Extrapolation back to T zero, before 1980

[Cerenkov]

Hello.

I have a question about how close (in time) the Hot Big Bang theories formulated before 1980 could be reliably extrapolated to T zero.

In his book... https://en.wikipedia.org/wiki/The_Inflationary_Universe ...Alan Guth recounts a lecture by Robert Dicke in 1978 which set the benchmark at 1 second from T zero.

I'd like to learn more (in basic terms please) about how this benchmark was set before Guth's 1980 papers on Inflationary theory, which enabled extrapolation back to 10_-35 seconds.

Thanks for any help given,

Cerenkov.

 

[kimbyd]

Hello.

I have a question about how close (in time) the Hot Big Bang theories formulated before 1980 could be reliably extrapolated to T zero.

In his book... https://en.wikipedia.org/wiki/The_Inflationary_Universe ...Alan Guth recounts a lecture by Robert Dicke in 1978 which set the benchmark at 1 second from T zero.

I'd like to learn more (in basic terms please) about how this benchmark was set before Guth's 1980 papers on Inflationary theory, which enabled extrapolation back to 10_-35 seconds.

Thanks for any help given,

Cerenkov.

I don't think the development of inflationary models really had an impact on how much we could extrapolate into the past.

Before inflation was conceived of, extrapolation into the past could only be really trusted back to the time of primordial nucleosynthesis (which took place in the first few minutes), because this was the earliest period which was measured by observation. This hasn't changed at all. It might change at some time in the future if we learn the properties of the dark matter particle. But for now, we just can't say all that much about the very early universe.

Inflation doesn't improve our ability to extrapolate back into the past because it isn't extrapolating backward: it's a model which sets up some initial conditions for the later evolution of the universe as described by the Big Bang theory. We can't extrapolate back to the time of inflation, because the stuff that caused inflation isn't around any longer (at least, it isn't measurable).

 

[Cerenkov]

Thanks on two counts, kimbyd.

First, for correcting my misunderstanding of this issue and second for doing so within an hour!

I appreciate the speed and clarity of your reply.

Cerenkov.