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PostPosted: Mon 21 Oct, 2013 4:51 pm 
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You claimed that Pluto would be Chad-11, but it would actually be Chad-12. Chad-11 is Ceres, discovered in 1801 and initially called a planet. Just like Chad-12 (Pluto) it was later stripped of its planethood.

Take another lap on the "Walk of Shame" mates! :D


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PostPosted: Tue 22 Oct, 2013 3:11 am 
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Joined: Tue 19 Feb, 2013 5:30 am
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Is there any experimental evidence that the photon has zero rest mass?

Alternative theories of the photon include a term that behaves like a mass, and this gives rise to the very advanced idea of a "massive photon". If the rest mass of the photon were non-zero, the theory of quantum electrodynamics would be "in trouble" primarily through loss of gauge invariance, which would make it non-renormalisable; also, charge conservation would no longer be absolutely guaranteed, as it is if photons have zero rest mass. But regardless of what any theory might predict, it is still necessary to check this prediction by doing an experiment.

It is almost certainly impossible to do any experiment that would establish the photon rest mass to be exactly zero. The best we can hope to do is place limits on it. A non-zero rest mass would introduce a small damping factor in the inverse square Coulomb law of electrostatic forces. That means the electrostatic force would be weaker over very large distances.

Likewise, the behavior of static magnetic fields would be modified. An upper limit to the photon mass can be inferred through satellite measurements of planetary magnetic fields. The Charge Composition Explorer spacecraft was used to derive an upper limit of 6 × 10−16 eV with high certainty. This was slightly improved in 1998 by Roderic Lakes in a laboratory experiment that looked for anomalous forces on a Cavendish balance. The new limit is 7 × 10−17 eV. Studies of galactic magnetic fields suggest a much better limit of less than 3 × 10−27 eV, but there is some doubt about the validity of this method.

References:
E. Fischbach et al., Physical Review Letters 73, 514—517 25 July 1994.

Chibisov et al., Sov. Ph. Usp. 19, 624 (1976).


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PostPosted: Wed 23 Oct, 2013 10:58 pm 
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About the fusion thing...it's not really "more energy than was put in". As much as I'd like it to be exactly that, it wasn't really. What actually happened was the energy of the neutrons from the implosion was more than the x-rays bouncing off the hohlraum (great word!) put into making the implosion. Since the NIF uses (according to this article) 1.8MJ and the result of this experiment was 14KJ...we're still, like, 2 orders of magnitude out. :(

Apparently this was another "science reporting fail". It seems like inertial confinement fusion is such a delicate dance that if the "power levels" aren't in perfect sync it doesn't even come close to working at all. Also, if I've been seeing the right TV shows (and I'm sure I have), it helps if you yell loudly. I think that the NIF reported it because they're kind of getting the hang of it a little bit and they're starting to get more of the fuel to actually "burn", and they said some things that the reporters misunderstood. That being said; I'm no expert, so don't take my word for it.

...AND YET ANOTHER ERROR! :o

Pika is not the sound electricity makes in Japanese (well, maybe it is for somebody, things sound differently depending who you ask). A Pika is this:

http://en.wikipedia.org/wiki/Pika

Maybe the name of the animal is coincidence, but most of the pokemon have names with double meaning or weird portmanteau, so I doubt it.

"Chu" is onomatopoeia for mousey noises.

Yes, I'm a nerd. Sorry. :mrgreen:

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PostPosted: Thu 24 Oct, 2013 11:57 am 
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Joined: Sat 08 May, 2010 2:35 am
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barnesm31 wrote:
Is there any experimental evidence that the photon has zero rest mass?


It's interesting the idea has been floated in an earlier time. The article we link to in the show notes does say the mass of the photon, if it has a mass, would be highly constrained by the physics we understand now. However, that doesn't mean it has to be zero.


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PostPosted: Thu 24 Oct, 2013 11:58 am 
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Joined: Sat 08 May, 2010 2:35 am
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Vince wrote:
About the fusion thing...it's not really "more energy than was put in". As much as I'd like it to be exactly that, it wasn't really. What actually happened was the energy of the neutrons from the implosion was more than the x-rays bouncing off the hohlraum (great word!) put into making the implosion. Since the NIF uses (according to this article) 1.8MJ and the result of this experiment was 14KJ...we're still, like, 2 orders of magnitude out. :(


Son of gun!

Fusion, Science.. get on it!


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PostPosted: Thu 24 Oct, 2013 12:59 pm 
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Joined: Wed 22 May, 2013 10:45 pm
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Yikes. Now we have 3 topics crammed into a single thread. That's what the "New Topic" button is for....


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