Why is there a normal galaxy sitting at the edge of the Universe?

Re:Why is there a normal galaxy sitting at the edge of the U... by noizejoy on Wednesday September 09, 2020 @03:12PM (#24424659)

I thought it was explained. Local gravity is moving things together much faster than general expansion is moving them apart. At super super long distances, gravity is weaker than expansion, so something very far is disappearing while something nearby may be collapsing.

However, that questions a different future I’ve seen in popular science talks: That the future becomes dark because of expansion. That makes less sense to me now, since it would seem that a merged set of galaxies would keep plenty of local stars in the skies. Assuming that stars are born as fast as they die (but I don’t recall seeing an answer to the ratio of star births vs star deaths at a local level).

[ Parent | on HN ]

Re:Why is there a normal galaxy sitting at the edge of the U... by ddevault on Wednesday September 09, 2020 @03:15PM (#24424693)

The rate of expansion is speeding up. If it continues to increase, eventually it'll have observable effects at interstellar scales, and even interplanetary scales, and ultimately tear everything apart in the "big rip". Note that I'm omitting a lot of context here, there's a lot of other factors which make the big rip scenario much less likely.

Also, the age of star formation will eventually end. Stars will stop forming somewhere between 1 trillion and 100 trillion years in the future.

[ Parent | on HN ]