What is the universe expanding into ? Eternal inflation

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SUMMARY

The discussion centers on the concept of the universe's expansion, specifically in the context of eternal inflation. It establishes that the universe is not expanding into anything but rather exists as a bubble within a vast, inflating space. The notion of expanding into inflating space is critiqued for suggesting that different patches of space can encroach upon one another, which contradicts the principles of local expansion. Ultimately, the universe's expansion is described as a localized phenomenon, unaffected by the surrounding inflating regions.

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  • Understanding of cosmic inflation theory
  • Familiarity with the concept of comoving coordinates
  • Knowledge of the standard model of cosmology
  • Basic grasp of general relativity principles
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  • Research the implications of eternal inflation on cosmic structure formation
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  • Study the differences between local and global expansion in the universe
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Astronomers, cosmologists, and physics enthusiasts interested in advanced concepts of cosmic expansion and the implications of eternal inflation on our understanding of the universe.

windy miller
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Normally when one is asked what is the universe expanding into, the answer is its not expanding into anything. Space itself can expand. However In the context of eternal inflation, our universe is a bubble in a sea of inflating space. And hence assuming eternal inflation is right, does the standard answer need revising? Should one say that its expanding into the inflating space?
 
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I don't see why it would need changing. Within the landscape of the eternal inflation, our universe is just a patch of space experiencing slower expansion than its surroundings.

The problem with saying something like 'expanding into inflating space' is that it implies that one patch of space somehow encroaches onto another - that a point in non-inflating patch can be carried by the 'regular' expansion into the inflating patch.
Whether points in the whole eternally inflating universe are within or without a non-inflating patch doesn't change them being comoving with whatever expansion is locally occurring. They can not be made to move past one another by expansion.
 
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