Double Slit Experiment: Exploring Probabilities & Interference

• LizardKing23
In summary, the conversation discusses different interpretations of quantum mechanics, particularly the idea of a photon taking every possible path to its destination and causing interference with itself. The concept of probabilities and how they are affected by interference is also discussed, as well the idea of a particle being in multiple places at once. The conversation concludes by mentioning the strange behaviors of particles in their sum-over-histories, including traveling faster than light and looping around in time. Overall, there is no consensus on what truly happens to particles during the time we don't observe them, and quantum theory simply predicts results of experiments without trying to explain the underlying processes.
LizardKing23
I just posted this as a reply, but i figured Id open a new thread for discussion.

correct me if I am wrong here.

according to the double slit experiment, a photon takes every possible path to it's destination, causing it to interfere with itself, right? My first question is, does each separate path have a different probability of occurring, or do they all have the same probability?
and if they do have the same probability, how would a photon know it's destination if more than one path intersects with an object? Couldnt the photon just as easily have appeared on the double slit cover rather than the photosensitive sheet? This would sort of signify that a photon knows it's destination before it get's there. otherwise, we might observe the same photon hitting more than one object, and therefore being at multiple places at one time.

am i looking at this completely wrong here?

add-on question: since only one path can be a straight line, the other paths would be larger, whch would mean the photon would take longer on those paths. "Every possible path", to me, means even the one that travels in 9 loops across the galaxy just to go three feet away. Wouldnt we observe that a photon arrives someplace more than once?

none of this makes sense to me.

Each time you think the photon has a path you are wrong. QM just says that you can get a probability to detect a particle somewhere and not the particle has a path (in the classical view).

Seratend.

There are many different mental pictures of what is happening to photons, electrons, etc. during the time when we don't see them. The many paths idea (originating with Feynman, I believe) is one of those descriptions. Nobody knows what really happens and to many physicists it just can't be described. Quantum theory predicts results of experiments extremely accurately, but it doesn't try to say what is going on otherwise.

The idea of many paths was due to Feynman. It is simply one explanation of single photon interference patterns (one which I happen to think is quite clever).

LizardKing23 said:
according to the double slit experiment, a photon takes every possible path to it's destination, causing it to interfere with itself, right? My first question is, does each separate path have a different probability of occurring, or do they all have the same probability?

They are all treated as being of equal importance but because of interference between the paths, all the numbers which could have been the probabilities of individual paths don't add together to equal one and so they are not probabilities, they are just numbers for the paths.

and if they do have the same probability, how would a photon know it's destination if more than one path intersects with an object? Couldnt the photon just as easily have appeared on the double slit cover rather than the photosensitive sheet? This would sort of signify that a photon knows it's destination before it get's there. otherwise, we might observe the same photon hitting more than one object, and therefore being at multiple places at one time.

It seems the modern way of looking at it is that ever possible history interferes with every other possible history to influence the final event we detect or see, so the histories in which the particle went through a single slit, bounced off the double slit cover, never made it out of the emittor, looped-the-loop for no reason, etc. all still have an influence on the final event even if the final event would appear to be quite different from almost all of the histories which influenced it.

add-on question: since only one path can be a straight line, the other paths would be larger, whch would mean the photon would take longer on those paths. "Every possible path", to me, means even the one that travels in 9 loops across the galaxy just to go three feet away. Wouldnt we observe that a photon arrives someplace more than once?

A particle can have paths in its sum-over-histories in which it travels faster than light, slower than light, backwards in time, in strange zig-zags across space and even loop around and around in time! It seems strange that a "particle of light" like the photon has countless possible paths in which it actually travels faster and slower than the "speed of light" but it does. The looping in time is a way to interpret the Casimir effect, so a particle actually can have its own detectable Groundhog Day.

1. What is the double slit experiment?

The double slit experiment is a classic physics experiment that demonstrates the wave-particle duality of light and other particles. It involves shining a light or particle beam through two narrow slits and observing the pattern formed on a screen behind the slits.

2. How does the double slit experiment demonstrate probabilities?

The double slit experiment demonstrates probabilities by showing that the pattern formed on the screen is not a single line, but rather a series of alternating bright and dark bands. This is because the particles of light or matter can behave like waves, and the probability of where they will land on the screen follows a wave-like pattern.

3. What is the role of interference in the double slit experiment?

Interference is a key aspect of the double slit experiment. It occurs when waves from the two slits overlap and either reinforce each other (constructive interference) or cancel each other out (destructive interference), resulting in the observed pattern on the screen.

4. Can the double slit experiment be done with other types of particles besides light?

Yes, the double slit experiment has been successfully done with electrons, protons, and even large molecules like buckyballs. It can be done with any type of particle that exhibits wave-like behavior.

5. What implications does the double slit experiment have for our understanding of the universe?

The double slit experiment challenges our traditional understanding of the universe as being made up of solid, discrete particles. It suggests that at the quantum level, particles can behave like waves and have probabilistic outcomes. This has led to further research and theories about the nature of reality and the interconnectedness of all things.

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