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Offline DoctorBeaver

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antiparticles
« on: 26/10/2005 14:35:47 »
It has been hypothesised that gravity is carried by particles called gravitons. Would they have an antiparticle equivalent? If so, could they be the cause of the acceleration in the expansion of the universe? Also, would an anti-graviton have to obey the laws on FTL? [xx(]


 

Offline McQueen

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Re: antiparticles
« Reply #1 on: 27/10/2005 08:27:57 »
quote:
Originally posted by DoctorBeaver

It has been hypothesised that gravity is carried by particles called gravitons. Would they have an antiparticle equivalent? If so, could they be the cause of the acceleration in the expansion of the universe? Also, would an anti-graviton have to obey the laws on FTL? [xx(]



It is interesting that you bring this up, what was at one time thought to be the definition of a  vacuum , was that it was a space  devoid of substance , now it turns out to be teeming with virtual interactions and particles . Apart from gravitons. the vacuum is also thought to be filled with quantum entangled particles such as electron/positron pairs. What does this do to our conception of the propagation of electromagnetic waves , surely it is reminiscent of the “ether” ( See: Questions on the ether in this forum) )which was so dear to classical physics? And since electron/positron pairs have  photons as both the causative and end factors in their existence ,  the propagation of electromagnetic radiation must be  closely involved with these “virtual” particles. But , and this is the question , how are they involved? Quantum mechanics ( or QED) gives a totally unsatisfactory answer to these questions. Am I right?
 

Offline Solvay_1927

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Re: antiparticles
« Reply #2 on: 27/10/2005 22:12:41 »
Doctor (mmm, nice) Beaver,
I recall reading that gravitons are their own antiparticles (in the same way that photons are their own antiparticles), so there's no such thing as an "anti-graviton".  So the answer must be (according to current theories, anyway): "no" - antigravitons can't be used to explain the accelerating expansion of the universe.  Gravity is always attractive, whether the particles it's acting on are matter or antimatter.


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Offline gsmollin

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Re: antiparticles
« Reply #3 on: 29/10/2005 16:39:53 »
quote:
Originally posted by McQueen
... And since electron/positron pairs have  photons as both the causative and end factors in their existence ,  the propagation of electromagnetic radiation must be  closely involved with these “virtual” particles. But , and this is the question , how are they involved? Quantum mechanics ( or QED) gives a totally unsatisfactory answer to these questions. Am I right?




As I understand it, virtual particles are closely involved with the transmission of forces from electromagnetic radiation. The magnetic forces you can feel are transmitted by virtual photons. The electrostatic force is transmitted by virtual photons. Virtual photons cannot perform work, however. Real photons are required for that.

"F = ma, E = mc^2, and you can't push a string."
 

Dr. Praetoria

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Re: antiparticles
« Reply #4 on: 31/10/2005 21:54:45 »
I believe that I read that possibly, anti-particles could be thought of has travelling "backwards in time" which would contradict Einstein's Special Relativity.
 

Offline gsmollin

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Re: antiparticles
« Reply #5 on: 01/11/2005 00:06:29 »
quote:
Originally posted by Dr. Praetoria

I believe that I read that possibly, anti-particles could be thought of has travelling "backwards in time" which would contradict Einstein's Special Relativity.



Anti-matter is only normal matter with opposite signs of charge. Time and space are the same.

"F = ma, E = mc^2, and you can't push a string."
 

Offline DoctorBeaver

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Re: antiparticles
« Reply #6 on: 03/11/2005 21:19:20 »
DrPraetoria - I seem to remember reading something similar but I think it was something to do with electrons not photons

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Dr. Praetoria

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Re: antiparticles
« Reply #7 on: 05/11/2005 21:30:17 »
It seems that there is more than electric charge reversal taking place when a particle is travelling "backwards in time"--I found three fundamental transformations of particles are involved in all this: the reversal of electrical charge (C), which changes particles into antiparticles and vice versa; parity reversal (P), the mirror reversal of every dimension in a particle (turning it inside out, so to speak), and time reversal (T).

Doc
 

Offline DoctorBeaver

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Re: antiparticles
« Reply #8 on: 06/11/2005 02:02:31 »
I think this is getting too heavy for my poor litte brain! *slides back under the sofa wishing he'd never asked*

We learn from history that we do not learn from history.
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Offline gsmollin

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Re: antiparticles
« Reply #9 on: 06/11/2005 12:35:04 »
Are you really referring to the reversibility of elmentary particle reactions? E. g., beta decay and inverse-beta decay.

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Dr. Praetoria

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Re: antiparticles
« Reply #10 on: 06/11/2005 21:48:00 »
It appears that "to no one's surprise, physicists at two big particle accelerators, one in Switzerland and the other in Illinois, proved that when certain particles go backward in time, their behavior is somewhat different from what it is when they go forward".  Just what is meant by "going backward in time" is still an unknown quantity in modern physics.
 

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Re: antiparticles
« Reply #10 on: 06/11/2005 21:48:00 »

 

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