Cosmological Redshift and Expansion of Space

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Thomas</i>
<br />This factor must obviously be the same everywhere in the universe and at all scales.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Not in the Big Bang, it isn't. Anything "gravitationally bound", such as a galaxy or cluster of galaxies, is exempt from expansion.

The fact that "gravitationally bound" is an arbitrary and almost meaningless concept has not phased its adherents. -|Tom|-

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by tvanflandern</i>
<br /><blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Thomas</i>
<br />This factor must obviously be the same everywhere in the universe and at all scales.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Not in the Big Bang, it isn't. Anything "gravitationally bound", such as a galaxy or cluster of galaxies, is exempt from expansion.

The fact that "gravitationally bound" is an arbitrary and almost meaningless concept has not phased its adherents. -|Tom|-
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I don't see how the fact that physical objects interact gravitationally (or otherwise) should prevent the space between them from expanding (if this is what happens), but let's for the sake of the argument assume that this is so and just take two galaxies that are not gravitationally bound, let's say one at a distance of 1 billion lightyears, the other at a distance of 10 billion lightyears. My point is that because apparently the wavelength is supposed to adjust itself instantaneously to the momentary size (scale factor) of the universe, the observed redshift should only depend on the <i>present</i> scale factor and thus be independent of the distance of the galaxy (if the space within our solar system has indeed not expanded at all, this should actually then be a zero redshift, as the wavelength would have re-adjusted itself to our local (non-expanded) space).

Thomas

Hello All

This is my first post.

I have been reading posts in varies topics. This is one forum that has its feet firm on the ground.

tvanflandern said

quote:

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Originally posted by Thomas

This factor must obviously be the same everywhere in the universe and at all scales.

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Not in the Big Bang, it isn't. Anything "gravitationally bound", such as a galaxy or cluster of galaxies, is exempt from expansion.

The fact that "gravitationally bound" is an arbitrary and almost meaningless concept has not phased its adherents. -|


You hit the nail on the head.

Smile and live another day

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Thomas</i>
<br />because apparently the wavelength is supposed to adjust itself instantaneously to the momentary size (scale factor) of the universe, the observed redshift should only depend on the <i>present</i> scale factor and thus be independent of the distance of the galaxy<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">A lightwave is emitted from a distant galaxy at its correct laboratory wavelength. En route to us, the lightwave encounters expanding space and gets stretched to a longer wavelength. The farther away it is, the more expanding space it encounters, and the more it gets stretched. Hence, its arrival wavelength does depend on the distance it travels (except when it is inside "gravitationally bound" galaxies). -|Tom|-

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by tvanflandern</i>
A lightwave is emitted from a distant galaxy at its correct laboratory wavelength. En route to us, the lightwave encounters expanding space and gets stretched to a longer wavelength. The farther away it is, the more expanding space it encounters, and the more it gets stretched. Hence, its arrival wavelength does depend on the distance it travels (except when it is inside "gravitationally bound" galaxies). -|Tom|-
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Consider following case:

assume our solar system would be located somewhere in intergalactic space. Due to it being gravitationally bound, the space within it has not participated in the general expansion of the universe since the solar system formed a few billion years ago. Now assume a photon emitted from a distant galaxy at the time the solar system formed is entering the latter. This means that (let's say within the space of a few hours or so) this photon will see the expanded intergalactic space shrink again to the non-expanded space in our solar system. Shouldn't this mean that the redshift of the photon should be completely reversed again, or is there any limit as to how quick this stretching or shrinking of the wavelength can be done?

Thomas

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Thomas</i>
<br />According to the general relativistic view, the cosmological redshift is explained as an expansion of space as such .... this obviously contradicts Hubble's law.
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A simpler observation which contredicts Hubble's law may be found in a paper of Eli Michael et al. (ApJ 593, 809, 2003) about supernova 1987A. The supernova remnant shows luminous points making a "necklace" due to a superradiant emission of a Strmgren sphere, more precisely of an almost spherical shell of excited atomic hydrogen. The disk limited by the necklace emits a very broad, redshifted Lyman alpha line of atomic hydrogen. The distance of the supernova may be evaluated by two methods:
- A comparison of the absolute size of the necklace [deduced from time propagation of light emitted by the star (when it was visible) to Earth (direct, or scattered by the necklace)] with its angular size.
- Hubble's law applied to the Lyman line emitted by the disk.
The results are 168 000 light-year by the first method, more than 2 Mly by Hubble's law. Michael (and me) consider than the first method is reliable, so that Hubble's law is wrong.
Other observations lead to the same conclusion, for instance a quasar observed in a galaxy, but objections are possible, the quasar could be seen through the galaxy; for SN1987A this objection cannot work, because a quasar appears as a point while for SN1987A, the source is exactly the disk inside the necklace.