Gary Eickmeier wrote:
I haven't studied this stuff as much as you, but I have a basic problem
with the Big Bang. The first thought is that if the universe is
expanding due to the Big Bang, then it will probably keep expanding and
never collapse. Why should it? If this is the case, and all of the
material in the universe came from the Big Bang, then how or why could
the Bang happen? In other words, if it wasn't the result of a collapse
of a previous universe until it got so tight and so hot that it had to
bang again, then where did it come from, or why would it happen? Seems
unfathomable.

The other thought is what if the totality of material in the universe
did not come from our Big Bang, but was always out there? Multiple Big
Bang theory, where there is infinite material in the universe, not a big
vacuum beyond our expanding universe. Many universes constantly
encountering each other and collapsing, then banging again. Just as
unfathomable. An infinite amount of anything is hard to understand, but
a finite universe is just as unexplainable.

Anyone know the latest thinking on this?

There is this:

Universe Creation by Quantum Fluctuation may be consistent with the
view of Dyson, Kleban, and Susskind in hep-th/0208013, where they say:

"... The conventional view is that the universe will end in a de Sitter
phase with all matter being infinitely diluted by exponential
expansion. ... In the following we will assume the usual connections
between quantum statistical mechanics and thermodynamics. These
assumptions{together with the existence of a final cosmological
constant - imply that the universe is eternal but finite. Strictly
speaking, by finite we mean that the entropy of the observable universe
is bounded, but we can loosely interpret this as saying the system is
finite in extent. On the average it is in a steady state of thermal
equilibrium. This is a very weak assumption, because almost any large
but finite system, left to itself for a long enough time, will
equilibrate (unless it is integrable). However, intermittent
fluctuations occur which temporarily disturb the equilibrium. It is
during the return to equilibrium that interesting events and objects
form. ... Let S be the final thermodynamic entropy of the gas. Then on
time scales of order Tr = exp( S ) the system will undergo Poincare
recurrences ... On such long time scales the second law of
thermodynamics does not prevent rare events, which effectively reverse
the direction of entropy change. Obviously, the recurrence allows the
entire process of cosmology to begin again ... What is more, the
sequence of recurrences will stretch into the infinite past and future.
.... Starting in a high entropy, "dead" configuration, if we wait long
enough, a fluctuation will eventually occur in which the inflaton will
wander up to the top of its potential, thus starting a cycle of
inflation, re-heating, conventional cosmology and heat death. The
frequency of such events is very low. The typical time for a
fluctuation to occur is of order Tr = exp( S - S0 ) ... where S is the
equilibrium entropy and S0 is the entropy of the fluctuation. The
fluctuations we have in mind correspond to early inflationary eras
during which the entropy is probably of order 10^10, while the
equilibrium entropy is of order 10^120. Thus Tr = exp( 10^120 ) ...
dismissing such long times as "unphysical" may be a symptom of extreme
temporal provincialism. ...

Thanks for the response, Jacob, but it doesn't seem to answer my basic
questions directly (and I'm not sure I understand it all).

Gary Eickmeier

wrote:

Gary Eickmeier wrote:

I haven't studied this stuff as much as you, but I have a basic problem
with the Big Bang. The first thought is that if the universe is
expanding due to the Big Bang, then it will probably keep expanding and
never collapse. Why should it? If this is the case, and all of the
material in the universe came from the Big Bang, then how or why could
the Bang happen? In other words, if it wasn't the result of a collapse
of a previous universe until it got so tight and so hot that it had to
bang again, then where did it come from, or why would it happen? Seems
unfathomable.

The other thought is what if the totality of material in the universe
did not come from our Big Bang, but was always out there? Multiple Big
Bang theory, where there is infinite material in the universe, not a big
vacuum beyond our expanding universe. Many universes constantly
encountering each other and collapsing, then banging again. Just as
unfathomable. An infinite amount of anything is hard to understand, but
a finite universe is just as unexplainable.

Anyone know the latest thinking on this?


There is this:

Universe Creation by Quantum Fluctuation may be consistent with the
view of Dyson, Kleban, and Susskind in hep-th/0208013, where they say:

"... The conventional view is that the universe will end in a de Sitter
phase with all matter being infinitely diluted by exponential
expansion. ... In the following we will assume the usual connections
between quantum statistical mechanics and thermodynamics. These
assumptions{together with the existence of a final cosmological
constant - imply that the universe is eternal but finite. Strictly
speaking, by finite we mean that the entropy of the observable universe
is bounded, but we can loosely interpret this as saying the system is
finite in extent. On the average it is in a steady state of thermal
equilibrium. This is a very weak assumption, because almost any large
but finite system, left to itself for a long enough time, will
equilibrate (unless it is integrable). However, intermittent
fluctuations occur which temporarily disturb the equilibrium. It is
during the return to equilibrium that interesting events and objects
form. ... Let S be the final thermodynamic entropy of the gas. Then on
time scales of order Tr = exp( S ) the system will undergo Poincare
recurrences ... On such long time scales the second law of
thermodynamics does not prevent rare events, which effectively reverse
the direction of entropy change. Obviously, the recurrence allows the
entire process of cosmology to begin again ... What is more, the
sequence of recurrences will stretch into the infinite past and future.
... Starting in a high entropy, "dead" configuration, if we wait long
enough, a fluctuation will eventually occur in which the inflaton will
wander up to the top of its potential, thus starting a cycle of
inflation, re-heating, conventional cosmology and heat death. The
frequency of such events is very low. The typical time for a
fluctuation to occur is of order Tr = exp( S - S0 ) ... where S is the
equilibrium entropy and S0 is the entropy of the fluctuation. The
fluctuations we have in mind correspond to early inflationary eras
during which the entropy is probably of order 10^10, while the
equilibrium entropy is of order 10^120. Thus Tr = exp( 10^120 ) ...
dismissing such long times as "unphysical" may be a symptom of extreme
temporal provincialism. ...

Gary Eickmeier wrote:
Thanks for the response, Jacob, but it doesn't seem to answer my basic
questions directly (and I'm not sure I understand it all).

The standard view right now is that there's a big bang and it expands
and gets diluted forever and that's it. As you say, that is not too
satisfying. The expand and contract idea would need some kind of
different than standard redshift interpretation which basically says
things aren't expanding as fast as we thought and then as you said in
another response, gravity could cause things to contract back into
another big bang. For particle physics reasons more than cosmological
ones, I personally don't like any of the redshift ideas though there
are good people working in that area. There's the instanton creating a
new big bang idea which I like. Information in the parent transfers to
the child but the child makes more something out of nothing so I
suspect this is not overly satisfying for you. It nicely gets rid of
energy/information in the parent but the extra energy/information
created by the child seems mysterious. It is like zero energy can be
seen as the sum of negative and positive energy and these energies are
useful even though they sum to zero. Kind of reminds me of the way a
zero probability in quantum physics can be seen as the some of negative
and positive probabilites. John