On 6/19/2015 6:25 PM, R. Dean wrote:
>
> Starting with the Big Bang the laws of Physics seems to show
> that the ration of the force of gravity and the rate of
> expansion was perfectly balanced. Had they been off balance
> by a fraction, the universe would have either collapsed back
> in a big crunch or expanded too fast for stars and galaxies
> to form. Without stars, no elements heavier than hydrogen
> or helium could exist. This is one of at least four fine
> tuned constants. And many scientist do accept the fine
> tuned argument. However, rather than see this as evidence
> of a designer/creator some scientist appeal to a concept
> of infinite numbers of universes. If this is true, then
> it just a matter of chance that at least one of these
> countless universes would have the necessary parameters
> for life to emerge even intelligent life. But how does
> one prove the existence of other universes?
> As I remember this hypothesis called the Anthropic
> Principle was first advanced by the English physicist
> Brandon Carter in 1973 And has been controversial ever since.
>
But the problem is even more difficult than just
trying to explain a special ratio at the Big Bang.
The problem is the Big Bang had to have a special
initial ratio set so that as it evolved over time
some...14 billion years later...the universe
would then be just right for life. This second puzzle
is called the cosmic coincidence problem.
And it's thought Dark Energy was an insignificant
component up until the current epoch, almost at
the same time humans first evolved on Earth Dark
Energy become the dominant force and produced
the current second period of universal inflation.
Here's a great paper explaining all this much
better from one of founders of the Big Bang
theory.
A Quintessential Introduction to Dark Energy
(excerpts)
3. Fine-tuning, cosmic coincidence, and the
quintessential solution
Whatever form the dark energy takes, two new cosmological
problems arise. First,the component must have a tiny
energy density (ca. 10¡47 GeV4) today. How does
this small value arise from a microphysical theory?
We will refer to this puzzle as the fine-tuning problem’.
A second problem arises when the cosmological model is
extrapolated back in time to the very early Universe,
at the end of inflation, say. The quintessence
energy density decreases at a different rate from
the matter density, and their ratio shrinks by many
orders of magnitude as we extrapolate back in time.
The observations tell us that, somehow, the ratio was set
initially just right so that now, fifteen billion years
later, the ratio is of order unity. Accounting for the
special ratio in the early Universe will be referred to
as the `coincidence problem’ (Steinhardt 1997). The
coincidence problem is a generalization of the flatness
problem pointed out by Dicke & Peebles (1979).
The fine-tuning and cosmic coincidence problems are vexing.
They are often posed as a paradox: why should the acceleration
begin just as humans evolve? In desperation, some cosmologists
and physicists have given renewed attention to anthropic
models (Weinberg 2000). But many continue to seek a dynamical
explanation which does not require the fine-tuning of initial conditions
or mass parameters and which is decidedly
non-anthropic.
A dynamical approach would seem to demand some sort
of quintessence solution, since it would have to
entail some interaction between the dark energy and
the matter radiation background.
http://physics.princeton.edu/~steinh/steinhardt.pdf
Paul J Steinhardt
Director, Princeton Center for Theoretical Physics
http://www.physics.princeton.edu/~steinh/darkenergy.html
s