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Author Topic: Direction of Radiation Emitted from Atoms  (Read 22396 times)

Offline JP

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« Reply #50 on: 19/12/2007 16:16:40 »
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a|1>+b|2>+∑|states missing the detectors> → |1>
That notation expresses my idea well. The only thing is that it doesn't explain what is happening when it is 'resolved' by one detector..
The fact that  it collapses into   a|1 → |1 needs, somehow, to be communicated to all the detectors which were included in the first expression, instantly (?). The collapse must be instantaneous. I am happy with that if you are.

I think most quantum physicists wouldn't have a problem with this in general.  The "collapse of the wavefunction" eliminates parts of the probability instantaneously at "faster-than-light" speeds.  But then again, so does entanglement.  If I entangle two particles and send them to opposite sides of the planet and I then measure one, regular quantum theory predicts that the other one instantaneously experiences a change (due to collapsing the wavefunction by measurement).  This was one of Einstein's big problems with quantum theory (it forms the basis of the EPR experiment which argues against quantum theory).  However, the best experiments out there to date seem to verify this result.  The caveat is that you can't send usable information at faster-than-light speeds, since you need to compare your measurements with other observers, and that requires that you send classical information.
 

Offline lightarrow

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« Reply #51 on: 19/12/2007 19:47:57 »
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quantum fluctuation of the void
You have introduced another idea here.
If you are suggesting that an emitted photon's energy is, somehow, absorbed into a general 'bank' of energy, which can turn up somewhere else in a position and time which are related by c, then that's fair enough. It's quite possible that you couldn't tell the difference. This depends on how complete the new idea / model is and how near it fits measurements to-date.

I think you are bringing in an irrelevant argument about effectively  'knowing which photon you detected'. QM doesn't let us assert anything like that but there are plenty of experiments which could link a significant number of received photons with a particular source; take a lamp and a light cell down a coal mine and you can be pretty well sure where the photons all came from! By that I mean that a photon model  which we have been discussing would reasonably indicate that the energy from the source was the energy detected. That's as much as you could say, though. Your alternative model could possibly give an explanation.

Don't know if I succeeded in explaining what I intended, so I try to explain better.
I prefer to think that the source generates only a classical electromagnetic wave and that it's the interaction of this wave with matter that is quantized.
I've just discovered that Max Planck thought the same:
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in 1907 in a letter to Einstein, he said I am not seeking the meaning of the quantum of action (light quantum) in the vacuum but rather in places where emission and absorption occur, and I assume that what happens in the vacuum is rigorously described by Maxwell's equations.

My idea is that the wave hits all the detectors simultaneously and only one of them clicks because...if 2 of them click, you will say that 2 photons arrived!
Summarizing: the EM wave hits all the detectors and so increases their sensitivity; then one will click because, statistically, in that instant it has a slightly greater sensitivity than the others and because of quantum fluctuations of the EM field near the detectors; then another detector, or even the same, will click randomly and so on.
 

Offline thebrain13

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« Reply #52 on: 19/12/2007 20:30:40 »
would this statement be correct about quantum entanglement. If you could change the spin of an entangled particle to whatever you wanted, you could break the theory of relativities prediction of nothing can travel faster than light?
 

lyner

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« Reply #53 on: 19/12/2007 22:13:01 »
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I've just discovered that Max Planck thought the same:
Well, you are in good company then! That means he was probably right?
 

lyner

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« Reply #54 on: 19/12/2007 22:14:18 »
would this statement be correct about quantum entanglement. If you could change the spin of an entangled particle to whatever you wanted, you could break the theory of relativities prediction of nothing can travel faster than light?
Well, this is the difficult bit. I think jpetruccelli's post at the top of the page puts it in a good way.
 

Offline lightarrow

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« Reply #55 on: 20/12/2007 12:28:15 »
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I've just discovered that Max Planck thought the same:
Well, you are in good company then! That means he was probably right?
No, it means I'm exactly one century later!   :)
 

Offline lightarrow

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« Reply #56 on: 20/12/2007 12:30:39 »
would this statement be correct about quantum entanglement. If you could change the spin of an entangled particle to whatever you wanted, you could break the theory of relativities prediction of nothing can travel faster than light?
Read the previous post of jpetruccelli: it's not possible to use entanglement to send information faster than c.
 

Offline thebrain13

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« Reply #57 on: 20/12/2007 17:07:53 »
But the reason you cant send information faster than light even though certain particles appear to interact with each other faster than the speed of light is because you cant control the information either particle is sending to the other.

It would be analogous to two radio towers placed far away from each other, that always played the same thing as one another. Like in entanglement each radio tower always played a random broadcast. Even though these towers communicate with each other faster than c, you couldnt use them to communicate faster than c because the tower always plays a random broadcast. No matter what, each tower would just view a random broadcast, thats useless.

However, if some clever engineer could figure out a way to affect the broadcasts of the towers, you could send information faster than c.
 

Offline lightarrow

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« Reply #58 on: 20/12/2007 21:20:10 »
But the reason you cant send information faster than light even though certain particles appear to interact with each other faster than the speed of light is because you cant control the information either particle is sending to the other.

It would be analogous to two radio towers placed far away from each other, that always played the same thing as one another. Like in entanglement each radio tower always played a random broadcast. Even though these towers communicate with each other faster than c, you couldnt use them to communicate faster than c because the tower always plays a random broadcast. No matter what, each tower would just view a random broadcast, thats useless.

However, if some clever engineer could figure out a way to affect the broadcasts of the towers, you could send information faster than c.
Ok, but according QM, that is impossible, it's not just a technological problem, it's a theoretical one. Anyway, noone prevents you to invent a new formulation of the quantum theory, in which that is possible. Of course all the other well established things have to work as well...
« Last Edit: 20/12/2007 21:24:05 by lightarrow »
 

lyner

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« Reply #59 on: 20/12/2007 23:44:57 »
I think it's time thebrain13 did some serious reading before he makes too many wild statements. This is not a subject that you can have 'ideas' about without basis. It is big boys' stuff and not magic or whimsy.
 

Offline thebrain13

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« Reply #60 on: 21/12/2007 00:32:17 »
dude, that was a question not a wild statement. If we could find a way to control spin, would that violate the nothing faster than light theorem?
 

Offline JP

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« Reply #61 on: 21/12/2007 03:39:02 »
The problem is that entanglement only works (to the best of my knowledge) with measurements.  If I send you a state that's 100% correlated so that if I measure spin "up," your state is in spin "up," and similarly with "down."  This correlation is 100% so long as I use only measurements.  However, if I rotate my particle, yours doesn't rotate, since this isn't a measurement.  I might then be in a situation where "left" is correlated with your "up" and "right" with your "down," but you can see I haven't gained anything.

Now, can you use measurements to send information faster than light?  Most physicists think not.  Let's say I want to send you the message "Up, Up, Down."  I measure a bunch of times, and get the result "Up, Down, Down, Up, Up, Down."  So you on the other end get the same result.  Then I somehow have to call you up and tell you "Disregard measurements 2,3 and 5, and what's left is my message."  This "calling you up" is why you're limited to the speed of light, since that communication has to happen at the speed of light or slower.
 

lyner

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« Reply #62 on: 22/12/2007 13:06:16 »
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dude, that was a question not a wild statement.
OK, fair enough - but I thought questions contained query marks somewhere?
 

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