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Q & A: Is all matter made out of photons?

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Most recent answer: 04/14/2013
Q:
Is all matter ultimately made out of photons (electromagnetic radiation)?
- Lakhi (age 50+)
Ann Arbor, MI
A:
No. Photons have no electrical charge, so you can't make a charged particle out of them. They also have integer spin, so you can't make half-integer spin particles (like electrons) out of them. We could go on about QCD (color) charge, etc., but this should suffice.

Mike W.

(published on 04/09/2013)

Follow-Up #1: Products of particle-antiparticle annihilations

Q:
Thanks. But do (low energy) particle and anti-particle annihilation interactions of all the Elementary Particles result ultimately in the production of photons? And if so, does this mean that all matter is ultimately made up of photons? If not, what happens ultimately with such particle/anti-particle annihilations of Elementary Particles such as quarks, gluons, etc? They cannot create any other particle pairs as they themselves are Elementary Particles. Thanks!
- Lakhi (age 50+)
Ann Arbor, MI
A:
Nice question.
Although a good fraction of these annihilations  end up with two or more photons, there are other states that can exist as well,  electron or neutrino pairs for example.  The only requirement is that the net quantum numbers and other conserved quantities be the same:  charge, net linear and angular moment, lepton and baryon number, etc.
To answer your fundamental question:  No, all matter is not made up of photons.  There are other fundamental constituents such as quarks and leptons. 

LeeH

(published on 04/13/2013)

Follow-Up #2: particle creation/annihilation

Q:
Thanks. However from: http://en.wikipedia.org/wiki/Annihilation "Energy may also be released by the direct annihilation of a quark with an antiquark. The extra energy can go to the kinetic energy of the released pions, be radiated as gamma rays, or into the creation of additional quark-antiquark pairs. When the annihilating proton and antiproton are at rest relative to one another, these newly created pairs may be composed of up, down or strange quarks. The other flavors of quarks are too massive to be created in this reaction, unless the incident antiproton has kinetic energy far exceeding its rest mass, i.e. is moving close to the speed of light. The newly created quarks and antiquarks pair into mesons, producing additional pions and kaons. Reactions in which proton-antiproton annihilation produces as many as nine mesons have been observed, while production of thirteen mesons is theoretically possible. The generated mesons leave the site of the annihilation at moderate fractions of the speed of light, and decay with whatever lifetime is appropriate for their type of meson." See also: http://van.physics.illinois.edu/qa/newquestion.php?follow=Products%20of%20particle-antiparticle%20annihilations&id=22217 It seems that even quarks can annihilate into particles such as pions which then decay into photons.
- Anonymous
A:
Thanks, but I don't follow the "however". These processes all follow the rules that Lee mentioned.

Mike W.

(published on 04/14/2013)

Follow-up on this answer.