NationStates Jolt Archive

I'm curious, I was reading the big-bang thread and it suddenly occured to me the I don't know whether or not anti-particles have negative mass. I assume they don't, of course, but I am not sure, and am too lazy to go look it up.

Mind you, if they don't have negative mass, they are not really anti-particles are they?

I'm curious, I was reading the big-bang thread and it suddenly occured to me the I don't know whether or not anti-particles have negative mass. I assume they don't, of course, but I am not sure, and am too lazy to go look it up.

Mind you, if they don't have negative mass, they are not really anti-particles are they?
No. I don't think you can have negative masses - at least, that is common consensus at the moment. They are still anti-particles because they have an opposite charge. Also, for particles such as leptons or baryons, they can also have different baryon number/lepton number. For example, a proton has charge +1 and baryon no. +1, whereas an antiproton has a charge of -1 and a baryone no of -1. I think it is just due to some fundamental difference - I am aware that an anti proton is two anti-ups and an anti-down - but apart from that I think it is just the way they interact that makes them a particle/anti-particle

No. Longton is right, they have positive mass but opposite charges.

Tachyons would have negative mass, but those are just theoretical particles, never observed.

Thanks, that clears it up. :)

Does anyone know what it actually is about particles and anti-particles that makes them so similar and yet so different? I understand (vaguely) that the charges cancel each other in an interaction, and I also know that annihilation creates two photons (at least the examples I was taught created photons) but what is it about them that causes the particles to completely annihilate into energy?

I had anti particles for breakfast...

wait, no those were corn flakes...

I had anti particles for breakfast...
Well, since you are what you eat ... ! :D

Does anyone know what it actually is about particles and anti-particles that makes them so similar and yet so different? I understand (vaguely) that the charges cancel each other in an interaction, and I also know that annihilation creates two photons (at least the examples I was taught created photons) but what is it about them that causes the particles to completely annihilate into energy?

It's a very long time since I took a'level physics. I started to say something, but I realize I have no idea.

It's a very long time since I took a'level physics. I started to say something, but I realize I have no idea.
Yeah, well I'm doing A-level physics and so far there has been a complete lack of teaching on why they are opposites that annihilate.

Does anyone know what it actually is about particles and anti-particles that makes them so similar and yet so different? I understand (vaguely) that the charges cancel each other in an interaction, and I also know that annihilation creates two photons (at least the examples I was taught created photons) but what is it about them that causes the particles to completely annihilate into energy?
Really bad case of the cooties?

I have read that it is because an antiparticle is travelling backwards in time, and when it meets a particle, travelling forwards, they simply cancel each other like a positive and a negative number. I don't understand it :(

String theory says that they're like two waves moving at the same frequency but with cusps and valleys inverted, so that they cancel each other when they meet. I don't understand it either :(

Really bad case of the cooties?

I have read that it is because an antiparticle is travelling backwards in time, and when it meets a particle, travelling forwards, they simply cancel each other like a positive and a negative number. I don't understand it :(

String theory says that they're like two waves moving at the same frequency but with cusps and valleys inverted, so that they cancel each other when they meet. I don't understand it either :(
That wave explanation makes a little sense. Sort of like destructive interference in waves, and I suppose that most (if not all) fundamental particles will have a de Broglie wavelength that allows them to exhibit wave particle duality. But with destructive interference, isn't it only destructive at the point where a peak and a trough cancel i.e. before and after that point of minimum the wave continues on as normal.

I have read that it is because an antiparticle is travelling backwards in time, and when it meets a particle, travelling forwards, they simply cancel each other like a positive and a negative number. I don't understand it :(


That can't be right though, because the only different physical property is the charge. If it was going back in time it would have -ve mass, which was why I asked earlier.

The only thing I can think of is that it is something to do with having opposite charges and being attracted to each other. But this would leave other unanswered questions for me. So like I said, I have no idea.

Maybe it is the string thing.

We don't really know why they anihilate each other, but we will if we find the Theory of Everything.

Perhaps charge is caused by the shape of the space-time dent created by a particle. When 2 collide that have the same amount but different direction of curvature, they "flatten out" the space-time dent, and release energy. This is a proposal, not something which is proven.

We don't really know why they anihilate each other, but we will if we find the Theory of Everything.

Perhaps charge is caused by the shape of the space-time dent created by a particle. When 2 collide that have the same amount but different direction of curvature, they "flatten out" the space-time dent, and release energy. This is a proposal, not something which is proven.
Your name makes me inherently believe you.

*believes*

That wave explanation makes a little sense. Sort of like destructive interference in waves, and I suppose that most (if not all) fundamental particles will have a de Broglie wavelength that allows them to exhibit wave particle duality. But with destructive interference, isn't it only destructive at the point where a peak and a trough cancel i.e. before and after that point of minimum the wave continues on as normal.
Good. Then we can all agree that it's a very very bad case of the cooties.

I went to the cern website. It was no help.

Anti particles do have mass. The name anti particle is a little bit of a misnomer. What they are are particles that are mirror images in all respects of the normal particles of our universe. This means that for all properties that have a sign, (which excludes mass) they have this property opposite to that of the normal particle. Thus a positron has a mass of 1/1872nd of a proton but has an electrical charge of +1 and a spin of -1/2, a boson no of 0 (as an electron has a boson no of 0)

When the two meet all the properties cancel. What is left is undefined mass, which is of course energy (E=MC^2). This energy can be released in the form of electromagnetic quanta or simply go back to where it was borrowed from (Virtual particle pair).

This is explained in string theory by the destructive cancelling of the waves, but this does not explain the electromagnetic energy released.

Mind you, if they don't have negative mass, they are not really anti-particles are they?
They have negative charge, foo'!

No. Longton is right, they have positive mass but opposite charges.

Tachyons would have negative mass, but those are just theoretical particles, never observed.

Tachyons would actually have imaginary (as in being multiplied by the square root of -1) since implicit (observable) mass is found by the following formula
Mass(observed) = (rest mass)*squareRoot((speed of light)^2 - (actual speed)^2). This assumes that tachyons are going faster than the speed of light, of course. All of this has NOTHING to do with particles of negative mass.

Tachyons would actually have imaginary (as in being multiplied by the square root of -1) since implicit (observable) mass is found by the following formula
Mass(observed) = (rest mass)*squareRoot((speed of light)^2 - (actual speed)^2). This assumes that tachyons are going faster than the speed of light, of course. All of this has NOTHING to do with particles of negative mass.
So they're imaginary particles... that's why dreams are so weird and fleeting, they must be made of tachyons!

Talking about destructive interference and stuff, can anyone explain how that works with the principle of the conservation of energy? How come two electromagnetic waves- an energy form- can interact and destroy eachother, and so, as far as I can tell, that energy?

Talking about destructive interference and stuff, can anyone explain how that works with the principle of the conservation of energy? How come two electromagnetic waves- an energy form- can interact and destroy eachother, and so, as far as I can tell, that energy?
Nah - the energy of the particles is converted into two identical photons of equal energy and hence equal frequency according to E=hf

EDIT: Chorley as in Chorley, Lancashire?

EDIT2: It is also because mass and energy are interchangeable according to E=mc2

Thanks for that, Longton.
Yeah, as in Lancashire. Tis my homeland, but I haven't lived there for a while.

They have negative charge, foo'!

Yes, thank you, Captain obvious, I wasn't aware of that. :rolleyes: It's all so clear now.

Have any links? I know enough to be able to explain it to a non-knower, but no enough to actually discuss it otherwise.