Sure. Let me go ahead and start by assuming that we need to exist
in an environment that began in a state of low entropy (so that life
can evolve during the "increasing entropy phase" - I could also
examine this assumption, but that's another discussion...). GR then
does some interesting things. First, gravity in GR couples to energy
and momentum, and everything has energy and momentum, so, er, it
couples to everything (binding them all together like the one ring I
suppose). It can thus essentially "get everybody on the same page"
when things are starting out - forcing "everybody" (all the particle
species) to "pay attention" and synchronize their behavior...
GR can then do something quite cool. If you feed the Einstein
equations with a scalar field that happens to have much more potential
energy than kinetic energy, then the spacetime responds by growing
exponentially (i.e. the curvature is in the time direction - the
spatial directions are driven to be very flat (i.e. the angles inside
a triangle add up to 180 degrees), with the overall scale factor
growing exponentially (i.e. the overall size of the triangle is
growing exponentially in time)). Thus, consider some complex universe
with a lot of entropy. Entropy is an extensive quantity, and thus if
we consider some tiny volume element dV then there can't be much
"stuff" inside dV, and therefore there is very little entropy inside
dV. If we can get a scalar field inside that dV to satisfy the
condition that its potential energy is much larger than its kinetic
energy, then blammo, we get inflation and that dV region can grow
larger than our Hubble volume in a tiny fraction of a second (and then
scalar field can decay, ending inflation, to be followed by a
"standard" big bang...).
It is by no means an open and shut case - there are lots of details
to be filled in - but I think the overall picture makes a lot of
On Jun 2, 6:35 am, Roc <roc...@gmail.com> wrote:
> nice answer.
> could you elaborate on this, though?
> Why then should spacetime be curved? There are at least 2 good reasons:
> 1) it allows for a big bang to happen, thus "starting things off" in a state
> > of low entropy.
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