Are All Fundamental Particles Truly Pointlike?

[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' dimention.
Points are (mathematical) geometrical concepts.

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

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' dimention.
Points are (mathematical) geometrical concepts.

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

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..

 

[Sean Torrebadel]

Yes, photons are polar, composed of two types, left and right circularly polarize components. No one ever did answer a thread where I asked if the two could be physically separated. Any idea?

 

[ZapperZ]

Yes, photons are polar, composed of two types, left and right circularly polarize components.

Can you show me in the mathematical description how a plane-polarized light is composed of left and right handed circular polarization?

Zz.

 

[malawi_glenn]

Sean: are photons a point, or have they now two components? And in your PM to me, you said that according to you: a photon is an electron - postron pair.

 

[Sean Torrebadel]

Is it possible that a photon is a relativistically altered electron positron pair, stripped of all its mass but still existing as a series of points. Would this not explain its polar nature, as well as provide an alternative explanation for annihilation and pair production. Is that impossible? Why is it also the case that gamma rays interact and leave tracks within a bubble chamber if they are not composed of charged particles?
Why do we constantly assume that neutral particles are not composed of equal and opposite charged particles?

What happens when an electron and a positron collide? How do they collide? How do they change shape and form into energy?

 

[Sean Torrebadel]

Can you show me in the mathematical description how a plane-polarized light is composed of left and right handed circular polarization?
Zz.

Please don't tell me that you don't accept the existence of circularly polarized light? I mean it is a well known chemical phenomenon, reproducable by the simplest means, and done in the lab by students. The question I asked is whether or not it is possible to isolate left circularly polarized light from right circularly polarized light?

Or are you saying that there is no mathematical formalism that deals with the subject. It just occurs to me that if light is composed of two different photon types, that it would be had for it not to be considered composite and therefore not a point...

 

[ZapperZ]

Please don't tell me that you don't accept the existence of circularly polarized light? I mean it is a well known chemical phenomenon, reproducable by the simplest means, and done in the lab by students. The question I asked is whether or not it is possible to isolate left circularly polarized light from right circularly polarized light?

Or are you saying that there is no mathematical formalism that deals with the subject. It just occurs to me that if light is composed of two different photon types, that it would be had for it not to be considered composite and therefore not a point...

I noticed that you are changing the subject here. Look at what you claimed, and look at my question. Don't turn this into something it isn't. I know fully well what circularly polarized light is since I WORK WITH IT!

Now it your turn to answer my very direct question. Please do not avoid it (and yes, that is a warning).

Zz.

 

[malawi_glenn]

Photons are the mediatiors of electromagnetic force, it couples to charges. Again, go back your textbooks about QED. Same holds for how electrons and positrons interact.

 

[sd01g]

And just to make sure it's clear, a point has volume; its volume is zero.

The problem is that something with zero volume does not empirically exist. Since electrons empirically exist, they must have some volume. This is a philosophic problem, not a physics or math problem.

 

[malawi_glenn]

The problem is that something with zero volume does not empirically exist. Since electrons empirically exist, they must have some volume. This is a philosophic problem, not a physics or math problem.

The problem is that you maybe extrapolate our ordninary day - experience to the quantum world...

 

[Sean Torrebadel]

Now it your turn to answer my very direct question. Please do not avoid it (and yes, that is a warning).

Zz.

Alright, and I suppose you don't want the classical equation. If I must provide a mathematical equation, then I suppose I will have to finish my reading. So I'll get back to you- cause I don't know the quantum probability description for polarized light... I don't know much about it at all. Which is why I asked the question: can plane polarized light be divided into two circularly polarized beams. Does this mean that there are two types of photons with spinning electric fields? Given that if there are two types, doesn't that infer structure? And therein deny the possibility of a photon being a point? Although it could very well be a set of spinning points... Is this off topic? Are we not discussing the validity of stating that particles or photons are points. This is a philosophy of science thread, isn't it? Do I need to adhere to QM, strictly, even here? If that is the case, then I will have to get back to you in about six months...

Respectfully, Sean

 

[ZapperZ]

Alright, and I suppose you don't want the classical equation. If I must provide a mathematical equation, then I suppose I will have to finish my reading. So I'll get back to you- cause I don't know the quantum probability description for polarized light... I don't know much about it at all. Which is why I asked the question: can plane polarized light be divided into two circularly polarized beams. Does this mean that there are two types of photons with spinning electric fields? Given that if there are two types, doesn't that infer structure? And therein deny the possibility of a photon being a point? Although it could very well be a set of spinning points... Is this off topic? Are we not discussing the validity of stating that particles or photons are points. This is a philosophy of science thread, isn't it? Do I need to adhere to QM, strictly, even here? If that is the case, then I will have to get back to you in about six months...

It is if you are making a physics statement. Since when is claiming that photons are made up of left and right-handed circularly polarized light is "philosophical" statement?

Our PF Guidelines covers ALL of PF forums. If you make a wrong physics claim in the Philosophy forum, you can still be penalized for it.

BTW, I'd like to see your support of that claim even using classical wave theory.

Zz.

 

[ZapperZ]

The problem is that something with zero volume does not empirically exist. Since electrons empirically exist, they must have some volume. This is a philosophic problem, not a physics or math problem.

The BCS theory of superconductivity exists. What is its volume?

Zz.

 

[Hurkyl]

The problem is that something with zero volume does not empirically exist.

That is exactly the opposite of what the empirical data says.

This is a philosophic problem, not a physics or math problem.

You are asserting that a particular mathematical notion does not arise in experiment. How in the tarnation did you convince your self that this is a "philosophic problem" rather than a "physics or math problem"?

 

[sd01g]

That is exactly the opposite of what the empirical data says.

You are asserting that a particular mathematical notion does not arise in experiment. How in the tarnation did you convince your self that this is a "philosophic problem" rather than a "physics or math problem"?

There are two problems: 1) Math equations do not tell what something is. They can quantify such terms as velocity, momentum, temperature, distance, and volume, but math will never tell us what an electron or graviton is or what was its ultimate origin--the empirical data describes characteristics of an electron but does not tell us what it actually is. 2) All mathematically expressed measurements, such as those above, that deal with empirical matter/energy, are approximate. It is impossible to measure zero volume. It is impossible to measure anything exactly. Every atom and subatomic particle is in constant motion. Every attempt to measure anything is going to be different from second to second. The more accurately one tries to measure something, the more one realizes that there will always be an error factor--the empirical data is never exactly exact. Note: assigning a number or an amount to something is not measuring it.

I believe that neither physics nor mathematics will ever tell us what anything actually or ultimately is--this leaves only philosophy to make the attempt.

 

[Hurkyl]

There are two problems: 1) Math equations do not tell what something is. They can quantify such terms ...

Even if you're correct, this is entirely irrelevant. You are making claims about quantifications.

2) All mathematically expressed measurements, such as those above, that deal with empirical matter/energy, are approximate.

Yep. Not all measurements are approximate; some measurements are simply "yes / no". But that's besides the point -- all experiments are consistent with electrons having zero volume, and more importantly, all experiments confirm the physical theory that asserts that electrons have zero volume.

I believe that neither physics nor mathematics will ever tell us what anything actually or ultimately is--this leaves only philosophy to make the attempt.

There are three problems with that:
(1) If this is your point, then why are you making claims about what empirical data says?
(2) What reason do you have to believe (non-scientific and non-mathematical) philosophy will do a better job than science or mathematics.
(3) You don't know what "actually is" means, or even if it is a sensible idea.

 

[Sean Torrebadel]

The problem we are having here relates to the reductionist nature of Aristotlean philosophy where it is proposed that the character of the very small reflects universal principles. In other words, what we observe here in the macroscopic world should refect itself within the microscopic.

The tendency of the predominating science, is to argue that quantum phenomenon is isolated from the universe we naturally identify with. It goes even further to suggest that quantum phenomenon cannot be described by one simple mathematical expression, rather statistical probablitity matrices are used to describe quantum phenomenon. The declaration is made that this approach is not merely a compromise, but that it represents an accurate representation of the nature of that microscopic universe. This is called the Copenhagen interpretation.

In other words, we should not be arguing about whether a point has a volume or not, but whether quantum theory has the right to exert itself over our philosophical discussion. Does the quantum perception of the minute have the right to dictate how we discuss the philosophy of what is and what is not? Likewise if someone asks, "does a fundamental particle have size and or volume", we should respect that there are two paths of discussion, one quantum one philosophical. If someone asks, " why does quantum theory consider an electron to be a point", we should expect an answer. If they say "that there is no reason why it should have a volume"-this in itself is not an answer. It follows that if there is no answer besides the absence of physical evidence, that there is no quantum answer. This opens a very valid door of questions: whether the electron or other such particles are points, or whether this is just a convenient mathematical way to treat them.

 

[ZapperZ]

An electron is not a philosophical quantity. There's no other way to describe it other than using physics. Because of that, you have to "play" by the physics rules. You can't make things up as you go along.

What makes no sense here is trying to criticize or even impose some "rule" here without fully understand what it is that you are questioning. Your description of what "quantum mechanics" is is very naive. This is what one would use when one only learned about quantum mechanics from pop-science books. It is a fallacy to think that you've understood what QM is based on something like that.

You have apparently not seen QM in action in condensed matter physics, atomic/molecular physics, quantum chemistry, etc. You have overlooked emergent phenomena that are the foundation of condensed matter physics, an area of study that you are currently benefiting from directly.

Furthermore, I think you should be the last person who should complain about not getting an answer to a question. I asked you a very simple, direct question that you have been unable to answer. Yet, you showed no qualm in making the statement in the first place. It appears that you are now looking for the answer AFTER the fact, when it should have been the other way around.

You have been given the answer to the question you asked. It is just that you did not like the answer because it clashed with your "tastes". That's tough! Nature doesn't care what you or I prefer. We have seen many times how our "common sense" can truly be wrong when we measure it against what we observe. All you have done is object to what you've been told based not on solid evidence, but on your personal preference to one thing versus another. Since when is this a valid challenge to any scientific ideas?

Show me how you can derive superconductivity simply based on "philosophical arguments", and then we'll talk. Till you can do that, I'd say you have zero choice but to rely on physics and quantum mechanics as the only verifiable means such description.

Zz.

 

[ZapperZ]

There are two problems: 1) Math equations do not tell what something is. They can quantify such terms as velocity, momentum, temperature, distance, and volume, but math will never tell us what an electron or graviton is or what was its ultimate origin--the empirical data describes characteristics of an electron but does not tell us what it actually is. 2) All mathematically expressed measurements, such as those above, that deal with empirical matter/energy, are approximate. It is impossible to measure zero volume. It is impossible to measure anything exactly. Every atom and subatomic particle is in constant motion. Every attempt to measure anything is going to be different from second to second. The more accurately one tries to measure something, the more one realizes that there will always be an error factor--the empirical data is never exactly exact. Note: assigning a number or an amount to something is not measuring it.

I believe that neither physics nor mathematics will ever tell us what anything actually or ultimately is--this leaves only philosophy to make the attempt.

Fine. Now tell me what is an electron.

I noticed that you did not answer me when I asked for the volume of the BCS theory, which is something that exists. Did you just realized the fallacy of your claim that anything that exists must have a volume?

Zz.

 

[Hurkyl]

In other words, we should not be arguing about whether a point has a volume or not, but whether quantum theory has the right to exert itself over our philosophical discussion. Does the quantum perception of the minute have the right to dictate how we discuss the philosophy of what is and what is not?

So long as we are in the "philosophy of science" forum, the answer is a resounding yes. Quantum mechanics has earned that right through its excellent agreement with experiment and accuracy in predicting new phenomena.

The same is true outside of this forum, except in a situation where the philosophy of science is explicitly rejected.

 

[malawi_glenn]

There are two problems: 1) Math equations do not tell what something is. They can quantify such terms as velocity, momentum, temperature, distance, and volume, but math will never tell us what an electron or graviton is or what was its ultimate origin--the empirical data describes characteristics of an electron but does not tell us what it actually is. 2) All mathematically expressed measurements, such as those above, that deal with empirical matter/energy, are approximate. It is impossible to measure zero volume. It is impossible to measure anything exactly. Every atom and subatomic particle is in constant motion. Every attempt to measure anything is going to be different from second to second. The more accurately one tries to measure something, the more one realizes that there will always be an error factor--the empirical data is never exactly exact. Note: assigning a number or an amount to something is not measuring it.

I believe that neither physics nor mathematics will ever tell us what anything actually or ultimately is--this leaves only philosophy to make the attempt.

Philisophy failes to describe quantum fenomena. What if the world now is so that things with zero "classical" volume exists? And there is more in this universe than our eyes see? The quantum physics discovered/developed in the eary 1900 showed us that, and that we also need a new language to describe the very smallest part of nature; mathematics.

"God used beautiful mathematics in creating the world" - Dirac (even though many belives that Dirac was atheist, this claim is the the "philosophy" of physics, that the world is made up in that way so you need mathematics to describe it).

And Sean: Nature (or rather the inventor of the nature, God if you are a theist) sets the rules, and we just have to deal with it. Nature is more than our daily life, we are not in the "center" all the time and at all places, so therefore it is very biased to assert that the microscopical world should behave exactly as our macrscopical. Philosophy is only one way for humans to describe and categorize things logical. Same holds for mathematics, but with a different logic appratus.

 

[sd01g]

Fine. Now tell me what is an electron.

I noticed that you did not answer me when I asked for the volume of the BCS theory, which is something that exists. Did you just realized the fallacy of your claim that anything that exists must have a volume?

Zz.

Tough question. Mathematics does not tell us what anything composed of matter/energy is. Physics uses mathematics to describe what matter/energy does-- not what it is. Philosophy using reason tells us that electrons exist with three spatial dimensions. We are currently speculating and guessing what an electron is. How about 'an electron is a composite particle composed of 3 photons and 7 gravitons'?

The claim was that nothing with zero volume can exist empirically--zero volume cannot be measured and does not exist. Measuring something's position or movement does not tell you anything about its volume. Mathematics is not how one verifies empirical existence. Theories are mental constructs that exist in the conscious brain and even they have more than zero volume.

 

[malawi_glenn]

Tough question. Mathematics does not tell us what anything composed of matter/energy is. Physics uses mathematics to describe what matter/energy does-- not what it is. Philosophy using reason tells us that electrons exist with three spatial dimensions. We are currently speculating and guessing what an electron is. How about 'an electron is a composite particle composed of 3 photons and 7 gravitons'?

The claim was that nothing with zero volume can exist empirically--zero volume cannot be measured and does not exist. Measuring something's position or movement does not tell you anything about its volume. Mathematics is not how one verifies empirical existence. Theories are mental constructs that exist in the conscious brain and even they have more than zero volume.

in that case, our/your philosophical ideas are also just something that exists in your brain and has nothing to do with reality. Also what if string theory is right? That we have 8 space-dimensions that subatomic particles "lives in" or something like that. Try to describe the volume of an 8dim object. And now if the electron has volume, then goahead and measure it. Are you against general and special theory of relativity also?

You are just extrapolating your every day life experience to the quantum world.

 

[Hurkyl]

Philosophy using reason tells us that electrons exist with three spatial dimensions.

How, pray dell, does reason tell us this? What is the deductive argument? Upon what axioms is that argument based? What reason do we have to accept those axioms?

The claim was that nothing with zero volume can exist empirically--zero volume cannot be measured and does not exist.

Fallacy: red herring. Our ability or inability to exactly measure volume has no bearing on the claim that nothing with zero volume can exist.

Furthermore, you appear not to understand the idea of empirical verification. There are two aspects here:

(1) That every experiment is consistent with the electron having zero volume is (extraordinarily!) strong empirical evidence that the electron has zero volume.
(2) That every experiment is consistent with a physical theory that predicts the electron has zero volume is (extraordinarily!) strong empirical evidence that the electron has zero volume.

Theories are mental constructs that exist in the conscious brain

What about on paper? Or in the internet?

and even they have more than zero volume.

Huh? To the best of my knowledge, the notion of volume is inapplicable to theories. This is gibberish.

 

[ZapperZ]

Tough question. Mathematics does not tell us what anything composed of matter/energy is. Physics uses mathematics to describe what matter/energy does-- not what it is. Philosophy using reason tells us that electrons exist with three spatial dimensions. We are currently speculating and guessing what an electron is. How about 'an electron is a composite particle composed of 3 photons and 7 gravitons'?

The claim was that nothing with zero volume can exist empirically--zero volume cannot be measured and does not exist. Measuring something's position or movement does not tell you anything about its volume. Mathematics is not how one verifies empirical existence. Theories are mental constructs that exist in the conscious brain and even they have more than zero volume.

Re-read what you have just written. You're doling nothing but making a description of the properties of an electron, and a speculative one too at that.

And you say that this is better than what physics is doing? A hand-waving, unverified description is better than a quantitative, verified description?

Zz.

 

[Owen Holden]

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.

"A point has zero volume, zero area, zero length, and cardinality 1."

All geometric concepts have no physical qualities.
Points do not have physical qualities at all.

"The phrase "X doesn't have volume" means that the concept of volume is inapplicable to X."

Wrong again.

X has zero volume, means, It is not the case that X has some volume.
X dosen't have volume, means, there is no amount of volume that X has.

Your assumption that zero is an amount is incorrect.

Herkyl:
"But zero volume is still a volume. When you say something has zero volume, you are making the assertion that the concept of volume is applicable to that thing, and the measure of its volume is equal to zero. This is very different from the assertion that the concept of volume is inapplicable to that thing."

I don't agree.

Ideas have (zero volume) no volume is true, and, the concept of volume does not apply to ideas.
Ideas have zero volume, (Ideas do not have volume) is true, because; It is not the case that volume applies to ideas.

Another example: The number three is blue, is false.
Because blueness does not apply to numbers. (numbers do not have colour).

The number three is blue, is not meaningless..because it is a statement, ie. a sentence with a meaningful subject and a meaningful predicate.

Another example: The present king of France is bald, is false...not meaningless, even though the present king of France does not exist.

Point-particles are oxy-moronic.
There are no (zero) such possibilities in reality!

 

[Sean Torrebadel]

Okay, point particles, and fundamental particles as points, and electrons as point particles. Volume. Do they have volume? Volume of what? What is their volume zero of? For the study of science is the study of matter, in its different forms. The concept of matter was philosophically defined by Aristotle to be the underlying material which is in a process of change and which changes from potential to actuality- the actuality of possessing 'body'.

Perhaps a reconcilliation is due on both fronts of this discussion. For if something of substance is to be asked "what are you made of". The answer should be matter in one of its different forms. Where matter as possessing body is suppose to move through void. Perhaps we should consider the possibility that the minute particles of our existence are becoming, that they are acquiring, that they are not only a body of some substantial nature, but also a process. Therein, applying an infinitesimal calculus to them, taking the limit of a volume as it approaches zero may be a concilation. For it may be possible for such things to exist as a process with a minimum of body.

In such a system the concept of volume is not as important as the point, the center or origin of that entity. In such a context it would be physically acceptable to see a particle as a point, to treat it as such. This, however, creates a discontinuity between it as a point and the influence that it exerts on the surrounding fields. If one supposes that such an influence is mediated and there is no evidence to the contrary then such particles remain valid as points. If however we connect the process to the point and suggest that the point is the center of a process which extends to the fields- this approach would make the point atonymous, and still it would be consistent with the definition of matter.

As an example, electrons shot through one slit of a two slit experiment produce a interference pattern, built up over time on a photographic plate. If I consider the electron as a point, I would be hard pressed to explain how it extends itself over both slits simultaneously. Even if I were to accept that the electron's field effects are mediated I would be hard pressed to explain what an individual, isolated, projectile is mediating with-since there are no other particles in the same trajectory or path to mediate with.

It is better, in my mind, to consider the electron as not only an infinitesimal point with a degree of body in a limit, but also as a process that extends beyond its own point like circumference. In other words, to open the idea that an electron is not only its physical center but also the influence that it has over the surrounding space.

This leads to the question: What is the nature of the surrounding space? For if any particle is to have an effect, even when alone, upon its own trajectory, then it must be simultaneously continuous with its surroundings and also have the potential for discontinuity. What this means is that the particle must have its own inertia, but it must also be connected by a process to the surrounding space. Returning to the one electron two slit interference phenomenon: The influence that an electron may possesses in a continuous manner with its surrounding space could possibly travel through the second slit of a two slit experiment and then become physically discontinous with the source electron that created it. It would therein serve as an echo or imprint of the electron's nature, that would reflect back and interfere with the path of the electron.

 

[malawi_glenn]

Okay, point particles, and fundamental particles as points, and electrons as point particles. Volume. Do they have volume? Volume of what? What is their volume zero of? For the study of science is the study of matter, in its different forms. The concept of matter was philosophically defined by Aristotle to be the underlying material which is in a process of change and which changes from potential to actuality- the actuality of possessing 'body'.

Who cares what Aristoteles said 2000 years ago? Physicists today have a more precise definition of matter.

As an example, electrons shot through one slit of a two slit experiment produce a interference pattern, built up over time on a photographic plate. If I consider the electron as a point, I would be hard pressed to explain how it extends itself over both slits simultaneously. Even if I were to accept that the electron's field effects are mediated I would be hard pressed to explain what an individual, isolated, projectile is mediating with-since there are no other particles in the same trajectory or path to mediate with.

Here it is very clear that you have not understand basic QM, particle - wave duality...
Is the description of electron as a small sphere going to solve the double slit experiment from a classic - physics point of view better? No..

The rest you wrote is also just just words words words.. how about some real formulas?

I meant, you posted the shrödinger eq in momentum representation to me, so I know you can =)

 

[Hurkyl]

I don't agree.

There's nothing to agree or disagree with. It's simply a matter of definition. If you don't like the technical definition of the word "volume", then make up a new word, and see if you can convince people to talk to you about that new word.

 

[Hurkyl]

The number three is blue, is not meaningless..because it is a statement, ie. a sentence with a meaningful subject and a meaningful predicate.

Grammatical correctness is not an indicator of meaning.

And besides, technical grammar is much more strict. Predicates have domains; if "3" is not in the domain of the predicate "is blue", then (mathematically speaking) the phrase "3 is blue" is grammatically incorrect.

Another example: The present king of France is bald, is false...not meaningless, even though the present king of France does not exist.

This is a different sort of thing all together. The problem with this is that there does not exist an interpretation of these words where the noun phrase "The present king of France" gets mapped onto someone who is presently a king of France.

 

[ZapperZ]

As an example, electrons shot through one slit of a two slit experiment produce a interference pattern, built up over time on a photographic plate. If I consider the electron as a point, I would be hard pressed to explain how it extends itself over both slits simultaneously. Even if I were to accept that the electron's field effects are mediated I would be hard pressed to explain what an individual, isolated, projectile is mediating with-since there are no other particles in the same trajectory or path to mediate with.

Again, you are basing this not on any physical grounds, but based on (i) your comfort level and (ii) based on what you know. This is what I have insisted as nothing more than a matter of personal tastes.

Open an intro QM text. Look at the first example of the application of schrodinger equation, i.e. solving for a free particle with V=0. Now look at the wavefunction that is the solution to such equation. What is <x>, the average position of the particle that you've just solved? With no boundary conditions, the average position is infinite, i.e. the particle is spread over all space! Look at the wavefunction, what is it telling you? The particle is smeared out simultaneously all over space! So how big is this particle, do you think? Using your logic with the double slit, you'd argue that this particle is HUGE, simply because it can "spread" itself over that large of a space!

This is an example of the fallacy of the logic you used with your double-slit example. Just because an electron can appear to "spread itself" between two slits have no bearing on its "size". I've just given you an example on how such a logic can be taken to utter absurdity. In fact, why restrict yourself to just such example? Why not tackle electron diffraction off a crystal such as in a typical Bragg diffracttion where it covers over several lattice constants! Would you like to argue that an electron can actually be more than 10 A wide just because I could actually get interference pattern from these experiments done on such a length scale?

Aren't you beginning to see a pattern here already?

Zz.

 

[Sean Torrebadel]

So what is the quantum mechanical solution that explains interference caused by one electron at a time/ two slit experiment? In one respect this thread is adamant that an electron is a point particle. In the next it evokes wave/particle duality to explain that electrons are spread out. Are you saying that an electron is a point particle that goes through both slits simultaneously and therein interferes with itself? I know one thing. The electron hits the photographic plate in a single ping. I would argue that it is more reasonable to state that an electron is a point particle whose nature extends into the surrounding space. But then we don't want to talk about aethers do we?

 

[ZapperZ]

So what is the quantum mechanical solution that explains interference caused by one electron at a time/ two slit experiment?

Read T. Marcella, Eur. J. Phys. v.23, p.615 (2002).

In one respect this thread is adamant that an electron is a point particle. In the next it evokes wave/particle duality to explain that electrons are spread out. Are you saying that an electron is a point particle that goes through both slits simultaneously and therein interferes with itself? I know one thing. The electron hits the photographic plate in a single ping. I would argue that it is more reasonable to state that an electron is a point particle whose nature extends into the surrounding space. But then we don't want to talk about aethers do we?

At what point do we actually OPEN A BOOK and look at what QM actually HAS said?

Does Feynman path integral ring a bell? What about "superposition of paths"? Would you also be surprised that I can actually get the same interference pattern when I have supercurrent going through two branches of paths in a superconducting circuit? It has nothing to do with the size of it. It has everything to do with the superposition principle. In the case of the double slit, it is the superposition of paths that each electron can take. This is what causes the interference. I can get the same thing with a glob of coherent electrons (supercurrent), or something as big as buckyballs! It doesn't matter! As long as these are quantum particles and I set up the experiment in such a way that I have no way to tell how which way they go, then I have set up a superposition of states and I get interference results! You have been distracted so much towards the electrons that you forgot (or maybe you didn't know) the principle involved in producing such effects!

I think this thread has ran its course and I don't see anything of benefit anymore in this discourse, especially when things that are available to be learned from are being ignored. Nothing that I've said here is news to anyone who has opened a standard QM text. It gets very tiring to keep having to backtrack and cover basic QM just simply to get rid of the misinformation or outright mistakes being made. Maybe someone else want to continue with this, but I think I'm done here. I don't see the point of having to repeat things that are available right out of a standard textbook.

Zz.

 

[Sean Torrebadel]

Perhaps you misunderstood me. One electron, one, shot at a time-say one a day. Over a period of time, say 200 days, an interference pattern is observed on the exposure.

Yes quantum mechanics can explain the path that each electron has followed. It does a wonderful job.

But explain why the electron chose that path when it was alone. What did it interfere with? When it was alone?

 

[Sean Torrebadel]

Does the electron know that another electron is comming behind it, in say an hour... Does it know that one came before it? What is this spontaneous interference? Just because there are two paths to choose, one through either slit, and just because there is an equation in quantum mechanics that can account for interference as a whole, does not mean that there is an explanation as to why interference occurs when

one electron a day travels through either of two slits...

Otherwise, everything around us would interfere with everything. In the subatomic realm, everything would interfere with everything.

 

[Sean Torrebadel]

Perhaps we should just say that quantum physics describes the path taken, mathematically- and admit that there is no easy explanation for this phenomenon. Zap

 

[Phred101.2]

Does the electron know that another electron is comming behind it, in say an hour... Does it know that one came before it? What is this spontaneous interference? Just because there are two paths to choose, one through either slit, and just because there is an equation in quantum mechanics that can account for interference as a whole, does not mean that there is an explanation as to why interference occurs when

one electron a day travels through either of two slits...

How can an "electron" know anything? Unless you mean it "communicates" by sending and receiving photons (to other electrons)? How does an electron "choose" to emit or absorb a photon? Why do you think these things have to "explain" something? Or what it "means" or "does not mean" to them? What, after all is an "explanation" except something humans "produce" (in their heads)?

 

[Sean Torrebadel]

How can an "electron" know anything? Unless you mean it "communicates" by sending and receiving photons (to other electrons)? How does an electron "choose" to emit or absorb a photon? Why do you think these things have to "explain" something? Or what it "means" or "does not mean" to them? What, after all is an "explanation" except something humans "produce" (in their heads)?

This is exactly the point. Do not infer that i am saying that this is the case.

The question is how ---one electron-- can interfere with its own path. If there is only one slit there is no interference. If there is two slits there is interference --even if only one isolated electron passes through the experiment, say, every hour. This does not mean that I do not understand the phenomenon of interference when there is a stream of particles. I understand the Uncertainty principle, and that the shrodinger has a definition for the electron's motion. I know that the paths which have been taken are consistent with interference.

What I want to know is how, an electron, if it is a point particle, and even if its smeared over some infinite space- how it interferes with itself?

For without an explanation to this, then my more philosophical rambling above remains valid.

 

[Hurkyl]

The question is how ---one electron-- can interfere with its own path.

Exactly in the way QM describes!

 

[Hurkyl]

Perhaps we should just say that quantum physics describes the path taken, mathematically- and admit that there is no easy explanation for this phenomenon. Zap

What other possible meaning could you give to the word "explanation"?

 

[malawi_glenn]

So what is the quantum mechanical solution that explains interference caused by one electron at a time/ two slit experiment? In one respect this thread is adamant that an electron is a point particle. In the next it evokes wave/particle duality to explain that electrons are spread out. Are you saying that an electron is a point particle that goes through both slits simultaneously and therein interferes with itself? I know one thing. The electron hits the photographic plate in a single ping. I would argue that it is more reasonable to state that an electron is a point particle whose nature extends into the surrounding space. But then we don't want to talk about aethers do we?

And when you examine which slit the electron passes, the interference pattern disappear. First you may read and study what contemporary physics is doing, at the real level... No one who has studied QFT at university level an has passed are devoted to aehter theories, as least not i know anyone.