The begining

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Eh

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If Occam's razor is important, "space" is not a good candidate for something that has existed forever, since we have absolutely no evidence (or reasons to believe) that space has any independent existence from the gravitational field. One would be adding an extra and unncecessary entity (space).

A cyclic universe can't be ruled out entirely, and there are still some models floating around that would allow it.
 

wolram

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some models FLOATING AROUND????????????????????????
 

Phobos

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My impression is that the Big Bang Theory acknowledges great uncertainty about what was "before" or "outside of" this universe. I don't think BB adherants are stuck on the idea of "nothingness" before/outside this universe. BBT is very successful at explaining the universe SINCE the beginning...and that is its strength and focus.
 

wolram

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i totaly agree PHOBOS, the problem with modern theories is that they predict an ultimate end to life, however far in the future that end is
it wont be acceptable to some.
and if heat death is the outcome our universe will be of limits to
new creation
this is why i prefer to think of space as infinite and eternal, at least then in the far far future if our universe ends our decendents
will have somwhere to go.
that of course depends on humans adapting to space etc etc.
anyone for the arc?
 

r637h

I tend to agree; but, if the universe should happen to be closed, it will become obvious to our posterity. And they have a few billion years to figure it out. Maybe they can "move out" when it closes and "move in" to the next one at an appropriate time.

But we homo sapiens are our own worst enemies; with a convoluted brain which is probably a poor evolutionary compromise.

Maybe the dolphins.....

But I don;t think we're Klingons, either. There may be a chance for us.

Which reminds me of a tasteless joke: How are the Starship Enterprise and toilet paper alike?
They both orbit around Uranus and knock off Klingons.

Sorry about the joke, but Thanks, Rudy
 
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wolram

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i am sorry Eh, but i cannot envisage what "no space" could be
the usual ansewer is its "unknowable".
the way i see it is that if there is no space for an event to
happen then nothing can happen.
does anyone have a view on what "no space" is?
oh i forgot there was also no time.
normally i bow to greater inteligence but no space is so counter intuitive i canot on this one.
 

Eh

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I don't think there is such thing as "nospace". A beginning is just a first moment of time, and does not require a previous state without space existing and so shouldn't present a problem. If the heat death scenario bothers you, cosmology seems to have less problems with that. Some inflation theorists will insist that virtually all models of inflation will most likely end up leading to a scenario where there is never ending creation of bubble universes, along with stars, galaxies, etc. This would at least allow life to survive indefinitely, even if the mother spacetime that spawns these bubble universe may require a beginning.
 

wolram

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where i can i read about bubble universes EH,do you have a link that wont exhuast my brain cell? by the way thanks for your time,
im not giving up yet though:wink:
 

Eh

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This should help. http://www.biols.susx.ac.uk/home/John_Gribbin/cosmo.htm [Broken]
 
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wolram

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Confused? So are the astronomers; but they are also intrigued by the possibility that whatever is out there may be different from anything the theorists have yet been able to imagine.
the big guns are all shooting but they seem to be missing the target.
this web page gives me very little if any confidence that current theories are correct.
to be honest some of the crackpot sites are more inspiring, the problem is they can be disproved ,whereas current main stream theories
cannot.
i am confused as to which way theorists are going with the current
models, there are far to many loose ends, WIMPs, MACHOs, GRAVITONs
DARK MATTER etc etc.
perhaps everyone will have to wait until space probes can provide actual data as to the existence or otherwise of these things
until then i am open minded to everything ,except the creation of space.
best wishes.
 

schwarzchildradius

Space is equivalent to the energy-momentum tensor, in the Friedman eq. So the geometry of space is dependant on the distribution of massive objects & energy in it - 'space tells matter how to move, matter tells space how to curve.' A homogeneous distribution of mass in space with universal gravitation causes a collapse of space. Some universal force must be acting against gravity to yield an expanding universe.
Why didn't the universe collapse at the moment of the big bang?
 

Eh

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In the link I posted, I think there is a section that covers the bubble universes in a self reproducing universe.
 

wolram

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Isnt space "shrinking" now?
 

Phobos

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Originally posted by Netme
Isnt space "shrinking" now?
No, it's apparently expanding at an accelerating rate.
 

wolram

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my question is what is shrinking, expanding? if it is
"space time", what is its unit of measure?
if one can say ST started at 0 dimentions what is the upper limit
to its expantion?
will space always stay in step with time?
to expand ,"increase volume" space has to have a" volume" to expand into, if that is true then a volume must always have existed.
best wishes.
 

Phobos

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Originally posted by wolram
my question is what is shrinking, expanding?
We see objects (galaxies) moving apart from each other, not because of their own movement through space (which can also be measured), but because more space is forming inbetween those objects. How can we be sure? Hmm...is there a cosmologist in the house? :smile:

if it is
"space time", what is its unit of measure?
The speed of light essentially.
The rate of expansion is measured in units of kilometers per second per megaparsec (all of which can be referred back to the speed of light which moves at a constant speed).

if one can say ST started at 0 dimentions what is the upper limit
to its expantion?
Unknown? Infinity?

will space always stay in step with time?
Unknown? Or, probably yes, since space & time are linked at the very fabric of the universe. See also below.

to expand ,"increase volume" space has to have a" volume" to expand into, if that is true then a volume must always have existed.
best wishes.
It does confound "common sense", but then again, so does Relativity, Quantum Mechanics, and the fact that this is a heliocentric solar system.

This question bugs me too. The easiest answer is "we don't know". Another answer that bugs me (due to implications of predestination which don't sit well with me) is that the new space (volume) comes from the future. In other words, the universe is made of space and time...and the time dimension may already be in-place and space is simply proceeding along that time line. We simply experience slices of the whole space continuum (which already exists) as the timeline unfolds.

But I'm speculating out on a limb here.
 
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Originally posted by Phobos
No, it's apparently expanding at an accelerating rate.
Ive heard that it has stopped expanding and is now shrinking at an accerlerating rate. How could you tell the difference between shrinking and expanding if there is no center point to extinguish it from? An infinite universe has always been questionable to me...
 
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marcus

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Originally posted by Netme
Ive heard that it has stopped expanding and is now shrinking at an accerlerating rate.
In my own thinking Ive found it helps to make a clear distinction between our personal views and the professional consensus (which is quite a new thing---cosmologists are still commenting with pleasure and astonishment about the emergence over the past 3 or 4 years of a "concordance" model of the universe)

The point though is that we dont have to accept it. We are free to imagine the universe and its history with the images we like.

But it would be a good idea to be familiar with the consensus picture that has emerged recently in cosmology. A good source is:

Lineweaver (a leader of the COBE team)
http://arxiv.org/astro-ph/0305179 [Broken]

but there are also articles online by other recognized people
Michael Turner---"Making Sense of the New Cosmology"
Plionis
Eric Linder
Ned Wright

They all say pretty much the same thing and it is the view
you are getting from Phobos too.

In particular they dont think the universe has started contracting at a accelerating rate!

But in my opinion it is great that you think this! Why should we not hold different opinions about the cosmos! Why should we
think we have to agree with the consensus of experts! There must be room for poetry and mysticism---radical as this sounds---the universe is not just the stuff of science it is the stuff of myths and free imagination. Like Blake said:

To see a World in a Grain of Sand,
And a Heaven in a Wild Flower,
Hold Infinity in the palm of your hand,
And Eternity in an hour.

Blake was not bound and constrained by the contemporary views of cosmologists circa 1800, thank goodness.

Having said this, however I believe what the cosmologists say---my view is similar to Phobos in most ways I guess
 
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marcus

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wolram said:

Originally posted by wolram
my question is what is shrinking, expanding?


to expand ,"increase volume" space has to have a" volume" to expand into, if that is true then a volume must always have existed.
---------------------------

there is a criterion for something to be standing still

and galaxies are mostly all approximately stationary
(at rest wrt the CMB and the things around them)
approximately

and the distances between them are growing


at bottom all "the expansion of space" means is if you
pick two points far apart
the distance between them is increasing
(in a linear way: the rate proportional to the distance)

atoms and apples and galaxies are not bothered by this because
they fall back together--under the control of the forces which give them structure----they are bound structures

the increase in distances between nearby points (in this galaxy, in this apple) is so slow that the organized bound structures easily adapt and compensate and STAY THE SAME SIZE

but distances between far apart things continually increase


space is not a material
it is not expanding into more space
it does not need space into which to expand (the way an
expanding material object would)
all it needs is a dynamic distance measure which
reads an increasing distance between any given two points.
 

wolram

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MARCUS it seems a large part of cosmology theory is dependant on
vacuum energy, is there a concensus as to the density of this
energy?, at what time in the inflation model did this energy form?
i may be getting confused but i read that the electron borrows
energy from the vacuum ,if that is correct then it is the
vacuum energy that supports matter.
im sure you can pre empt my next thought.
best wishes.
 

marcus

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Originally posted by wolram
MARCUS it seems a large part of cosmology theory is dependant on
vacuum energy, is there a concensus as to the density of this
energy?, at what time in the inflation model did this energy form?
i may be getting confused but i read that the electron borrows
energy from the vacuum ,if that is correct then it is the
vacuum energy that supports matter.
im sure you can pre empt my next thought.
best wishes.
I cannot predict your next thought. I have often if not always found your thinking rather deep and therefore unpredictable,
at least as far as coming up with questions goes.

The cosmologists CALL their general agreement on some basic featuires and percentages a "consensus" several even use the term "concordance model"

but that may seem to overstate the agreement.

About cosmological constant or vacuum energy or "dark energy" the only consensus I have detected is that "we dont know what it is"

They agree that it is 70 percent (some say 73 plusminus something) but they also agree they dont know what it is and dont have any immediate means of reliably distinguishing between the various possibilities.

So maybe it is OK to say that at the moment there is an unusual degree of a agreement among cosmologists (in the past they have been a contentious bunch and inclined towards factional strife)
but if it can be described as agreement then it is a consensus with a lot of big gaps and unanswered questions in it.

More I cannot say. Maybe some others who watch the scene more closely can fill in more detail for you.

......well, I will try to respond in more detail. I'll go for a second post.
 

marcus

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Originally posted by wolram

vacuum energy, is there a concensus as to the density of this
energy?, at what time in the inflation model did this energy form?
The dark energy (which the simplest explanation of it seems to be that it is intrinsic vacuum energy-----which standard quantumfieldtheory predicts too much of and no one understands why there is the amount there is)

is begorra agreed by the experts to be 73 percent of the
total average energy density.

the mind reels that they could have come up with this number and all decided to believe it, well no matter, onwards!

AT WHAT TIME
yes of course, very good question!
but here is a subtle point, it could have been there from time zero
but masked by more dynamic energetic things

you know occams razor, when in doubt choose the simplest model.
well the simplest model of dark energy or vacuum energy is that it is an absolutely constant energy density, not varying either in space or time. vacuum is vacuum now or yesterday here or in the next galaxy

something, say a joule per cubic kilometer, I forget, but something

so when the universe was young, a cubic kilometer (besides this joule of vacuum energy) had a vast lot of OTHER stuff crowded into it---hot radioactive buzzing around stuff
percentagewise the vacuum energy wasnt very important back then

so when the universe was young the vacuum energy was the last thing anyone would care about or would have any affect on events


only NOW when there is SO MUCH VACUUM in comparison with other stuff, light neutrinos, dust , gas, stars, dark matter. Now, with so much vacuum around, this vacuum energy is starting to play a significant role.


This IS THE BASIC REASON that the universe growth curve, the plot of the scale factor, is initially a convex ramp and then a concave (accelerated growth) ramp. Because at first the vacuum energy was unimportant and drowned out by other factors and expansion was decelerating, but then vac energy became a more important part of the picture (because space was emptier) and expansion began to accelerate due to the vacuum energy effect.

There is a kind of S shape to the growth curve that is good to
know about

At any rate you asked AT WHAT TIME did this vacuum energy form and I have to say

because it is simplest let us assume it was always there, but unimportant relative to other things

and there was a much more dynamic thing LIKE vacuum energy (a scalar field, an "inflaton field") that existed briefly and caused inflation-----so people say. I think of it as a different kind of vacuum energy, far more powerful, that was turned on for a split second very near time zero. But I dont think people have a clear idea of what that was----so it is not likely, I would guess, to help much to speculate about the relation between the feeble vacuum energy we see today causing the very gradual acceleration and the very strong vacuum energy (if it was that) which briefly caused the rapidly accelerating expansion we call inflation.



wolram continued

...but i read that the electron borrows
energy from the vacuum ,if that is correct then it is the
vacuum energy that supports matter.
Hmmm, like the banking system supports the industrial economy.
As long as we have a healthy vacuum sector, business will prosper and create jobs for the rest of us etcetera. Wolram I must let you go on without me at this point. You like crashing through the undergrowth and I like sticking to the beaten path.
More power to you, notwithstanding
 
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wolram

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abstract from wikipidia.
http://www.journaloftheoretics.com/Links/Papers/Setterfield.pdf
A paper published in May 1987 shows how the problem may be resolved69. The Abstract
summarizes: “the ground state of the hydrogen atom can be precisely defined as
resulting from a dynamic equilibrium between radiation emitted due to acceleration of
the electron in its ground state orbit and radiation absorbed from the zero-point
fluctuations of the background vacuum electromagnetic field…” In other words, the
electron can be considered as continually radiating away its energy, but simultaneously
absorbing a compensating amount of energy from the ZPE sea in which the atom is
immersed. In a similar way, a child on a swing gets a push just as the swing starts to slow
down, and a resonance is set up between the period of the swing and the frequency of the
pushes. So the orbiting electron also gets resonantly timed pushes from the ZPE that keep
it going. This had been explained earlier in a parallel, but even more enlightening way as
part of a course on stochastic processes applied to physics. The statement was made47:
“With somewhat more quantitative estimations, Boyer 70 and Claverie and Diner 71 have
shown that if one considers circular orbits only, then one obtains an equilibrium radius
of the expected size [the Bohr radius]: for smaller distances, the electron absorbs too
much energy from the [ZPE] field…and tends to escape, whereas for larger distances it
radiates too much and tends to fall towards the nucleus.

A paper published in May 1987 shows how the problem may be resolved69. The Abstract
summarizes: “the ground state of the hydrogen atom can be precisely defined as
resulting from a dynamic equilibrium between radiation emitted due to acceleration of
the electron in its ground state orbit and radiation absorbed from the zero-point
fluctuations of the background vacuum electromagnetic field…” In other words, the
electron can be considered as continually radiating away its energy, but simultaneously
absorbing a compensating amount of energy from the ZPE sea in which the atom is
immersed. In a similar way, a child on a swing gets a push just as the swing starts to slow
down, and a resonance is set up between the period of the swing and the frequency of the
pushes. So the orbiting electron also gets resonantly timed pushes from the ZPE that keep
it going. This had been explained earlier in a parallel, but even more enlightening way as
part of a course on stochastic processes applied to physics. The statement was made47:
“With somewhat more quantitative estimations, Boyer 70 and Claverie and Diner 71 have
shown that if one considers circular orbits only, then one obtains an equilibrium radius
of the expected size [the Bohr radius]: for smaller distances, the electron absorbs too
much energy from the [ZPE] field…and tends to escape, whereas for larger distances it
radiates too much and tends to fall towards the nucleus.
 
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wolram

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thankyou for your input MARCUS ,your views are alaways
unbiased and honest.
 

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