Are All Fundamental Particles Truly Pointlike?

[malawi_glenn]

How can two points collide? An electron must have a physical body to collide. Otherwise the photoelectric effect is meaningless, as well as the compton theory.

The picture that particle collides is a classical picture, again go back to QED ;)
Interaction is done by emssion of field quanta...

 

[Sean Torrebadel]

So your point is that a philosophy of science is now invalid, because QM, QT, QED, is pre-emptory...

 

[malawi_glenn]

Experiments and real nature has higher priority than philiosophy that man has made.
You have real problems with the quantum world. In QM particles don't follow well defined trajectoires, and they don't collide as two balls etc. Takes some time to melt.. Remember the Bohr-Einstein debate. Einstein: "There must be another, better theory than QM". Bohr: "No the theory is very good, it is nature itself that is strange".

 

[Sean Torrebadel]

Electron internal spin:

http://hyperphysics.phy-astr.gsu.edu/hbase/spin.html

 

[malawi_glenn]

Electron internal spin:

http://hyperphysics.phy-astr.gsu.edu/hbase/spin.html

There is nothing there that supports your thesis that electrons have internal structure

Now you said that they had proven that electrons is made up of quarks, can you show us?

"Classically this could occur if the electron were a spinning ball of charge, and this property was called electron spin."

Note the word "Classically" this COULD occur as if the electron was a spinning ball.

 

[Sean Torrebadel]

There is evidence that the electron has an intrinsic angular momentum in addition to its orbital angular momentum. It has a spin 1/2 or -1/2. Even if QT treats the electron differently, the evidence still exists.

 

[malawi_glenn]

yes of course, no one is against that the electron posesses instrinsic spin, the question is HOW it gets it. Is it a ball spinning around its own axis? Or has it to the with something else?

The discussion was if the electron has internal structure and spatial extension. Neither me or Hurkyl has rejected that the electron don't posesses spin, but we argues that the it is consistent with the physical formalism and math that the electron can be point particle AND posess spin at the same time. You said that this is a paradox, and the electron MUST be seen as a small ball (or something with spatial extension), but here we are against you and we are arguing that the electron is pointlike and that you must skip the nonmathematical philosophy in order to discuss the properties of electron, matter and nature.

So this senctance
"Classically this COULD occur if the electron were a spinning ball of charge, and this property was called electron spin."
It is not saying that the electron IS a spinning ball of charge. This is also an example of the wave-particle duality; is matter particles, waves? what is it?


so where is the proof you said you had that the electron was composite of quarks?..

 

[Hurkyl]

So your point is that a philosophy of science is now invalid, because QM, QT, QED, is pre-emptory...

No; the point is that quantum field theory is a very different theory than classical mechanics. Therefore, we should expect the ontology of quantum field theory to be very different than the ontology of classical mechanics. (And, indeed, it is!)

 

[Sean Torrebadel]

Protons are suppose to be composed of quarks, protons are treated as point particles as well are they not? So the same argument should hold via viz for protons as electrons-even if there is no proof of an electrons internal structure. Still, an internal spin of an electron infers structure. Since, there is no way for even a mathematical point to spin -internally.
Look, its okay to treat an electron, to ignore its size and dimension, as a point. But that treatment doesn't justify that it is a point.

 

[Hurkyl]

Look, its okay to treat an electron, to ignore its size and dimension, as a point. But that treatment doesn't justify that it is a point.

Of course not. The justification comes from the fact that all experimental data agrees with this treatment.


P.S. "ignoring the size of an object" is very different from "asserting that an object has the size of a point."

 

[malawi_glenn]

Protons are suppose to be composed of quarks, protons are treated as point particles as well are they not? So the same argument should hold via viz for protons as electrons-even if there is no proof of an electrons internal structure. Still, an internal spin of an electron infers structure. Since, there is no way for even a mathematical point to spin -internally.
Look, its okay to treat an electron, to ignore its size and dimension, as a point. But that treatment doesn't justify that it is a point.

No protons are not treated as point particles, since we know that they are composite of quarks, and have structure factors and so on.
You must argue that the electron has internal structure from the laws of physics and then prove it experimentally. The laws of physics here is NOT classical mechanics, but QFT and Elementary particle physics. Of course can you have this spin even without an internal structure, because its instrinsic angular momenta responces same to an external magnetic field AS IF it was a spinning ball of charge. Separate the fenomenological classical ANALOGY with real fact.
And as Hurkyl said, all evidence that we have now points to that the electron is a point, so you can't really trow that away.. You must first invent a new theory than QFT then you should have it tested to confirm it.

 

[LewDog]

so are you saying that a quark is made up of charges, so charges are the building blocks of everything? If that is the case then what makes up a charge?

 

[malawi_glenn]

so are you saying that a quark is made up of charges, so charges are the building blocks of everything? If that is the case then what makes up a charge?

what where when? :S

 

[LewDog]

sorry i miss read the as if in "Of course can you have this spin even without an internal structure, because its instrinsic angular momenta responces same to an external magnetic field AS IF it was a spinning ball of charge". But what in theory do they think makes up a quark and give it's properties, if it is made up of something?

 

[malawi_glenn]

there are many theories, string theories and so on, that deals with multidimensional space (more than three dimensions). But Iam not an expert on that. In the standard model of elementary particles if I don't missmind quarks are also (as electrons) treated as point particles. And also all experiments don't show us anything else (as far as I know of).

The point is that, I don't say that elementary particles MUST be point particles, but the way you must argue is with physical models, theoreis and experiment, not the philosophical non-mathematical / classical physics reasoning as for example Sean Torrebadel has done in this thread.

 

[Sean Torrebadel]

Alright, I'm a little lost here. Can you explain how an electron and a positron collide, how they annihilate completely into a photon? Is this a mediated process too? For it still sticks in my mind that if these two are points, that two points cannot collide. M or U.

It is interesting, though, because if I were to treat anything as a point it would be a photon.

 

[Owen Holden]

Originally Posted by sd01g
It seems to me that it is impossible to measure something of zero volume

Why is that?

Your insistence that all mathematical truths have (interpretation) meaning with respect to a particular application (physics) is false.

It is clear to me that there are no physical things that have zero volume.
All physical objects have some volume.

There are no physical things that are not three dimensional.

That we can mathematically talk about more or less than three dimentions does not entail that there are more or less than three dimentions in physical reality.

The concept of point-object is absurd, in physics.

The BB does not entail a beginning at all.

There cannot be, logically, a beginning of time ..with or without magical Gods.

 

[ZapperZ]

Originally Posted by sd01g
It seems to me that it is impossible to measure something of zero volume



Your insistence that all mathematical truths have (interpretation) meaning with respect to a particular application (physics) is false.

It is clear to me that there are no physical things that have zero volume.
All physical objects have some volume.

There are no physical things that are not three dimensional.

That we can mathematically talk about more or less than three dimentions does not entail that there are more or less than three dimentions in physical reality.

The concept of point-object is absurd, in physics.

The BB does not entail a beginning at all.

There cannot be, logically, a beginning of time ..with or without magical Gods.

But you also need to look at your objection here, because it is based on nothing more than a matter of personal tastes. You have not shown why such mathematical description isn't consistent with the empirical evidence that we have. That, is "physical reality". It isn't a "physical reality" when you object to something simply because it doesn't sit well with you.

Something is absurd in physics if one demands that something is valid without no empirical evidence to back it. One must also consider that one is using the word "particle" in the CLASSICAL SENSE, which would also be another absurdity because of what we already know about the behavior of quantum particles such as electrons. Do not get hung up on the ordinary common word while ignoring the physics definition and description. This is what seems to be going on here, and you are putting the cart before the horse. From what I can see, this is the root cause of this "debate".

Zz.

 

[Owen Holden]

Of course not. The justification comes from the fact that all experimental data agrees with this treatment.


P.S. "ignoring the size of an object" is very different from "asserting that an object has the size of a point."

What is the size of a point?

Surely there are no physical objects of 'one' dimension.
Points are (mathematical) geometrical concepts.

How does a physical object have size if it has no dimension??

Dimentions are mathematical concepts not physical concepts.

 

[ZapperZ]

What is the size of a point?

Surely there are no physical objects of 'one' dimension.
Points are (mathematical) geometrical concepts.

How does a physical object have size if it has no dimension??

Dimentions are mathematical concepts not physical concepts.

But a "point" is a CLASSICAL concept!

We are stuck with using many identical words, but the physics is DIFFERENT! A "particle" and a "wave" in quantum mechanics do not resemble ANY of the classical concepts that we are familiar with. Try finding the physical spatial boundary of an electron! When such an idea isn't even defined in physics, then this makes the idea of a "volume" for such an object highly absurd as well! This is what you are demanding that it has!

Zz.

 

[Phred101.2]

I've just finished reading thru the previous stuff in this thread. Looks like there is some difficulty with understanding certain concepts.
Zero is the concept of some reference. This point, which cannot be reached by our finite brains, is nonetheless useful, despite its unavailability. Like infinity, there is, of course "no such thing", because we can't (and never will be able to) fit it in our heads. This, of course, does not prevent our logic from employing such a concept to construct models (of the world).

Fundamental particle "structure" or topology is unlike the large objects that we "see", or encounter through our other senses (the I/O channels to the external and real). Concepts like spin imply some existential object with dimensionality rotating about some axis. Unfortunately, this "big things" model cannot be used or mapped to the fundamental particles, like electrons. We need new kinds of "spectacles" to look at them.

 

[Owen Holden]

But a "point" is a CLASSICAL concept!

We are stuck with using many identical words, but the physics is DIFFERENT! A "particle" and a "wave" in quantum mechanics do not resemble ANY of the classical concepts that we are familiar with. Try finding the physical spatial boundary of an electron! When such an idea isn't even defined in physics, then this makes the idea of a "volume" for such an object highly absurd as well! This is what you are demanding that it has!

Zz.

"Originally Posted by Owen Holden
What is the size of a point?

Surely there are no physical objects of 'one' dimension.
Points are (mathematical) geometrical concepts.

How does a physical object have size if it has no dimension??

Dimentions are mathematical concepts not physical concepts."


I don't have a problem with volume for non-objects.
Perhaps we should think of electrons etc, as moving fields or some such thing, but not as objects.

 

[ZapperZ]

"Originally Posted by Owen Holden
What is the size of a point?

Surely there are no physical objects of 'one' dimension.
Points are (mathematical) geometrical concepts.

How does a physical object have size if it has no dimension??

Dimentions are mathematical concepts not physical concepts."I don't have a problem with volume for non-objects.
Perhaps we should think of electrons etc, as moving fields or some such thing, but not as objects.

How do you think these things are defined in QED, which is what Hurkyl has been trying to describe here? Do you think QED's description of "electrons" are like ping-pong balls with "no size"? These were never described as classical objects. That's the whole point of all this. Invoking QED way in the beginning should already made many of you look up what it is.

It appears that this whole discussion has been rather moot then, no?

Moral of the story here is that before people argue about things they don't like, maybe they should first understand what exactly it is that is being argued. It would save a lot of time and grief.

Zz.

 

[Owen Holden]

How do you think these things are defined in QED, which is what Hurkyl has been trying to describe here? Do you think QED's description of "electrons" are like ping-pong balls with "no size"? These were never described as classical objects. That's the whole point of all this. Invoking QED way in the beginning should already made many of you look up what it is.

I don't care at all about your re-defining of words that are clear and distinct.
You sound like a theist who wants to define classical words as they please??

Why do you think I should be concerned about your special definition of object etc.

If you want to talk about point-objects, then you had better get a new dictionary of these terms for they do not have sense otherwise.

 

[Phred101.2]

I don't care at all about your re-defining of words that are clear and distinct.

Can you define "clear" or "distinct"? Let's see you do this.

 

[ZapperZ]

I don't care at all about your re-defining of words that are clear and distinct.
You sound like a theist who wants to define classical words as they please??

Why do you think I should be concerned about your special definition of object etc.

If you want to talk about point-objects, then you had better get a new dictionary of these terms for they do not have sense otherwise.

No, I'm not an "theist". I'm an experimentalist who do more than just "talk" about stuff. I do stuff. I test some of them and see if these theories are valid. That is the nature of physics.

The problem here is that you are using physics concepts without understanding the physics. You are welcome to use your dictionary if you want, but such a source isn't relevant or else we can simply throw away all the physics books and rely on such things to study physics.

Everything in physics has clear, unambiguous definition with underlying mathematical description. That is not negotiable. It is irrational to object to something without understanding what it is. That is pure ignorance. If you are happy with that, then there's nothing I can do about it. But do not attack me simply because you do not wish to learn what you do not know.

Zz.

 

[Phred101.2]

Perhaps math and physics require new words for things like "real", "measure", "motion", "information" and so on.
But these words are used in science and in "ordinary" usage. If there are difficulties with conceptualisation of some term, or its meaning to science, whose job is it to clarify?
Could it be perhaps the woefully inadequate "education" that many undergrads appear to have (like not knowing what an adverb or a preposition is, or where to put an apostrophe)?

No, of course, an education is not a necessary thing for understanding, but I think its probably a big help...

 

[Hurkyl]

Why do you think I should be concerned about your special definition of object etc.

Because ZapperZ's "special definition of object etc." is what is used in quantum field theory, which is ostensibly the subject of discussion.

 

[Hurkyl]

What is the size of a point?

It depends on your measure. A point has zero volume, zero area, zero length, and cardinality 1. (All of this in the sense of Euclidean geometry)

And just to make sure it's clear, a point has volume; its volume is zero. The phrase "X doesn't have volume" means that the concept of volume is inapplicable to X.

 

[malawi_glenn]

Alright, I'm a little lost here. Can you explain how an electron and a positron collide, how they annihilate completely into a photon? Is this a mediated process too? For it still sticks in my mind that if these two are points, that two points cannot collide. M or U.

It is interesting, though, because if I were to treat anything as a point it would be a photon.

From your classical point of view no, but you have not taken into account the formalism that are relevant, QED.

So a Photon is a point?.. ;) photons have intrinic angular momenta..