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Author Topic: Virtual and anti particles  (Read 4339 times)

Offline hamza

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Virtual and anti particles
« on: 05/10/2007 16:35:28 »
Could someone please briefly explain the difference between the ANTI-PARTICLES and VIRTUAL-PARTICLES. Heard alot about them but still could'nt figure out the difference :(.


 

Offline DoctorBeaver

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Virtual and anti particles
« Reply #1 on: 05/10/2007 18:13:31 »
Anti-particles are identical to "normal" particles in every respect except they have opposite charge. For instance, an electron has negative charge and its anti-particle, the positron, has positive charge.

Virtual particles are particles that appear spontaneoulsy by quantum effects and disappear again. These will often appear as particle/anti-particle pairs which instantly annihilate each other.

One of our resident physicists will be able to explain it better than I can, but that's roughly it.
 

another_someone

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Virtual and anti particles
« Reply #2 on: 05/10/2007 19:57:31 »
An anti-particle is a real particle that has the opposite qualities (in particle, the opposite electrical charge) to a non-anti particle (so you have an electron, that has a negative charge, and an anti-electron (also known as a positron), that is exactly like an electron, but has a positive electrical charge).

If a particle, and its anti-particle (an electron and a positron) collide, they will annihilate each other in a burst of gamma rays.

Heisenberg's uncertainty principle says that there is some uncertainty about where matter is, and how much energy is has.  What this means is that is a very small region of space, you cannot be sure if matter exists there, or does not exist there.  Because energy is equivalent to mass, it means that in a very small region of space, you cannot be sure if a massive particle exists, and the smaller the space you are looking at, the greater the range of masses that you are uncertain of (in a very large region of space, even the lightest particle cannot exist, but in the very smallest region, very very heavy particles can very momentarily exist and disappear).

Ofcourse, the sudden creation of a particle will actually violate all sorts of conservation laws, so what is actually suggested is that if momentarily a particle, and exist exact anti-particle were created in a very tiny region of space, then you would get around the various conservation laws, and if that particle and anti-particle then quickly annihilate each other, then yoy also recover the energy used to create the particle, and so are not left with an energy deficit (but this can only happen within the very very small region of space over which there is an uncertainty as to whether something exists or not - it cannot escape outside of that space).  This fleeting existence of a particle and its anti-particle is known as a virtual particle pair (it is virtual because it cannot ever really be seen, because it is constrained within a space about which you cannot actually know what is happening, so it is in reality unprovable whether these particles exist or not, so you can get away with assuming they exist without violating any large scale conservation laws).
 

another_someone

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Virtual and anti particles
« Reply #3 on: 05/10/2007 19:58:31 »
OK - it seems Doctor Beaver keeps beating me to it :)
 

Offline DoctorBeaver

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Virtual and anti particles
« Reply #4 on: 05/10/2007 22:51:12 »
OK - it seems Doctor Beaver keeps beating me to it :)

But you explain things so much better  ;)
 

lyner

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Virtual and anti particles
« Reply #5 on: 05/10/2007 23:06:22 »
Don't meet up, you two - you might annihilate each other in an explosion of total information. All that would be left would be two smoking keyboards.
 

Offline DoctorBeaver

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Virtual and anti particles
« Reply #6 on: 05/10/2007 23:09:00 »
 :D
 

Offline hamza

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Virtual and anti particles
« Reply #7 on: 06/10/2007 08:35:11 »
Thanx another_someo. I got completely what u said.
 

Offline Ultima

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Virtual and anti particles
« Reply #8 on: 11/10/2007 22:30:50 »
Hey guys, very long time no see ;D how is everyone?

Virtual particles are also used to explain the interaction of forces between other particles. So virtual photons carry the force information between two charged particles. So instead of imagining electro magnetic fields as a field, you can also think of them as charged particles radiating and exchanging virtual photons. So as you get further away from a charged particle the virtual photons are more diffuse and so the force is weaker. These virtual particles might not exist in reality but it is a quantum mechanical explanation of force interactions.

;) I'll wait for one of the massive Physics brains to come in and correct what I just said.
 

Offline DoctorBeaver

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Virtual and anti particles
« Reply #9 on: 12/10/2007 07:20:04 »
Hi Ultima.

Your explanation sounds good to me.
 

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Virtual and anti particles
« Reply #9 on: 12/10/2007 07:20:04 »

 

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