantum Physics is probabilistic and any interaction changes the outcome. So no “rebuilding” or “simulating” will ever work to the extent that a “deterministic” definition requires.

However for most everyday uses the probabilities are so close to 1, that you wont generally notice any difference.

It is deterministic.

The idea that the universe is probabilistic is based on the standard model of quantum physics. But quantum physics can be explained as deterministic by the pilot wave model.

Oh it’s most certainly probabilistic. Heisenberg’s uncertainty principle, the butterfly effect, and chaotic systems practically mandate that.

Down at the smallest level of things, things behave as either a particle or a wave. When they interact with other things, they act like a particle. Definite, measurable, and real. When they’re not interacting with other things (ignoring gravity), then they act like a probabilistic wave-form. They exist everywhere they COULD exist. And weirder still, they’ll interfere with their own wave. The [dual-slit experiment is trippy](https://en.wikipedia.org/wiki/Double-slit_experiment). It shows us that a single photon aimed two slits will have a waveform that interferes with itself in determining where it’ll land on the other side. This can be replicated with electrons, atoms, molecules, big beefy molecules, and there’s no reason to believe it doesn’t scale up. It’s just harder to isolate big stuff. It’s poetic and flowery, but our interactions are what make us real.

If the smallest stuff is inherently probabilistic then any chaotic system like a dice tumbling about where tiny changes can have big macro-sized differences is also inherently probabilistic. So are things like… every atom of the sun decaying overnight. But I’ll bet you sun still rises because the odds are beyond astronomical.

We don’t know, and may never know.

It *seems* to be probabilistic at a subatomic level, but there’s no way to tell if probabilistic results are fundamental or just caused by an underlying deterministic function that you’re unable to observe.