Volume of Electrons -2 Particles in Motion

[DrClapeyron]

Do physicist use uncertainty and probability due to resolution problems when exploring subatomic or quantam properties? I can imagine a physicist somewhere running and experiment and getting a lot of output values for every input value, and trying to make sense by assigning some sort of equation to what the output should be for every input.

I can also imagine that the physicist would use some sort of graphing or statistical analysis to come to a very close approximation of what should be going on in the system, but never exactly what should happen just something very close.

Do those things lead to the separation between classical physics and quantum physics, and is that anypart of why quantum theory uses a lot of statistical analysis for things like determing the point of an electron?

 

[Drakkith]

Do physicist use uncertainty and probability due to resolution problems when exploring subatomic or quantam properties? I can imagine a physicist somewhere running and experiment and getting a lot of output values for every input value, and trying to make sense by assigning some sort of equation to what the output should be for every input.

I can also imagine that the physicist would use some sort of graphing or statistical analysis to come to a very close approximation of what should be going on in the system, but never exactly what should happen just something very close.

Do those things lead to the separation between classical physics and quantum physics, and is that anypart of why quantum theory uses a lot of statistical analysis for things like determing the point of an electron?

Nope. It has been shown that things are actually uncertain at the quantum level. It is not simply a result of our measurements.

 

[vinniewryan]

Spin is a fundamental quality of all subatomic particles. It is just as fundamental as mass or charge. Asking what controls it is like asking what controls charge or mass. The only answer is that we don't know what, if anything, is "controlling" it.

Then how is it that spin can be induced in an electron by lasers? Would that not suggest that the energy of a stream of light particles can send an electron into a spin?

 

[Drakkith]

Then how is it that spin can be induced in an electron by lasers? Would that not suggest that the energy of a stream of light particles can send an electron into a spin?

I'm not sure what you are talking about. The actual spin of a particle cannot change, but its direction can. Hence the +1/2 or - 1/2.

 

[vinniewryan]

ah, my mistake. I was mixing up two articles. I was confusing spin with putting an electron into a superposition of two states of density distribution.

This is what I meant to refer to:
http://www.sciencedaily.com/releases/2007/11/071101144942.htm

"Researchers Katja Nowack and Dr. Frank Koppens therefore forced an electron to move through a rapidly-changing electric field. Working in collaboration with Prof. Yuli V. Nazarov, theoretical researcher at the Kavli Institute of Nanoscience Delft, they showed that it was indeed possible to turn the spin of the electron by doing so."

 

[toombs]

Then how is it that spin can be induced in an electron by lasers? Would that not suggest that the energy of a stream of light particles can send an electron into a spin?

First of all, it is not an induced spin, it is an induced change in spin. The former would imply the electron had no spin to start with, which isn't true.

A laser can change an electron's spin state because the energy of an electron in a magnetic field is a function of this state. This is one of the measurable consequences of spin. Despite what lasers can do to an electron's spin, the electron is definitely not spinning in the usual sense of a revolving mass. The reason is because the mathematical description of an electron's spin is much different from the description of that of a rotating mass and both kinds of system can be described in the mathematics of quantum physics. (Molecules are good examples of rotating masses.)

To understand what I mean completely, you'd need to look at the actual math, the most complete, accurate and unambiguous description of just what the hell is going on. For now, I'll just say that a spinning particle's total angular momentum squared has the form L^2 = h_bar^2 n(n+1) where n is a non-negative integer, but the total angular momentum of an electron squared is always L^2 = h_bar^2 1/2 (1/2 + 1) = h_bar^2 3/4! (an exclamation point; not a factorial.) The last statement means that it is impossible to try to get an electron to spin faster. It is impossible to try to stop an electron from spinning. This is very very unlike the behaviour of the rotating mass, for which both these things are possible. Just change n to change the total momentum squared and set it to zero for no total momentum. You'll also notice that for the electron, n = 1/2, something that the rotating mass cannot do.

Now, it seems spin is unimportant because the total spin doesn't change. Even in classical physics there is more to angular momentum than the total. Angular momentum also has a direction. Similarly, there is more to spin than the total spin. There is a direction involved here too. This is the spin state of the electron.

As a caveat, the above is not a completely accurate statement of just what the hell is going on either, but it's not bad. Unfortunately, the next most accurate description constitutes half of a third year undergraduate physics course and I don't care to repeat it all here in a single post. Our textbook was introductory quantum mechanics by Griffiths, otherwise known as Griffiths. It would do a better job of explaining things further than I could.

So like any situation where you don't know what's going on, do what we all do: RTFM. Ask questions later.