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Author Topic: Do electrons rotate?  (Read 28094 times)

Offline JP

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Do electrons rotate?
« Reply #25 on: 19/02/2010 10:11:19 »
But as I'm, ah, ever so slightly weird myself I think I get it, a very nice explanation. In that motto a superposition will be how you define a given wave by using approximations to narrow it down to a 'best answer'?

But can there be a definite answer to such a procedure, doesn't it just goes on and on?
But very very good explanation of the mathematic principle for it. Sweet one JP.
In many cases, it does go on and on, like in the case above.  This is one of the cases where physicists can use infinities to do some useful stuff, like keep track of the infinite number of sine waves in my above example.

Quote
And a 'wavepacket', if you tried to define it like this, or could I see this as a 'reversed wavepacket procedure' sort of? You should be able to do this both ways mathematically, shouldn't you? I think of a wave packet as what it seems to say, like a 'packet of waves' together.
A wavepacket is also like what I showed above.  It's a wave of short length that you can break into a superposition of waves just like how I did it above.  You just change the step function I showed to a packet of your choice.  Of course, the recipe for how to add sine functions to get the wave packet changes, depending on the packet. 

Quote
This one though, could you expand on how you mean here?

"Why this is important is that in quantum mechanics, you choose what you want to measure, and then essentially "write" your wave in terms of other waves that have well-defined values of that quantity and then your measurement picks one wave from among these.  It can only pick one answer, so it picks among them randomly (with some rules giving the probabilities of picking each particular answer)."
Quantum mechanics is all about measurements.  It gives you recipes to predict the probabilities of getting different measurements.  Let's say you have a wave function (like the step function I showed above), and you want to predict the probability of measuring a certain value X of some measurable quantity.  Your original wave function usually doesn't have an exact value of your measurable quantity: for example, the step function above doesn't have an exact value of sine-wave frequency since it's not a sine wave, but in quantum mechanics you can still make a measurement of sine-wave frequency and get a single answer.  So how do you make predictions about the answer that you get?

The rule for making that prediction is to write your wave function as a superposition of simpler waves, where each simpler wave has an exact value of the thing you're trying to measure, which is exactly what I did above by writing that step function in terms of sine waves.  Then the probability of making each measurement is the amplitude (in other words "how much") of that particular simpler wave.  So in the example above, the amplitude of the sine waves would correspond to the probability of measuring that sine-wave frequency in an experiment.

By the way, the collapse of the wave function just says that after you make the measurement, your original wave function becomes the one you measured.  So if I measured one particular sine wave, from that point on, my wave function would actually be that sine wave, and the step would have ceased to exist.

Quote
Hey, I know what it reminded me of now :) A analogue signal to digital, right? And that makes sense, it's 'cut outs' right? A way to treat the universe as 'quanta' so to get a 'over see able' system?

Or am I bicycling in the blue younder again?
I think that's a bit of a stretch, since it loses the idea that each simple wave has an exact value of something you're trying to measure.
 

Offline JP

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Do electrons rotate?
« Reply #26 on: 19/02/2010 10:24:00 »
By the way, I'm happy to go on about superpositions and quantum mechanics (I find this stuff really cool), but maybe we should start a new thread if you have more questions, since it's a bit off topic?
 

Offline yor_on

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« Reply #27 on: 19/02/2010 19:15:10 »
It's okay JP, i see your point there. Why we started it was when I asked about how to see those wave packets, and I think I've gotten a very good explanation to that :)

And that helps me see how the idea is mathematically. And yes, I agree, QM is really cool :) but (as you said) we might need to steer this back to electrons. So I'm still wondering if those orbitals transitions take time? And if there is a state where they are gone /'superimposed'/not defined? And if there is, shouldn't it be measurable?
===

Why I'm asking it is because I need to know :)

It's about how I should look at electrons in general. As entities or as probability functions (wavepackets). You can look at it this way too. When a electron is alone orbitaling the nucleus its energy is well defined as I understands it? But when together with other electrons their energies seems to become a function of them all? Very confusing :)

And then my question is, can we say that those 'jumps' take a measurable time inside our arrow? Or how should I look at it? As wave functions subtly changing depending on interactions but without any defineable 'transition times'. Don't know if this makes sense at all, but I'm interested in your views.
« Last Edit: 19/02/2010 19:58:16 by yor_on »
 

Offline Soul Surfer

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« Reply #28 on: 19/02/2010 22:06:48 »
JP  you already appear to understand Fourier transforms so it is perfectly obvious to you that any wave that starts and stops CANNOT BE A SINGLE FREQUENCY so why are you worried about this?  A single photon cannot possibly be a pure sine wave of a single frequency because such a sine wave goes on (and has gone on)for ever with a constant amplitude and no one ever said it was.  The wave packet has its maximum energy at a particular frequency and tails off  at frequencies on either side of this according to its line width.  (this is a property of a spectrum line that can be predicted from quantum mechanics and measured to show that the prediction is accurate).  You are taking simple descriptions that are approximations used to describe things to scientists who are starting to learn and applying them absolutely.  As you and everyone else should realise.  EVERYTHING IN PHYSICS IS AN APPROXIMATION there are absolutely no absolutes.  These absolutes only exist in mathematics  which is NOT physics.

Nearly all the arguments in these pages are caused by people realising that all approximations fail under certain limiting  conditions and then either trying to apply them beyond their limits of suitability or finding alternative hypotheses to get round the "problem" suggesting that the main core of scientific opinion does not really know what it is talking about.
« Last Edit: 19/02/2010 22:22:10 by Soul Surfer »
 

Offline yor_on

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« Reply #29 on: 19/02/2010 22:59:04 »
No disrespect meant here Soul Surfer, but I hope you don't mean me now? I'm fully in agreement with your definition of approximations and the need for understanding why they exist, and as far as I know I'm not trying to go around anything? I just want to see them better, to do that I ask :)

And JP gave me a tool to understand your thoughts better here. I think that he too is aware of that it's only an approximation, but for me and as I guess, for some others :) his description gave me an idea of how they are thought to work.

As for a sine wave not having an end? It will have in its interaction, won't it? As a mathematical concept it won't as it is an idealization of a smooth repetitive oscillation, with the weight put upon 'repetitive'. But what you seem to say here is that a wavepackets then have limits, which they need if they ever will have a resemblance to what we call photons, but it's  mathematically I presume? In which way do those waves in wavepackets then differ from sine waves?

After reading your thoughts I went up to look some more on waves and superpositions . And there they had this definition of a wavepacket?

--Quote--

The regions of large wave amplitude are called wave packets. Wave packets will play a central role in what is to follow, so it is important that we acquire a good understanding of them. The wave packets produced by only two sine waves are not well separated along the x-axis. However, if we superimpose many waves, we can produce an isolated wave packet. For example, figure 1.9 shows the results of superimposing 20 sine waves with wavenumbers k = 0.4m, m = 1,2, \ldots , 20, where the amplitudes of the waves are largest for wavenumbers near k = 4.

--End of quote--

As I said Soul Surfer, I'm not trying to rewrite QM, just trying to see where the ideas stands today.
« Last Edit: 19/02/2010 23:01:05 by yor_on »
 

Offline Soul Surfer

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« Reply #30 on: 19/02/2010 23:22:07 »
No I was referring to jPs  apparent insistence that photon wave packets only included a single frequency pure sinusoid.  Note they could contain a single frequency gaussian amplitude modulated sinusoid.  This would produce the normal line widths observed in spectrum lines.  This is probably the best way to imagine what the waveform of a photon is like.

My definition of a photon wave packet is a burst of energy of a specific frequency that starts small builds to a peak and falls away to zero over a specific time period longer than a single wave. This is not like a bell which starts with an impulse and then dies away.  mind you some of the more extreme pulse modulators nowadays can produce light waveforms that are just about a single wave.

 

Offline yor_on

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« Reply #31 on: 20/02/2010 01:08:29 »
Soul Surfer I got to admit that I fail to see what a 'single frequency gaussian amplitude modulated sinusoid.' might look like? Can you simplify your description somewhat so I might get an idea :)

If I look at a single photon I would say that it has an energy but no waves. and for it to get a wavelike property you will have to superimpose them in 'place' and possibly 'arrange' them so that they will differ in energy over times arrow?

And for a photon to exist you will need an interaction right? And then an EM field is needed, am I correct? And when you have an EM field and a atom interacting you can't really define it as only a single photon, or can you? Is there any way to guarantee that your wavepacket only will represent a discrete energy level?

(Hey, soon I will decide that there can be no single photons:)
==

As I understand it a photon has no magnetic field (it's zero) and without that how can there be any EM fluctuations? If I want one photon to be representative of waves, won't I need those fluctuations present in times arrow intrinsic to that photon?
==
Awh, this is really confusing. I'm trying to see how a photon can be seen as a wavepacket, and mathematically it seems to work, but only when choosing appropriate 'cutoff's'. Or am I loosing it again ::))
« Last Edit: 20/02/2010 01:48:23 by yor_on »
 

Offline JP

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« Reply #32 on: 20/02/2010 02:01:31 »
No I was referring to jPs  apparent insistence that photon wave packets only included a single frequency pure sinusoid.  Note they could contain a single frequency gaussian amplitude modulated sinusoid.  This would produce the normal line widths observed in spectrum lines.  This is probably the best way to imagine what the waveform of a photon is like.

Soul Surfer, I agree with you completely, but I think you've misinterpreted what I said.  A photon doesn't have a well-defined spatial representation by its nature, so it can't be a sinusoid.  However, it does have a precise frequency, which has to do with its energy, and is modeled as an excitation of a harmonic oscillator.  (If you've dealt with quantum harmonic oscillators, you know that the frequency of the oscillator isn't sinusoidal.)  You can check a textbook like Mandel and Wolf for details, and some of it is online here.

Is it worth starting a new post about the bandwidth of photons or the photon model?  I don't want to drag this any more off topic.  Soul Surfer, since you had the original question on photons and bandwidth, do you want to do so?
« Last Edit: 20/02/2010 02:15:10 by JP »
 

Offline yor_on

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« Reply #33 on: 20/02/2010 02:41:04 »
E = h nu?
But how? Is a relationship the same as saying that "as it exist it must be, at all times"?
Or does it speak about interactions, as that's where we draw those conclusions from as I see it. And from there my next question must become. Can we speak with surety of anything while it's not interacting?

Yeah, I know :)

sleep, right?
==

"higher frequencies mean shorter wavelengths"
So what is the energy of virtual photons in that motto?
Or their frequency?
==

So, if I accept that, photons must have a frequency, right?
And then I will have to state that a single photon oscillates too :)
And from there?

So from being a particle of no geometric size and with a EM field of zero, to a oscillating particle of an extremely short wavelength(?) being well defined in space; And also simultaneously defined to an extremely long(?) wavelength and therefore diffused geometrically. But now definitely of some defined placement in SpaceTime depending on frequency aka energy, even as a photon. My headache is now astronomical :)

And you're right JP, in a way, but it's difficult to discuss electrons without interactions in time :)
==

As if I assume that even if a photon of high energy would be better defined in SpaceTime it would still matter which way I was traveling, and what speed I had relative it, right? And the same goes for its energy. And it can do this without any magnetic field whatsoever. And it won't emit any radiation.
==

Sorry, saw that it wasn't that clear what I meant :)
Hope its reads better now
« Last Edit: 20/02/2010 06:16:45 by yor_on »
 

Offline yor_on

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« Reply #34 on: 20/02/2010 17:28:03 »
And there's one more thing that disturbs me. As I understands it we say that virtual photons are under Planck time right? And we use this phenomena for describing a lot of strange possibilities, like being able to get out from a Black Hole. Maybe I'm thinking wrong here but to me there are major differences between macroscopic SpaceTime and what we have under Planck time.

But reading about 'Rindler Observers' and the way their observations will differ from a observer being at rest with f.ex. Earth they , if i got it right, will see virtual particles as being real. That opens major questions for me. For one I can't help wondering about the arrow of time, if I assume that this phenomena now have passed some sort of threshold as it exists continuously in the observations by those Rindler observers? And what should  the definition of inside versus outside our arrow of time be. Why should 'virtual particles' become real particles due to a uniform acceleration. It's like SpaceTime exist on a sliding scale of 'reality'?

But I'm neither doubting photons as particles or as waves. When it comes to wavepackets I've tried to avoid them as I have enough troubles trying to understand photons as particles:) But as wave packets are able to predict a lot of behaviors they are working, right? But I'm still wondering what a photon is? and 'times arrow' too.

When it comes to wave packets I understands that your starting presumptions and definitions are of the utmost importance when it comes to the decide the outcome of a experiment?

--Quote--

Wave packet propagation is a useful technique for solving quantum mechanical problems over a wide range of applications. Since very few quantum mechanical problems can be solved exactly, each propagation technique can only provide an estimate to the actual solution. For a propagation algorithm to be useful it must be fast in addition to being accurate. With most algorithms a high accuracy can be reached by taking a small time step between propagation calculations. However, if the time step is too small too much time is needed to reach a final answer, so a balance between speed and accuracy is needed for each algorithm. In addition, the parameters of the energy spectrum I am interested in calculating must be taken into account, since the energy range of the spectrum determines the maximum time step that can be taken, and the energy resolution of the spectrum determines the length of time that the wave packet must be propagated.

The different propagation techniques I have studied include the Feit & Fleck split operator method, a time dependent modified Cayley method, a second-order differencing scheme, an iterative Lanczos reduction, and a Chebyshev polynomial expansion. Various coordinate systems have been used for the propagations, including normal coordinates, Jacobi coordinates and Radau coordinates. Finally, different methods for calculating the kinetic energy of the system have been explored, including FFT's and various finite-difference schemes.

When normal coordinates can be used, the Feit & Fleck split operator propagation technique, using FFT's to calculate the kinetic energy, is the most robust and fastest of the various combinations studied. However, normal coordinates do not preserve the symmetry of the OClO molecule and therefore cannot always be relied upon to produce accurate results. In such cases Radau coordinates must be used, and in order to reproduce the reflectional symmetry of the angle coordinate a finite-difference scheme must be used to find the kinetic energy, rather than an FFT. We use a 25-point finite difference method because we found it gave the best compromise between accuracy and speed. Since FFT's cannot be used with Radau coordinates the split operator propagation technique is no longer viable; a Chebyshev expansion is instead used to propagate the wave packet.

--End of Quote-- Wave packets

And perhaps?
Back to electrons:)
 

Offline Soul Surfer

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« Reply #35 on: 20/02/2010 21:42:49 »
yor-on From your writings in the previous few replies (as opposed to your quotations) it is clear to me that your mental image of electromagnetic waves in general and photons in particular is extremely confused and inaccurate.  A lot of your quotations appear to be either from advanced texts or spoof garbage texts (there are a lot of fake pseudo scientific texts around on the web that look learned but are really just rubbish)  that are not relevant to the problems that you have with understanding. 

I would recommend that you read a good well established basic physics textbook on the topics and try to understand initially classical electromagnetic wave theory and then extend this to the most basic quantum theory.  To go back to square one and put it all in here is more work than I am prepared to do at the moment
 

Offline yor_on

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« Reply #36 on: 20/02/2010 22:02:56 »
Well Soul Surfer, your opinion is your own of course. But all together with the way you reacted towards JP I can't say I'm surprised :)

Be cool.
==
Btw: What's so apparently wrong in my comments?
Never said I understood wave packet theory?
I said I tried to stay away from it, more or less :)

As you imply, that may make me a 'fossil' not understanding anything about waves.
Sh* never said I did, you do then :)
Come on Soul Surfer, give your solution to us mortals.

We need it...
« Last Edit: 20/02/2010 22:08:54 by yor_on »
 

Offline Soul Surfer

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« Reply #37 on: 20/02/2010 23:11:28 »
Well lets have a go.  You appear to make a lot of categorical statements about electromagnetic waves and quanta please forget all these and we will start from the beginning.

A varying electrical field in space causes an electrical current to flow as space itself is charged up to crate the field.  An electrical current creates a magnetic field.  A varying magnetic field creates an electrical field as the magnetic polarisation of space itself changes.  This is a property of space in the same way as mass and gravitation.  This as Maxwell realised creates the possibility of waves (like waves in the sea) where energy is propagated by moving between electrical energy and magnetic energy within space even when nothing else was present.

The velocity of these waves is determined by the electrical permittivity and the magnetic permeability of free space and is equal to the well known velocity of light.  the wavelength of the waves is defined as in all wave motions by the equation wavelength times frequency equals velocity.  The velocity of the waves is constant for all frequencies in free space.

Wavelengths and frequencies of electromagnetic radiation can vary over a vast range from kilometres as in long waves  through meters and centimetres for TV, phones and microwave cookers  to nanometers for light and very much shorter for X-rays and Gamma rays (ionising radiation).

An electron is a single negative electrical charge  a proton is a single positive electrical charge but much heavier than an electron.

Let us consider (in a purely classical physics sense) what might happen as a single electron approaches a single proton to form a hydrogen atom if the electron has some angular momentum it could go into orbit around the proton like the earth around the sun and let us ignore any motion of the proton around the common centre of gravity.  This could in theory be a stable situation except that the electron as it orbits would create a varying electrical and magnetic field in space and would lose energy by radiating electromagnetic waves and the proton and electron would quickly fuse together but this does not happen.  For certain very specific orbits the electron it is found by experiment that it is stable for quite a long time before it decays and at one particular state the ground state it is permanently stable in the absence of major disturbances.

When the electron moves between  two of the metastable states it radiates a pulse of electromagnetic waves.  this consists of a wave of a particular frequency that starts builds up over a few cycles and then decays taking a time that is related to that particular change.  This pulse of electromagnetic waves which is in effect usually much larger that the atom that originates it because of the wavelength and time it takes to radiate.

Please note again this is all totally classical physics and was in effect observed and accepted long before quantum theory was considered.

The metastable states are a bit like resonant cavities where the electron that is trying all the time to radiate its energy is in effect having energy fed back to it from the fields that it is creating in a continuous feedback loop.

Quantum mechanics just explains this classical process in a slightly different way and allows the energy levels to be calculated to a great degree of accuracy via quantum electrodynamics the most accurate physical theory that we have at the moment.

As an interesting aside let me add one other fact.   It can be observed that although electrons are particles they can also behave like waves and show interference patterns etc.  The wavelength of the waves depends on the momentum (mass times velocity) of the electron.  If one considered the metastable states of the electron and work out the "wavelengths" of the electrons as waves when they are in these orbits you find that the metastable states correspond to whole numbers of wavelengths of the electron that is the electrons are resonant structures then.  Again all this is classical physics and measurable without ant recourse to quantum theory for an isolated hydrogen atom.

Similarly all quantum processes have a solid bedrock in classical physics although once you get more electrons in an atom the calculations become incredibly complex.

Nowadays physics teaching tends to dive straight into quantum processes without fully explaining the classical physics background and this causes severe confusion in some peoples minds.

« Last Edit: 20/02/2010 23:23:28 by Soul Surfer »
 

Offline yor_on

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« Reply #38 on: 20/02/2010 23:56:18 »
Soul Surfer, let's call my expressions about photons and wavepackets as born out of frustration here :) And let me add that I'm glad you took it this way.

As for if a photon has a frequency in a mathematical sense bound to it's energy I know, actually I do even though i tend to forget it as i look at it. But what's interest me are those 'single ones' aka 'what the he* is a photon?' and those I think to be non-classical, and in that motto it, to me that is, becomes impossible to understand how they are thought to act as common waves in their single state?

I will read you and see how you think.
Nice.
 

Offline yor_on

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« Reply #39 on: 21/02/2010 03:14:46 »
Thanks for your lecture Soul Surfer. A nice view of a classical approach.
And single photons will in your eyes then be a bell formed (Gaussian)wave packet with its 'cutoff's' decided by what? And should I understand that as a classical approach too?

And your use of 'free space' I assume to include some sort of particles, not being a 'perfect vacuum' as it's normally defined in classical physics? Or do you mean that electromagnetism will propagate in a free space in the classical sense. That's one of my main questions in fact, as if we define that 'space' as containing nothing, and consider an EM wave as something obeying our macroscopic arrow of time (above Planck time/size) then, for this question, I will ignore 'virtual energy/particles'. As I believe that everything needs an interaction (medium if you like) to propagate, be it billiard balls or waves, that one is quite interesting to me?
==

I'm presuming that you are using 'free space' here in the meaning of how it relates to electromagnetic theory (Maxwell). In that idea 'virtual energy or particles' (quantum vacuum) have no place, as I understands it?
« Last Edit: 21/02/2010 03:33:58 by yor_on »
 

Offline JP

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« Reply #40 on: 21/02/2010 06:26:48 »
Yor_on, the photon picture doesn't have a classical wave model.  It's used because in certain cases, the classical wave theory breaks down.  The link between the two models is mathematically complex.  This is because they simply don't have a nice wave function that you can draw in space.  They have a very precise definition in terms of energy, but it turns out that you can't draw them in space.  A classical wave is a superposition of photons in a particular way, but that's incredibly hard to visualize without a grasp on the mathematics, simply because you can't write down what a photon's wave function looks like in space, whereas you can write a classical wave in space.  It can, however, be done.  (The link above to Mandel and Wolf is a good place to start, but you need to be ready for some heavy math and you want a working knowledge of quantum mechanics.) 

Photons are important because there are cases where knowing about energies is much more important than knowing about what it looks like in space, and there are cases where you can make approximations to get some idea of what they'd look like in space.  However, in most cases, you don't need the photon model.  Even though it should be right, treating most everyday problems in terms of photons is so incredibly complex that no one would want to do it.
 

Offline Soul Surfer

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« Reply #41 on: 21/02/2010 10:11:01 »
when I say free space I mean a total vacuum with absolutely no other particles in it.  they only disturb the picture and are not required. a slight lack of perfection i.e. the odd particle does not have any significant effect.

As with an exponential decay the gaussian bell function goes off to infinity mathematically in both directions and is never zero.  physically it becomes to small to matter at a few standard deviations from the peak.   This is the big difference between mathematical things and physical things.

Some of your problems seem to be associated with mathematical absolutes.   in this sense every particle in the universe extends throughout the entire universe in all space and time
 

Offline Soul Surfer

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« Reply #42 on: 21/02/2010 10:55:13 »
It suddenly struck me.  maybe you are thinking about what is sometimes called "the quantum mechanical vacuum"  which is a seething mass of virtual particles that only exist within the limits allowed by the uncertainty principle.  This is not what i am talking about because the details of that can never be known in any other way than the statistics of the uncertainty principle.  what I am talking about is the observable classical vacuum of standard physics.
 

Offline Farsight

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« Reply #43 on: 21/02/2010 12:39:22 »
But Farsight, you will need to be able to explain the properties of an electron going through a Stern-Gerlach magnet too for your proposal to become a theory, don't you agree? Or maybe you already have?
It isn't my proposal, yor_on. Williamson and van der Mark used to be at CERN. The former is a senior lecturer at Glasgow University, the latter is chief scientist at Philips. Qiu-Hong Hu is a researcher at the University of Gothenburg. Don't let ad-hominems like "crank" deter you. This really is leading edge stuff, see this week's New Scientist and the article on page 15 http://www.newscientist.com/article/dn18526-atom-smasher-shows-vacuum-of-space-in-a-twist.html. Here's an excerpt - it's not done to repeat the whole thing:

Quote
Atom smasher shows vacuum of space in a twist

Ephemeral vortices that form in the vacuum of space may have been spotted for the first time. They could help to explain how matter gets much of its mass.

Most of the mass of ordinary matter comes from nucleons protons and neutrons. Each nucleon, in turn, is made of three quarks. But the quarks themselves account for only about 1 per cent of the mass of a nucleon. The remainder of the mass comes from the force that holds the quarks together. This force is mediated by particles called gluons.

A theory called quantum chromodynamics is used to calculate how quarks and gluons combine to give mass to nucleons, but exactly how this phenomenon works is not fully understood.

One possibility is that the fields created by gluons can twist, forming vortex-like structures in the all-pervasive vacuum of space, and when quarks loop through these vortices, they gain energy, making them heavier.

Now the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory (BNL) in Upton, New York, has seen signs of such vortices...
« Last Edit: 21/02/2010 12:42:13 by Farsight »
 

Offline Farsight

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Do electrons rotate?
« Reply #44 on: 21/02/2010 12:50:38 »
Farsight: in addition to the properties you have discussed, the electron model that you propose which dimensions would have? Does the model also predict the wavelike properties of the electron?
It's three-dimensional, lightarrow, like a bagel with a twist only there's no actual surface to it. I wouldn't say the model predicts the wavelike properties of the electron, because that's what we observe. Rather it explains them because it describes the electron as a double-wrapped electromagnetic wave going round and round in a circle.
 

Offline yor_on

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Do electrons rotate?
« Reply #45 on: 21/02/2010 20:31:41 »
JP you say that "A classical wave is a superposition of photons in a particular way" If I would guess :) then this math describing it is introducing some concept more than just 3D + time. It can't be enough with defining different vectors/tensors, can it?

No SoulSurfer I was thinking straightly 'classically' when I asked you about it, and that's why went some way to define what I meant too. It's easy to see that light somehow can' make it' through space, some of the solutions I've seen suggested is just that "the quantum mechanical vacuum" you thought of. Then you have other solutions too :) that somehow seems to expect both a sink (eye) and a source (sun) present for any 'wave' to exist, meaning that they won't do it until our two prerequisites are fulfilled.

The interesting thing to me is that in a classical sense a vacuum is a 'nothing'. Let's say that you compress it, well, try to compress it :) It will be extremely easy to do so on earth. In fact the energy spent will be to create it, not compress it. So what exactly are those waves propagating through? Is a vacuum a 'medium'? And how, if so, should I understand that 'medium'?

Okay Farsight, keep forgetting that :) So did you find an description of how they explain the properties of an electron going through a Stern-Gerlach magnet?
 

Offline Farsight

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Do electrons rotate?
« Reply #46 on: 22/02/2010 01:47:55 »
No, I didn't look for it. I know it anyway. That's easy.
 

Offline PhysBang

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Do electrons rotate?
« Reply #47 on: 22/02/2010 02:02:22 »
This really is leading edge stuff, see this week's New Scientist and the article on page 15 http://www.newscientist.com/article/dn18526-atom-smasher-shows-vacuum-of-space-in-a-twist.html.
Why would you post this? This obviously has nothing to do with electrons?
It's three-dimensional, lightarrow, like a bagel with a twist only there's no actual surface to it. I wouldn't say the model predicts the wavelike properties of the electron, because that's what we observe. Rather it explains them because it describes the electron as a double-wrapped electromagnetic wave going round and round in a circle.
So how does this explain the wavelike properties?
No, I didn't look for it. I know it anyway. That's easy.
How can we take this answer seriously? If it's so easy, please demonstrate how your proposal produces the appropriate Stern-Gerlach magnet effects. It looks like you are merely trying to avoid answering the question, but surely that cannot be the case.
 

Offline yor_on

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Do electrons rotate?
« Reply #48 on: 22/02/2010 02:49:26 »
I know we are getting of course now but I found this experiment when I was searching on experiments done with superimposing photons. Now, before someone tells me that this can't be done :) We have the idea and we use it to explain a lot of things, don't we? Which to me seems to imply that you can't used a 'flawed model' to build further proposals on, right?

The reason why it seems to be hard to do is HUP (Heisenberg's uncertainty principle) as I understands it. "You can't get photons that have perfectly defined position and trajectory. Photons with a perfectly defined trajectory must have an uncertainty in their wavevector direction of zero, which implies that the wavefunction of the photon is an infinite plane wave. Since the wavefunction is infinite in extent, the uncertainty in position is infinite. (by Claude Bile)" Remember that this answer is referring to when 'trying to superimpose photons', and not about superimposing waves.

In this experiment they say some, to me, remarkable things "The physicists allowed the photon to pass through the loop five times. They then found that one of the photons had fanned out into a chain of several wave packets which formed a superimposed state."

So they start with one photon, right? "They create this state by using a polarizer to first generate a photon oscillating in a horizontal or vertical direction. This is then moved to the superimposed state by means of a half-wave plate. The half-wave plate acts, to a certain extent, like the pin of a classical Galton board, except that it does not force the photon to adopt a specific direction but ensures that it figuratively continues to move in both directions." And here they seem to get a superimposition from only one photon. How is that done? Ah well it's the same principle as for creating a entanglement, right. But then we talk about waves, not 'photons'?

By the recirculating of those two 'new photons' superimposed, but going two different paths, one longer than the other, back to the half-wave plate (five times), they at last ends up with how many photons (wavepackets)? they must mean 32 like 2, 4, 8, 16, 32 or? Furthermore, after that first 'superimposition/split' they suddenly refer to them/it as wavepackets, why? Because they were treated as waves in the first 'split'? "They then found that one of the photons had fanned out into a chain of several wave packets which formed a superimposed state." 

'One of the photons'? Not wave packets suddenly but photons? And, one of what? They started with only one photon, superimposed it to ? wavepackets. Do they mean that one of those wavepackets now is treated as a singular photon, that in its turn make that chain they are referring too? Or are they still discussing our original photon, but now superimposed into several? And in the end they use a detector that only registers the photon as a particle, which then will give them, one photon again, right?

So it gives me a headache :)
They 'superimpose' a photon into several, which may be allowed according to HUP? From that they get several superimposed wavepackets but traveling different lengths in time, that then 'transforms' into a photon again, as I understands it?

Source.

If you have any understanding of how this is thought to be done, I'm very interested.
If you understands it that is. I know I don't.
==

And, can you really jump from calling it a photon to a wave, alternative wavepacket, like this?
==

Why I put a question mark after writing 'They 'superimpose' a photon into several, which may be allowed according to HUP?' Is because they call it a photon, not a wave.. to me those have different properties, and what you can observe and do with a wave you can't do with a 'photon', well, as I (still) see it :)

So yeah, I'm an old 'fogey', or 'stofil'  as we say in Swedish :)
==
One last question, how do they 'know' that 'they' take both paths experimentally?
Measuring it? Won't that collapse the 'photons' superposition/wavepackets?
« Last Edit: 22/02/2010 05:57:26 by yor_on »
 

Offline JP

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Do electrons rotate?
« Reply #49 on: 22/02/2010 05:51:50 »
Yor_on, you don't need quantum optics to explain what they did.  A classical version of the experiment could be done by using a pules of light, and splitting it into two parts.  One part takes a longer path than the other and they recombine later on before they hit a detector.  What you'd see is that part of the pulse arrives first while the part that took the longer path arrives later.  It sounds like that's essentially what they did, except they had it working with only one photon at a time so that you could either detect it early or late, rather than seeing both pulses every time.

They don't give a lot of mathematical details on what they're doing and assuming in this problem, so its hard to comment on the wave packet terminology.  You can describe wave packets in terms of non-space variables, which is one way to describe photons, or you can make approximations to based on the fact that it's in a fiber in order to write a spatial wave packet in this case. 

By the way, this site should be useful as an introduction to photons.  If you can understand the basics on that site, you should be a long way to understanding photons and how they relate to classical waves.
« Last Edit: 22/02/2010 05:56:27 by JP »
 

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Do electrons rotate?
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