Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: yor_on on 25/02/2009 15:19:11
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The electron can be treated as a particle in which case the restrictions of matter apply.
Or as a wave in which case (?) it still have to obey the basic restrictions of light.
But what I find extremly interesting is the question whether one can say that there are any 'moving' parts in a electron cloud.
That as single electrons fired one at a second or slower into two slits still will create a 'wave pattern'.
That means that it 'covers' both slits at the same time.
The experiment transfers a third possibility to our electron, that it under some circumstances don't seem to 'exist' until observed.
Or that it do exist 'everywhere' until observed, and that is in fact the same difficulty we seem to have with photons in a vacuum.
The property of only them existing as an interaction.
So, is the electron cloud moving around a atom?
If so, do they 'orbit' in different directions?
And the last question I ask is when you think this 'phase transition' between the electron, having no defined motion or localization, as compared to our more classical way of observing electrons for example in a battery, happens :)
http://www.eurekalert.org/pub_releases/2007-11/dbnl-tws110807.php
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I'm not sure what you're getting at. The different models you bring up are just that--different mathematical models for what an electron does. In small-scale problems or those designed to exploit the quantum nature of the electron, like the double slit experiment, the QM model of particle-as-wave is accurate. In larger-scale applications or those in which the QM information isn't important, such as classical electromagnetism, treating the electron as a point-particle is accurate.
Most physicists would tell you that the physics acting at a small scale is the same as the physics acting at a large scale. In other words, if we had computers powerful enough to calculate the QM effects of all electrons in a classical circuit, we would get the same answer that the classical model gives us. However, it might be possible that QM breaks down for some other (yet unknown) reason as your system gets larger. No one knows yet, but some folks are working on probing the region where this transition happens.
As for your question about moving parts in the electron cloud: It really doesn't make sense to consider an electron as orbiting around an atom, since an orbit implies a particle-like object moving on a classical path around some other object. The electrons in an atom behave like waves, not points. An electron cloud for a simple (i.e. Hydrogen) atom in equilibrium takes on the form of a standing wave around the atom, so each individual cloud isn't moving. However, each cloud has different angular momentum properties (to be specific, each cloud has 3 unique numbers describing its properties: angular momentum, one component of its angular-momentum vector, and the spin of its electron). In that sense, each cloud is behaving differently.
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Thanks jpetruccelli.
Can you explain what this standing wave consists of and how it is 'stopped' outside the atoms nucleus?
You see, the idea of a 'standing wave' have always confused me, how can a electromagnetic wave be expected not to move in spacetime. That is if we see it as something 'there' at all times. That matter when transformed into energy will have frequency's etc, is very reasonable to me though.
But us being created out of 'standing waves' is more than a little strange? How does those waves keep its energy, and why do we need any energy at all if we now are created out of it, amongst other questions? There is definitely a strong mathematical relation between matter and light but they are very different 'states' to me. You can accelerate matter (to lend the words from another:) but can you accelerate waves?
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But us being created out of 'standing waves' is more than a little strange? How does those waves keep its energy, and why do we need any energy at all if we now are created out of it, amongst other questions? There is definitely a strong mathematical relation between matter and light but they are very different 'states' to me. You can accelerate matter (to lend the words from another:) but can you accelerate waves?
I like to think of the electron as a pure bundle of energy with no solid core. So far, there has never been an experiment that found any size for an electron. My own speculation is that there is nothing to an electron that is smaller than a circumference equal to the electron's equivalent wave length.
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The standing waves I described are standing with respect to the atom's nucleus. They're confined to the atom and will move as the atom moves. This is similar to the standing waves on a guitar string. You can pluck the guitar string and walk around the room with the guitar at the same time. You still have standing waves on the guitar string, but they're now moving about the room. Similarly, you have standing electron waves about the atom, but the atom itself doesn't have to be stationary. You can certainly accelerate all kinds of waves, especially these standing waves as they're confined to the atom: just accelerate the atom!
Be very careful in thinking about the meaning of the QM electron waves. They're waves, which means we can think about them using the mathematical tools of waves, but they don't have the same physical meaning as classical electromagnetic waves.
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Vern - how would that fit in with electron scattering such as in the Rutherford (I think) experiment?
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yor_on
That as single electrons fired one at a second or slower into two slits still will create a 'wave pattern'.
That is not strictly true. There is only one result when you measure where a 'diffracted' electron arrives. It does not form a wave pattern. The statistics of a vast number of electrons takes the form of a wave pattern.
The wave concept of an electron near an atomic nucleus is, again, more of a statement of the probability of it being found in a particular position.
I feel that people keep making the mistake of trying to discuss these totally esoteric matters in terms which are far too concrete. We talk of waves and mass and stuff and hold pictures in our minds of water waves and waves on guitar strings. But, apart from the Maths which can be used to describe both the tangible and the intangible waves of QM, they have less in common than we think.
We are on to a sure fire loser if we really expect to explain these 'new' concepts in terms of simple mechanical analogies. Many of the anomalies that people keep finding with the pictures are only there because they are failing to realise that they are only dealing in metaphor and analogy. As I said, it may be only the Maths that they have in common which describes a part of their natures. There is no reason to expect the analogy to be complete.
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" They're waves, which means we can think about them using the mathematical tools of waves, but they don't have the same physical meaning as classical electromagnetic waves."
Jp, do you have any good links about this?
What is seen as the differences between 'classical EM waves' and QM:s 'standing waves'?
And Vern, you are definitely correct in that we don't have any definite size for a electron.
But think of those 'photographing' electrons, knowing the lights frequency and what atom they are looking at, shouldn't it be possible to get some inkling towards the possible 'size' depending on how many electrons there are seen as 'orbiting'?
Depending on if they could be 'defined' that way of course :)
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Yes SC, I stand corrected, sloppy writing from me.
As we shoot single electrons through the slits it creates a wave pattern, over time, on the 'detector plate'.
And I agree in finding little correlation between how 'particles' behaves, when compared to 'ordinary matter', like a chair for example, especcially when seeing them as waves.
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Vern - how would that fit in with electron scattering such as in the Rutherford (I think) experiment?
Rutherford scattered electrons off of heavy atomic nucleus to get an idea of the size of the nucleus. The view of an electron existing only at its electromagnetic diameter might effect the calculated size of the nucleus if the size of the electron were taken into account. I think Rutherford considered the electron to be a point charge.
Edit: If the electron exists only at a circumference equal to its energy-equivalent wave length, it will be the largest of the particles at roughly 5 times the size of a neutron.
I made a little calculator program to compare sizes of a shell structure for particles. It is purely speculative with no standing anywhere, but I thought it interesting enough to do.
Here is the source code (http://photontheory.com/mevs.c) written in C.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fphotontheory.com%2Fmevs.jpg&hash=f8666195b5b4d739f2527429c6cf40a1)
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Heisenberg would suggest that an electron in the bound state in an atom would have a very large 'size' / wavelength in view of its very well defined energy. Hence, the probability distribution / standing wavelength will take up the relatively huge 'orbital' space around the nucleus. But this refers to its de Broglie wavelength - not any 'electromagnetic' wavelength.
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But think of those 'photographing' electrons, knowing the lights frequency and what atom they are looking at, shouldn't it be possible to get some inkling towards the possible 'size' depending on how many electrons there are seen as 'orbiting'?
I think it was Erwin Schroedinger who discovered that electrons must populate atoms only in discrete multiples of their wave length. My personal speculation is that the reason for that is a need for the electromagnetic property of an electron to be in resonance at all times. Any time an electron's resonance is broken, as in introducing it to it's oppositely charged partner, it abandons its electron state of matter and zips off in a straight line at the speed of light.
This site has some interesting quotes (http://www.spaceandmotion.com/Physics-Erwin-Schrodinger.htm) of Schroedinger's.
Here's one I like. It shows Schrödinger's hatred for Quantum Mechanics [:)]
Let me say at the outset, that in this discourse, I am opposing not a few special statements of quantum physics held today (1950s), I am opposing as it were the whole of it, I am opposing its basic views that have been shaped 25 years ago, when Max Born put forward his probability interpretation, which was accepted by almost everybody. (Schrödinger E, The Interpretation of Quantum Physics. Ox Bow Press, Woodbridge, CN, 1995).
I don't like it, and I'm sorry I ever had anything to do with it.
(Erwin Schrodinger talking about Quantum Physics)
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" They're waves, which means we can think about them using the mathematical tools of waves, but they don't have the same physical meaning as classical electromagnetic waves."
Jp, do you have any good links about this?
What is seen as the differences between 'classical EM waves' and QM:s 'standing waves'?
What I was trying to get at is (1)QM waves are "probability waves" while classical waves are waves of some physical "stuff," and more generally (2)Maxwell's equations are not the same as Schrodinger's equation, either in physical meaning or in form, although they both admit wavelike solutions.
It's hard to go into detail without getting really complicated, however, since the simplest example is light, and then you end up discussing photons. I guess one way to see this is that there are forms of light that are only explained by QM:
http://en.wikipedia.org/wiki/Nonclassical_light
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Jon - I just read that Wiki article. Can you explain what phase noise is?
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Short answer: phase noise is the uncertainty in any measurement you try to make of light's phase. Light is an oscillating wave, and phase is the thing that tells you at which point of the oscillation you are.
Long answer:
It's related to the uncertainty principle. Quantum mechanical wavepackets have a variety of conjugate variables, such as position/momentum. If you know one well, you know the other poorly, which is a basic statement of the uncertainty principle. Now, let's take position, x, and momentum, p, for example. The uncertainty principle tells us that
ΔpΔx≥h/2,
where Δx is a measure of the width of the wavefunction expressed as a function of position, and Δp is a measure of the width of the wavefunction expressed as a function of momentum. Some states (they're Gaussian wavepackets) are minimum uncertainty states. In other words, they are at the lower bound of the uncertainty relation:
ΔpΔx=h/2.
Now, for these Gaussian wavepackets, it turns out that they have a Gaussian shape in both x and in p, and the uncertainty relation basically says that the wider they are in x, the narrower they are in p. If you "squeeze" the state to be narrower (better-defined) in position, it gets wider in momentum. If you "squeeze" it narrower in momentum, it gets wider in position.
It turns out that when dealing with light, the natural variables are the field quadratures, amplitude (Q) and phase (P), rather than position and momentum. I spent a while trying to come up with a nice explanation, but this page does it much better than I could, and it has nice pictures, too:
http://gerdbreitenbach.de/gallery/
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Jon - Thank you. I understood the short answer [:D]
That's an interesting site you posted the link to. I think I shall have to womble through it a couple more times to make sure I understand it all properly.
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Interesting, so when you think of Louis de Broglie's 'matter waves' you see them as a 'probability weave' then (using my poetic 'right of way' here:) Jp? I have to admit that this is easier to understand than to see them as actual 'electromagnetic standing waves', no offense meant by that Vern. It's just me and and 'matter' :)
I will definitely look up both your links and try to see.
(I ..really.. like this forum:)
But Vern, what you wrote, about how Einstein thought regarding Lorentz contraction, is still gnawing on my mind.
Every time I try to look it up it's seems to get mentioned only in passing, like we all should know how he thought about it? And then comes an argument why it it should be seen as this way or that way... Well, I don't even know how and why he would differ(ok, I might guess, but I don't know:), so if there is a good link/thread (historical?) about it I'm still interested.
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Every time I try to look it up it's seems to get mentioned only in passing, like we all should know how he thought about it? And then comes an argument why it it should be seen as this way or that way... Well, I don't even know how and why he would differ(ok, I might guess, but I don't know:), so if there is a good link/thread (historical?) about it I'm still interested.
I had that same problem when trying to understand relativity phenomena. Then I realized that Einstein and Lorentz had completely different views about its cause. You have to understand it from one or the other. Either works as solutions to relativity problems, but you can't use part one and part the other. For a long time I was trying to use part one and part the other. So I would think of Lorentz contraction of matter and try to fit it into Einstein's distortion of space and time. That doesn't work. The Lorentz view is distortion of matter because of movement. The Einstein view is distortion of space-time, with matter only following the distortion of space because it lives in it.
But we can't abandon the Einstein view because most all the work of understanding relativity uses the Einstein concept.
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I have always thought that Lorentz contraction was a solution for relativity to do with movement. Now you say it is something outside of GR?
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Reading your analogy with a guitar string again, do you see it as going back to string theory Jp?
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I have always thought that Lorentz contraction was a solution for relativity to do with movement. Now you say it is something outside of GR?
The Lorentz-Fitzgerald solution for relativity phenomena came before Einstein's theory of Special Relativity. The Lorentz version attributes all the dimensional as well as time-experience distortion to matter.
Edit: Yes; of course, the distortion in both cases is due to movement. The Lorentz version lends itself to causal analysis; that cause being: The final irreducible constituent of all physical reality is the electromagnetic field.
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Thank you, Vern. I am not particularly au fait with the history of science.
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Interesting, so when you think of Louis de Broglie's 'matter waves' you see them as a 'probability weave' then (using my poetic 'right of way' here:) Jp?
I see them that way, though I'm not sure what you mean by "weave". The waves associated with QM seem to be just probabilities telling you where you're likely to find a particle should you try to measure it. Wave effects such as interference and diffraction change this probability.
Disclaimer: QM is so weird that there's other ways to explain the meaning of it: http://en.wikipedia.org/wiki/Interpretation_of_quantum_mechanics
Reading your analogy with a guitar string again, do you see it as going back to string theory Jp?
No! A guitar string is just a nice simple way of seeing a standing wave that's confined to one object. String theory is way too complicated to bring into this (also, I don't know a thing about it).
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Ok.
Just curious :)
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vern
Any time an electron's resonance is broken, as in introducing it to it's oppositely charged partner, it abandons its electron state of matter and zips off in a straight line at the speed of light.
There seems to be some confusion here.
An electron is an electron - it doesn't go anywhere at the speed of light. It changes its energy state and a photon ('speed of light') is released / captured. If the electron goes away it can be at any speed - according to the energy it is given - it could be a few m/s.
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There seems to be some confusion here.
An electron is an electron - it doesn't go anywhere at the speed of light. It changes its energy state and a photon ('speed of light') is released / captured. If the electron goes away it can be at any speed - according to the energy it is given - it could be a few m/s.
Yes; I know; maybe I should have said; abandons its electron state, becomes a photon, and zips ...
I know that for a time folks liked to think that there was some solid something that was the electron and that the energy it gave up when it ceased to exist was a property of the electron. John Wheeler suggested that the solid something that was the electron hid itself in an invisible foam-like property of space. But I didn't think that idea caught on.
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If an electron does not move what moves in an electrical circuit?.
Cheers
justaskin
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Isn't it the exchanging of photons that causes it?
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If an electron does not move what moves in an electrical circuit?.
Cheers
justaskin
I didn't see any suggestion that an electron does not move; just that it does not move at the speed of light.
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If an electron does not move what moves in an electrical circuit?.
Cheers
justaskin
Reading you I felt 'forced' to share a good friend of mine ( and I don't care in the least if he refuses to recognize this relation :)
A bright answer from a bright guy, once again..
Corvidae said.. 'Apropos electrons and charge'..
to help me see :)
"
Maybe a mammalian analogy would be more enlightening. Think of a conductor as a long field of gopher holes. Every hole is an atom with it's own set of gophers. There is exactly enough room in each gopher hole for 29 gophers (copper gopher holes). And every gopher hole needs 29 gophers to keep itself maintained.
Along comes farmer Battery and he shoots a gopher on one end of the field and releases one gopher on the other end of the field. The gophers in the hole where one was shot, now need an extra gopher. However the new gopher is WAY on the other end of the field. It's much easier to steal a gopher from a nearby hole. So the gophers charge (Yup, the mystical charge) over to the other hole (atom), and steal a gopher (electron). Now that gopher hole needs a new gopher and does the same thing to another hole that's closer to the new gopher.
Rinse and repeat until you get greasy grimy...no wait wrong analogy..Until you reach the far end of the field, and the new gopher gets pulled into the nearest hole that's missing a gopher.
In the end, the new electrons (gophers) don't actually move very far, since there is always a nearby atom needing a negative charge. For an electron to actually move all the way down the field, it'd take a whole lot of gopher killing.
If you want to get really confused about it. Try figuring out the actual electron flow involved in receiving an FM radio signal. "
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And then follows another good friends explanation :)
bm1957 writes...
"
Corvidae's analogy covers one of the points I was going to make. Electrons have negative charge and protons have positive charge, but it's only the electrons which move. When one electron moves from where it was, it leaves a 'virtual' positive charge there. This is referred to as a 'hole'. The movement of negative electrons in one direction is entirely equivalent to the movement of positive holes in the other direction. Protons very rarely move in an electrical circuit (except maybe when ions are conducting, off point though.).
The transfer of energy (according to currently accepted theory) is entirely through the transfer of photons between electrons; an electron receiving a photon becomes excited and jumps to a higher energy level. When it falls back down to its original energy level, it releases a photon. This is the proposed mechanism for the electromagnetic force. Photons can easily transfer across a junction between the socket in the wall and the plug which is inserted into it, as can electrons flow both ways (equivalent to positive holes moving in opposite directions to the electrons) across the junction. This is also true if it was your finger which went into the socket and completed the circuit to ground.
Back to AC. The electrons are still moving, but the net flow rate is zero. They go backwards and forwards on the spot, about 20 times a second (at 50Hz). The distance they go backwards and forwards depends on the voltage. The average DC current being transferred is zero. If you somehow tweak your 'receiver' to flip every cycle (as motors and electronic circuits can), then you extract the energy of the 'positive DC electrons' then flip, and extract the energy of the 'negative DC electrons'. Since you flip in between, the energies add together because they were 180deg out of phase before the flip, and are now exactly in phase. The wiki rectifier link should clarify this.
Hopefully this is all following logically??? "
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I think I'd better gopher my tea now [;D]
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Both of those guys are so very good :)
And I think (?) this is a main stream explanation.
Even though I still wonder why those poor gophers gets shot.
Bad breath? Entropy??
Or was it just that their time was in, sort of???
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Yes; I know; maybe I should have said; abandons its electron state, becomes a photon, and zips ...
When does this happen, Vern? That is my confusion. Are you talking of some Gamma Ray interaction?
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Yes; I know; maybe I should have said; abandons its electron state, becomes a photon, and zips ...
When does this happen, Vern? That is my confusion. Are you talking of some Gamma Ray interaction?
I was thinking of electron-positron collisions where both become gamma ray photons. The confusedly way of saying it was an attempt to evoke the thought that maybe the electron was a gamma ray photon all along, and only needed a little nudge to break out of its entrapment and continue on its way [:)]
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Thanks yor-on that was my understanding without any gophers having to be shot. [:D]
I must have misunderstood what was written.
Give us your electron or the gopher gets it.
Cheers
justaskin
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Give us your electron or the gopher gets it.
Cheers
justaskin
Yep, and then run of with all the loot:)