


From cosmological measurements such as WMAP,




  • $\begingroup$ Just a side note - we cannot see galaxies made of antimatter because it interacts with light in the same way as ordinary matter (there is no antiphoton). $\endgroup$ – Leos Ondra Apr 19 '12 at 21:43
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    $\begingroup$ @LeosOndra The way we expect to see from the earth anti galaxies is by the distinctive lines in the gamma spectrum. These annihilations will be by the dust and clouds of antimatter surrounding such a galaxy, at the interface with the space surrounding a galaxy. The intergalactic region will be rife with annihilations of the dust and the particle clouds, which will have characteristic lines in the spectrum. These have not been detected. $\endgroup$ – anna v Apr 20 '12 at 6:27
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    $\begingroup$ continued: If there were as many galaxies as anti galaxies, collisions would have a probability, and when colliding they would be a great source of distinctive gammas from annihilations. These have also not been detected. Had they been, we would have seen an antigalaxy, except maybe we would not be able to know which of the two colliding ones was the anti. $\endgroup$ – anna v Apr 20 '12 at 6:31


  • Baryon $B$ violation
  • C-symmetry violation and CP-symmetry violation
  • Interactions out of thermal equilibrium











  • $\begingroup$ What $\eta$ do we get from the Standard Model using CP violation? $\endgroup$ – Marton Trencseni Apr 20 '12 at 10:15
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What if the gravitational force between matter and anti-matter is repulsive rather than attractive (an experiment is underway at CERN to answer this question)? Then the anti-matter galaxies would all be bound by gravity into super clusters (just like the matter galaxies) and we would not see any collisions between matter and anti-matter galaxies because their respective super clusters would be repelling each other. Furthermore, the space between super clusters would have been voided by a combination of annihilation between matter and anti-matter and the repulsive gravitational interaction long ago, allaying the concerns expressed above by @anna v. The observed asymmetry could be an artifact of our limited power of observation (of anti-matter signatures) outside our local super cluster. Could this also explain dark energy?

For this to be compatible with the observed distribution of dark matter in the large scale universe (connected filaments separated by voids with ordinary matter super clusters arrayed like beads on a string), it would be necessary for dark matter particles (whatever they are) to be their own anti-particles (like photons) and for them to attract both matter and anti-matter of the ordinary type via gravity.

  • $\begingroup$ I call shenanigans, let's see your reference. $\endgroup$ – Jim Oct 21 '14 at 15:03

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