I think I have a decent grasp on the dual-slit experiment, but I don’t know how the waveforms know when to collapse into a particle. Also, what counts as an observation and what doesn’t?
In: 8
That’s one of the fundamental questions of quantum mechanics. To keep it simple, we don’t know. There’s different hypothesis and interpretations about »wave function collapse«. That’s the phrase for the thing you’re describing.
You’re probably familiar with the Many Worlds interpretation where the collapse simply doesn’t happen and instead, both slits are passed in different realities that can’t influence each other anymore.
Another hypothesis is pilot wave theory. For the latter, I can’t really break this down in simple terms.
In any case, I would highly recommend checking out the YouTube channel »PBS Space Time«. Their most recent video is exactly on this topic. And they did many more on that subject, even on bleeding edge research papers. Again, highly recommend them and sorry for the next few hours taken away from you by recommending them 😀
“Observation” in this case is a less fancy way of saying “Perturbation” which is a necessary step in observation.
If you want to see something with your eyes, what’s required for that to happen? Well you need to bombard the target with light in the visible spectrum, that’s perturbation of the system you’re observing.
If you want to know where anything is you need to perturb it in some way, even if it isn’t visible light, you need to interact with it in some way. That act of interaction changes the system being observed.
Note that this is not the same as what’s described by the Uncertainty Principle, that is a fundamental behavior of quantum systems even when they’re isolated.
basically an ‘observation’ somehow interacts with the system, and this interaction causes the collapse
there are 5 interpretations (basically disagreements on what counts as an ‘observation’ and how the ‘observation’ causes the collapse) – it goes a little beyond ELI5 for the explanation though
basically we know that observing a system requires interaction and that this results in a waveform collapse, but there is disagreement (Many-worlds theory) about if the collapse actually happens
They don’t care if you look at them. That’s just PopSci mumbo jumbo.
The double slit experiment is about **measuring** and the fact that you can’t measure tiny tiny particles without affecting them.
Think about it like this. You are blind and want to check if there’s a ball on the table in front of you. You can reach out your hand to touch it, but no matter how slightly you touch it you will always slightly move it. That’s what’s happening in this experiment.
There’s just no way to measure which slit a particle went through without interacting with it, and this interaction will cause a different result.
Think of particles not as actual ‘things’ that exist but a 3d field in which the energy can potentially manifest itself anywhere in that field. For our mathematical models, and for our logical understanding, the energy exists at all points in that field at once. But it doesn’t really ‘exist’ or ‘manifest’ itself until it interacts with something. At that point, the energy is where it’s at, not any of it’s potential places – hence the potential places (waveform) collapses.
we dont exactly know. one mechanism we’ve come up with is decoherence which is the idea that when the superposition interacts with the first layer of particles in the detector, all of their wave functions become entangles with the wave function of particle. Those all then get entangled with the particles of the next layer and so on and so forth until eventualy the signal is displayed on your computer screen. This is called a von neumann chain. When particles become entangled their wavefunctions are combined together. Each of those components adds a random vector component causing the total wavefunction to be perturbed. All of the vector components cancel out the superposition leaving only one possibility remaining.
Imagine you wanted to work out the speed of a car and the only way you could do it was by throwing a basket ball at it and measuring where the basketball bounced to after impact.
This is fine for cars because basketballs are comparatively light and so don’t affect the car at all.
However if you wanted to measure the speed of a ping pong ball after Co tact the ping pong ball is going to be going at a new speed and direction because of the impact of the basketball
You must interact with the particle to observe it. That changes it somehow, it introduces a slight amount of energy or whatever. That collapses the wavefunction. “Observation” isn’t the best term, it’s how you make the observation that collapses it. “unobserved” means nothing has interacted with the particle.
It’s worth mentioning that the Copenhagen interpretation, which is the one that talks about this collapse business, isn’t really taken seriously by anyone in this field.
How can you say you have a decent grasp of the concept while also thinking particles “know” they’re being observed?
Latest Answers