this post was submitted on 18 Oct 2023
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Double-slit (lemmy.ml)
submitted 11 months ago by [email protected] to c/[email protected]
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[–] [email protected] 13 points 10 months ago (1 children)

Can someone who understands science explain this to me (what im getting at is its a pregnancy test)

[–] [email protected] 34 points 10 months ago (2 children)

The double slit expiriment demonstrates the duality of the nature of a photon: that it's both a wave and a particle.

When a photon is "observed" (or detected) it has the properties of a particle. However when it's travelling it acts like a wave and can demonstrate interference patterns with other photons.

So when you pass photos through two tiny slits, instead of them just passing right through like a particle, they interfere with each other and when the wave pattern collapses when it is observed on the wall, you see the interference.

That being said, I don't think this cartoon makes sense. I get what they are driving at, as they are saying it acts differently when not observed, but this is not what happens. Also this isn't a ln experiment that deals with observation forcing an outcome, but as I noted it's about the duality. Additionally, the wave pattern on the top is what you would you observe when looking at, so I'm not sure why that is what it would be like if you were looking away.

But maybe I'm missing something.

[–] [email protected] 19 points 10 months ago (2 children)

The double slit experiment is about observation.

When you fire photons through the double slits, one photon at a time, they cause wave interference patterns with themselves as if each photon travelled through both slits.

Yet if you set something up to measure which slit each photon passed through, they no longer interfere with themselves, and give you the two straight lines pattern, rather than the interference pattern.

[–] [email protected] 9 points 10 months ago

When you fire photons through the double slits, one photon at a time, they cause wave interference patterns with themselves as if each photon travelled through both slits.

You're right, I forgot about this part of it.

[–] [email protected] 1 points 10 months ago* (last edited 10 months ago)

The interference pattern only appears after firing many many photons. They're still a photon (packet of energy) when creating an interference pattern. It's the distribution and probability of its location that changes. Not the physical "shape".

Edit: to clarify further

When not being detected, it's still just one dot that appears on the sheet. As more and more are fired, the interference pattern shows to show as each photon hits the screen

It's all about the distribution possibilities.

[–] [email protected] 3 points 10 months ago (1 children)

Thanks mate.

[–] [email protected] 3 points 10 months ago* (last edited 10 months ago)

The meme confuses two things in quantum mechanics. One is the double slit experiment, which confirms that light behaves both as a wave and a particle. That's what the meme is showing here.

However it's also throwing in Schrodinger's, which states that until you look at something it exists in all states - the classic theoretical example being the cat in a box, which is both alive and dead until you open the box. That doesn't make much sense in the real world, but when looking at quantum particles it is provably true.

Here is another meme that more accurately explains things: https://mander.xyz/post/5143468

Just to complete the set of "principles of quantum mechanics that people know of but don't fully understand", there's the Heisenberg Uncertainty Principle, which states that you can either know the position of something or its momentum (ie where it's going). The more accurately you measure one of these, the less accurate any measurement is of the other.

Edit: However there's also what /u/[email protected] said below:

The double slit experiment is about observation.

When you fire photons through the double slits, one photon at a time, they cause wave interference patterns with themselves as if each photon travelled through both slits.

Yet if you set something up to measure which slit each photon passed through, they no longer interfere with themselves, and give you the two straight lines pattern, rather than the interference pattern.

So maybe the meme was referring to this variation on the double slit experiment, rather than Schrodinger.