Infinite Universe from finite bubble

[Dmitry67]

I am puzzled with the following explanation of Max Tegmark:

http://space.mit.edu/home/tegmark/multiverse.html

Can a finite universe grow infinite?
From Mark Tranchant, mtranch2@ford.com, Tue Apr 15 03:41:08 2003
Q: Your Level I calculations rely on two assumptions:
A Big Bang approximately 14 billion years ago
Infinite space to play with
How do you reconcile these two - how do we get from a tiny expanding sphere to infinite space in finite time? Incidentally, congratulations for writing the first article I've read to use a number larger than a googolplex...
A: If space started out finite (curved up like a hypersphere, say), then it always remains finite. Conversely, if it is infinite now, it was infinite from the very beginning. For more details on this, check out Ned Wright's cosmology FAQ. A interesting exception to this is inflation (see next question), which can create something infinite out of something finite.

How can you make an infinite universe in a finite bubble?
From David Coule, David.Coule@port.ac.uk, November 29, 2003 19:39:41
Q: In the Level I case, where does it say that a spatially infinite universe is a prediction of inflation? There is suposedly a geodesic incompletness theorem of Borde, Guth and Vilenkin, gr-qc/0110012, that shows that only a finite time worth of inflation could have happened.So if the initial patch is finite there is still at present only a finite volume created. Garriga and Vilekin's philosophical mussings contradicts this result!

A: The trick is that you generically obtain an infinite universe even after a finite abount of inflation. The subtle trick involves the t=constant spatial hypersurvaces perceived by observers curving upwards in spacetime towards the infinite future time direction. Loosely speaking, the infinite future time direction gets warped into an infinitete space. Please see Garriga & Vilenkin 2001, Phys. Rev. D 64, 043511 and references therein for details.

Check bold
Any help?

 

[AndyW]

I can offer some insights to help clarify this explanation by Max Tegmark.

First, it is important to understand that the concept of an infinite universe is a theoretical concept and cannot be proven or disproven. It is based on mathematical models and assumptions, and as Tegmark mentions, it relies on the assumption of an infinite space to work with.

The Big Bang theory, which is the most widely accepted explanation for the origin of our universe, suggests that the universe began as a singularity - a point of infinite density and temperature. This singularity then expanded rapidly, leading to the formation of our universe as we know it.

In regards to the question of how a finite universe can become infinite, Tegmark explains that it is possible through a process called inflation. Inflation is a theory that proposes that the universe underwent a period of rapid expansion in its early stages, causing it to grow exponentially in a short amount of time. This rapid expansion could lead to the creation of an infinite universe from a finite initial state.

However, there are also other theories and calculations, such as the geodesic incompleteness theorem mentioned by David Coule, that suggest a finite universe is still a possibility. This highlights the uncertainties and ongoing debates within the scientific community about the true nature of our universe.

In conclusion, Tegmark's explanation offers some potential explanations for how a finite universe could potentially become infinite. However, it is important to remember that these are theories and assumptions, and we are still far from fully understanding the complexities of our universe.