steevey

That sums up my whole problem with the emphasis on the math. To me, the big issue lies in the relationship between photon frequencies, electron frequencies, etc. . . not in the calculation of predictive amounts. Those predictions could come in handy if I had a practical situation to deal with or plan, but for theoretical purposes I want to understand why these various quantum phenomena are related to one another and how they influence the behavior of matter-energy at observable levels.

 

 

 

If you want to know how this applies on an observable level, you really need to think, because quantum mechanics is all about what you can't actually see, with the exception of the colors of photons.

Otherwise, trying to use quantum mechanics to describe a something like a ball is just too difficult right now because theres literally trillion trillions of atoms in it, its just very complex and in order to use quantum mechanics to completely describe a physical object probably takes some more research in it. What your talking about is essentially like trying to use a single cell of your body to describe your entire body, which can be done to an extent with a ton of work with mapping out the genes and running simulations of those genes and looking at the cell cycle and what other cells it could have become and etc.

We still haven't even filled in all the gaps with why fores work the way they do and what they are comprised of.

"Physics combined with math?" This is making me think about starting a thread about what math actually is. Is it a means of representing quantifiable relationships in an exact manner or something else? And would it be possible to do math if something unquantified would be the basis? E.g. if photons were the basis for force, force could be quantized. But force turns out to be the basis for photon energy, and force-fields turn out to be malleable without constituent particles, how do you deal with that mathematically?

Math combined with physics are things put into terms of numeric values which represent something, which is why without physics or something to describe what things in math mean, numbers would be meaningless.

People noticed that atoms are quantized, so right off the bat we can put that into terms of numeric values to describe it, like for describing emitted photons, just take any whole number multiplied by Planck's constant times the frequency of light to get the energy of a photon emitted by an electron. But, the whole number, Planck's constant and the frequency would have no meaning unless we actually told people what they are describing.

The problem arises from the fact itself that math has no meaningless unless you say what it describes, so you could write an equation for something and it would make sense, yet that thing doesn't have to exist since when its being described just by numbers, which is why you have all these extra-dimensional theories.

So in physics when you use math, and you have an "equals" sign, you are inherently saying what two things are or are equivalent to. So in the example I showed earlier, it doesn't describe the behavior of anything at all, it describes what the energy of a photon actually is or how is equal to, which is [math]E=nhv[/math]

I think that scientists are looking for a needle in a haystack at our present level of knowledge.

 

We are up to what, 16 other dimensions to make ideas of super strings work and is it 8 to make branes work.

 

Do scientist look like they are doing science. Not as much as in the past.

 

Belief in science is on the wane somewhat I think because we are behind in prooving some of these stranger notions. See you in the multi-verse # 12236

 

Regards

 

DL

 

 

Those extra-dimensional theories are just the most popular theories, or the theories with the most attention, they aren't the only explanations scientists have for how the universe works.

There's also virtual particles which appear out of the nothingness of space, so that's something to think about before the big bang. There didn't have to be much of anything before it, but the big bang itself might have arose out of some improbability.

I rarely think about protons as being more than sources of mass/gravity and positive electrostatic charge, but I saw something today that made sure to highlight their transparency as consisting of different-directional quarks. I bet that before protons were known to consist of quarks, a physicist like you would have said that the question of whether protons consist of sub-particles or other constituent mechanics is not physics. It's ALL "potential physics." However, there's no way of knowing whether professional physicists will actually choose one direction or another.

 

Personally, I think it's interesting when some issue is not formal physics (yet) because it allows anyone with tacit knowledge to contemplate how physics would or could approach the problem. I suppose that would be a "speculations" issue, but I still think it is potential physics research. The easy question I was trying to pose with regard to this, however, is simply whether physics is leaning toward establishing primacy for either force or energy. I mean, you could either try to dissect forces for energy-relations that constitute them OR consider force-fields as fundamental entities that express energy but are themselves neither energy nor reducible to it. This sort of gets back to the ever-resurfacing conflict between nouns and verbs, though, I think. I.e. between objects and motion.

 

 

 

If you can represent of a force as a composite of numeric values, then if its equal to something, your describing what that is. Like E=mc^2, so the amount of energy is mass times the speed of light squared, which is physics combined with math.

Seriously? I tell you physics doesn't do that, so you ask anyway?

Yeah, how would spin physically behave, but refsmmat has already said we can't answer it anyway, so you don't need to respond.

As I've mentioned to Lemur, one has to be careful about what one considers "real" or "a physical thing" in physics. Physics describes how things behave, not what they are. But that's for another thread.

Ok, physics describes how things behave, so now that we've gotten that out of the way, tell me what spin is physically like. Or, How exactly could a magnetic field of an electron rotate but not the electron itself? Or can we not answer it with our current knowledge because we don't know exactly what comprises a magnetic field?

Also, can't physics describe what things are made of too? Through physics and testing of experiments and observation, we determined what an atom is, or is that just science in general?

In what waves? In the electron's wavefunction? I don't know that spin appears in the wavefunction at all; I don't know enough about the subject to be certain, though.

 

Other forms of quantization can be expressed in terms of the boundary conditions imposing limitations on the waves as you described, but they usually allow for harmonics and higher-energy modes. (For example, a wave on a string is limited to certain frequencies, but it can also be any integer multiple of those frequencies.) Spin does not exhibit this behavior.

Spin doesn't appear in Schrödinger's equation, but spin is used to describe physical effects of the properties as a wave. So how does spin have a physical effect if it isn't a physical thing? It's how the magnetic field is oriented isn't it? And by the way I've seen it, I haven't seen the electron itself spinning, only the magnetic field in a certain direction, but how is the magnetic field rotating then if the electron isn't?

Spin is quantized though, which means there's a reason particles don't posses just any and all spins, which I'm guessing has something to do with wave interference, but if that isn't true for spin which I don't know if it is, its still true for an electron's energy or angular momentum. An electron cannot posses any and all possible energies because not every value of energy allows a non destructive wave.

Physical explanations of spin also cannot account for its quantization -- there are only two possible spin states for electrons. They also cannot account for protons and electrons having the same spin, despite protons being composed of three independent particles which each have their own spin. And so on.

A proton is made up of three quarks which can only have only two possible spin states. So, two quarks will have opposite spins which will cancel out, then what's left over is an extra up quark which could account as a sort of net spin.

...in classical physics.

 

 

There is no physical way for an electron to spin fast enough to generate the requisite magnetic field. It's that simple. Quantum physics doesn't involve spinning electrons, and it does not need spinning electrons.

 

Physical explanations of spin also cannot account for its quantization -- there are only two possible spin states for electrons. They also cannot account for protons and electrons having the same spin, despite protons being composed of three independent particles which each have their own spin. And so on.

 

Simply put: Physics has no need of a physical explanation of spin.

Then what's moving the electrical field? If angular momentum isn't even a physical thing, why would that move it?

Also, can't quantinization be explained by destructive interference in the waves? If an electron could posses any energy or any spin or any etc, then the waves would be too destructive to be coherent or form really any matter. So quantinization is the result of only the possible non destructive waves existing. So if electrons with only whole integer energies can exist without producing destructive wave interference, then those are the only ways they will exist.

That won't work, because orbitals overlap. You'd end up proving that atoms can't have more than one or two electrons at all.

 

In any case, you can have two electrons in the same orbital, so long as they have opposite spins.

Well, according to the definition of a magnetic field, there has to be a specific motion that makes the electrical field rotate in the specific oriented way that it does.

No, that's not what swansont said. Just because you don't understand how something could work does not mean it cannot work. Just because you can't see how there's no physical motion does not mean it's impossible.

That's exactly what he seems to be doing though. Its as if he can't accept the possibility it might be a real physical thing thats going on just because I'm stating that possibility. I already know it might not be physical, but I also know that it could too be physical.

Because there are real effects that result from it, such as the Casimir force.

Isn't that just one explanation for it? There doesn't seam to be actual proof of virtual particles, but rather just evidence that would make sense in describing certain things, and wouldn't that also violate the statement that matter and energy can't be created or destroyed? Or is there some quantum mechanical thing about their determination and indetermination too?

Which doesn't matter. Argument from personal incredulity isn't a valid argument.

So just because I point something out its automatically invalid? That seems sort of, uh...ludicrous.

Anyway, a magnetic field is a moving electrical field, which means the electron has to be causing the motion of the electrical field in some way.

This is not true. Orbitals are not well-defined trajectories, so you can't say they are occupying the same physical orbit.

Electrons take up physical space, that's why when you have a bunch of them, you can see a physical 3D object. Its like saying paper is only 2D, yet if I stack them, I make a 3D object because they are actually 3D. And since as an undefined wave state the electron occupies the entire orbital, then the physical space being taken up by the electron is the entire orbital.

And there is no gamma involved in that process.

How can scientists detect them then and know they exist?

It's not my belief.

 

Take the electron charge and the experimentally determined size limit of the electron. Calculate how fast it would need to spin in order to generate the magnetic moment. Compare with c.

 

In that case though, wouldn't an electron have to have a magnitude and a direction? And the "angular momentum" is just the pattern of the electron's most probable place. We don't actually know that the electron is or isn't moving in a spherical way (or etc), but with spin, I don't see how there can't be some physical movement to generate a magnetic field.

Also, if spin truly isn't physical, why is it that when two electrons are forced to occupy the same physical orbit or distance from the nucleus, that their spins are forced to be come opposite? Because then the opposite spin would be the result of a physical force, and if a physical force is effecting it, I don't see how it isn't physical. Even virtual particles are physical for a short amount of time.

you know when an atom (which spins in a direction around its origin), is spinning around an outer point,

 

it just looks like how a planet is moving through space in a group ...

Well, swan's going to probably punch you because he firmly believes that spin isn't physical in any sense.

Though I do have to point out that a magnetic field is a moving electrical field, so when an electron has a magnetic field oriented which ever way, what's moving the electrical field if not the particle itself in some way?

Hello BoB ,

 

 

I seem to have got as far as the antisymmetry aspect of 2 electrons attempting to be in the same energy level , where this is only possible by one of two states described as up spin and down spin. What I am having some difficulty is how this exclusion works in practical reality as opposed to a mathematical formulae.

If the spins didn't weren't opposite, then the electrons would cancel out each others existence. I think existing is useful for accomplishing pretty much anything. And I think because two electron can't occupy the same exact place at the same time, that if you can play around with spins and charges the right way that you can force electrons out of an atom to build up a charge. I think there's some type of medical equipment that relies on spin to do that, it might be a defibrillator. Now that I think about it, it might rely on the spin of protons of hydrogen nuclei.

The constraint is the slit. The HUP tells you as you limit the spatial extent, the uncertainty in momentum gets larger. You're only doing that in one dimension.

So there's literally different amounts of momentum from photon to photon as I constrain the slit even more? Why not just an uncertainty in one direction as I constrain the other?

You said:

 

 

 

Which I interpreted as a question of probability of finding it in a certain energy state, not a certain position.

I guess that makes sense. But, what I'm saying is, if I have an electron in the ground state or I suppose any state, then it could appear pretty much anywhere in the universe, but the chances of its position being anything like that away from its most probable location is highly unlikely, right? Even for a bound electron to appear any observable distance away from its most probable place is 1 in a very large number.

I didn't. I was pointing out that you were talking about the probability of finding an electron in a certain energy state, not a certain position. They are completely different things. There is an uncertainty relation for energy as well as position and momentum.

But I was talking about an electron at the ground state having a probability of its position extending indefinitely through space, however its position appearing large distances away from its most probable location is highly improbable.

 

 

I never said they weren't.

Then why did you point out that I was describing an atom in the ground state if its true for every other state the electron has?

But what you mentioned was the probability of finding an electron in the ground state, which is a question of energy, not position.

But if its energy changes, so will its position anyway. Also, why would that only apply for a single electron at the ground state? Atoms in other orbitals are subject to the same type of randomness aren't they?

No, that was after I said for the umpteenth time that electrons you find in an atom are not virtual particles. Annihilation of real electrons with real positrons produces 2 or 3 gammas. Virtual particles are a completely different topic. They involve either force carriers or the energy uncertainty of the vacuum, and (by themselves) do not produce real particles at all.

I didn't say virtual particles in an atom, I said a pair, because as I've heard it, pairs of virtual particles seem to come into existence in a vcuum, or otherwise everywhere, then annihilate each other. I know that they are also associated with Gauge Bosons, but that's not what I'm talking about.

You're only constraining it's horizontal position, and thus unconstraining it's horizontal momentum.

3 degrees of freedom, x, y, z are independant. That includes the uncertainty principle as it applies individually to each (and to time, just the same)

How is the momentum being unconstrained though? The photons of the beam generally have the same wavelength and frequency, but it seems as though when I constrain one direction, how it moves in the other direction is less constrained, it doesn't seem like the momentum is changing, just where the particles of the beam end up.

That doesn't make sense. Probability of finding an electron in an energy state is not a spatial function. It's found by using the hamiltonian operator on a wave function. How can it have a wavelength or go on infinitely?

Because its improbability. You can find an electron really far away from the atom its bond to, but its just really unlikely. Think of it this way: Gravity goes on indefinitely through space, but its force gets very very weak over large distances. Its the same sort of principal with the electron acting as a wave. Its wave extends indefinitely through space, which other physicists have told me causes a lot of confusion, but its just very improbable to find the electron large distances away from its most probable place.

Doesn't apply? Who said this and where?

I think it might have been more about a wavelength

I think you might be misunderstanding what the Pauli Exclusion principle is.

 

http://en.wikipedia....usion_principle

 

You can read a bit about the derivation (a simplistic one, but generally helpful) in the "Connection to quantum state symmetry" section of that article. Symmetry, also, has a few "shapes" to it; try reading a bit about the difference between bosons and fermions, for instance.

 

Boson particles obey Bose-Einstein statistics, while Fermions go by Fermi-Dirac statistics. They differ in behavior and in the type of symmetry that they can have. Fermions are restricted by the Pauli exclusion principle.

 

Electrons are fermions, which are related to an "antisymmetric" wave function: no two fermions can occupy the same quantum state at the same time. Either they have the same orbital but different spins or they have the same spin but different orbitals.

 

Here's another good article to start from: http://en.wikipedia.org/wiki/Fermion

 

If you want to know why this is, you should look at where the Pauli Exclusion principle came from. I can't find an online source for the derivation, but many printed quantum physics books have the explanation of where this came from and why. I have Griffith's "Introduction to Quantum Mechanics" and there's a whole chapter about it with the mathematical principles as well.

 

~moo

 

P.S, this is another good source to read about superposition and spin-states of fermions and bosons: http://en.wikipedia....tistics_theorem

I think there's multiple contexts for symmetry. One can be used to describe a wave function equation, if you add the wave functions of two different particles instead of subtracting them, its symmetrical. The shape of an s orbital is symmetrical. And then there's also super-symmetry which is something about equivalent fermions and bosons which differ in spins or something like that.

They generate gamma rays? What reaction are you thinking of?

Like a particle and its anti-particle appearing out of nothing then eliminating each other. Or is there some other way random unbound virtual particles disappear more often? I'm actually thinking of a post you made in another thread and a wiki article stating the process of a virtual particle pair anihilating each other once they appeared in space generates 2-3 gamma rays. There's also a bunch of stuff Stephen Hawking said about this, and how radiation might seen to be coming from a black hole because virtual particle pairs didn't always annihilate if one of the particle got sucked in.