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nisse's avatar

How did you react to the laser double-slit experiment?

Asked by nisse (1986points) June 21st, 2010

For those who don’t know, the double slit experiment demonstrates the wave/particle properties of light.

Here is an easy primer on it on youtube (a bit childish, but really clear):

Here’s a longer but more precise intro:

I just read a book that made a good argument that this could not be explained well, without accepting that the photon exists in multiple universes simultaneously, according to the author proving that we are living in a multiverse.

Apart from being an awesome experiment, showing that there are lots of things in nature which are still unknown, that the easiest and most sensible explanation includes “proof” that multiple universes really exist really blew my mind.

What’s your take on the double-slit experiment? How do you interpret the results? Can it be (sensibly and logically) understood without multiple universes? Did the experiment change your view of the scientific reality?

Oh and spare me religious answers and double entendres ;)

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20 Answers

Coloma's avatar

I think anything is possible, and a whole lot that’s not even probable as well.

We are such a puny little species of vastly limited intelligence. lol

Cruiser's avatar

I only dabble in Quantum Physics only because I lack the foundation to truly appreciate the beauty of it all. The double slit though was special in how it shattered many of the absolutes in Physics up to that point in time. Plus it helps me better accept the notions of multiverses and many of the newer discoveries being debated these days.

Zyx's avatar

I suspect quantum mechanics will be disproven and everyone will feel silly.
How do they observe the light? I have not seen proof of anything.

SmashTheState's avatar

Ah Zyx, you poor naive materialists are still clinging desperately to physical matter 150 years after it became completely debunked. The two slit experiment makes me very content. I love to throw it in the laps of naive materialists and watch them sputter and pop their monocles with 19th century dudgeon at the Universe pooping on their quaint religious faith in physical matter.

PhiNotPi's avatar

I believe the theory that photons act as a wave untill a collision forces the photon to act as a particle. The photon acts like a wave, goes throught both slits, and interferes with itself. When the wave hits the screen, it has to choose a point on the screen for the particle to hit, based on on a probability distrubution (interference pattern).
Another veiw of the same theory- The photon goes through one slit, while a ghost copy goes to the other. These two interfere with each other and produce interferance.
Check out the elitzur-vaidman (spelled right?) bomb tester, it is weird.

ETpro's avatar

The experiment itself is fascinating. Claiming it proves the multiverse is a stretch, though. See this.

BarefootChris's avatar

Just another drop in the bucket of amazing experiments that make you realize how little we truly understand about our world. For all the observations we’ve made using our human senses, there’s an antithetical phenomenon that occurs unseen by the human eye.

Reminds how beautiful that mystery is, huh?

gorillapaws's avatar

The universe is a strange place indeed. Who needs ghosts, loch-ness monsters and homeopathy when we have real mysteries like these to solve?

gorillapaws's avatar

Out of curiosity, what happens when the experimenters try to “fake out the particle” (by setting up the observation equipment but either not turning it on, or turning it on, but not actually recording the data, etc.)? To put it another way, how “omniscient” are electrons?

ETpro's avatar

@gorillapaws Cute comment. The problem is you really can’t fake out a subatomic particle. You can set up the measurement apparatus and not make a measurement, or not record the measurement you make. But in that case, you don’t know what happened, so it helps not at all.

In short, subatomic omniscience rules!

HungryGuy's avatar

I followed the lecture up to the point where he says he “observes” the electron. But how, exactly, does he observe a single electron without disturbing it?

mattbrowne's avatar

The multiverse hypothesis is more appealing than the Copenhagen interpretation. But I actually think physicists will come up with a completely new explanation within the next 50 years. Something no one is expecting today. And it will lead to a unified quantum gravity theory.

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ETpro's avatar

@mattbrowne The grand unification theory… I’ sure it is out there… I’m sure we will eventually figure out what it is… I’m sure I’ll be thrilled to know what it is… I’m just not sure what you can do with the knowledge. :-)

Elm1969's avatar

My take on this is a little unusual. Try and imagine standing on a bridge over a motorway / highway with hundreds of cars zooming along they seem to be like one big flowing snake . You observe traffic, just lots of it. However if you concentrate on recording only the red cars for example, you will no longer be looking at the majority of traffic, any car other than the red ones will just pass by with little interest and you will only record how many red cars pass.

Is this similar to the observation effect that they talk about in the double slit experiment

ETpro's avatar

@Elm1969 I’m glad you asked about the double slit experiment. Here are three successive steps into the rabbit hole. The first is the cartoon Dr. Quantum link from the OP. The other two build on that to really illustrate how mind boggling reality is.

Welcome to the rabbit hole. Go as deep as you dare.!

Elm1969's avatar

@ETpro great clips. The third one puzzled me with regards to the particles super position.
If particles are in super position what are the odds of anyone seeing the same things at the same time? Yet we do. Mind blowing

ETpro's avatar

@Elm1969 That’s a very interesting question. The mere act of knowing a particle’s position collapses its superposition, and we observe it to be in a particular position even though my mind is screaming that, given superposition and quantum entanglement, position doesn’t even really exist and we are all still in the original singularity. Maybe the Big Bang and resulting spacetime is the illusion and quantum effects the reality.

But looking at your question from what I know as a layman, it would seem unlikely that two observers would “know” a particle’s collapsed position at exactly the same time. If the two observers were in a photo-finish, the one across the finish line first would win and establish the position for both observers. However, while time is very finely divided, we cannot measure any interval shorter than one Planck Time. If both observed it in the same Planck Time, what would they see; one position, or two? You’ve got me there.

Elm1969's avatar

@ETpro Maybe suggestion changes the view. If I point or direct you to the particle’s collapsed position and you “see” the same as me from my suggestion does that have the same effect as the observation effect. You may not “see” exactly the same as me but my observation effects yours, so we concur. Would this mean that our Planck time becomes syncronised or is that similar to what you are saying?

ETpro's avatar

@Elm1969 Suggestion might influence opinion of view. But it is easily testable whether suggestion controls view, and it does not. If it did, we would never disagree about anything. Now, if all elementary particles are still quantum entangled from the Big Bang, then what I observe and thing DOES influence the brain of all other life forms at least at the quantum level. But when we produce quantum entanglement in a particle accelerator, it is extremely short lived. This short period of entanglement has been one of the major hurdles to overcome in developing large-scale quantum computers.

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