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Author Topic: Can an electron be in two places at the same time?  (Read 34008 times)

Offline PmbPhy

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Re: Can an electron be in two places at the same time?
« Reply #50 on: 19/09/2014 22:54:54 »
Quote from: David Cooper
Brian Cox recently discussed a diamond in a locked box and the possibility of it suddenly appearing outside the box because the probability of this unlikely event occurring is supposedly not quite being zero.
I disagree with this kind of response to the problem of macroscopic problems and probabilities. I believe that it's quite literally impossible for that to happen, not just a small probability.

I checked this with the author of the textbook which I learned QM from saying that I don't buy that kind of thing for a moment and asked him if he did. His response was I guess so, but it's a silly remark, designed to mislead.

Keep that in mind when people make those kinds of assertions.
« Last Edit: 20/09/2014 02:47:14 by PmbPhy »
 

Offline JohnDuffield

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Re: Can an electron be in two places at the same time?
« Reply #51 on: 20/09/2014 15:00:39 »
I never said it wasn't real. The probabilities are real too, dictated by a real mechanism which I have never denied (because I have never believed in magic and have never been a fan of the Copenhagen interpretation).
Good stuff.

Recent advances are enabling the mechanism to be detected, as anyone on this forum can't fail to have noticed, but it makes no change whatsoever to the issue of whether something is in two places or not at the same time. A thing can be spread across multiple places, but it cannot in totality be in two places at the same time.
Fair enough. IMHO the important point is that something like a photon is more like a seismic wave than a billiard ball.

So, I'm still trying to determine whether there's a real issue in conflict between what you're saying and what I've been led to believe. Brian Cox recently discussed a diamond in a locked box and the possibility of it suddenly appearing outside the box because the probability of this unlikely event occurring is supposedly not quite being zero. This would, I assume, depend on the diamond behaving in a wavy way such that every part of it too is spread out across space and all of those parts could spontaneously decide that they are outside the box instead of in it. So, do you disagree with him and think the diamond is so localised that it cannot get out of the box in such a way at all? The whole diamond is wavefunction and it enables the diamond to show itself as being located outside the box even though it was seen as being located inside it when it was locked in there: mechanism and probabilities intact.
Yes, I disagree with him. See pmb's response above. Brian Cox has done some nice TV programs, but IMHO he doesn't always get the physics right.
 

Offline evan_au

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Re: Can an electron be in two places at the same time?
« Reply #52 on: 20/09/2014 22:27:53 »
The "Principle of Conservation of the Center of Gravity" suggests that if by some unlikely chance the diamond is displaced to the right, then the box must be displaced to the left....
 

Offline alancalverd

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Re: Can an electron be in two places at the same time?
« Reply #53 on: 21/09/2014 00:09:53 »
Fair enough. IMHO the important point is that something like a photon is more like a seismic wave than a billiard ball.
 

You can propagate a billiard ball, but not a seismic wave, through a vacuum
 

Offline Bill S

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Re: Can an electron be in two places at the same time?
« Reply #54 on: 08/12/2014 20:48:29 »
Pete, although this is not the source of the idea it is certainly one of the dissemination points.

http://www.askamathematician.com/2009/12/q-can-things-really-be-in-two-places-at-the-same-time

 

Offline PmbPhy

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Re: Can an electron be in two places at the same time?
« Reply #55 on: 08/12/2014 22:10:21 »
Pete, although this is not the source of the idea it is certainly one of the dissemination points.

http://www.askamathematician.com/2009/12/q-can-things-really-be-in-two-places-at-the-same-time
I myself reject what's said in that page. The wave function tells the probability of where a particle will end up. To say that a photon interferes with itself is to say that the wave "is" the photon instead of merely being a tool to tell you probability.
 

Offline JohnDuffield

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Re: Can an electron be in two places at the same time?
« Reply #56 on: 08/12/2014 23:20:51 »
Fair enough. IMHO the important point is that something like a photon is more like a seismic wave than a billiard ball.
You can propagate a billiard ball, but not a seismic wave, through a vacuum
As far as we know you can propagate a gravitational wave through a vacuum. Have a read of the LIGO website:

"When large masses move suddenly, some of this space-time curvature ripples outward, spreading in much the way ripples do the surface of an agitated pond. Imagine two neutron stars orbiting each other. A neutron star is the burned-out core often left behind after a star explodes. It is an incredibly dense object that can carry as much mass as a star like our sun, in a sphere only a few miles wide. When two such dense objects orbit each other, space-time is stirred by their motion, and gravitational energy ripples throughout the universe..."

OK an electromagnetic wave isn't a gravitational wave, but you must have read Maxwell saying light consists of transverse undulations. Light is a wave, photon energy is E=hc/λ, it's λ for wavelength. It's a wave, and it's moving through space. When an ocean wave moves through the sea, the sea waves. When a seismic wave moves through the ground, the ground waves. When an electromagnetic wave moves through space...

Note that you can diffract electrons. Electrons are waves too. The dual slit experiment can be easily explained if detection at a slit or the screen performed something akin to an optical Fourier transform and converted an extended-entity wave into a dot.

Bill: I reject the Copenhagen Interpretation along with the idea that the wavefunction is some probabilistic mystic thing. See Jeff Lundeen's website here and catching sight of the elusive wavefunction and this article where he says wavefunction is real.   
« Last Edit: 08/12/2014 23:26:23 by JohnDuffield »
 

Offline Bill S

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Re: Can an electron be in two places at the same time?
« Reply #57 on: 09/12/2014 15:33:17 »
Quote from: Pete
To say that a photon interferes with itself is to say that the wave "is" the photon instead of merely being a tool to tell you probability.

Now I’m confused.  I know that’s not unusual, but perhaps we can sort it this time.  :P

I doubt that you are saying that a photon does not have characteristics of a wave.  So when you say the wave is “a tool to tell you probability”, are you referring to the wave function, as distinct from the wavelike characteristic of a photon?
 

Offline PmbPhy

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Re: Can an electron be in two places at the same time?
« Reply #58 on: 09/12/2014 15:43:37 »
Quote from: Pete
To say that a photon interferes with itself is to say that the wave "is" the photon instead of merely being a tool to tell you probability.

Now I’m confused.  I know that’s not unusual, but perhaps we can sort it this time.  :P

I doubt that you are saying that a photon does not have characteristics of a wave.  So when you say the wave is “a tool to tell you probability”, are you referring to the wave function, as distinct from the wavelike characteristic of a photon?
The wave function describes exactly what the wavelike characteristic of a photon is, i.e. the probability of where to find the photon.
 

Offline lightarrow

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Re: Can an electron be in two places at the same time?
« Reply #59 on: 09/12/2014 19:17:23 »
Quote from: Pete
To say that a photon interferes with itself is to say that the wave "is" the photon instead of merely being a tool to tell you probability.

Now I’m confused.  I know that’s not unusual, but perhaps we can sort it this time.  :P

I doubt that you are saying that a photon does not have characteristics of a wave.  So when you say the wave is “a tool to tell you probability”, are you referring to the wave function, as distinct from the wavelike characteristic of a photon?
The photon is a particle described by quantum electrodynamics and as such it's described using a "wavefunction" exactly as the electron is (not the same wavefunction, but still a wavefunction). Maybe you are confusing a photon with the electromagnetic field, which instead is described by a real wave (not a "wavefunction")?

--
lightarrow
 

Offline PmbPhy

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Re: Can an electron be in two places at the same time?
« Reply #60 on: 09/12/2014 23:27:20 »
Quote from: lightarrow
The photon is a particle described by quantum electrodynamics and as such it's described using a "wavefunction" exactly as the electron is (not the same wavefunction, but still a wavefunction). Maybe you are confusing a photon with the electromagnetic field, which instead is described by a real wave (not a "wavefunction")?
I'm happy you said that, lightarrow. If you hadn't then I'd accept what Wikipedia had to say about it, i.e.
http://en.wikipedia.org/wiki/Photon
Quote
Like all elementary particles, photons are currently best explained by quantum mechanics and exhibit wave–particle duality, exhibiting properties of both waves and particles.
And I'd have accepted it. However you challenge me quite often which keeps me sharp so I contacted a friend of mine (an author of a QM text) and he said
Quote
I don't think so.  Photons really have no place in (nonrelativistic) quantum mechanics, since they are quintessentially relativistic entities.
So although he's not 100% certain he makes a good point in that photons are relativistic particles and thus they belong to a relativistic theory which quantum mechanics is not since it's a non-relativistic theory.

So please keep up the good work my friend. :)
 

Offline yor_on

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Re: Can an electron be in two places at the same time?
« Reply #61 on: 13/12/2014 20:23:23 »
"f you think that only a three-dimensional world is "real" because "we experience this one only", and that the 4-dimensional world of GR (for example) is "just an idea", then you are wrong: it simply depends on how you interpret your perceptions; even "three-dimensional" is a concept just in our minds, "the reality" doesn't exist. "

Would expect nothing less of you Lightarrow :)
Imagination is all, then comes proof.
 

Offline Bill S

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Re: Can an electron be in two places at the same time?
« Reply #62 on: 17/12/2014 20:02:28 »
This seems to have drifted a bit.  My original comments were:

Quote from: Bill S.
It also depends on how you define “place”.
 
 In general it must be defined as a position in space.  Space must be restricted to the three dimensions that we experience.

and:

Quote
Any additional dimensions that may be suggested are mathematical concepts which may, or may not, bear any relation to reality.

So Lithtarrow’s comment:

Quote from: Lightarrow
If you think that only a three-dimensional world is "real" because "we experience this one only", and that the 4-dimensional world of GR (for example) is "just an idea", then you are wrong: it simply depends on how you interpret your perceptions; even "three-dimensional" is a concept just in our minds, "the reality" doesn't exist. 

while, in itself, accurate, is not appropriate.

The 4-dimensional world of GR refers to spacetime, not just to space.  What I meant was that any additional dimensions of space were just mental concepts.

I acknowledge that our three spacial dimensions may also be mental concepts, but they are concepts of which we have a physical perception; which would not be the case for a 4th spacial dimension.
 

Offline Bill S

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Re: Can an electron be in two places at the same time?
« Reply #63 on: 17/12/2014 20:14:53 »
Alan, you have contributed a number of erudite comments to this thread, but unless I have missed something, which I accept is quite possible, you have not directly addressed the question in the OP. 

“Can an electron be in two places at the same time?”

As learning is my primary objective, I would really appreciate your input on this.
 

Offline Bill S

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Re: Can an electron be in two places at the same time?
« Reply #64 on: 10/02/2015 22:06:17 »
http://www.mpg.de/511738/pressRelease20051011

This seems to have some interesting stuff that is relevant to the OP.  It is almost 10 years old, so I suppose it could be out of date.
 

Offline jeffreyH

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Re: Can an electron be in two places at the same time?
« Reply #65 on: 11/02/2015 00:04:41 »
Can I be in more than one place at a time? Well my head is in a different location to my feet and I am considered to be a whole thing, a human. The distribution of my parts occupy more than one location. With uncertainty and not knowing the exact nature and distribution of individual particles it is not unreasonable to think that they too could be in more than one place at a time. Unless they really are point particles with zero distribution, which I very much doubt.
 

Offline jccc

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Re: Can an electron be in two places at the same time?
« Reply #66 on: 11/02/2015 01:54:24 »
There is one place, called space. There is one time, called now.

All is connected, all is confused.

I need my pipe.

I should be in your place by now.
 

Offline Ethos_

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Re: Can an electron be in two places at the same time?
« Reply #67 on: 11/02/2015 02:14:44 »
There is one place, called space. There is one time, called now.

All is connected, all is confused.

I need my pipe.

I should be in your place by now.
Actually Jccc, one can't separate space and time when defining a location. Physicists refer to this 4 dimensional reality as space/time. And the reason why it takes more than 3 dimensions to describe reality is that one moment ago, you were in a different location than you are at present. Not only are there 3 spatial dimensions of linear measure which describe a location, but that location changes as time advances to another location in the future. And to make another important point, absolute motionlessness is only possible when one frame of reference is considered for a pair of objects. One of the objects can be considered motionless relative to the other. But nothing is motionless relative to space, everything is moving thru space/time.
« Last Edit: 11/02/2015 02:18:39 by Ethos_ »
 

Offline PmbPhy

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Re: Can an electron be in two places at the same time?
« Reply #68 on: 11/02/2015 02:27:53 »
Let's remember that the assertion that a particle can be in two places at the same time is quite wrong.
 

Offline jccc

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Re: Can an electron be in two places at the same time?
« Reply #69 on: 11/02/2015 02:34:39 »
Let's remember that the assertion that a particle can be in two places at the same time is quite wrong.

How about a thing can be particle and wave at the same time?
 

Offline Ethos_

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Re: Can an electron be in two places at the same time?
« Reply #70 on: 11/02/2015 02:38:30 »
Let's remember that the assertion that a particle can be in two places at the same time is quite wrong.
Absolutely Pete,..............and that's because it is never the same time for any two separate locations. Space/time is a composite and one has no real meaning without the other.

One cannot separate space and time when defining a location,"place".
« Last Edit: 11/02/2015 02:57:13 by Ethos_ »
 

Offline PmbPhy

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Re: Can an electron be in two places at the same time?
« Reply #71 on: 11/02/2015 02:45:17 »
Quote from: jccc
How about a thing can be particle and wave at the same time?
That's not something found in quantum mechanics. In fact it says that, for example, an electron, photon etc. can have particle properties and it can have wave properties, depending on what experiment is being performed. But they cannot have both properties at the same time.

See http://abyss.uoregon.edu/~js/21st_century_science/lectures/lec15.html
Quote
Wave-particle duality does not mean that a photon or subatomic particle is both a wave and particle simultaneously, but that it could manifest either a wave or a particle aspect depending on circumstances.
...
No experiment can ever measure both aspects simultaneously and so we never see a mixture of wave and particle.
 

Offline JohnDuffield

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Re: Can an electron be in two places at the same time?
« Reply #72 on: 11/02/2015 13:53:38 »
Actually Jccc, one can't separate space and time when defining a location. Physicists refer to this 4 dimensional reality as space/time. And the reason why it takes more than 3 dimensions to describe reality is that one moment ago, you were in a different location than you are at present. Not only are there 3 spatial dimensions of linear measure which describe a location, but that location changes as time advances to another location in the future. And to make another important point, absolute motionlessness is only possible when one frame of reference is considered for a pair of objects. One of the objects can be considered motionless relative to the other. But nothing is motionless relative to space, everything is moving thru space/time.
I'm somebody who roots for relativity, but I don't share this view at all. Take a look at A World without Time: The Forgotten Legacy of Godel and Einstein. The reality is space and motion. That's motion through space, not spaceitme. Spacetime is a combination of space and time, but it's an abstract thing. The map is not the territory. You cannot move through spacetime because it represents space at all times. When some particle is motionless in space, as determined from the CMB rest frame, it isn't actually moving through spacetime. Other particles are moving through space, that's all.

Let's remember that the assertion that a particle can be in two places at the same time is quite wrong.
I must take exception to this. Its quantum field theory, not quantum point particle theory. The electron's field is what it is, and it doesn't have an edge. Saying a particle can't be in two places at once makes as much sense as saying the wind can't be in two places at once.
« Last Edit: 11/02/2015 13:56:31 by JohnDuffield »
 

Offline Ethos_

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Re: Can an electron be in two places at the same time?
« Reply #73 on: 11/02/2015 15:00:29 »
The reality is space and motion. That's motion through space, not spaceitme. Spacetime is a combination of space and time, but it's an abstract thing.
Are you suggesting that we should not view time as the fourth dimension? Because if your idea is correct, space/time would only be an abstraction.

The dimensions of space are evident and we need no motion to understand their reality. And they consist of three dimensions.

Motion is the evidence that the fourth dimension is also a reality. And the path thru it is as real as the other three.

I must respectfully disagree with your position on this issue John.

 

Offline jccc

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Re: Can an electron be in two places at the same time?
« Reply #74 on: 11/02/2015 15:52:31 »
The reality is space and motion. That's motion through space, not spaceitme. Spacetime is a combination of space and time, but it's an abstract thing.
Are you suggesting that we should not view time as the fourth dimension? Because if your idea is correct, space/time would only be an abstraction.

The dimensions of space are evident and we need no motion to understand their reality. And they consist of three dimensions.

Motion is the evidence that the fourth dimension is also a reality. And the path thru it is as real as the other three.

I must respectfully disagree with your position on this issue John.

Still think light is particle?
 

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Re: Can an electron be in two places at the same time?
« Reply #74 on: 11/02/2015 15:52:31 »

 

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