Re:Universe's expansion 'is now slowing, not speeding up'
by Erem on Thursday November 06, 2025 @07:24PM
(#45842275)
Wait but decelerating forever does in fact imply recollapse doesn't it?
Re:Universe's expansion 'is now slowing, not speeding up'
by pdonis on Thursday November 06, 2025 @08:02PM
(#45842508)
No. The simplest example is a matter-dominated universe at exactly the critical density. It decelerates forever but never quite stops expanding--the expansion rate asymptotes to zero.
Re:Universe's expansion 'is now slowing, not speeding up'
by deepthaw on Thursday November 06, 2025 @07:28PM
(#45842295)
I assume decelerating forever means asymptotically approaching not collapsing.
Re:Universe's expansion 'is now slowing, not speeding up'
by cwillu on Thursday November 06, 2025 @08:44PM
(#45842713)
An object on an escape trajectory from another mass is forever decelerating, but it still escapes.
Re:Universe's expansion 'is now slowing, not speeding up'
by jimbo808 on Thursday November 06, 2025 @09:09PM
(#45842840)
Would it not enter the viscinity of other objects which would eventually coalesce into local centers of mass (maybe like one per observable universe diameter or something)?
Re:Universe's expansion 'is now slowing, not speeding up'
by ridgeguy on Friday November 07, 2025 @01:04AM
(#45843909)
Nope, cosmic Zeno's Paradox. Collapse never quite happens.
Re:Universe's expansion 'is now slowing, not speeding up'
by xerox13ster on Friday November 07, 2025 @04:09AM
(#45844753)
Nope, that would be velocity changing sign, which means acceleration would increase.
Re:Universe's expansion 'is now slowing, not speeding up'
by SideburnsOfDoom on Friday November 07, 2025 @04:25AM
(#45844814)
No, in much the same way that a speeding vehicle slowly decelerating towards a stop doesn't mean that it will return to where it started the journey.
Actually it's worse than that, "decelerating forever" doesn't even mean that it ever even comes entirely to a stop. let alone return to where it started.
I don't think so. Deceleration does not imply recollapse. AFAIK none of this changes the basic fact that there isn't enough matter in the universe to cause it to recollapse. The expansion will just decelerate forever, never quite stopping.