I just saw a comment that linked to an article explaining how Nobel prize winners recently discovered the universe is not locally real. My brain isn’t functioning properly today, so can someone please help me understand what this means?
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Classic physics assumes that things exist in the way that we perceive them. That is to say, if I have an apple sitting on a table, classic physics assumes that the apple has a fixed position (on the table) and a fixed speed (sitting still) and that these are absolute, 100% true values.
In reality, things only look that way because humans are gigantic compared to subatomic particles, and at human scales things do behave in a predictable manner.
On subatomic scales this isn’t true. All fundamental particles have a sort of dual existence. If you could somehow freeze time for a particle, then while it is frozen in time it will have the absolute properties that classic physics ascribes to it. IE, that particle would have a fixed position and speed.
So if you imagined the universe as a strip of movie film, where each frame was a distinct moment in time, you could theoretically capture a particle’s position and speed in each of those frames. But what about in between the frames? The answer is that in between frames, the particle ceases to exist in the way that we understand existence.
In between frames, particles exist as a probability. So imagine that frame 1 had a particle in position 0, traveling forward at a speed of 1. In frame 2, the overwhelming majority of the time, the particle will appear to have advanced by 1 and moved to position 1. However, that’s not always true.
The particle will rarely advance by 2 and move to position 2 or advance by 0 and stay in position 0. It will even sometimes move backwards by 1 and end up in position -1. This also means that particles can teleport through one another.
So for example, if our particle was at position 0 and another particle was at position 1, sometimes our position 0 particle will move to position 2 despite the fact that it *should* have been blocked by the particle at position 1.
Even if you know everything about a particle at a given point in time, that isn’t enough information to *know* where that particle came from in the past, or where it will be in the future. Particles have an element of randomness to their movement that makes them unpredictable, which is what physicists are talking about when they say that the universe isn’t locally real.
The universe appears to be locally real to us, as humans, because this randomness is affecting particles that are very, very, very small. An electron is about the same relative size to you as you are to the entire universe. Because all of this randomness is happening on such a tiny scale, it ends up cancelling itself out to give the appearance of a fixed reality.
So what does this all mean? You can know what the position and speed of an apple sitting on your desk is. But in the real world where you can’t just freeze time, it is impossible to know what the exact position and speed of any of the subatomic particles that make up the apple are because those particles don’t really have a fixed position and speed as humans typically understand those concepts.
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