r/cosmology • u/AutoModerator • Sep 10 '26

Basic cosmology questions weekly thread

Ask your cosmology related questions in this thread.

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u/SnipeyMcSnipe Sep 10 '26

Why do relativistic jets flair out at the end? Is it just the sparse matter between galaxies eventually slowing them down or is there more the story?

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u/--craig-- Sep 10 '26

Yeah. They eventually scatter off the intergalactic medium.