Multiverse and dark energy (split from BICEP2 discussion)

[NeoClassic]

I'm not that good on my astrophysics, but considering many models point to a multiverse, why couldn't the effects of gravity of the outside universes be propelling the increased expansion of our own? the "dark energy" we indirectly detect is speeding up the expansion of our own universe, but as i mentioned, couldn't the gravity from neighboring universes be pulling on each other and driving this expansion?

[imatfaal]

I'm not that good on my astrophysics, but considering many models point to a multiverse, why couldn't the effects of gravity of the outside universes be propelling the increased expansion of our own? the "dark energy" we indirectly detect is speeding up the expansion of our own universe, but as i mentioned, couldn't the gravity from neighboring universes be pulling on each other and driving this expansion?

 

All a bit off-topic Neo-Classic - feel free to ask questions about dark energy and the multiverse in threads of their own. This topic is on the inflationary epoch almost immediately after the big bang and first signs of the gravitational waves impacting on the cmbr.

[swansont]

!

Moderator Note

Split from the BICEP2 discussion

[Cosmobrain]

In order for gravitational information to flow, it requires space. Another universe wouldn't have space connecting itself with out universe, so I assumo gravity can't affect that other world

[swansont]

!

Moderator Note

Speculation on multiverses and the validity of the big bang has been split http://www.scienceforums.net/topic/82575-multiverses/

 

This thread is for discussion of answers to the question posed using mainstream science

[Schneibster]

I'm not that good on my astrophysics, but considering many models point to a multiverse, why couldn't the effects of gravity of the outside universes be propelling the increased expansion of our own? the "dark energy" we indirectly detect is speeding up the expansion of our own universe, but as i mentioned, couldn't the gravity from neighboring universes be pulling on each other and driving this expansion?

 

No. Gravity travels at the speed of light, and if we can't see galaxies because they're moving faster than light, we also can't be affected by their gravity.

[BearOfNH]

No. Gravity travels at the speed of light, and if we can't see galaxies because they're moving faster than light, we also can't be affected by their gravity.

 

Imagine some time in the past we saw a galaxy that was deep red-shifted, i.e., moving away from us rapidly. At some point the galaxy disappears and we no longer see it. Ergo, we no longer feel its gravity either.

 

Presumably this is going on continuously, for galaxy after galaxy disappearing from view. Hence over time we're feeling less and less gravity. Is there any way to measure this and get an idea of, say, the rate at which galaxies are disappearing?

[Schneibster]

Yes. This is how cosmologists say how long it's likely to be until the universe undergoes the Big Rip.

 

Remember though that the fact that we no longer feel its gravity doesn't mean the rest of the universe doesn't. In fact, somewhat more than a third of the visible universe still does; it hasn't disappeared over their horizon.