Backward Time and Antimatter

[CarbonCopy]

So, I read somewhere that antimatter can be considered as normal matter but moving in backward time. This might make sense theoretically, but, what does it mean physically ?

It is a bit absurd, if you think about it.

[Mike Smith Cosmos]

So, I read somewhere that antimatter can be considered as normal matter but moving in backward time. This might make sense theoretically, but, what does it mean physically ?

It is a bit absurd, if you think about it.

 

We are so concerned with the forward relentless day and night movement of time . Atomic particles are more involved with ' change ' thats' all that matters to the particle . We call the particle going in the other direction " anti matter " So we might be worried but the particle is occupied more with change, rather than does the sun come out today.

Edited January 17, 2013 by Mike Smith Cosmos

[imatfaal]

So, I read somewhere that antimatter can be considered as normal matter but moving in backward time. This might make sense theoretically, but, what does it mean physically ?

It is a bit absurd, if you think about it.

It works fine in QED and QCD - and remember they are models that provide predictions - amazingly accurate predictions. It is the predictions we test against reality - we do not test the ideas against our notions of common sense or absurdity. One of the members here has a lovely quote as their signature from Feynman about finding a universe that suits your own philosophy - I will dig it out and repost it

[swansont]

One thing you must realize about models is that they do not claim to perfectly mirror reality, only that they can predict behavior. So saying that a positron behaves like an electron moving backward in time isn't a claim that it is, just that it behaves that way. If you want to know if that's physically what is going on, you'd have to devise a test that would distinguish the two cases.

[CarbonCopy]

One thing you must realize about models is that they do not claim to perfectly mirror reality, only that they can predict behavior. So saying that a positron behaves like an electron moving backward in time isn't a claim that it is, just that it behaves that way. If you want to know if that's physically what is going on, you'd have to devise a test that would distinguish the two cases.

 

Have such tests been done ?

[swansont]

 

Have such tests been done ?

 

I doubt it (at least, successfully), since the whole idea is that the two situations are not distinguishable.

[SamBridge]

This property wouldn't happen to be called time symmetry would it? It seems like anti matter isn't necessarily going backwards in time, but rather it just has the reverse oscillation which would make its net oscillation "0" in infinite places when combined with normal matter. When the matter field's net probability is 0, all that's left is the potential energy that went into raising that matter to the energy state it was in at the time of annihilation which particles have a lot of energy him them without the matter.

Edited January 24, 2013 by SamBridge

[beefpatty]

This property wouldn't happen to be called time symmetry would it? It seems like anti matter isn't necessarily going backwards in time, but rather it just has the reverse oscillation which would make its net oscillation "0" in infinite places when combined with normal matter. When the matter field's net probability is 0, all that's left is the potential energy that went into raising that matter to the energy state it was in at the time of annihilation which particles have a lot of energy him them without the matter.

 

It's actually matter, not anti matter that is going backward in time. A negative energy particle going backward in time can also be interpreted as a positive energy antiparticle going forward in time.

[SamBridge]

It's actually matter, not anti matter that is going backward in time. A negative energy particle going backward in time can also be interpreted as a positive energy antiparticle going forward in time.

But what makes it an anti particle in the first place?

[beefpatty]

But what makes it an anti particle in the first place?

 

We consider it anti because it's basically a mirror image in properties of its matter counterpart. Every antiparticle has the same mass as its particle, but opposite charge (if it has any) and anticolor (if it's a quark). That, and it also annihilates with matter.

[SamBridge]

We consider it anti because it's basically a mirror image in properties of its matter counterpart. Every antiparticle has the same mass as its particle, but opposite charge (if it has any) and anticolor (if it's a quark). That, and it also annihilates with matter.

Yeah I know that, but I mean on a more complex level. Obviously when they combine the net matter field is 0, but what makes them opposite? I thought I remembered there was some way to turn matter into anti-matter, but I want to know the actual cause-difference, and why that difference permits them to exchange bosons in a different manner.

[beefpatty]

Yeah I know that, but I mean on a more complex level. Obviously when they combine the net matter field is 0, but what makes them opposite? I thought I remembered there was some way to turn matter into anti-matter, but I want to know the actual cause-difference, and why that difference permits them to exchange bosons in a different manner.

 

Experimentally we observe this to be true. In theory, say for example spin-1/2 particles, there are two solutions to Dirac's equation. Each corresponds to a different particle of identical mass but opposite charge, and we interpret these as particles and antiparticles. As for turning matter into anti-matter, one could take the example of electron-positron annihilation into a muon and antimuon pair. In this case, I suppose you could say that the energy of the electron went into the creation of the antimuon, but really there's no way to distinguish this. If you are instead thinking of something like an electron turning into a positron, this would violate charge conservation.

[SamBridge]

Experimentally we observe this to be true. In theory, say for example spin-1/2 particles, there are two solutions to Dirac's equation. Each corresponds to a different particle of identical mass but opposite charge, and we interpret these as particles and antiparticles. As for turning matter into anti-matter, one could take the example of electron-positron annihilation into a muon and antimuon pair. In this case, I suppose you could say that the energy of the electron went into the creation of the antimuon, but really there's no way to distinguish this. If you are instead thinking of something like an electron turning into a positron, this would violate charge conservation.

I guess I could see the two solutions, one is on one side of the axis, and the other is on the other side right? But what differences does that actually cause? Besides, isn't -1/2 the same as 3/2 if you're talking about a modular system of 1?

Edited January 25, 2013 by SamBridge

[elfmotat]

The idea that antimatter is just matter with negative proper time isn't really too strange if you think about it. To simply demonstrate the idea, consider Coulomb's law between two like charges of equal magnitude:

 

[math]m\frac{dv}{dt}=kqq/r^2[/math]

 

If we "reverse time" where [math]t\rightarrow -t[/math] (you can think of it as playing a movie backwards), then we get:

 

[math]-m\frac{dv}{dt}=kqq/r^2[/math]

 

But this is exactly the same law that governs the force between two opposite charges of equal magnitude:

 

[math]-m\frac{dv}{dt}=kqq/r^2 ~\Leftrightarrow ~m\frac{dv}{dt}=kq(-q)/r^2[/math].

 

With the "movie analogy" this is obvious: if we record what happens when we place two like charges near each other and then run the movie backwards, it looks exactly like what we would find if we place two opposite charges near each other (well, over small distances at least).

Edited January 25, 2013 by elfmotat

[beefpatty]

I guess I could see the two solutions, one is on one side of the axis, and the other is on the other side right? But what differences does that actually cause? Besides, isn't -1/2 the same as 3/2 if you're talking about a modular system of 1?

 

I'm not sure what axis you are referring two, but by two solutions I mean the following.

 

Given the Dirac equation (which applies to fermions),

 

 

there are two unique solutions that when you plug them into psi the equation is satisfied. When we quantize the Dirac field we interpret these two solutions as separate particles, and when you calculate some observable such as charge we find they are opposite each other. I'm afraid I don't understand what you mean by a modular system of 1. Could you explain in more detail?

[derek w]

How can you have stability in the present moment of time,if particles can go back in time and interfere with the past position of particles?

[alpha2cen]

So, the current positron is a phantom image of the past electron?

Edited January 25, 2013 by alpha2cen

[SamBridge]

there are two unique solutions that when you plug them into psi the equation is satisfied.

Yeah I see what you mean now in a better sense, the axis was the wrong term, but I meant it in an analogy to refer to how a similar thing happens with quadratic polynomials even though this is pretty different, the way I picture it in my head makes sense. When I look at the equation, I feel like the two solutions is caused by the almost limiting process by having "2pi" in the denominator otherwise the range that it applies over would yield more than two solutions, but I might be thinking of a different Dirac equation. I'm sorry to sound so vague there's a lot of math that I interpret visually so I can deal with it better, which is why I hate spin and imaginary numbers.

 

there are two unique solutions that when you plug them into psi the equation is satisfied. When we quantize the Dirac field we interpret these two solutions as separate particles, and when you calculate some observable such as charge we find they are opposite each other. I'm afraid I don't understand what you mean by a modular system of 1. Could you explain in more detail?

 

I'm still not sure what spin is exactly, but if it is the property that I think it is, we don't see particles with spins of "2" because "2" is the same of one, and that type of property is caused by modular mathematics, which is typical of trigonometric functions such as those used to create models of bound particles.

Edited January 26, 2013 by SamBridge

[beefpatty]

So, the current positron is a phantom image of the past electron?

 

It would be the future electron, but phantom image isn't really the right word. They are two possible interpretations for the same object, although most people would just say it is a positron moving forward in time. The possibility that it can be interpreted as a negative energy electron moving backward in time is, as far as I can tell, just a product of the math. Whether that has any real physical meaning, I don't know.

 

Yeah I see what you mean now in a better sense, the axis was the wrong term, but I meant it in an analogy to refer to how a similar thing happens with quadratic polynomials even though this is pretty different, the way I picture it in my head makes sense. When I look at the equation, I feel like the two solutions is caused by the almost limiting process by having "2pi" in the denominator otherwise the range that it applies over would yield more than two solutions, but I might be thinking of a different Dirac equation. I'm sorry to sound so vague there's a lot of math that I interpret visually so I can deal with it better, which is why I hate spin and imaginary numbers.

 

 

I'm still not sure what spin is exactly, but if it is the property that I think it is, we don't see particles with spins of "2" because "2" is the same of one, and that type of property is caused by modular mathematics, which is typical of trigonometric functions such as those used to create models of bound particles.

 

2 pi in the denominator? There are in fact an infinite number of solutions that correspond to different spin and momentum states of the particle, but they can all be expressed in terms of the two unique solutions.

 

As far as I know the graviton could have a spin of 2. Atoms can have spins of any integer multiple of 1/2 or 1, for example 3/2, 4, etc. Spin is just the intrinsic angular momentum of a particle. If you have a particle completely at rest, that is it has zero momentum, then you still measure a discrete angular momentum. It also behaves like a vector, in that it can have a direction and magnitude and points in the same direction as the orbital angular momentum.

[michel123456]

The idea that antimatter is just matter with negative proper time isn't really too strange if you think about it. To simply demonstrate the idea, consider Coulomb's law between two like charges of equal magnitude:

 

[math]m\frac{dv}{dt}=kqq/r^2[/math]

 

If we "reverse time" where [math]t\rightarrow -t[/math] (you can think of it as playing a movie backwards), then we get:

 

[math]-m\frac{dv}{dt}=kqq/r^2[/math]

 

But this is exactly the same law that governs the force between two opposite charges of equal magnitude:

 

[math]-m\frac{dv}{dt}=kqq/r^2 ~\Leftrightarrow ~m\frac{dv}{dt}=kq(-q)/r^2[/math].

 

With the "movie analogy" this is obvious: if we record what happens when we place two like charges near each other and then run the movie backwards, it looks exactly like what we would find if we place two opposite charges near each other (well, over small distances at least).

Sorry, stupid question:

we have 2 positive charges that repell each other.

Playing the movie backwards do we have 2 negative charges that attract each other?

 

Or reversing the movie changes the sign of only one of the 2 charges?

Edited January 26, 2013 by michel123456

[elfmotat]

Sorry, stupid question:

we have 2 positive charges that repell each other.

Playing the movie backwards do we have 2 negative charges that attract each other?

 

Or reversing the movie changes the sign of only one of the 2 charges?

 

Only one charge's sign is reversed. It's really only an analogy to help demonstrate the idea, so don't take the Coulomb's Law thing too seriously. What's actually going on has to do with the time reversal operator in QFT.

[ydoaPs]

It's actually matter, not anti matter that is going backward in time. A negative energy particle going backward in time can also be interpreted as a positive energy antiparticle going forward in time.

No. Anti-matter has positive energy just like normal matter.

[elfmotat]

No. Anti-matter has positive energy just like normal matter.

 

A negative energy particle with negative proper time is equivalent to a positive energy particle with positive proper time.

[ydoaPs]

A negative energy particle with negative proper time is equivalent to a positive energy particle with positive proper time.

"Equivalent" is a strong word. An electron-positron system releases energy in the annihilation. If the positron was negative energy, there'd just be the energy from the momentum from the two for the resultant photons.

[SamBridge]

"Equivalent" is a strong word. An electron-positron system releases energy in the annihilation. If the positron was negative energy, there'd just be the energy from the momentum from the two for the resultant photons.

No read some of the answers, I'm sure what they are saying doesn't make sense in reality but it should make sense mathematically, if there's two solutions to the coefficients of the equations that describe matter fields then basically the difference is more in how those types of matter oscillate rather than actually how they travel in time.