Re: Question about the Big Bang and Dark Matter
- From: "dlzc" <dlzc1@xxxxxxx>
- Date: 23 Aug 2006 10:21:12 -0700
Dear Jeff Root:
Jeff Root wrote:
David A. Smith replied to Rising-Star8471:
When I think of the Big Bang, I think of an explosion...
It wasn't an explosion of stuff, but an inflation of space.
Can you explain why one should think so?
I will assume you mean "why one would think the Big Bang was an
explosion of space"?
The distribution of matter at the time of the CMBR was uniform, hard to
do with anything except a very special initial mass. There is no
"central ember" visible in any direction that we can see, not possible
with even the most special explosives. The most successful theory of
gravitation we have indicates that a classical explosive beginning was
not necessary to arrive at what we *do* see today.
Newton says that anything put into motion will
continue to be in motion until some outside force
interacts with it to slow it down or stop it.
Which wouldn't apply to inflating or expanding space,
since it wasn't a kinetic explosion.
Why wouldn't it apply? Until just a few years ago it was
assumed that the expansion is slowing because of the
mutual gravitational attraction of all the matter. It is still
believed that the expansion slowed during the first few
billion years, until the "dark energy force" -- whatever
it is -- became stronger than the gravitational force.
Gravitation is not any kind of force. Therefore, "slowing down" is
only some path along a geodesic in spacetime involving *no* force
carriers. Dark Energy is not any kind of force either, yet it is
constantly described as such in literature.
Ignoring the dark energy force, are you saying that galaxy
clusters are moving apart because the space they are in
is expanding? If so, what causes that space to continue
to expand, billions of years after the Big Bang? It sounds
like your cosmology has four causes of the expansion:
1) The initial Big Bang which started everything.
2) Inflation, between 10E-36 second and 10E-33 second.
3) Continuing expansion, first measured by Edwin Hubble.
4) Acceleration of the expansion, discovered in 1998.
I thought that (1) was explained at least in part by the
enormously high temperature of matter in the Universe at
the instant of the Big Bang, and (3) was explainable as
the inertial motion of the products of the Big Bang. But
if expansion of space itself is the cause of (3), then
what causes the expansion of space? Heat wouldn't
cause space itself to expand. So (1) is completely
unexplained in your cosmology. You have four apparently
separate events to explain, although you may consider
two or more of them to have a common cause.
They all "four" have the same cause. It is believed that there was no
matter in the Universe at the instant of the Big Bang, so temperature
would not be necessary to initiate expansion. At some point in the
inflationary period (2), matter is believed to have congealed. The
history of cosmological expansion is more convoluted than you show
above, but you know that. Energy also has an affect on curvature, so
will tend like matter to keep "things" close.
What causes expansion is the second law of thermodynamics. An
expanding Universe has increasing entropy.
If I light a firecracker and it explodes, the pieces
of paper that make up the firecracker will continue
to fly away from it until gravity and air resistance
slow them down and they fall to earth.
And there is a considerable concentration of little bits
of paper and smoke at the center.
Not necessarily. An explosion could spread the products
uniformly throughout a spherical volume.
No. Like the rear axle of the rental truck used to blow up the Edward
J. Murrough building in Oklahoma City... something is left behind. Not
only that, but the distribution of debris decreases with distance (like
1/r^2, without gravity). There is no such distribution in this
Universe. Additionally, there is a range of velocities from an
explosion, depending on where in the "load" the particular chunk
started. The distribution of velocities is such that there is either
no "explosive center", or we are fortunate enough to be in it right
now.
*Our* center is in every direction.
That statement is practically designed to confuse. We
can see no center. As far as we can tell, there is no
center. But we can't really tell.
The CMBR was emitted between us and the center. The CMBR was last
emitted some short time after the Big Bang. The CMBR is very uniformly
distributed around us in every direction. The "center" was everywhere
(since we started out "smaller than an atom"), and is on the other side
of the CMBR from us... in spaceTIME.
If there was absolutly nothing around whatever
object exploded, no air, no gravity, no nothing,
would the particles generated in the explosion
continue to expand forever?
Yes. Unless space was not expanding, then they would
continue race around and around a closed Universe...
If space were not expanding then the Universe would simply
collapse. Particles would not "race around".
The Universe could have inflated to a size, then ceased expansion. It
would not have to continue expanding, nor would it have to contract.
(Suspending the second law of theromodynamics, of course.)
Or would the minute particles and their tiny
gravity clump together to form other things?
This is what happens in fulid solutions with
contaminants... it is called "coagulation".
He said "gravity". Dust particles in vacuum can also
attract one another and clump by electrostatic forces.
This same behavior is also seen in fluids in Nature, right here on
Earth. And yes, it is seen with stars, planets, moons, asteroids, and
comets.
At what point would the expanding particles
loose their inertia, if ever?
That depends on the value of omega.
You just substituted a jargon term for a description.
That doesn't help the original poster unless he goes
on to look up the term "omega", and manages to find
something on the particular meaning of "omega" in
cosmology.
Good. A cognate that will allow him to search for more information.
Something that a hungry mind will worry with until sustenance is had.
One value has the Universe slowing down and collapsing
(not this Universe, from all indications). Another value
has it expanding essentially forever, getting slower and
slower (looks about like ours).
If not for the acceleration of the expansion. What you
describe is what the Universe was presumed to be doing
until 1998.
Correct. I had assumed he knew the direction we were heading. A
search for omega in this context would have given him that.
Could Dark matter be the "wrapper" of
whatever object exploded in the Big Bang?
Good question. At one time the CMBR was proof that
Dark Matter wasn't present at that time, and now it
supposedly is.
I don't think the CMBR was ever "proof that Dark Matter
wasn't present at that time", nor is it proof that dark
matter was present at that time. Can you lend support
to your assertions?
http://groups.google.com/group/sci.astro/msg/f58305ffbd7285b0
<QUOTE>
"There are factors that could either distort the
harmonics themselves or the way we see those harmonics today," Smoot
says, naming a number of possibilities including topological defects in
the early universe; a universe that contains more ordinary matter today
than our best estimates; a universe in which some matter decayed before
the moment of recombination; or an unsuspected role for neutrinos.
"There
is no agreement on any of these," he says. "It's new physics."
<END QUOTE>
http://groups.google.com/group/sci.astro/msg/da744144344d35b8
<QUOTE>
IIRC, the COBE satellite results of the cosmic microwave background
suggest that dark matter concentrated first. COBE found fluctuations
in the CMBR, presumably resulting from regions of higher and lower
density in the early Universe. The size scale of those regions is far
larger than that seen among galaxies today. Ergo, dark matter was
already beginning to condense when the CMBR formed. (Again, all IIRC.)
<END QUOTE>
.... I am unclear here if Dr. Lazio is saying that DM predated the
"quench" of the CMBR. I guess DM could have existed uniformly
distributed, and I simply misunderstood.
David A. Smith
.
- References:
- Question about the Big Bang and Dark Matter
- From: Rising-Star8471
- Re: Question about the Big Bang and Dark Matter
- From: N:dlzc D:aol T:com \(dlzc\)
- Re: Question about the Big Bang and Dark Matter
- From: Jeff Root
- Question about the Big Bang and Dark Matter
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