Is electron spin a perpetual motion?

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Discussion Overview

The discussion revolves around the concept of electron spin and whether it can be considered a form of perpetual motion. Participants explore the nature of electron spin, its implications, and its distinction from classical motion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether an electron will continue to spin indefinitely if not excited or depressed.
  • Another participant clarifies that intrinsic spin is a fundamental property of particles like electrons and cannot be stopped, distinguishing it from classical perpetual motion machines.
  • It is noted that electron spin is not classical motion but rather an intrinsic property that contributes to angular momentum.
  • A participant emphasizes that the term "spin" is somewhat misleading, as it does not imply actual rotation like a spinning ball.
  • Some participants discuss the relationship between electron spin and macroscopic angular momentum, referencing the Einstein-de Haas effect as experimental evidence.
  • Questions arise regarding the implications of electron spin on experiments like the Stern-Gerlach experiment and how to conceptualize spin without associating it with rotation.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of electron spin and its implications, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There are limitations in the discussion regarding the definitions of spin and motion, as well as the assumptions made about the nature of electron properties and their implications in experiments.

member 141513
suppose we do not excite it or depress it, will it perform spin forever?
 
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Dont confuse the perpetual spinning of a particle, or even that of a planet or other object as a perpetual motion MACHINE. Particles such as electrons posess intrinsic spin that is as much a part of their makeup as their mass is. You CANNOT stop this spin. Even to call it "spin" is only semi-correct, as it is NOT like a spinning ball, but merely a property of the particle that gives it angular momentum i believe.

In short, you could call the spin of a particle or a planet perpetual motion, but that does not violate any rules of nature. A perpetual motion machine would however, as that requires a conversion of energy into work or another form, and that MUST be accompanied by a loss in energy.
 
Electron "spin" (more properly, "intrinsic angular momentum") is not a "motion" in the classical sense. It's simply an intrinsic property of the electron, like its mass and charge.

Don't think of an electron as a tiny ball that spins around its axis. That kind of classical picture doesn't work at the quantum-mechanical level.
 
Really, "spin" (and "iso-spin) is so-called only because it transforms like a classical angular momentum. Similarly "Color", as applied to elementary particles, is given that name only because it appears to have three "basis vectors" in much the way we can use "Blue", "Red", and "Green" as "basis vectors" for acxtual colors. It doesn't have anything to do with an actual color of the particle!
 
HallsofIvy said:
Really, "spin" (and "iso-spin) is so-called only because it transforms like a classical angular momentum.

I would say that with "spin" the connection is stronger than that, because it's been experimentally established that the "spin" of individual electrons contributes to the total macroscopic angular momentum of an object (e.g. the Einstein - de Haas effect).
 
jtbell said:
I would say that with "spin" the connection is stronger than that, because it's been experimentally established that the "spin" of individual electrons contributes to the total macroscopic angular momentum of an object (e.g. the Einstein - de Haas effect).

that means electron spin is an intrinsic property of an electron that hv effect on the stern-gerlech magnet? but they don't really "rotate" to hv that effect?
also, this experiment is throught to give evidence that an electron really have a size
but if no rotation, how that evidence was from?
so how can i imagine?
thx
 

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