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Re: Size and Age of the Universe

Posted: Fri Jan 14, 2011 6:11 pm
by Beyond
Chris Peterson wrote:So, from the instant of the Big Bang to now, nothing is moving very much, nothing was propelled, nothing felt any forces from the Big Bang.
So the things of this realm that we can see, to way out in the vastness of space, are being carried along by "something" that we can't see, but can tell It's there, because of the constantly growing distances between the things that we can see. And the farther we are carried along, the faster the distances between things grow. So scientists are trying to find out just what this "expansion" stuff really is. Whether it is common to this realm that our Universe is in, or if perhaps it came from another realm that might have "leaked". Either way i don't think there's a darn thing that anyone now here could do about it, but it may be nice to know what the heck this expansive stuff really is. For all we know, it could be an unseen hand from "somewhere", taking SpaceShip Universe to a better place.

Re: Size and Age of the Universe

Posted: Tue Jan 18, 2011 3:50 pm
by dougettinger
Chris Peterson wrote:Let's go back to the balloon analogy. The universe is the surface of the balloon, so this is a 2D universe we are considering. You can stick little dots all over the surface to represent galaxies. As the balloon expands, these galaxies are getting farther apart. But are they moving? You could argue that they are not. If you were perched on one of those dots, you'd feel no forces in the plane of your universe. No acceleration, even if the expansion rate was not uniform. Of course, from our vantage point we understand that you'd feel a force in what we'd call the vertical or radial direction... but that direction isn't accessible to those living on the balloon, because they only perceive two dimensions. And if you look at what direction the dots are actually traveling, it isn't a direction along the surface, but is in a straight line away from the center of the balloon- a point that isn't even in that spatial universe.

Now, if you can, extend the analogy to our own Universe. We inhabit the 3D surface of a 4D universe. Distant objects aren't really moving with respect to each other (except in a minor, non-cosmological way). What's happening is that the Universe is expanding, and all these essentially stationary objects are staying in place. The only direction anything is moving is away from the 4D center of the Universe- the point where t=0. We are moving on the radial (time) axis of the Universe. We don't feel any forces on this axis. We can't see along this axis ("outward", the direction we are expanding, is the future; "inward", the direction we came from, is the past).

So, from the instant of the Big Bang to now, nothing is moving very much, nothing was propelled, nothing felt any forces from the BB.
I am trying to enhance your balloon analogy. The 3D surface that you refer to can be considered as the skin of the balloon that has a thickness of the "observable" universe. If not for gravity, all matter inside this 3D surface would be expanding uniformly. We do not know the age of the overall universe; we only speculate the age of the "observable" universe. Is this a further enhancement ?

I now add another thought experiment only for your enjoyment. Your balloon analogy is an excellent way to explain how each and every bundle of matter expands in a similar fashion - such as stars, planets, and our own bodies. I believe that our thinking is still very self-centered in believing that only galaxies expand in this manner. Each bundle of matter is increasing its entropy to return to the void of Dark Energy. The properties of light help to collaborate this belief.

Doug Ettinger
Pittsburgh, PA
01/18/11

Re: Size and Age of the Universe

Posted: Tue Jan 18, 2011 4:05 pm
by Chris Peterson
dougettinger wrote:I am trying to enhance your balloon analogy. The 3D surface that you refer to can be considered as the skin of the balloon that has a thickness of the "observable" universe. If not for gravity, all matter inside this 3D surface would be expanding uniformly. We do not know the age of the overall universe; we only speculate the age of the "observable" universe. Is this a further enhancement ?
No. The surface has no thickness. The observable universe is a region on the surface (not in it) around each observer. Gravity is the force that holds things together within small regions- essentially, causing them to slide on the surface as it expands, rather than staying with that surface. We do know the age of the overall universe, because our observations of the observable universe tell us that.
I now add another thought experiment only for your enjoyment. Your balloon analogy is an excellent way to explain how each and every bundle of matter expands in a similar fashion - such as stars, planets, and our own bodies. I believe that our thinking is still very self-centered in believing that only galaxies expand in this manner.
Each and every "bundle of matter" does not expand. Galaxies don't expand, either, nor even galaxy clusters. Dark energy (which again, is not driving expansion) does not work over these relatively small scales.

To put it a little differently, matter does not expand. The Universe itself is what is expanding, and matter is carried along or not, depending on the degree to which it is bound gravitationally to other matter.

Re: Size and Age of the Universe

Posted: Tue Jan 18, 2011 7:31 pm
by dougettinger
I mis-stated that "only galaxies expand". I really meant that the space between galaxies expands. And yes, matter does not expand. I am only toying with that idea of matter expanding. Most of matter is space itself and those particles in that space making up matter could be converted to energy. Depending on our perspective the dividing lines between space, energy, and matter are very fuzzy.

Doug Ettinger
Pittsburgh, PA

Re: Size and Age of the Universe

Posted: Tue Jan 18, 2011 7:53 pm
by Chris Peterson
dougettinger wrote:Depending on our perspective the dividing lines between space, energy, and matter are very fuzzy.
I disagree. Energy and matter are the same thing, and you could make a case that there are states where it might be a bit ambiguous which term best applied. But space is not matter/energy, and there is no confusion between space and matter/energy.

Re: Size and Age of the Universe

Posted: Tue Jan 18, 2011 8:08 pm
by dougettinger
The explanation for space expanding at an increasing rate is Dark Energy. So what is the connection then between space and energy ? Is Dark Energy a misnomer ?

Doug Ettinger
Pittsburgh, PA

Re: Size and Age of the Universe

Posted: Tue Jan 18, 2011 8:19 pm
by Chris Peterson
dougettinger wrote:The explanation for space expanding at an increasing rate is Dark Energy. So what is the connection then between space and energy ? Is Dark Energy a misnomer ?
The fact that space and matter/energy can interact does not mean they are the same thing, or that there is any fuzzy area between them.

Re: Size and Age of the Universe

Posted: Tue Jan 18, 2011 10:06 pm
by dougettinger
So how do cosmologists compute the percentages of Dark Energy being 72% and Dark Matter & regular matter as 28% ? In this case obviously matter and energy are equivalent. I know how the percentages of Dark Matter and regular matter are computed.
The idea that Dark Energy pervades all of expanding space is unavoidable.

Doug Ettinger

Re: Size and Age of the Universe

Posted: Tue Jan 18, 2011 11:01 pm
by Chris Peterson
dougettinger wrote:So how do cosmologists compute the percentages of Dark Energy being 72% and Dark Matter & regular matter as 28%?
The most accurate numbers come from calculations based on the WMAP data for the CMB. Less accurate numbers, but very consistent with the WMAP analysis, come from looking at the large scale structure of the Universe, that is, how matter clumps. This produces an estimate for matter of about 30%, leaving dark energy to account for the rest of the total energy budget.
The idea that Dark Energy pervades all of expanding space is unavoidable.
I don't know that it is unavoidable, but that is certainly consistent with current theory. The exact nature of dark energy, however, would determine if it is uniformly distributed or not.

Re: Size and Age of the Universe

Posted: Wed Jan 19, 2011 2:33 pm
by dougettinger
What kind of calculations based on the WMAP data are used. Are the volumes or areas of the voids between matter calculated and determined to be a percentage of all energy ? ?

I believe that space, or the voids between matter, or hard vaccuum, or the separations between galaxies, or whatever you wish to call it - is filled with energy. One can divide space from our pespective three ways. There is the space inside each and every hadron, atom and molecule; there is space between the stars and planets; and finally the incomprehensible space between galaxies. At the first level there are the photons, bosons and gluons permeating space that create energy. At the second level photons, neutrinos, and isolated electrons permeate space. At the third level space contains the second level items including the dominating Dark Energy. If conglomerations of matter move away from each other they gain potential energy. The Big Bang(s) cannot be envisioned without the dark void having energy. This is how see the connection between energy, matter, and space.

Doug Ettinger
Pittsburgh, PA
01/18/2011

Re: Size and Age of the Universe

Posted: Wed Jan 19, 2011 4:05 pm
by Chris Peterson
dougettinger wrote:What kind of calculations based on the WMAP data are used.
As I understand, it has to do with the different scales of observed structure, which imply critical wavelengths early in the Universe. You'd have to go to primary sources for details, it's not something I've ever looked closely at.
I believe that space, or the voids between matter, or hard vaccuum, or the separations between galaxies, or whatever you wish to call it - is filled with energy.
One major view of dark energy is that it uniformly fills space in this way (at an extremely low density). The other view is that while its density is uniform on a large scale, it is locally distributed. If the second view is correct, there may be no dark energy at all in the space within atoms, for example.

I think it is a mistake to "believe" either of these. Both are valid ideas, subject to test, but not yet tested. Either may turn out to be correct, or given how little is known about dark energy, neither. This is a good time to keep an open mind and wait for more data.

Re: Size and Age of the Universe

Posted: Fri Jan 28, 2011 12:41 am
by The Code
Chris Peterson wrote:One major view of dark energy is that it uniformly fills space in this way (at an extremely low density). The other view is that while its density is uniform on a large scale, it is locally distributed. If the second view is correct, there may be no dark energy at all in the space within atoms, for example.

I think it is a mistake to "believe" either of these. Both are valid ideas, subject to test, but not yet tested. Either may turn out to be correct, or given how little is known about dark energy, neither. This is a good time to keep an open mind and wait for more data.
Firstly, I must say, what an excellent thread. Thanks guys.

Secondly, I see a comparison. The distribution of Matter in the observable Universe, And the observable phenomena seen in the Orion nebula. Why do I see this comparison ?

Thirdly, Does Gravity expel, Dark Energy ? Or is there more to think about ?

tc

Re: Size and Age of the Universe

Posted: Fri Jan 28, 2011 3:39 pm
by dougettinger
Gravity is holding Dark Matter and regular matter together. Dark Energy is expelling gravity's influence by expanding the spaces between matter on a large scale (between galaxies) and possibly on smaller scales (such as between the stars).

Doug Ettinger
Low Ranking Science Officer