Why are there only three massless particles and not four? I thought for each kind of matter particle there is a corresponding particle. What makes this any different from everything else?
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$\begingroup$ I'm sorry, but I am a bit lost. First of all I think, that the firs question addresses the standard model, where the massless particles are neutrinos (3), photons and gluons. What fourth massless particle would you expect? Are you referring to SUSY in your second question, where every particle has its super symmetric partner? $\endgroup$– CleverCommented Feb 1, 2015 at 9:54
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$\begingroup$ Well yes im referring to the SUSY. I figured that there being four fundamental force's that there would be one massless particle designated to each force. The odd number is part of it also I my self havent heard of that many odd numbers reliated to properties of mass and particles though I just recently started studying physics agen but would like to know of others. $\endgroup$– Longlost13Commented Feb 1, 2015 at 10:12
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2 Answers
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Electrons, protons, neutrons as well as their antiparticles are able to receive and to emit photons. The photon exchange is possible between each of this particles and antiparticles and this does not change the properties of photons.
Once emitted photons are the linear propagation of energy in the form of a oscillating electric and a oscillating magnetic field. Both fields are dipoles and in addition to the energy content there are only two possible states for this field called spin. In vacuum the two vectors of this fields are perpendicular to each over (and perpendicular to the direction of propagation).
Suppose one looks in the direction of propagation and see the electric vector at one moment vertical down. For half the photons the magnetic vector will be directed then to the right and for half the photons to the left. So the electric and magnetic vectors following each other clockwise ore anticlockwise. Energy content and spin - that's the full characteristic of photons. No net charge, no constant magnetic dipole direction. Photons are their own antiparticles.
answered Feb 1, 2015 at 9:51
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$\begingroup$ Yes I do understand that. But what im looking for would be, is there a particel with the same properties as photons. Being its own antiparticel with zero mass. Or is a photon The only Zero point. $\endgroup$ Commented Feb 1, 2015 at 10:24
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Are you arguing that because particles come in pairs - particle and anti-particle - then there should be an even number of massless particles?
If so, the argument fails because the photon is its own antiparticle i.e. there is no antiphoton.
answered Feb 1, 2015 at 10:24
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$\begingroup$ Yes I believe in a even structure. Is there not another zero particle with no mass and no anitparticle. Or is a photon the only one im not looking for an exact opposite such as a anti particle but just one that holds simular position. When you are building a structure you start with at least two parallel points to keep it balanced. $\endgroup$ Commented Feb 1, 2015 at 10:43
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$\begingroup$ @Longlost13 Nice idea about two points. My unusual point of view en.m.wikipedia.org/wiki/User:HolgerFiedler/… $\endgroup$ Commented Feb 1, 2015 at 11:03
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$\begingroup$ That was a good peace. So from the the start of the photon and its existence its charge and spin can fluctuate according to other particles it encounters. $\endgroup$ Commented Feb 1, 2015 at 11:55
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$\begingroup$ @Longlost13: uncharged gauge bosons are generally their own antiparticles. So for example the Z and the Higgs are also their own antiparticles. The photon is the only massless uncharged gauge boson (well, unless you include the graviton, but whether that exists is still uncertain). At energies above the electroweak transition, i.e. for the first few moments after the Big Bang, all particles are massless so in these conditions the Z and Higgs are also massless particles that are their own antiparticle. $\endgroup$ Commented Feb 1, 2015 at 12:14
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$\begingroup$ Ok so if the graviton did exist it would be what i am now calling a zero particle (do to no mass or antiparticle) as like the photon? $\endgroup$ Commented Feb 1, 2015 at 12:28