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Old 06-04-2009   #11 (permalink)
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Re: Eternal Generation Cosmology?

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Originally Posted by modest View Post
My understanding is that you can model redshift as recession with one coordinate choice or you can model it with expanding space with another coordinate choice. Essentially: either galaxies are redshifted because they have a recession velocity or they are redshifted because space between them expands. I don't see how you could apply both.
Hi ,

That appears to be 2 ways of looking at the same thing: the recession velocity of distant galaxies is due to the expansion of space between them (they are directly related values).

To be clear (and this is not directed at anyone's comments, but rather to draw attention back to the main topic), the decrease in wavelength to space ratio is still present whether or not there is a redshift (or blueshift) due to an observer's velocity.

As space is increasing size (metric expansion of space) and the wavelength of light emitted does not change in transit, the ratio of the wavelength of light to the size of space is getting smaller as the size of space increases.
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Old 06-05-2009   #12 (permalink)
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Re: Eternal Generation Cosmology?

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As space is increasing size (metric expansion of space) and the wavelength of light emitted does not change in transit, the ratio of the wavelength of light to the size of space is getting smaller as the size of space increases.
Wavelength increases with expansion. See the first link in my last post.

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Old 06-07-2009   #13 (permalink)
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Thumbs down Re: Eternal Generation Cosmology?

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Originally Posted by modest View Post
Wavelength increases with expansion. See the first link in my last post.
I've covered that: wavelength increase is due to recession velocity (which in turn is due to expansion).

Recession velocity redshift (increase in wavelength) has nothing to do with the ratio of the wavelength of a photon to the size of space.

The original point is this: that as space expands, and a photons wavelength stays the same, the photons wavelength becomes smaller in comparison to the "size" of space.

Last edited by Kharakov; 06-08-2009 at 05:23 PM..
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Old 06-11-2009   #14 (permalink)
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Re: Eternal Generation Cosmology?

G'day from the land of ozzzzzzzz


If by definition the universe is all.

Where does space expand into?

How can space without matter expand?

What does the expansion?
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Old 06-11-2009   #15 (permalink)
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Re: Eternal Generation Cosmology?

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The original point is this: that as space expands, and a photons wavelength stays the same, the photons wavelength becomes smaller in comparison to the "size" of space.
Well, if the photons' wavelength stayed constant I would agree, but this does not seem to be the case.


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Old 06-14-2009   #16 (permalink)
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Re: Eternal Generation Cosmology?

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If by definition the universe is all.

Where does space expand into?
Even if the universe is defined as the whole (all), all is not just space: it is space and matter.
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How can space without matter expand?
I don't know. Really, the expansion of space is relative to the size of matter.
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Old 06-14-2009   #17 (permalink)
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Re: Eternal Generation Cosmology?

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Well, if the photons' wavelength stayed constant I would agree, but this does not seem to be the case.
How so? A photon's wavelength does not change in transit, rather the Hubble redshift is due to our recession velocity from the photon's source.
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Old 06-14-2009   #18 (permalink)
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Re: Eternal Generation Cosmology?

G'day from the land of ozzzzzz


So you are saying that spcae doe not expand.

Matter expands in space.
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Old 06-15-2009   #19 (permalink)
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Re: Eternal Generation Cosmology?

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How so? A photon's wavelength does not change in transit, rather the Hubble redshift is due to our recession velocity from the photon's source.
Yes that is the redshift effect, but photons from the CMB for example started of at at wavelength corresponding to 3000K and cooled down to 2.73K due to expansion of space,primarily at least.


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Old 06-15-2009   #20 (permalink)
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Re: Eternal Generation Cosmology?

An expansion will increase entropy. While an increase in entropy can occur if it can absorb energy. For example, if we expand a gas, the gas will get colder because the increase in entropy absorbs energy. I can see the CMB and loss of energy from 3000K being the fuel for higher entropy, with the entropy increase causing the red shift as it absorbs energy value from this energy. One can do this in the lab, using IR and a canister of gas, causing a red shift in the IR, as the canister cools and entropy absorbs heat.

Because the energy remaining in the CMB is close to absolute zero, there is less energy for entropy from that source. So there needs to be other sources of energy to account for the entropy of further expansion. One possible source is nuclear fusion and the loss of entropy due to galaxy formation. That could explain the entropy increase of the universe, relative to the galaxies but not within the galaxies. While simply increasing the number of fusing stars and the order and superorder within galaxies over time, could explain the energy source for the increasing entropy of an accelerated expansion.

This does not preclude dark matter or dark energy. If dark matter is forming matter it has to lower entropy to merge into something less elusive and more tangible. This would also give off energy for additional entropy but for elsewhere. We can also toss in the CMB for energy, with that level of energy, only useful for subtle entropy, such as rotating and vibrating water molecules.

Expanding space-time, via GR, is just a special case of entropy increasing but not the whole story, since it doesn't take into account all the entropy details with any frame of reference. If we form a star from gas cloud, and contract space-time, the entropy lowers as the pressure of the contraction reduces the space between matter. It is not just space-time contracting with everything maintaining relative distances, but the actual distances between things are lowering with system entropy decreasing.

With SR everything does not fuse, like a star, due to actual distance changes, but rather relative distances are maintained in the reference. The entropy within SR is connected to velocity and the entropy created relative to the observer. If it is heading toward us, the entropy is lowering for the observer-source system, giving off energy, for a blue shift. If it is moving away, it is increasing entropy for the observer-source system and will absorb energy and red shift. The universe is working in terms of net effects, with entropy increasing, absorbing energy.

If we started with a singularity, it has zero entropy or minimum entropy. It has to absorb energy to increase entropy to become something other than a singularity. This creates an interesting question. Does entropy have a push of its own absorbing energy, or does energy push entropy? If entropy walks to the beat of its own drum, there needs to be a potential to create disorder, so it can absorb energy. This sort of implies empty space outside the singularity. As space fills and the energy lowers we will need other sources to meet the entropy demand for energy. If energy is pushing entropy, it doesn't matter what the space around is, it can be contracted, as long as energy is pushing it.
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