How do we know all electrons are the same?

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In summary, the author claims that all electrons are identical and this statement bothers the author. However, without infinitely precise measurements we can only be sure to a certain degree and we can't prove that something like a different mass electron doesn't exist. Vanadium raises a good point that the periodic table is the way it is and explains why elements discovered since 1929 fit into this scheme. The author also protests that electrons cannot be identical.
  • #1
omayer
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Today I was reading for my Modern Physics class and something I read struck me in a way. The author claimed that all electrons are identical; they have the same measured mass, electric charge and magnetic dipole moment. This statement bothers me, and I haven't been able to stop thinking about it. So I come to you for some closure.

How do we know that all electrons are the same?

I understand that electrons are measured to have the same characteristics, but without infinitely precise measurements we can only be sure to a certain degree.
 
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  • #2
True, it's more an article of 'faith' that Occam's razor works - with no evidence that electrons differ we assume they are the same just because the universe would be annoyingly complex if they were different.
 
  • #3
We can never prove that something (like a different mass eletron) doesn't exist.

I suppose particle physics tells us that all fits into a nice grid. If electrons were different we would have to abandon the nice symmetrical model. But usually scientists are successful in assuming that laws of physics should be nice and simple at its core.
 
  • #4
I think the question of “are electrons identical” is a metaphysical question.
 
  • #5
Electrons are the same per definition. They are part of human made model of reality. And this model says they are the same.
but without infinitely precise measurements we can only be sure to a certain degree.
How is this different from anything in physics?
 
  • #6
We can only be sure of anything to a certain degree. We haven't observed an electron with different mass, charge, magnetic dipole moment, etc. in thousands of experiments carried out in the last few centuries, which all obey the known laws of physics. We have no reason to believe that electrons with different properties exist. Are you asking out of curiosity about the merits of this statement, or because you see a reason why some electrons should be different?
 
  • #7
I am going to take a different direction. Both thermodynamics and quantum mechanics treat identical particles differently from non-identical particles. If there were two kinds of electrons, that were otherwise very similar in properties (so similar that we can't tell with today's technologies) we'd still know this from the periodic table - helium would be a fairly reactive metal and oxygen would be an inert monatomic gas.

Since this is not what we observe, we can draw the inescapable conclusion.
 
  • #8
Vanadium 50 said:
... we'd still know this from the periodic table ...
Vanadium raised a very good point here. The Pauli Exclusion principle explains why the periodic table is the way it is and explains why elements discovered since 1929 fit in this scheme. If all electrons were not indistinguishable, would the exclusion principle still apply?
 
  • #9
I protest; electrons cannot be identical. I once found an electron in stairwell at 5th and Broadway. Some moments later there was another two floors down. They could not have been identical, but distinct. They differed in position. Not only that, the first was moving a tad bit faster.
 
  • #10
Thank you Vanadium, this is the kind of thinking I am looking for.

Vanadium 50 said:
helium would be a fairly reactive metal and oxygen would be an inert monatomic gas

Could you go into some detail about how you arrived at this. I'm afraid I do not know very much on the subject.
 
  • #11
Because there would be no Pauli exclusion principle between "Type A" and "Type B" electrons, atomic orbitals can hold twice as many electrons. So, helium, instead of having a full shell, would have a half-full shell.

My description Oxygen includes a mistake. Today it has a full shell + one shell that's missing two electrons. (2+6). It would instead have a full shell + a half full shell and would have chemical properties more similar to carbon. The inert gas would have an atomic number of 4+16 or 20, so it would be calcium.

The noble gasses would be beryllium, calcium, and halfnium.
 
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What is the evidence that all electrons are the same?

One of the major pieces of evidence is the fact that electrons all have the same charge, which is measured as -1 on the atomic scale. This is a fundamental property of electrons and has been consistently observed in experiments.

How can we be sure that all electrons have the same mass?

The concept of "mass" is defined as the amount of matter in an object, and electrons have been found to have a consistent, measurable mass. This has been confirmed through experiments such as the Millikan oil drop experiment and the observation of electron behavior in particle accelerators.

What about the spin of electrons? Are they all the same?

Yes, electrons all have the same spin - specifically, a spin of 1/2. This has been observed and confirmed through experiments such as the Stern-Gerlach experiment, where a beam of electrons is passed through a magnetic field and their spins are observed to be either "up" or "down".

Is there any variation in the behavior of electrons?

While electrons themselves are consistent in their properties, their behavior can vary depending on the environment they are in. For example, electrons can behave differently in a vacuum compared to when they are in an atom or a solid material. However, these variations do not change the fact that all electrons have the same fundamental properties.

Are there any exceptions to the rule that all electrons are the same?

So far, there have been no exceptions found to the fact that all electrons are the same. This is a fundamental principle in physics and has been consistently observed in all experiments and observations. However, as our understanding of the universe continues to evolve, it is possible that new discoveries may shed more light on the nature of electrons.

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