# SciContest! Why can't matter be made of photons?

Discussion in 'Physics & Math' started by BenTheMan, Aug 11, 2008.

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1. ### VernRegistered Senior Member

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If you add the energy to a golf ball via a club you increase its momentum directly. Adding heat to it increases its mass, so if it is moving and everything must be; we're still in orbit I think; if it is moving its momentum increases.

Poincare's contribution to SR is widely known. Why do you object to it?

3. ### flamethrowerJuniorRegistered Senior Member

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My 2 cents.

Conservation laws. By abiding to the energy-mass conservation law, by converting photons into an electron, for example, we violate other conservation laws such as spin and charge.

5. ### gluonBannedBanned

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Not true.

In some form or another conservation laws are running the show. Take the idea that two particles an electron and a positron come together, the conservation law of momentum states that at least two photons be created. So from ordinary matter, we can make photon energy, and we can make matter from photons as well. Everything is conserved, or this process would be lost.

7. ### John ConnellanValued Senior Member

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i have heard that a photon of sufficiently large energy (high frequency) can be converted into a matter particle and it's anti-particle using a clever trick. The trick is to fire it close to the nucleus so that the the particle and it's anti-particle seperate enough to exist independently

8. ### BenTheManDr. of Physics, Prof. of LoveValued Senior Member

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Ok. I promised myself that I wouldn't forget about this, then I did. Then I remembered, then I got busy.

This thing was resolved in September, and I never made public the results.

Congratulations Janus58, for your nice dimensional analysis argument.

Feel free to continue the discussion, but the matter is settled.

9. ### VernRegistered Senior Member

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Hi BenTheMan; your reference to the Fine Structure Constant sent me into a month- long study that concluded with how the fine structure constant relates to a photon-only universe. I had not thought of that before. I still think you are one of the few people in this universe who is capable of resolving Einstein's greatest dream. His unification of the forces.

Hope I'm not causing you any grief.

10. ### prometheusviva voce!Registered Senior Member

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No argument from me here, although strictly speaking momentum is being transferred from the club to the ball, or you are transferring kinetic energy from the club to the ball. Energy and momentum are not interchangeable.

Wrong. I assume you're thinking that increasing something's temperature increases the kinetic energy of the constituent particles and that means they get more relativistic mass. Well relativistic mass is an extremely poor concept because it's not really a mass, it's an energy so we could say that the internal energy of the body has increased, not the mass.

In a bit more depth, mass cannot be velocity dependant because it is defined to be the invariant norm of the momentum four vector. Notice the word "invariant" in there. Mass as defined does not depend on velocity. If you want mass to depend on velocity then the theory becomes mathematically inconsistent, Poincare or not.

Sorry, but this is gibberish.

11. ### prometheusviva voce!Registered Senior Member

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FYI here is the winning post linky

Congrats Janus58!

12. ### VernRegistered Senior Member

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I thought momentum was mass times velocity, I think I remember someone using p = mv to determine the momentum p.

Congrats to Janus58. However the diameter of the electron was assumed to be less than a certain value because that was the measuring limits and nothing was detected. There is another possibility, however. The other much more likely possibility is that there was nothing there to detect. The electron only exists at its electromagnetic diameter.

13. ### prometheusviva voce!Registered Senior Member

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Wrong again. In general $p = \gamma mv$

14. ### prometheusviva voce!Registered Senior Member

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Invariant norm of the momentum four vector means

$\eta^{\mu \nu} p_\mu p_\nu = \frac{E^2}{c^2}-\vec{p} .\vec{p}=m^2c^2$

With a bit of rearranging you get

$E^2 = \left| \vec{p} \right|^2 c^2 + \left(m c^2\right)^2$

which clearly reduces to $E = mc^2$ when $\vec{p}=0$ or in the rest frame of the particle.

15. ### VernRegistered Senior Member

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You don't even have to do a trick. All you need is enough energy at the right frequency and photons become massive particles.

prometheous: Your arithmetic is good, so I'll change my thinking. A photon is not mass. It is only potential mass. Any time it is confined such as bouncing around inside a mirrored box, or between atoms, it then becomes mass.

16. ### gluonBannedBanned

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Oh how wonderful of you to finally remember... months later...

Oh well Janus, you've won strictly on erreneous grounds, meaning the thread was giving out a false contest supposing matter could not be made of photons. Oh well, we live and learn.

17. ### VernRegistered Senior Member

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I think the Janus58 entry was a good choice since the OP asked for the BEST entry. Not necessarily one that could show the concept false.

But let the record show, there was no entry that could qualify as a killer for the photon-only concept.

18. ### Janus58Valued Senior Member

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And here I am without an acceptance speech ready. I mean, who would have thought that the son of an iron miner, raised on a farm in the Mesabi range, would grow up to win this contest.

So anyway, I'll just thank Ben for sponsoring and judging the contest. It was fun.

19. ### gluonBannedBanned

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The only one, that could ever teach me...

..was the son of a ...

Sorry, got lost in the moment.

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congradulations on winning the 'physicists choice' award!

that sentence

Each photon would have to have a fraction of the energy equivalence of the electron, and as the energy of a photon decreases, its wavelength increases. is true (see radio vs gamma)

did you have another point?

21. ### gluonBannedBanned

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I think the point was that the wavelength of matter is miniscule... almost vanishing.

22. ### John ConnellanValued Senior Member

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Probably true. Just that using the positively charged nucleus trick means that one can generate particles at smaller energies

23. ### VernRegistered Senior Member

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Interesting; I had never seen that before. Do you have a reference as to where you came across this info?