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Does an electron have an internal structure?

by Qubix
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Qubix
#1
Jan24-09, 10:29 AM
P: 76
Ok, I know this question is very old, and it has probably been answered by now, but if the electron does not have an internal structure (like the proton for example), how does it maintain itself as an entity? Why does it not disintegrate?
I've asked this question a couple of times before ,and people answered with things like "it's a fundamental particle so it does not have an internal structure"... this is obviously not a scientific answer, for 100 years ago, we might have said the same about the atom.
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muppet
#2
Jan24-09, 11:15 AM
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Quote Quote by Qubix View Post
Does an electron have an internal structure?
Ok, I know this question is very old, and it has probably been answered by now, but if the electron does not have an internal structure (like the proton for example), how does it maintain itself as an entity? Why does it not disintegrate?
I've asked this question a couple of times before ,and people answered with things like "it's a fundamental particle so it does not have an internal structure"... this is obviously not a scientific answer, for 100 years ago, we might have said the same about the atom.
What's not scientific about it?
Science is the investigation of the physical world by means of experiment in order to advance our understanding of nature such that we not only know why we obtain the results of the experiments already perfomed, but are able to predict the outcome of future experiments (or explain why a certain experiment is intrinsically impossible to perform, or why a certain prediction is intrinsically impossible to make, etc.) Sometimes an experiment proves a well-established theory wrong, and that's when science is perhaps most interesting. But at other times you have to accept that the scientific method is intrinsically incapable of proving something beyond absolutely all doubt, and you just have to accept that a theory which continually churns out the right answers is probably at least a very good appproximation to what's going on, an approximation that is so good you might as well call it correct for expedience's sake until something proves it wrong.
The theories that are currently the best we have predict that the electron is a structureless, fundamental particle with zero size. It doesn't disintegrate because there is nothing for it to disintegrate into, and nothing to "maintain". At some point, it is almost logically necessary for such a fundamental particle to exist, or you'd have an infinite regress- how would the particles which made up the electron maintain their structural integrity?
We know that atoms aren't fundamental for lots of reasons, but perhaps the most obvious piece of evidence that they have structure is that we can smash them into bits. You can't do this with an electron. People have tried investigating the size of the electron, which if it were non-zero would tell us that our present best theories are wrong. So far the upper bound on any potential size of the electron is (I think) about 10^-18m -or a one-hundred millionth the size of the atom.
Qubix
#3
Jan24-09, 03:26 PM
P: 76
Quote Quote by muppet View Post
What's not scientific about it?
Saying something is "fundamental" is the same as saying "it was made by god". It is not a scientific definition because if you do not have a theory capable of understanding a phenomenon, it does not mean that the phenomenon itself is the problem, but most likely, your theory.
What if I asked another question: What is the electric charge? The purpose of the question is to go beyond (or around) the "it's fundamental" lame answer, and to see if modern theories (even hypotheses like string theory), can say something about it.


People have tried investigating the size of the electron, which if it were non-zero would tell us that our present best theories are wrong. So far the upper bound on any potential size of the electron is (I think) about 10^-18m -or a one-hundred millionth the size of the atom.
In the first sentence, you are implying the size of the electron is 0? Size 0 would mean the electron is a point. Can you really have a point in a (at least) 3 D space?

malawi_glenn
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Jan24-09, 03:59 PM
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Does an electron have an internal structure?

Yes it is a point. The thing is that our ideas of the world in our daily life contradicts what is going on in the Quantum level. Also the problem might lay in the mathematical language we use, which was developed to explain classical physics (Newton etc.)

But you know that geometric series etc converge to a finite value, even though each terms goes to zero but never becomes zero? That also contradicts how we add things in our daily life, but in the world of math it is just fine.

So if we want to be really pragmatic scientific, the answer is that our theories for electrons (The Standard Model) has a delta-function as the electrons charge distribution and that quantity can be tested experimentally - the form factor should then equal unity. And that is what is found in all experiments so far, the upper limit for the electron radius is around 10^18m. So that is the most scientific answer you can get today.
DrChinese
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Jan24-09, 04:03 PM
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Quote Quote by Qubix View Post
Saying something is "fundamental" is the same as saying "it was made by god". It is not a scientific definition because if you do not have a theory capable of understanding a phenomenon, it does not mean that the phenomenon itself is the problem, but most likely, your theory... In the first sentence, you are implying the size of the electron is 0? Size 0 would mean the electron is a point. Can you really have a point in a (at least) 3 D space?
First, welcome to PhysicsForums, Qubix.

Electrons have mass and charge even though they act as point particles. Same thing is true of quarks, the other major building blocks of matter. However, electrons and quarks can act as either a particle or a wave according to how they are observed.

Saying a particle is fundamental is not at all the same as saying it was made by god. The theory says that an electron is fundamental (i.e. does not degenerate to other particles like free neutrons do, for instance). It does not do so as far as anyone knows (and people have looked).

Theory also says an electron is a point particle, and it acts like a point particle. So yes, you can have a point in spacetime. (There are a lot of that are seen in physics that are counter-intuitive, no point in denying what is known to occur.) Experiment again matches theory.

What do YOU think an electron is? How does your concept differ from accepted theory? And do you have any experimental basis for your opinion?
Algr
#6
Jan24-09, 04:10 PM
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Is it perhaps better to say "We can't see any evidence that the electron has an internal structure." ?

I take it then that we have never seen an electron decay or turn into anything else without something impacting it first.

BTW, protons and neutrons are made of quarks - are there any particles that have electrons in them? Or are electrons always solitary?
malawi_glenn
#7
Jan25-09, 01:31 AM
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DrChinese, we should not perhaps encourage doubters to do wild speculations here?

Algr, the atom has electrons. You would then say that an atom is not a particle, but then I would not call the proton a particle. It is all about energy scales here.

And to the OP, suppose THAT the electrons was made up of smaller particles, or strings, we would then ask the question "what are those particles made of?", so we have to accept that a smallest entity exist I think.
dx
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Jan25-09, 07:57 AM
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We don't know whether the electron has internal structure. If it does have internal structure, it is not accessible at the energy levels that we can currently probe.
AEM
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Jan25-09, 08:29 AM
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So if an electron has no internal structure and for all intents and purposes can be regarded as a point particle, what is the origin of its mass?
ZapperZ
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Jan25-09, 09:09 AM
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Quote Quote by AEM View Post
So if an electron has no internal structure and for all intents and purposes can be regarded as a point particle, what is the origin of its mass?
If the LHC finds the symmetry breaking in the electroweak sector, then that's your possible source of leptonic mass.

Zz.
Qubix
#11
Jan25-09, 10:52 AM
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Quote Quote by DrChinese View Post
What do YOU think an electron is? How does your concept differ from accepted theory? And do you have any experimental basis for your opinion?
Well, besides what the accepted theory tells us, I do not know what the electron is, that was the whole purpose of my question :)

Thank you for all your answers, I hope we find out more about the electron in the future.
AEM
#12
Jan25-09, 11:59 AM
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Quote Quote by ZapperZ View Post
If the LHC finds the symmetry breaking in the electroweak sector, then that's your possible source of leptonic mass.

Zz.
Can anyone cite a reference that will elaborate on this a little?
friend
#13
Jan25-09, 12:00 PM
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Quote Quote by Qubix View Post
Saying something is "fundamental" is the same as saying "it was made by god". It is not a scientific definition because if you do not have a theory capable of understanding a phenomenon, it does not mean that the phenomenon itself is the problem, but most likely, your theory.
I think your question is the same as what reason do we have to believe that the electron is fundamental. You don't trust experimental results because experiment can only rule out some theories, but never prove a theory since we might not be doing the right experiment (not high enough energy, or not done the experiment enough times, etc.)

Others here can correct me if I'm wrong or expound on this idea. But IIRC, particles emerge from symmetries of spacetime, you know SU(3)XSU(2)XU(1). And it seems that the electron has all the properties of one or some of these properties which indicate that it is fundamental.

If this is true, then it is interesting to consider what particles say about spacetime itself. And I'd have to wonder how quantum gravity theories would change the description of particles.
ZapperZ
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Jan25-09, 12:29 PM
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Quote Quote by AEM View Post
Can anyone cite a reference that will elaborate on this a little?
http://arxiv.org/PS_cache/arxiv/pdf/...704.2232v2.pdf

Zz.
AEM
#15
Jan25-09, 01:17 PM
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Thanks. Precisely what I was looking for.
humanino
#16
Jan25-09, 11:15 PM
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Quote Quote by friend View Post
particles emerge from symmetries of spacetime, you know SU(3)XSU(2)XU(1)
This is not spacetime symmetry, this is gauge symmetry.
Algr
#17
Jan26-09, 03:46 AM
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Quote Quote by malawi_glenn View Post
Algr, the atom has electrons. You would then say that an atom is not a particle, but then I would not call the proton a particle. It is all about energy scales here.
Well that defines some terms, but doesn't answer the question at all. Is there anything smaller then an atom that has an election as a component?
malawi_glenn
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Jan26-09, 03:48 AM
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Quote Quote by Algr View Post
Well that defines some terms, but doesn't answer the question at all. Is there anything smaller then an atom that has an election as a component?
Well it was due to a sloppy usage of the word "particle" that I raised that issue.

No, there are no other composite particles which are made up of electrons.


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