How do inflation, and the zero energy flat universe tie into one another?

In summary, the ideas of inflation, zero energy universe, and a flat universe are all important concepts in cosmology. They are each necessary for a particular type of model for the universe. The idea of a "zero energy flat universe that came from nothing" ties all of these ideas together, as it suggests that the universe must have started with no energy and must end up with zero net energy. While there are other ideas about the nature of the universe, the standard inflationary scenario suggests that inflation is what makes the universe appear flat. However, there are other theories that suggest a universe that came from something may also undergo inflation and appear flat. Therefore, observing a flat universe does not necessarily tell us whether the universe came from something or nothing
  • #1
neugie92
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0
New to cosmology and somewhat confused. I get all the ideas indvidually, that inflation is the exponential growth in the beginning of the universe, than that gravity and matter cancel each other out to make the zero energy universe, and that a flat universe is the only one that is zero energy and could come from nothing. I'm just confused on how all those ideas kind of relate to one another to form the idea of the "zero energy flat universe that came from nothing."

This may be elementary for most of you but as I said I'm new to this stuff.
 
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  • #2
They are each ideas that a particular kind of model for the Universe has to satisfy in order to be that kind of model. However, your question kinda provides it's own answer: just reverse it -

Presuppose that the Universe came from nothing - then it must have started out with no energy too (nothing means nothing), so it must end up with zero net energy which makes it a zero-energy universe. The only one that does that (says your question) is a flat one. There - you've tied all the concepts together :)

There are other ideas about the nature of the Universe too.
 
  • #3
My understanding is slightly different from what you have written, so I'd be interested to get any other feed back.
As I understand a closed universe under certain assumptions has a zero net energy. If a closed universe were to tunnel into existence in a way suggested by Vilenkin in order for it to have the properties we see it would have to inflate. In the standard inflationary scenario inflation makes the universe appear flat to us no matter whether it started off as flat or not. So the flatness of the universe is taken as a sign that it underwent inflation. As small universe that nucleated from "nothing" would have had to have inflated and flat universe is what we should expect to see in simple inflationary models.
My problem with this is a universe that came from something i.e a non singular bounce may also have undergone inflation and in fact may predict inflation.
See here :
This has been discussed on the forum here:
https://www.physicsforums.com/showthread.php?t=514640
So observing the universe to be flat doesn't tell us anything about whether the universe came from something or nothing.
 

1. How does inflation explain the rapid expansion of the universe?

Inflation is a theoretical concept that proposes that the universe underwent a rapid period of expansion in the first fractions of a second after the Big Bang. This expansion explains the large-scale homogeneity and isotropy of the universe, as well as the lack of observed magnetic monopoles.

2. What is the relationship between inflation and the flatness of the universe?

Inflation also offers an explanation for the flatness of the universe, meaning that the universe appears to have a nearly uniform density on a large scale. During inflation, the rapid expansion smoothed out any potential curvature, resulting in a flat universe.

3. How does the concept of zero energy tie into the inflation theory?

Inflation theory proposes that the total energy of the universe is exactly zero. This means that the positive energy of matter and radiation is balanced by the negative energy of gravity. This concept of a zero energy universe is consistent with the idea of an expanding, flat universe.

4. Can inflation theory and the zero energy universe concept be tested?

While there is currently no direct evidence for inflation or the concept of a zero energy universe, there are ongoing experiments and observations that are searching for evidence of inflationary gravitational waves and other signatures. These findings could provide support for these theories.

5. How does the concept of inflation tie into the current understanding of the universe's evolution?

Inflation is a crucial part of the current understanding of the universe's evolution. It helps explain the observed homogeneity, isotropy, and flatness of the universe, and provides a potential solution to several cosmological problems. However, it is still an active area of research and further evidence and observations are necessary to fully understand its role in the universe's history.

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