Speed of light

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Nereid said:
If the particle had mass, it could never be propelled to the speed of light, even if the power company had access to all the energy in the universe ... of course, if the particle were an electron, and the power company allowed you to have as much power as a small city (and you could covert the energy to making the electron go faster efficiently), your electron would be moving very close to the speed of light :wink:

Do you know how to calculate how close to the speed of light it would go?
I told him to get a particle with mass to the speed of light you'd need infinite energy and that would cost you. :rofl:

I don't know how to calculate anything with this stuff. I just read this stuff for fun. :eek:
 

Chronos

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whydoyouwanttoknow said:
I told him to get a particle with mass to the speed of light you'd need infinite energy and that would cost you. :rofl:

I don't know how to calculate anything with this stuff. I just read this stuff for fun. :eek:
Read the rules for posting.
 

Chronos

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zoobyshoe said:
The way I explain the photon to myself to account for the fact it has no mass is to bear in mind that it is a wave in an electric field.
Not entirely, it is a dual wave-particle thing. That is hard to conceptualize, but it is the best known description.

The properties of an electric field are such that it propagates all disturbances to it at one speed only, c, no faster, no slower and while it can transfer the energy of a disturbance from one location to another, no mass whatever accompanies that transference, just energy.
Technically, that is not a property of an 'electric field'. It is a property of all massless particle. That distinction is important.
The field is real, but its reality is limited, somehow, to the function of a potential direction for the travel of its waves. The photon has no mass because the medium that carries it, the electric field, has no mass. The photon is the energy of a small, intense disturbance to the position of the electron, traveling away from the electron via its electric field, at the only speed the field is capable of propagating such disturbances.
Field effects are not limited and there is no 'medium that carries' it. To say otherwise implies 'aether'. A photon is emitted when an electron falls to a lower energy level [which normally only occurs after it receives energy from an incoming photon]. After that, the photon is on its own.
 
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Chronos said:
Not entirely, it is a dual wave-particle thing. That is hard to conceptualize, but it is the best known description.
The way this was explained to me the other day in another thread was that all EM energy is essentially waves but that at a certain point the waves become so short and compact that they begin to interact with everything else as particle-like packets of energy. This made alot of sense and no one came along and objected to it.
Technically, that is not a property of an 'electric field'.
Not quite sure if you mean it's not exclusively the property of the elecric field or if you mean nothing propagates in an electric field at c?
It is a property of all massless particle. That distinction is important.
I had no idea there were any other massless particles besides photons. Which are they ?
Field effects are not limited and there is no 'medium that carries' it. To say otherwise implies 'aether'.
I'm not suggesting that there is a medium for the electric field. It is its own thing, and isn't the aether. The electric field, to the best of my knowledge, is the medium for EM energy.
A photon is emitted when an electron falls to a lower energy level [which normally only occurs after it receives energy from an incoming photon]. After that, the photon is on its own.
The other day someone suggested things to the effect the photon wasn't "on it's own". I had actually previously thought it was. The question came up when I asked where the transition from EM "wave" in a field to independent photon occured in the EM spectrum. This person said there was no actual transition, it was all the same thing, but that the waves become short enough at some point to exhibit exclusively "particle-like" behaviours in interactions.
 

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zoobyshoe said:
I had no idea there were any other massless particles besides photons. Which are they ?
AFAIK, the only one we know of today would be the neutrino. All three types - electron, mu, tau - have no measurable mass, in the best experiments to date (though the mass of tau possible within experimental limits is still huge). For quite some time many thought that all neutrinos were massless. However, in the last decade it's become clear that neutrinos are sneaky little things - they 'oscillate' between 'flavours'; different mixtures of flavours give each of the types we observe. Unless there's some really new physics involved that we are quite unaware of, this behaviour means that at least one neutrino flavour has mass, and possibly all three (I'm not so sure of this last point).

In the theoretical physicists' zoo, there are many a new particle waiting to be found - it depends on how the Standard Model is extended, modified, or supplanted. As there are no solid observations to guide one around this hypothetical zoo, one is free to consider any - or none - of them seriously. No doubt someone else will make a post about their favourites, including any that are massless (the graviton, for example).
 
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Thanks, Nereid. Those neutrinos sound like a fine can of worms to try to sort out.
 

selfAdjoint

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Nereid, the gluons, which of course are not observed, are also massless, along with the photon. These are all bosons. The neutrinos, before the recent discoveries, were regarded as the only massless fermions.
 

Nereid

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selfAdjoint said:
Nereid, the gluons, which of course are not observed, are also massless, along with the photon. These are all bosons. The neutrinos, before the recent discoveries, were regarded as the only massless fermions.
Oops, :redface: Clearly my coffee wasn't strong enough (or last night's wine too good).

So the carriers of two of the forces are massless, and the carriers of one quite massive (and the graviton is hypothetical), with all force carriers being bosons.

Does the gluon travel at c?
 

selfAdjoint

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Nereid said:
Does the gluon travel at c?
Necessarily it does, since it's massless, and the standard model obeys special relativity, because the Lorentz transformations require that for a massless body.
 
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Neutrinos are flavorful, gluons are colorful.

"In quantum chromodynamics (QCD), today's accepted theory for the description of the strong nuclear force, gluons are exchanged when particles with a color charge interact. When two quarks exchange a gluon, their color charges change; the gluon carries an anti-color charge to compensate for the quark's old color charge, as well as the quark's new color charge. Since gluons thus carry a color-charge themselves, they can also interact with other gluons, which makes the mathematical analysis of the strong nuclear force quite complicated and difficult. Even though there are theoretically nine unique colour combinations for gluons, (r-ar, r-ag, r-ab, g-ar, g-ag, g-ab, b-ar, b-ag, and b-ab) in reality there are only eight."


Gluon
Address:http://www.fact-index.com/g/gl/gluon.html
 

selfAdjoint

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That account might be a little confusing unless you know that in QCD, each gluon carries two charges, one of the colors and one of the anticolors. Each gluon is represented by a 3X3 matrix, in a representation of the gauge group SU(3). Rows correspond to the color charges and columns to the anti-color ones. Since there are three choices for each of these, the number of possibilities would seem to be 3X3 = 9. But the requirement that the matrices representing the gluons be unitary means you can derive algebraic relations from which given any eight components you can calculate the ninth. So there are really only eight INDEPENDENT components of the 3X3 gluon matrix.
 

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