|
|
#51
11-09-2007, 01:51 PM
|
|||
|
|||
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
[ QUOTE ] For this thread we probably shouldn't mention the Afshar experiment. Most people I've talked to have serious doubts about the setup and conclusion. Even if the Afshar experiment is correct I still think 4 would be wrong since it could be used to send information faster than C. [/ QUOTE ] I'm actually inclined to agree [img]/images/graemlins/ooo.gif[/img] I only really brought it up, because as it is you cant say for sure that its invalid or for that matter that it is. And sending information faster than C is totally ok, as long as its not classical information (spooky action at a distance already says that information can travel faster than C). [/ QUOTE ] The way it is worded now, it seems that I could send information. In the EPR paradox you can't send information so it is not a problem. In 4, i could take the pictures far away and flip a coin. Heads I destroy them, tails I look at them. You can look at the screen after some time has passed and you will know if I flipped heads or tails. Am I wrong or does this make sense? 
|
|
#52
11-09-2007, 01:52 PM
|
|||
|
|||
|
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
What youre talking about here is called the "Delayed-Choice Quantum Eraser" experiment. This is an extention of the beam-splitter experiment. Since we are talking about a double slit experiment in this thread, a simple version of the quantum eraser experiment is all that is necessary to convey my point. Both the eraser experiment you mentioned and the one I delineated are valid in explaining this counterintuitive phenomena. [/ QUOTE ] Except I believe yours is not physically possible, and mine is. This seems like nittiness, but if there were no way to actually set up an experiment that would measure something like this then it would be a worthless subject to argue. Even in the Bohr-Einstein style thought experiments to try and hash out whether the uncertainty principle made sense, a key point was that they were always talking about real physical systems and behavior.
|
|
#53
11-09-2007, 02:01 PM
|
|||
|
|||
|
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
And sending information faster than C is totally ok, as long as its not classical information (spooky action at a distance already says that information can travel faster than C). [/ QUOTE ] It's unfortunate that Einstein used that phrase. There is nothing spooky about an observation unless we go into it with an expectation of how nature 'should' be. If we go in with 'nature is how we find it' then it wouldn't occur to us to label it spooky. A mystery, since we don't have a grasp of the situation, but nothing more. Tribesmen attribute thunder/lightening to spooks and DS keeps up our innate animism with the latest mystery. Iow, the OP is nothing more than our 40,000 year old habit showing it's still part of our makeup. There is no sense in which the slit experiment 'violates' any part of reality, merely our preconceptions of it. luckyme
|
|
#54
11-09-2007, 02:08 PM
|
|||
|
|||
|
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
In 4, i could take the pictures far away and flip a coin. Heads I destroy them, tails I look at them. You can look at the screen after some time has passed and you will know if I flipped heads or tails. Am I wrong or does this make sense? [/ QUOTE ] Makes sense, except in this experiment there is no picture to destroy. The setup David suggested will always produce point particle patterns. No matter what happens to the film, we looked so the interference got destroyed. The Afshar experiment should always produce interference patterns, no matter what. But then again he is not really looking (which is the big point of contention afaik). I think David is confuses about observing. Its not about who, its about the act (be it a film, a conscious observer, a photon detector or whatever).
|
|
#55
11-09-2007, 02:10 PM
|
|||
|
|||
|
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
Not exactly. I could be wrong, but I'm pretty sure that in vacuum photons do not interact (or if they do because of some weird vacuum fluctuation / quantum field theory reasons that I don't understand, [/ QUOTE ] This is second quantization and is where quantum field theory begins. For just the double slit you don't really need it though.
|
|
#56
11-09-2007, 02:15 PM
|
|||
|
|||
|
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
It's unfortunate that Einstein used that phrase. There is nothing spooky about an observation unless we go into it with an expectation of how nature 'should' be. If we go in with 'nature is how we find it' then it wouldn't occur to us to label it spooky. A mystery, since we don't have a grasp of the situation, but nothing more. Tribesmen attribute thunder/lightening to spooks and DS keeps up our innate animism with the latest mystery. Iow, the OP is nothing more than our 40,000 year old habit showing it's still part of our makeup. There is no sense in which the slit experiment 'violates' any part of reality, merely our preconceptions of it. luckyme [/ QUOTE ] Depends. I think you misunderstand spooky action at a distance. Take a photon, split it in to two entangled photons. At this point their spin is in a superposition. Move the photons some distance apart (as far as you like). Now measure the spin on one of them. You get up, the other will measure as down - instantly. Prior to measuring you had two photons with a spin that was in a superposition, after you have two photons in distinct states up and down (not up up or down down). Unless you believe in hidden variables, some information has to have been passed between these two photons. Otherwise you wouldn't always get up + down or down + up (you would get an equal distribution of up up / down down / up down / down up). The information that was exchange was not classical - in other words you cannot use it to communicate, but it was still exchange, and instantly no matter the distance.
|
|
#57
11-09-2007, 02:29 PM
|
|||
|
|||
|
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
[ QUOTE ] It's unfortunate that Einstein used that phrase. There is nothing spooky about an observation unless we go into it with an expectation of how nature 'should' be. If we go in with 'nature is how we find it' then it wouldn't occur to us to label it spooky. A mystery, since we don't have a grasp of the situation, but nothing more. Tribesmen attribute thunder/lightening to spooks and DS keeps up our innate animism with the latest mystery. Iow, the OP is nothing more than our 40,000 year old habit showing it's still part of our makeup. There is no sense in which the slit experiment 'violates' any part of reality, merely our preconceptions of it. luckyme [/ QUOTE ] Depends. I think you misunderstand spooky action at a distance. Take a photon, split it in to two entangled photons. At this point their spin is in a superposition. Move the photons some distance apart (as far as you like). Now measure the spin on one of them. You get up, the other will measure as down - instantly. Prior to measuring you had two photons with a spin that was in a superposition, after you have two photons in distinct states up and down (not up up or down down). Unless you believe in hidden variables, some information has to have been passed between these two photons. Otherwise you wouldn't always get up + down or down + up (you would get an equal distribution of up up / down down / up down / down up). The information that was exchange was not classical - in other words you cannot use it to communicate, but it was still exchange, and instantly no matter the distance. [/ QUOTE ] Right, but in entangled state you can not force the electron to be up or down. If you could do that then it would violate special relativity as you could use it to instantly communicate something over long distances.
|
|
#58
11-09-2007, 02:29 PM
|
|||
|
|||
|
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
[ QUOTE ] What youre talking about here is called the "Delayed-Choice Quantum Eraser" experiment. This is an extention of the beam-splitter experiment. Since we are talking about a double slit experiment in this thread, a simple version of the quantum eraser experiment is all that is necessary to convey my point. Both the eraser experiment you mentioned and the one I delineated are valid in explaining this counterintuitive phenomena. [/ QUOTE ] Except I believe yours is not physically possible, and mine is. This seems like nittiness, but if there were no way to actually set up an experiment that would measure something like this then it would be a worthless subject to argue. Even in the Bohr-Einstein style thought experiments to try and hash out whether the uncertainty principle made sense, a key point was that they were always talking about real physical systems and behavior. [/ QUOTE ] It is possible. It's been done. My source is "The Fabric of the Cosmos" page 192.
|
|
#59
11-09-2007, 02:33 PM
|
|||
|
|||
|
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
Right, but in entangled state you can not force the electron to be up or down. If you could do that then it would violate special relativity as you could use it to instantly communicate something over long distances. [/ QUOTE ] Exactly. Hence the difference between quantum information and classical information. But I only wrote all that to say why he used the word spooky. And it is spooky, quantum information was exchange, yet it did so instantly. So violating C is fine, as long as its only done with quantum information.
|
|
#60
11-09-2007, 02:54 PM
|
|||
|
|||
|
Re: Do I Misunderstand The Double Slit Experiment
[ QUOTE ]
[ QUOTE ] It's unfortunate that Einstein used that phrase. There is nothing spooky about an observation unless we go into it with an expectation of how nature 'should' be. If we go in with 'nature is how we find it' then it wouldn't occur to us to label it spooky. A mystery, since we don't have a grasp of the situation, but nothing more. Tribesmen attribute thunder/lightening to spooks and DS keeps up our innate animism with the latest mystery. Iow, the OP is nothing more than our 40,000 year old habit showing it's still part of our makeup. There is no sense in which the slit experiment 'violates' any part of reality, merely our preconceptions of it. luckyme [/ QUOTE ] Depends. I think you misunderstand spooky action at a distance. Take a photon, split it in to two entangled photons. At this point their spin is in a superposition. Move the photons some distance apart (as far as you like). Now measure the spin on one of them. You get up, the other will measure as down - instantly. Prior to measuring you had two photons with a spin that was in a superposition, after you have two photons in distinct states up and down (not up up or down down). Unless you believe in hidden variables, some information has to have been passed between these two photons. Otherwise you wouldn't always get up + down or down + up (you would get an equal distribution of up up / down down / up down / down up). The information that was exchange was not classical - in other words you cannot use it to communicate, but it was still exchange, and instantly no matter the distance. [/ QUOTE ] Yes, this data rules out the idea of a local universe. This just means that we have to update our "classical" model of reality.
|
 |
|
|
Linear Mode
