Do I Misunderstand The Double Slit Experiment

[madnak]

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Maybe I am slow but I still do not understand what will happen here. I can't see an interference pattern because the observer would be able to look at the experiment a minute later and see which slit the electrons went through. (Which would be both if there is an interference pattern)

If I see a particle-type pattern, then that would seem to indicate that the light forced a wave collapse whether or not the light was observed. I was taught that this will not happen if the light is not observed.

The only other possibility I can think of is that the observation one minute in the future caused a collapse, which seems impossible.

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How are you observing the photons passing through the slit from so far away? I don't think a telescope is sufficient. Based on my understanding, you have to actively interfere with the experiment in order to observe those photons, which is the issue. If you're a light-minute away, you can't interfere with the experiment. If observation is happening then it must happen before the photons enter the slits - it might take a minute for information about the observation to reach you, but that's just "lag." If nobody is "getting their hands dirty" at the location of the experiment, I think you'll just see a wave-like interference pattern through a telescope.

[luckyme]

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What?

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erhmmmm..

We can understand how the moon effects seal mating and how humans evolved from single cells.
Now I find a light wave that seems to want to act like a particle to me at times, etc ... and NOW I'm supposed to want to call in a designer?

What would that explain? when all the spin-offs (me included) are where the complexity is.
At the quantum level, god could play dice, light does it's weirdsy stuff and everything would be as it is today.. no designer need apply.

luckyme

[Schweitzer]

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How are you observing the photons passing through the slit from so far away? I don't think a telescope is sufficient. Based on my understanding, you have to actively interfere with the experiment in order to observe those photons, which is the issue. If you're a light-minute away, you can't interfere with the experiment. If observation is happening then it must happen before the photons enter the slits - it might take a minute for information about the observation to reach you, but that's just "lag." If nobody is "getting their hands dirty" at the location of the experiment, I think you'll just see a wave-like interference pattern through a telescope.

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Ok, so I shine high frequency light upon the experiment. If I observe the light I should be able to detect the electrons as particles and determine which slit they went through. (I realize they were a wave before this and the measurement will collapse them to being in front of one of the slits)
In this system I will certainly see a particle pattern.

If, however, I shine the light on the experiment but the light is not observed, will I not see an interference pattern? And if that is the case, wouldn't someone with a powerful detector be able to detect the light from this experiment after the experiment has been finished?

[madnak]

If you shine the light, then you're observing. I'm pretty sure that whether you choose to look at the light is irrelevant - by shining the light you're causing the particle pattern because you're measuring (even if you aren't looking at those measurements).

It's not like the photons have a psychic awareness of whether you're paying attention. It's just that the amount of interaction necessary to take measurements happens to be exactly the amount of interaction necessary to affect the result. But I'll defer to someone with greater knowledge of the subject.

[ChrisV]

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You are making a terrible analogy. As I told madnak almost all unexplained events in this day and age don't strike scientists as totally mysterious. For instance if we discovered that two people could truly communicate telepathically it wouldn't be evidence for God. The double slit experiment however, if I understand it correctly, is more than just unexplained. It seems to defy logic, not just science. And it seems to invoke human consciousness.

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David,

The idea that this invokes human consciousness is as a result of the vagueness of the Copenhagen Interpretation, which fails to properly define "observer" or even "measurement. Steven Weinberg quoted on the Wikipedia page about the Copenhagen Interpretation:

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Bohr's version of quantum mechanics was deeply flawed, but not for the reason Einstein thought. The Copenhagen interpretation describes what happens when an observer makes a measurement, but the observer and the act of measurement are themselves treated classically. This is surely wrong: Physicists and their apparatus must be governed by the same quantum mechanical rules that govern everything else in the universe. But these rules are expressed in terms of a wave function (or, more precisely, a state vector) that evolves in a perfectly deterministic way. So where do the probabilistic rules of the Copenhagen interpretation come from?
Considerable progress has been made in recent years toward the resolution of the problem, which I cannot go into here. It is enough to say that neither Bohr nor Einstein had focused on the real problem with quantum mechanics. The Copenhagen rules clearly work, so they have to be accepted. But this leaves the task of explaining them by applying the deterministic equation for the evolution of the wave function, the Schrödinger equation, to observers and their apparatus.

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You should also look up the transactional interpretation, which removes the weirdness at the expense of allowing limited backwards-in-time causality (not the kind you can send messages with). Bottom line is that although the maths of quantum mechanics works, how we interpret what is happening is very much still up in the air. Schroedinger's Cat and that sort of thing is entirely a product of the Copenhagen Interpretation, which is untested (and currently untestable).

[goofball]

DS,

Nobody understands quantum mechanics.

[mrick]

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There's a disclaimer in Wikipedia.

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This article may require cleanup to meet Wikipedia's quality standards.

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OK I removed the disclaimer. You can use that article now. It's safe.