What will happen to the universe?

[KrazyHorse]

Certainly it's possible that there existed a singularity at some point prior to the start of the inflationary epoch, but there is no need for one, and its location in time can certainly not be located by any means available today.

[Ecthy]

Did time exist before the inflation epoch? How long was that epoch? Like 10^-20 seconds or something?

[KrazyHorse]

Originally posted by Ecthy
Did time exist before the inflation epoch? How long was that epoch? Like 10^-20 seconds or something?

There is no reason for time not to have existed. Please note that we don't even understand the physics of inflation very well, so the physics of the pre-inflationary period are pretty much a mystery.

The length of the inflationary epoch is not well-determined. There are certain upper bounds which can be put on it, but not too many lower bounds.

[KrazyHorse]

Many of the guesses for the length of the inflationary epoch are in the 10^-25 to 10^-35 s range

[KrazyHorse]

I believe the standard guess for the change in the scale factor over that time period is ~10^26

[Ecthy]

For general understanding, what limits are used to define the inflationary epoch? If there are grey ares to both ends (as I assume), what would be a sensible upper bound to use?

[KrazyHorse]

No physicist would seriously suggest that inflation began and ended at a well-defined point in time. The rate of expansion began increasing, ran at a high level for a while, and then decreased to something which we can explain using standard physics. We don't know what the shape of the expansion curve is during inflation, so nobody's bothered to define a conventional "beginning" and "end". The Universe has been expanding for some time at a rate which agrees with normal physics. At some time in the distant past this cannot have been the case. An inflationary epoch of undetermined length and speed preceding the "normal" expansion explains a lot of problems, so we go with that. As yet, there is no known physical method to explain inflation, so the only measurements of it are cosmological, and are not very good.

[Ecthy]

As far as the question "why should there not have been time" goes: is there a model that assumes time in a similar manner as space, that it just got into being together with space, like during the inflation epoch? May the process of spatial expansion have been linked to the expansion of time? or something?

[KrazyHorse]

Have you ever heard of general relativity?

[Addled Platypus]

great book to read on this subject, just finished

"Big Bang" by Simon Singh

[Ecthy]

Well KH, I've heard of it. How does it help me here? You're the physics guy, explain.

[KrazyHorse]

You want me to explain what general relativity has to do with an expanding universe?

**** off. I charge 20$ an hour.

[KrazyHorse]

http://en.wikipedia.org/wiki/Robertson-Walker_coordinates

[Ecthy]

No no no... I want to know if time existed when the expansion began. You said it might well have existed, my understanding was it did not exist because only when it came int being could the expansion take place.

Elaborate Here are your virtual 20$

[Geronimo]

Originally posted by KrazyHorse
I believe the standard guess for the change in the scale factor over that time period is ~10^26

what is the nature of the relationship between the current ongoing expansion and the expansion during the inflationary "epoch"?