Andeh Posted December 28, 2011 Share Posted December 28, 2011 I was wondering why opposite charges attract and like charges repel, so I considered what would happen if they didn't... So in pair production, two photons of neutral charge can create an electron (negitive charge) and a positron (possitive charge.) This entire process is conserved, in other words it can be reversed, so that an electron and positron can anhillate and produce two photons. Since the particles are of opposite charge, they attract, then anhillate. But if opposite charges didnt attract--if they repeled, this wouldn't happen. The eletron and positron would repel instead of attract, and so they couldnt anhillate. This would violate conservation laws, and would be impossibe--the universe simply can't work that way! Link to comment Share on other sites More sharing options...
mathematic Posted December 28, 2011 Share Posted December 28, 2011 I was wondering why opposite charges attract and like charges repel, so I considered what would happen if they didn't... So in pair production, two photons of neutral charge can create an electron (negitive charge) and a positron (possitive charge.) This entire process is conserved, in other words it can be reversed, so that an electron and positron can anhillate and produce two photons. Since the particles are of opposite charge, they attract, then anhillate. But if opposite charges didnt attract--if they repeled, this wouldn't happen. The eletron and positron would repel instead of attract, and so they couldnt anhillate. This would violate conservation laws, and would be impossibe--the universe simply can't work that way! What is your point? Link to comment Share on other sites More sharing options...
MigL Posted December 29, 2011 Share Posted December 29, 2011 Uncharged particles also have antiparticles, and some are their own antiparticles !?!? Link to comment Share on other sites More sharing options...
guenter Posted December 30, 2011 Share Posted December 30, 2011 (edited) Uncharged particles also have antiparticles, and some are their own antiparticles !?!? E.g. photons, neutrinos Uncharged particles don't annihilate with their antiparticles. Edited December 30, 2011 by guenter Link to comment Share on other sites More sharing options...
swansont Posted December 30, 2011 Share Posted December 30, 2011 E.g. photons, neutrinos Uncharged particles don't annihilate with their antiparticles. I'm pretty sure neutrons and antineutrons do. I don't see what would prevent it. There are some uncharged particles that are identical with their antiparticles (e.g. photons) that would not. Link to comment Share on other sites More sharing options...
imatfaal Posted December 30, 2011 Share Posted December 30, 2011 (edited) I'm pretty sure neutrons and antineutrons do. I don't see what would prevent it. There are some uncharged particles that are identical with their antiparticles (e.g. photons) that would not. Is that because the neutron / anti-neutron are not elementary and the component quarks/anti-quarks will annihilate because they are different - but the photon and its self-similar antiparticle are fundamental and there are no underlying different structures? \edited for spelling Edited December 30, 2011 by imatfaal Link to comment Share on other sites More sharing options...
swansont Posted December 30, 2011 Share Posted December 30, 2011 Is that because the neutron / anti-neutron are not elementary and the component quarks/anti-quarks will annihilate because they are different - but the photon and its self-similar antiparticle are fundamental and there are no underlying different structures? \edited for spelling The standard model does not have any neutral fermions as their own antiparticle (Majorana particles) though there is investigation into neutrinos. I suspect that Fermi statistics has something to do with this, i.e. the underlying reason for the Pauli exclusion principle. Link to comment Share on other sites More sharing options...
guenter Posted December 30, 2011 Share Posted December 30, 2011 Is that because the neutron / anti-neutron are not elementary and the component quarks/anti-quarks will annihilate because they are different - but the photon and its self-similar antiparticle are fundamental and there are no underlying different structures? Neutron and antineutron do annihilate, because they consist of charged particles. The criterion is the existence of opposite charges, not the question whether or not the particles are fundamental. Link to comment Share on other sites More sharing options...
swansont Posted December 30, 2011 Share Posted December 30, 2011 Neutron and antineutron do annihilate, because they consist of charged particles. The criterion is the existence of opposite charges, not the question whether or not the particles are fundamental. Electron neutrino-antineutrino annihilations are thought to occur in supernovae. Since they are uncharged and interact only weakly you need a high density to ensure the reaction, otherwise it would be unlikely. But not forbidden, as long as they are not Majorana particles. 1 Link to comment Share on other sites More sharing options...
guenter Posted December 30, 2011 Share Posted December 30, 2011 Electron neutrino-antineutrino annihilations are thought to occur in supernovae. Since they are uncharged and interact only weakly you need a high density to ensure the reaction, otherwise it would be unlikely. But not forbidden, as long as they are not Majorana particles. Oh, interesting. So annihilation isn't restricted to electric charges. But something else must distinguish then neutrinos and antineutrinos to offer the possibility to annihilate, their chirality? And what is the reaction product? I am not at all familiar with neutrino physics. In case the search for Majorana neutrinos is positiv, would it mean the neutrino is its own antineutrino, like it is true for photons? Link to comment Share on other sites More sharing options...
swansont Posted December 30, 2011 Share Posted December 30, 2011 Oh, interesting. So annihilation isn't restricted to electric charges. But something else must distinguish then neutrinos and antineutrinos to offer the possibility to annihilate, their chirality? And what is the reaction product? I am not at all familiar with neutrino physics. In case the search for Majorana neutrinos is positiv, would it mean the neutrino is its own antineutrino, like it is true for photons? If it is a Majorana particle, then it is its own antiparticle. Link to comment Share on other sites More sharing options...
MigL Posted December 31, 2011 Share Posted December 31, 2011 (edited) The only particles I know of that are their own antiparticles are both bosons. One is the previously mentioned photon, the other is the Z particle which carries ( along with +/-W particles ) the weak interaction. Being bosons they follow bose-einstein statistics and don't abide by the exclusion principle, they can bunch-up and have overlapping states. Edited December 31, 2011 by MigL Link to comment Share on other sites More sharing options...
guenter Posted January 1, 2012 Share Posted January 1, 2012 So annihilation isn't restricted to electric charges. But something else must distinguish then neutrinos and antineutrinos to offer the possibility to annihilate, their chirality? And what is the reaction product? As stated here neutrinos and antineutrinos annihilate via virtual Z-Bosons into charged particle-antiparticle pairs (leptons, quarks). Thus finally- at least theoretically - photons could be produced. Link to comment Share on other sites More sharing options...
Andeh Posted January 7, 2012 Author Share Posted January 7, 2012 I dont really have a dignified point. I'm not suggesting that this is the cause of the behavior of charge. I'm just interested/astounded that this is the only way that things could work--like the universe is just put together perfectly. It's not like alternative history, where if x event didnt happen, history would be completely different...but that the universe could not exist any other way; it's physically impossible. What is your point? Link to comment Share on other sites More sharing options...
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