B The accelerating expansion of the universe

[kolleamm]

Just a thought I had today. I read an article that mentioned how the universe is expanding faster and faster and how dark energy may be the cause for this, but I wondered, what if the accelerating expansion of the universe is not caused by dark energy but simply by the gravitational attraction of our universe to other universes around us?

Looking forward to your thoughts on this.

 

[mfb]

There are no "other universes around us", there is not even an "around us" outside the universe. It's like asking what is north of the North Pole or searching the "East Pole".

 

[ngrunenberg]

As far as I am aware, dark energy and dark matter are placeholder words for a phenomenon which cosmologists have coined in order to explain a curious feature of our universe; observable matter only constitutes about 5% of our observable universe, DM ~27% and DE ~68% (as well as the fact that galaxies are receding away from us at a rate faster the further away they are).

As for your thought, it would almost certainly be impossible (given current, and likely near term, technology) to figure out if there are other universes; then if those universes exist, what kind of influence they exert over our own. Occam's Razor should be applied with many of these conjectures as it could be the case that the placeholder words 'DM and DE' are explained by other universes, higher dimensions, exotic particles, etc. Obviously one would assign higher prior probabilities to some of these being true than others, however we simply don't have enough information about what is actually going on to make any guesses like that.

If there was a universe pulling ours toward it though, I imagine we would notice an acceleration toward a certain area, depending on the geometry of the space that other universes occupy of course, rather than uniformly like we are now. Though to be fair, this last statement might be false due to my basic understanding of relativity and gravity in general.

TL:DR; Your claim would be fairly close to impossible to prove empirically at this moment, which is why scientists are using models and theories which are more likely to yield results in the near future.

 

[mfb]

(as well as the fact that galaxies are receding away from us at a rate faster the further away they are)

That would be true without dark matter and/or without dark energy as well. "The universe is expanding" and "the universe is isotropic" are sufficient for that.