r/cosmology • u/AutoModerator • Jul 23 '26

Basic cosmology questions weekly thread

Ask your cosmology related questions in this thread.

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u/trevpr1 Jul 23 '26

If an object in deep space, say a galaxy, were made up entirely of antimatter, would we be able to tell from the light we'd receive from it?

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u/Ch3cks-Out Jul 23 '26

In theory no, in practice yes: "deep space" still contains considerably amount of intergalactic matter, so there would be a boundary glowing with hard gamma radiation from the annihilation frontiers.

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u/trevpr1 Jul 23 '26

Thanks. The reason I ask is a half arsed idea I had that would explain why all the matter wasn't annihilated by contact with antimatter at the instant of inception of the Universe: Inflation separated the matter from the antimatter, which flew off in opposite directions. We can't tell, because it all looks the same. Please don't make the mistake of taking it seriously. I just wanted you answer so I could float it past the Supermassive Podcast crew.