Electron And Positron

[robinpike]

If they are both point-like particles, do we know what the physical difference is between the electron and the positron?

 

 

[elfmotat]

They have opposite charge, so they will move in different directions when placed in an electric field.

[robinpike]

Thanks, but what I meant is:

 

What is the physical difference between the two particles in the sense of their form.

[krash661]

according to these images,

there's also this,

Electron–positron annihilation

http://en.wikipedia.org/wiki/Electron%E2%80%93positron_annihilation

Edited May 3, 2013 by krash661

[elfmotat]

Thanks, but what I meant is:

 

What is the physical difference between the two particles in the sense of their form.

I don't really know what you're asking. What do you mean by "form?"

[swansont]

according to these images,

This is from 123dspace, about "hypothetical elementary energy systems" i.e. it's unconfirmed speculative crap, giving zero confidence that anything is right, as far as a discussion about actual science is concerned.

 

edit: moot

 

Thanks, but what I meant is:

 

What is the physical difference between the two particles in the sense of their form.

They are point particles, as far as theory states and what experiment can confirm. There is no "form" to discuss.

[krash661]

ohh, ok, i will delete that image then.
thanks.
I did not realize that.

[robinpike]

according to these images,

 

 

 

there's also this,

 

Electron–positron annihilation

 

http://en.wikipedia.org/wiki/Electron%E2%80%93positron_annihilation

 

You see in the above picture, how the electron has got a dash character drawn on it, and the positron has got a plus character drawn on it. They have been drawn differently, they have been given a different form in the diagram.

 

But the above is a diagram, not a picture, it is not a physical representation of the electron and positron.

 

If they are point like particles, fair enough, but then how is the electron different from the positron, how is their physical form different from each other?

 

If you say that they have no physical differences, then that is the same as saying that they are identical particles.

 

In which case, how do you explain their different behaviour?

 

(By the way, it was useful to have the replies with examples of what they do differently - thanks - but no need to give any more examples of what they do differently, I am asking how they are able to behave differently.)

[swansont]

You see in the above picture, how the electron has got a dash character drawn on it, and the positron has got a plus character drawn on it. They have been drawn differently, they have been given a different form in the diagram.

 

But the above is a diagram, not a picture, it is not a physical representation of the electron and positron.

 

If they are point like particles, fair enough, but then how is the electron different from the positron, how is their physical form different from each other?

 

If you say that they have no physical differences, then that is the same as saying that they are identical particles.

 

In which case, how do you explain their different behaviour?

 

(By the way, it was useful to have the replies with examples of what they do differently - thanks - but no need to give any more examples of what they do differently, I am asking how they are able to behave differently.)

 

The answers have already been given to you. The particles have opposite charge. There is no difference in their "physical form"

[Royston]

If they are point like particles, fair enough, but then how is the electron different from the positron, how is their physical form different from each other?

 

If you say that they have no physical differences, then that is the same as saying that they are identical particles.

 

You seem to be caught up with the word 'form'. If you mean attributes like spin, mass et.c they're identical. However, it shows on the diagram they have opposite charge, so that's the difference.

In which case, how do you explain their different behaviour?

 

Well, a demonstration of this difference would be to fire them through a magnetic field. The electron will curve in an opposite direction to a positron, which shows they have opposite charge.

 

EDIT: swansont replied while I was posting.

Edited May 4, 2013 by Royston

[robinpike]

The answers have already been given to you. The particles have opposite charge. There is no difference in their "physical form"

 

I don't understand what you mean by opposite charges have no difference in physical form.

 

Can you explain how this is possible please.

 

To help, here is an example of one type of opposite form: My left hand is constructed in an opposite way to my right hand - they are both made of the same substance but one is constructed as a mirror image of the other - as such they have opposite physical forms.

 

You seem to be caught up with the word 'form'. If you mean attributes like spin, mass et.c they're identical. However, it shows on the diagram they have opposite charge, so that's the difference.

 

 

Well, a demonstration of this difference would be to fire them through a magnetic field. The electron will curve in an opposite direction to a positron, which shows they have opposite charge.

 

EDIT: swansont replied while I was posting.

 

You have replied to my question of: How are they different? by giving yet another example confirming that they are different.

 

Thanks, but I already know that they are different: I would like to what it is that makes them different?

 

Saying that the difference is charge, is just a statement, it is not adding anything as an explanation.

 

it is a bit like answering the question: How does gravity work? by saying: Gravity works by pulling you to the ground!

[Royston]

You have replied to my question of: How are they different? by giving yet another example confirming that they are different.

 

My example was to show that charge has inherent properties (displayed by the dynamics of the electron / positron). For instance, if they curve in opposite directions this implies symmetry, no ?

Thanks, but I already know that they are different: I would like to what it is that makes them different?

 

Charge.

Saying that the difference is charge, is just a statement, it is not adding anything as an explanation.

 

Not really, charge is well defined in physics, so it's certainly more than 'just a statement' http://en.wikipedia.org/wiki/Charge_(physics)

Edited May 4, 2013 by Royston

[swansont]

I don't understand what you mean by opposite charges have no difference in physical form.

 

Can you explain how this is possible please.

 

I can buy a car and choose its color. My choice of color has no effect on the car's physical form. Charge is a property (as is color), not a physical thing attached to the electron or positron. It has no effect on the "physical form" (which, again, is a meaningless description for a point particle)

[krash661]

You see in the above picture, how the electron has got a dash character drawn on it, and the positron has got a plus character drawn on it. They have been drawn differently, they have been given a different form in the diagram.

 

But the above is a diagram, not a picture, it is not a physical representation of the electron and positron.

 

If they are point like particles, fair enough, but then how is the electron different from the positron, how is their physical form different from each other?

 

If you say that they have no physical differences, then that is the same as saying that they are identical particles.

 

In which case, how do you explain their different behaviour?

 

(By the way, it was useful to have the replies with examples of what they do differently - thanks - but no need to give any more examples of what they do differently, I am asking how they are able to behave differently.)

this might help.

 

Point particle

http://en.wikipedia.org/wiki/Point_particle

 

Positron

http://en.wikipedia.org/wiki/Positron

 

Electron

http://en.wikipedia.org/wiki/Electron

[robinpike]

Those articles are interesting, and taking them in order...

 

Because calculations outside of the electron produce the same result, regardless how small the size of the electron is set in the equations, should not be used as evidence that the electron has no size.

 

That would be like saying that the effect of the moon on the tides in the oceans does not alter, regardless what size the mass of the moon is put into. Therefore it is valid to set the moon as being a black hole?

 

Now to the positron... The article does not explain how the positron is different to the electron. And please don't suggest that the positron is an electron going backwards in time!?

 

The last one on the electron says that the electron has no known size or sub-structure. That does not mean that the electron has no size or sub-structure.

 

Indeed, since the electron and positron are equivalent particles, with some properties the same and some properties equivalent but opposite, this suggests that the electron and positron do have a size and shape in order for them to be different! How would point-like particles be different?

I can buy a car and choose its color. My choice of color has no effect on the car's physical form. Charge is a property (as is color), not a physical thing attached to the electron or positron. It has no effect on the "physical form" (which, again, is a meaningless description for a point particle)

 

If charge is like the color of a car (metaphorically speaking), then please explain how a non physical quality makes electrons and positrons behave physically differently?

[michel123456]

Those articles are interesting, and taking them in order...

 

Because calculations outside of the electron produce the same result, regardless how small the size of the electron is set in the equations, should not be used as evidence that the electron has no size.

 

That would be like saying that the effect of the moon on the tides in the oceans does not alter, regardless what size the mass of the moon is put into. Therefore it is valid to set the moon as being a black hole?

 

Now to the positron... The article does not explain how the positron is different to the electron. And please don't suggest that the positron is an electron going backwards in time!?

 

The last one on the electron says that the electron has no known size or sub-structure. That does not mean that the electron has no size or sub-structure.

 

Indeed, since the electron and positron are equivalent particles, with some properties the same and some properties equivalent but opposite, this suggests that the electron and positron do have a size and shape in order for them to be different! How would point-like particles be different?

 

 

If charge is like the color of a car (metaphorically speaking), then please explain how a non physical quality makes electrons and positrons behave physically differently?

It looks like you have an alternative explanation.

[swansont]

Those articles are interesting, and taking them in order...

 

Because calculations outside of the electron produce the same result, regardless how small the size of the electron is set in the equations, should not be used as evidence that the electron has no size.

It's not just theory. Experiments are consistent with zero as well, as mentioned in the wikipedia article.

That would be like saying that the effect of the moon on the tides in the oceans does not alter, regardless what size the mass of the moon is put into. Therefore it is valid to set the moon as being a black hole?

No, it wouldn't be like that at all.

Now to the positron... The article does not explain how the positron is different to the electron. And please don't suggest that the positron is an electron going backwards in time!?

Sure it does. It says that it has the opposite charge of the electron. That's how it's different.

The last one on the electron says that the electron has no known size or sub-structure. That does not mean that the electron has no size or sub-structure.

If you want to claim it does, by all means calculate the effect this will have e.g. on the hydrogen spectrum, and go find it experimentally.

 

Indeed, since the electron and positron are equivalent particles, with some properties the same and some properties equivalent but opposite, this suggests that the electron and positron do have a size and shape in order for them to be different! How would point-like particles be different?

How does it "suggest" that?

 

If charge is like the color of a car (metaphorically speaking), then please explain how a non physical quality makes electrons and positrons behave physically differently?

I didn't say it wasn't a physical property, I said it wasn't a physical thing, i.e. something with a shape. Like color being a physical property, unaffected by shape.

http://en.wikipedia.org/wiki/Electric_charge

[MigL]

Below the lowest energy level, ie below the ground state, of every atom, there exists a sea of electrons, also known as the Dirac sea, and wherever an electro is absent in this sea, the 'hole' is termed a positron. In effect, a positron is the absence of an electron. This is how P.A.M. Dirac first postulated the positron in the 30s. The general idea has somewhat changed since then.

 

Or it could be as swansont has suggested, both are dimensionless points but one is red and the other blue, corresponding to their different charges. But as far as the rest of us are concerned, the only difference between the two is their respective charges.

 

If that still doesn't answer your question maybe you should be asking 'What is charge ?'

[robinpike]

Yes, you could say I should be asking "What is charge", as this is something that electrons and positrons differ on, but that has come from the more general question of how is the electron different from the positron, if they are not different in some physical way as well?

 

Swansont, the key question here is: How can two point-like particles differ from each other? I don't understand how this possible.

 

The reason for asking being: If that cannot be explained, then perhaps the starting premise that the electron and positron are point-like is incorrect.

 

I can't think of an example, can you give an alternative one to color?

 

(The analogy of color does not work, for example, an atom of red paint is physically different to an atom of blue paint.)

[swansont]

Swansont, the key question here is: How can two point-like particles differ from each other? I don't understand how this possible.

 

The reason for asking being: If that cannot be explained, then perhaps the starting premise that the electron and positron are point-like is incorrect.

 

Nature is not guaranteed to be understandable, and physics is not in the business of explaining the fundamental "why" or "how" questions. We observe what happens and make models to explain that. We observe there is this property that causes particles to repel or attract each other. We call it charge. Particles with the property behave in certain predictable ways, thus we have a model. That we still don't know what charge "is" does not invalidate the models.

 

 

I can't think of an example, can you give an alternative one to color?

 

(The analogy of color does not work, for example, an atom of red paint is physically different to an atom of blue paint.)

 

All analogies fail at some point, when you take them too far. That's why it is an analogy and not an identity. I did not say charge is exactly like color.

 

Identical twins. One is nice, the other is a complete prat. No difference in shape.

 

A perfect 1 cm diameter sphere, but made of different materials will have a different mass. No difference in shape.

[Przemyslaw.Gruchala]

Swansont, the key question here is: How can two point-like particles

differ from each other? I don't understand how this possible.

 

Electron and positron are self antiparticles.

 

Result of collision of particle and its antiparticle is annihilation and production of gamma photons.

http://en.wikipedia.org/wiki/Annihilation

And reverse- collision of gamma photon with other gamma photon with enough energy produces particle and its antiparticle.

http://en.wikipedia.org/wiki/Pair_production

 

Other example of particles and their antiparticles are:

 

muon- and muon+

tau- and tau+

pion- and pion+

kaon- and kaon+

proton and antiproton

 

This list is long for 260+ entries, because scientists gave different name to bunch of energies that live as short as f.e. 10^-22 second.

 

List of baryons

http://en.wikipedia.org/wiki/List_of_baryons

 

List of mesons

http://en.wikipedia.org/wiki/List_of_mesons

 

Leptons particles and antiparticles are modeled in Standard Model as having no internal structure, because there is no scientific way to examine it.

[swansont]

Leptons particles and antiparticles are modeled in Standard Model as having no internal structure, because there is no scientific way to examine it.

 

Not quite. They are modeled that way and the models work. The experimental evidence is in agreement with the model. To say that there is no scientific way to examine it is wrong.

[Przemyslaw.Gruchala]

Not quite. They are modeled that way and the models work. The experimental evidence is in agreement with the model. To say that there is no scientific way to examine it is wrong.

 

I disagree. Annihilation of them and then absorption of gamma photons and then emission at lower frequencies is physical evidence of current Standard Model particles are made of even smaller elementary particles.

 

You have 1 electron with E=511 keV, and 1 positron with E=511 keV, they annihilate, two gamma photons each E=511 keV are produced.

Then gamma photon is colliding with other particle, which is emitting photon at lower frequency, and from 1 gamma photon with f0 we have 2 gamma photons with f0=f1+f2, then this process can be repeated over and over again, and result is such that energy accumulated in single point like electron and positron is spread across millions of particles as their kinetic energy..

[MigL]

Why do you assume the difference has to be physical Robin ?

 

The abstract definition of charge is the generator of the U(1) symmetry of electromagnetism, such that, as per Noether's theorem, the electric current is conserved. The associated ( radiated ) gauge field, when quantised, is the gauge boson known as a photon.

 

Does this sound at all like an observable, physical difference ?

[robinpike]

Why do you assume the difference has to be physical Robin ?

 

The abstract definition of charge is the generator of the U(1) symmetry of electromagnetism, such that, as per Noether's theorem, the electric current is conserved. The associated ( radiated ) gauge field, when quantised, is the gauge boson known as a photon.

 

Does this sound at all like an observable, physical difference ?

 

The reason for thinking that the difference is physical, is because the electron and positron do different things in a physical way.

 

For example, electrons don't do much if they get near to each other, similarly, positrons don't do much if they get near to each other.

 

But an electron and a positron do - they change into photons.

 

How is any difference in behavior between the electron and positron explained, if not by a difference in a physical quality?

 

This could be down to a difference in shape of their substance, or an actual difference in substance, etc.

 

If their difference in behavior is not down to a difference in physical form of some sort or other, then how is their different behavior to be explained?

 

A perfect 1 cm diameter sphere, but made of different materials will have a different mass. No difference in shape.

 

But you have used physical qualities in your example of how they can be different: size of 1 cm, different material.

 

Since point-like particles cannot be different in size, then are you saying that the electron and positron behave differently because they are made of different materials?