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A particle in different places at the same time

by MathematicalPhysicist
Tags: particle, places, time
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MathematicalPhysicist
#1
Nov26-03, 11:23 AM
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can someone provide me a link to a movie file (prefferablly for wmp) of an experiment that shows that a particle can be in different places at the same time?




thanks in advance.
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Tom Mattson
#2
Nov27-03, 04:14 PM
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Experiments do not show that particles can be in two places at the same time. That is just one (untestable) interpretation of the quantum mechanical probability density.
Sniper__1
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Nov27-03, 05:22 PM
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a better question or request is how people think particles communicate is it by faster than light communication or another means of quantum communication in 0.000001 seconds over any distance even light years away.

jcsd
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Nov27-03, 05:56 PM
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A particle in different places at the same time

Well the 'communication' is instaneous, it takes no time at all whatver the distance. You just have to recognize that the wavefunction is essientally non-local and there's no real communication between the two particles.
MathematicalPhysicist
#5
Nov28-03, 06:01 AM
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Originally posted by Tom
Experiments do not show that particles can be in two places at the same time. That is just one (untestable) interpretation of the quantum mechanical probability density.
in this pdf file there's a summary of experiment that shows what i reffered to, they dont about it being an interpretation of the quantum mechanical probability density:
http://www.google.co.il/search?q=cac...hl=iw&ie=UTF-8
jcsd
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Nov28-03, 08:44 AM
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Conventionally the experiment is explained as the photon not having a well defined postion 'til it hits the screen, though you can intepret it as the photon being in two places at the same time and it's quite often explained like that in pop. sci. books.
MathematicalPhysicist
#7
Nov28-03, 11:16 AM
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Originally posted by jcsd
Conventionally the experiment is explained as the photon not having a well defined postion 'til it hits the screen, though you can intepret it as the photon being in two places at the same time and it's quite often explained like that in pop. sci. books.
it can also be argued that the photon is everywhere not just in two places, couldnt you?
jcsd
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Nov28-03, 03:54 PM
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Originally posted by loop quantum gravity
it can also be argued that the photon is everywhere not just in two places, couldnt you?
It depends on the probailty distribution, but in physically relaistic situations, yes.
Tom Mattson
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Nov28-03, 10:46 PM
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Originally posted by loop quantum gravity
in this pdf file there's a summary of experiment that shows what i reffered to, they dont about it being an interpretation of the quantum mechanical probability density:
LQG, you need to learn to be more analytical, methinks. It doesn't matter what "they" say about the result. The fact is that the photon makes one--and exactly one--mark on a photographic plate. Not two, not three, and not a half.

Based on the interference pattern that developed when only one photon at a time passes through the slit, they inferred that the photon passed through both slits simultaneously. An inference is not the same as an observation.

It is exactly as I said: The "particle being in 2 places at once" thing is an untestable interpretation of quantum theory. There are other interpretations that differ from that one, and yet are equally consistent with the data.
d00dz
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Dec6-03, 09:06 PM
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correct me if im wrong but i once read that someone was awarded the nobel prize for demonstating this...something to do with a particle being in two places at the same time? Another state of matter? If what i wrote is completely worng then forget i ever wrote it...just wanna know.
Ed Quanta
#11
Dec7-03, 09:02 PM
P: 297
I think what was demonstrated was the difference in interference patterns of the two slit experiment when firing one electron at a time and observing the resulting state in comparison to not observing the electrons while fired. It is crazy how quantum mechanics enforces that the inability to separate yourself from the experiment.
quantum
#12
Dec10-03, 09:56 AM
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Isn't this known as quantum entanglement? Try typing that into www.google.com, you may get lucky. =-]
TheAtheistKing
#13
Dec16-03, 10:14 AM
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Originally posted by loop quantum gravity
can someone provide me a link to a movie file (prefferablly for wmp) of an experiment that shows that a particle can be in different places at the same time?




thanks in advance.
I have a question, does anyone know of a line of reasoning which leads to the conclusion that one particle can be in two places simultaneously?
selfAdjoint
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Dec16-03, 11:57 AM
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In order to accomodate this property with a logical form of reasoning, you have to deny the exclusion of the middle, which says that a property is either possesed or it isn't. In this cse the fact that the particle is here would contradict the possibility that it is over there. So excluded middle has to go.

Now mathematicians are familiar with logical systems like that, some nondistributive lattices are like boolean algebra (a distributive lattice) without the law of the excluded middle. So these structures have been studied as "Quantum Logic" (qg). A lot of work has been done, but I don't think anything earth-shattering has been discovered.
TheAtheistKing
#15
Dec16-03, 12:31 PM
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In order to accomodate this property with a logical form of reasoning, you have to deny the exclusion of the middle, which says that a property is either possesed or it isn't. In this cse the fact that the particle is here would contradict the possibility that it is over there. So excluded middle has to go.

Now mathematicians are familiar with logical systems like that, some nondistributive lattices are like boolean algebra (a distributive lattice) without the law of the excluded middle. So these structures have been studied as "Quantum Logic" (qg). A lot of work has been done, but I don't think anything earth-shattering has been discovered.


The law of the excluded middle is a statement about statements:

LEM: For any statement X, X or not X

Suppose LEM is false, it therefore follows that there is at least one statement X, such that not (X or not X). Let S denote one such statement, hence

not (S or not S)

Using truth tables the previous statement is logically equivalent to the following statement:

S and not S

At this point we must conclude that the LEM is true, and cannot be abandoned.

Next I would like to say that I do not see why one would have to abandon the LEM, in order to reach the conclusion that one particle can be in two places simultaneously.

Consider the following argument.

Suppose that any body is composed of an integral number of particles. It would follow that the simplest body of all is a two particle body. Consider the creation of a body. You would have to have two particles headed for the same place at the same time. Neither could ever get there. Eventually they would be as close as they are ever going to get. The question is this, when they are one state change away from being at the same place at the same time, where will they be at the very next moment in time, since neither of them can be at the collision point. Use conservation of energy and momentum.

Either they reflect or they do not reflect. If they must reflect then bodies dont exist, contrary to fact, hence there are collisions in which two particles "stay together". A proper analysis of this will reveal that energy and momentum are conserved if at the very next moment in time neither particle is in the plane of collision, but rather both particles are now in orbit around a common center of mass, forming a new body. AND THIS BRINGS ME TO THE POINT. Suppose you accept that bodies are created by point particles colliding, and then spinning around a center of mass, why would they spin clockwise as opposed to counterclockwise?

Now, the mathematical logic of this will lead you to the conclusion that either they spin clockwise or they spin counterclockwise. But the 'OR' here is inclusive OR, not exclusive OR, hence there is no contradiction in saying that right after collision, the particles spin clockwise AND counterclockwise. But if that is true, then each particle is now at two locations on the circumference of a circle, and so it would be correct to say that it is possible for one particle to be at two places at the same time. This is the most intriguing concept of physics I have ever come across.

I have done the analysis for a collision angle of 90 degress, and the right conclusion is that each particle is now at two different vertices of a regular hexagon, in an orbital plane.

Now here is an interesting point. If particles are literally point masses, the probability of any two just happening to be headed for the exact same place at the exact same moment in time is zero, and so one would expect that there shouldn't be too many large bodies of matter in the universe, contrary to fact.

So let me really go into detail here. Suppose we have two particles just moving, they will not be headed for the same place at the same time by luck alone. But if there MUST be a force of attraction between them, then they will pull each other towards a collision of some kind. This kind of reasoning really leads to new physics. Can any particle be truly free from all force? If not, then every particle must be accelerating in an inertial reference frame, and hence there are no truly free particles. But supposing that there must be a force of attraction, what mediates the force?
wasteofo2
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Dec26-03, 05:13 PM
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Originally posted by jcsd
Well the 'communication' is instaneous, it takes no time at all whatver the distance. You just have to recognize that the wavefunction is essientally non-local and there's no real communication between the two particles.
In the january 2004 of Scientific American there's an article about loop quantum gravity, in which it is proposed that timespace is composed of small pieces(the same way matter is composed of atoms) and that time procedes in intervals of 10^-43 seconds. Therefore, something can only happen intervals of 10^-43 seconds, and not instantaneously.
Tom Mattson
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Dec26-03, 05:40 PM
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Originally posted by wasteofo2
In the january 2004 of Scientific American there's an article about loop quantum gravity, in which it is proposed that timespace is composed of small pieces(the same way matter is composed of atoms) and that time procedes in intervals of 10^-43 seconds.
OK, so that's what Loop Quantum Gravity says.

Therefore, something can only happen intervals of 10^-43 seconds, and not instantaneously.
Did SciAm also tell you that LQG is almost completely untested? It is not even a finished theory!

It's too soon to make statements such as this.


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