Say I present my friend a box. The box contains a coin. I ask my friend whether the coin is heads or tails. Unable to see what’s inside, she answers she could only give a set of probabilities: 50% heads, 50% tails. It is only when I open the box that she finally knows for sure the state of the coin.
Physicists can generate a wave function that gives sets of probabilities regarding the position and velocity of a subatomic particle. However, upon observation, this wave function collapses to just one outcome.
I want to know why this is a frustrating problem for physicists. If they observe a subatomic particle, and they get a definite answer, isn’t that a good thing? Doesn’t that mean they figured out that electron’s position or velocity accurately? I thought that’s what probability means: the likeliness that something is at a particular place. It doesn’t mean that it will certainly be there.
I’m just puzzled about why this seems such a big deal among physicists.
In: Physics
The issue isn’t that you lack information like in your example. You change the outcome by measuring it.
Before you measure a particle it truly “hasn’t decided” wich side of the wave function it is on. We can prove that with the bell inequality wich disproves that the state existed before you measure it through statistics.
In your box example you could figure out wich position the coin is in by tracking previous information, like wich face was the coin put into the box, and did someone move the box. For quantum physics this information only starts existing when the wave function collapses.
This is weird because it only works when one of two very fundamental principles are violated. Either the world isn’t deterministic (same action doesn’t always lead to the same outcome) or the world isn’t local (information of your particle depends on other particles very far away). Both of these are basic blocks of how we originally understood the world, and now we know at least one of them must be wrong.
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