Q&A 85: Am I Optimistic About Humanity? And More...
In this week's questions show, I think about the future of humanity, wonder what would happen if Olympus Mons erupted and how big observatories clean the dust off their telescopes.
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Comments (3)
Something I haven't heard explained is whether there is a discernible difference between universal expansion and motion through space. If a distant galaxy is getting farther away because the space between us is expanding, is that any different from a star in our own galaxy moving away from us because of its velocity through our local, galactic space? Does it even make sense to talk about the momentum of matter imparted by the Big Bang? I thought galaxy clusters aren't being propelled through space - they are sitting still while the space between them expands. Can we even tell the difference?
Yes, as long as the dark matter can overcome the local expansion.
Ok, the universe isn’t expanding where there are concentrations of matter. Does that include dark matter?