Seeing Less of the Future Universe

Most recent answer: 02/20/2015

As the expansion of the universe accelerates un checked and approaches the speed of light - will physicists of the distant future be able to 'see' as much of the universe as is available to those now. Implications?
- Tom (age 66)
Cypress, Texas, USA

Yes, as the expansion of the universe accelerates parts that are within our horizons now keep receding beyond our horizons. So less and less is observable. You can more or less think of those parts as traveling away from us faster than the speed of light. The speed limit in general relativity applies to local speeds, not overall expansion.

Whether this accelerating expansion will go on forever is not known for sure, since it's driven by something mysterious, perhaps "dark energy". If the dark energy were to change, through a phase transition of the vacuum, the acceleration would change. The process would also wipe out all observers, so in that sense it would make even less (none) of the universe observable, unless some sort of new evolution of observers got going after a while.

Mike W.

(published on 02/20/2015)