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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You look at table, you can touch it, smell it, see it, knock on it, table is there, table will be there tomorrow unless you move it.
Now you look at table with microscope, table is gone, it is no longer there and you only see atoms.
Table does not exist for microscope, only for human.
Now replace “table” with “universe”
Locality is the principle that information and interactions cannot happen faster than the speed of light. If you turn on a flashlight, a distant observer cannot know about it before the photons from your flashlight reach their eyes.
Reality, in this context, means that phenomena can have properties independent of interaction. A red apple is always a red apple, even if its color is never measured by anyone or anything.
The 2022 Nobel Physics Prize winners showed that both of these principles cannot be true at the same time. You have to give up one or the other. Either some systems can communicate faster-than-light, or some properties are undetermined until they are measured. This on its own is nothing new; it has been theorized since the 1960s when quantum mechanics as a field of study was being developed. This prize was awarded for an experimental setup that is believed to have finally closed all possible “loopholes”, meaning that there is no alternative explanation that allows for local reality to be preserved.
An analogy- the universe is kind of like a soup. When you dip your spoon in it, you probably have a great idea of what is going to end up on your spoon, but you can’t know for sure because stuff is kind of swirling around and floating in there. People thought it was really a poke bowl where the rice and veggiea and fish are all just sitting there so if you know where to put your spoon, you know exactly what you would get on it. Scientists proved that it really is soup not poke.
So there’s two terms; local and real.
“Real” means an object exists and has definite properties when it’s not being observed. For example, if you park your car in your driveway, it’s going to stay in your driveway whether or not you are looking at it. Whatever color your car is, it will still be that color. The wheels will not change, etc.
“Local” means what it sounds like, the car is subject to things going on in its immediate vicinity. But an exploding star happening light years away is going to have no observable effect on it. Another part of being “local” is that you can’t be affected by things going faster than light.
However, when we get into the very tiny world of sub-atomic particles, locally real seems to not be a thing. In the very smallest building blocks of our universe, particles either spin up or spin down. However, they won’t “choose” whether they’re spinning up or down until someone looks at them. In other words, these particles *do not* have definite properties *unless* we’re looking at them; they’re not “real” based on the classical definition.
Now, if you have two particles that are linked or “entangled”, then one particle has to spin up and one has to spin down. Like we said previously though, they don’t “choose” one until someone looks at them. What they found was that, even if these two particles are on opposite sides of the universe, if you measure one as spinning up, the other entangled particle will instantly become “real” and spin down. This breaks Einstein’s theory of relativity, because the information between the two particles is instantaneous regardless of distance. In other words, *information* can travel faster than the speed of light. So this messes with both ideas of locality, being affected by things near you and being affected by something going faster than light.
Since these extremely tiny particles make up the entire universe, it can be said that the universe itself isn’t” locally real”, in other words, it does not have definite properties. At this macroscopic level, we live in a universe that has definite properties. Your red car will continue to be red no matter what. But the universe at the quantum level deals with probability.
One of the biggest question in physics today is how to combine these two theories, the determinate large scale universe governed by Einstein’s relativity, and the probabilistic very small scale universe ruled by quantum mechanics.
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