The accelerating expansion of the universe

In summary, the conversation discusses the idea that the accelerating expansion of the universe may not be caused by dark energy, but rather by the gravitational attraction of other universes. However, this is difficult to prove empirically and current models and theories suggest that dark energy and dark matter play a significant role in the expansion of the universe.
  • #1
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.
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  • #2
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".
  • #3
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.
  • #4
ngrunenberg said:
(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.
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1. What is the accelerating expansion of the universe?

The accelerating expansion of the universe is the observed phenomenon where galaxies and clusters of galaxies are moving away from each other at an increasing rate, rather than slowing down as expected due to the force of gravity. This expansion is believed to be caused by a mysterious force called dark energy.

2. How do we know that the universe is expanding?

Scientists have observed the redshift of light from distant galaxies, which is a result of the Doppler effect. This means that the light waves from these galaxies are stretched out, indicating that they are moving away from us. This redshift is also found to be greater for more distant galaxies, showing that the expansion is happening on a large scale.

3. What is dark energy and how does it contribute to the acceleration of the universe?

Dark energy is a hypothetical form of energy that is believed to make up about 68% of the total energy in the universe. It is thought to have negative pressure, which causes the expansion of the universe to accelerate. However, its exact nature and origin are still not fully understood.

4. Is the accelerating expansion of the universe a recent discovery?

No, the idea of an expanding universe was first proposed by Belgian astronomer Georges Lemaître in the 1920s. However, the evidence for the accelerating expansion was not discovered until the late 1990s, from observations of supernovae by teams of scientists including Saul Perlmutter, Brian Schmidt, and Adam Riess.

5. What are the implications of the accelerating expansion of the universe?

The accelerating expansion of the universe has significant implications for our understanding of the universe and its ultimate fate. It suggests that the universe will continue to expand indefinitely, eventually leading to the "heat death" of the universe. It also challenges our current theories of gravity and requires the existence of dark energy, which is still not fully understood by scientists.

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