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View Full Version : Flip an electron, roll a neutrino?



Solfe
2012-Nov-07, 01:23 PM
I am having a logical failure on this. Is it possible to mechanically roll or flip a point like elementary particle?

Literally, as "I rolled the ball" or "I flipped the coin".

When I try a simple thought experiment of rolling a molecule or atom on a table, obviously, there is the issue that atoms and molecules aren't little balls. They can be orientated many ways but they won't "roll" on a table. Since I can picture these items being orientated in many ways, I am inclined to say they can "rolled over" but it isn't the mechanism of rolling such as the case of a ball on a surface.

When it comes to point like particles, my brain balks. Its a point, how do you distinguish if has turned over in any way? Every side or from every direction looks like a point.

Now, up until this point, I have ignored the word "spin". This is on purpose, that property was not what I was trying to picture.

Grey
2012-Nov-07, 05:38 PM
When it comes to point like particles, my brain balks. Its a point, how do you distinguish if has turned over in any way? Every side or from every direction looks like a point.We can't distinguish it. There's no way to determine if an electron is "facing" one way or another, and although they have spin, electrons don't ever behave as though they are rotating classically. That's one of the reasons that we can successfully treat them as point particles in the first place: they don't appear to have size or shape in any meaningful way.

BadTrip
2012-Nov-07, 06:31 PM
We can't distinguish it. There's no way to determine if an electron is "facing" one way or another, and although they have spin, electrons don't ever behave as though they are rotating classically. That's one of the reasons that we can successfully treat them as point particles in the first place: they don't appear to have size or shape in any meaningful way.

Not meaning to argue... looking for an education, as always... ....having said that....

An electron is a charged particle which behaves as would a rotating bar magnet, no?....i.e.; it exhibits properties of having magnetic poles of equal magnitude but reversed polarity. I believe that experiments have proven that one can influence the electron's orientation with respect to those magnetic poles via an external magnetic field. If this is true then wouldn't we tend to say that we can indeed determine if the electron is"facing" one way or another?

Grey
2012-Nov-07, 06:38 PM
Electrons do have spin, which (if you squint) behaves a little like rotation, hence the name. It's true that the spin can be aligned or not aligned in some direction (such as the spin of another particle, or an external magnetic field). But it's not really like a classical rotation, and Solfe specifically said that he was not thinking about spin when asking his question.

BadTrip
2012-Nov-07, 07:00 PM
Electrons do have spin, which (if you squint) behaves a little like rotation, hence the name. It's true that the spin can be aligned or not aligned in some direction (such as the spin of another particle, or an external magnetic field). But it's not really like a classical rotation, and Solfe specifically said that he was not thinking about spin when asking his question.

Ah yes... indeed. Sorry...the weight of the last statement of the OP. I was lead off on the tangent from the statement of "how do you distinguish if has turned over in any way? Every side or from every direction looks like a point." So to tell if it's turned over you could track/trace the orientation of the poles.
Thanks!.. Sorry... Carry on! *bows out*

FarmMarsNow
2012-Nov-07, 09:06 PM
Does it take time for an electron to change spins? Where does time come into play?

John Jaksich
2012-Nov-08, 11:16 AM
Does it take time for an electron to change spins? Where does time come into play?

It does take *time* to flip an electron from one state to another----and the concept of *history* should come into play in the OP question. (For purists like ---the late and great Wolfgang Pauli-- it is a mathematical concept and an affront to QM to imply that one can flip or roll a particle such as an electron or neutrino.)

However, if one can envision a *large* conglomerate of an "electron" ---i.e. a Bose-Einstein Condensate-----If I am not mistaken ----the energy required to flip such a cold (> 0.01 K) Rb type is very large. (Two well-known experts would be Drs. Wolfgang Ketterle, & Carl Wieman).

According to Wikipedia----Ketterle and Wieman took 2000 Rb-87 atoms in the gas phase and *laser-cooled* them to 170 nano-Kelvin---(that takes a lot of energy)

The following image is from Wikipedia and credit is given to NIST (USA) and was funded by U. S. taxpayer dollars---I am hoping it will not violate any rules of the forum.


17698

The description is as follows: The left is *gaseous" Rb atoms---The center is the Bose-Einstein Condensate----The right is a partial evaporation of the Condensate


At this state--the center--here is a *new* phase of matter (BCS condensate) that "if one can imagine(?) flipping or rolling it---would consume a great deal of "energy"

I am unsure of how much---because it (unfortunately) is beyond my current capability :( ---but the diagram is (a type) of (crude) history because one is *seeing* a "velocity-distribution" of how 2000 Rb 87 atoms undergo a phase change from gas to Bose-Einstein condensate---to partially evaporated condensate.

IMHO the OP question is *possible* --but how *many years* before it will take to achieve ---I am unaware.

Others in the forum will have a better (hopefully) answer.

ShinAce
2012-Nov-08, 01:18 PM
Spin flip isn't mystical. It's been done.

One recent example is the spectroscopy of antihydrogen:
http://physicsworld.com/cws/article/news/2012/mar/07/internal-structure-of-antihydrogen-probed-for-the-first-time

John Jaksich
2012-Nov-08, 03:56 PM
Spin flip isn't mystical. It's been done.

One recent example is the spectroscopy of antihydrogen:
http://physicsworld.com/cws/article/news/2012/mar/07/internal-structure-of-antihydrogen-probed-for-the-first-time

Spin flip is not mystical at all--but the OP asked if it could be performed in mechanical manner---it is done by putting the so-called *particle* (i.e. electron) in a different state--which is QM.

Your post is interesting--I had forgotten about the "isolation" of the anti-matter proton ---but it took a quantum mechanical "means" to *excite* it from one state to another.

Please don't misquote me & my don't mistake my humility as a sign of weakness :(---I never called it mystical.

The phenomenon of electron spin resonance is not mystical and has long been utilized as a research tool.

ShinAce
2012-Nov-08, 05:02 PM
Please don't misquote me & my don't mistake my humility as a sign of weakness :(---I never called it mystical.


This is quoting.

I did not quote you. I wrote a short post in response to the OP. My post has nothing to do with yours. Intentionally, that is. I simply hesitated in posted earlier because flipping the spin of an individual electron is something I wonder about as well. My post is about flipping the spin of an atom. Which allows people to hand wave it away. This might be more useful, but a little more abstract:
http://phys.org/news4297.html