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 JMB</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 />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 Stromgren 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.
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<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 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.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Not so. It means only that, during the few hours that the photon traverses the solar system, no additional stretching will occur.

Once the lightwave is stretched, the stretch cannot be reversed. There is no difference between new space being continually added between galaxies, and old space that was there since the Big Bang. But as time goes on, there is more and more of the new space. And anything not gravitationally bound and traveling through a region where new space is being added everywhere will find itself spanning more space than it did before the stretch. -|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 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.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Not so. It means only that, during the few hours that the photon traverses the solar system, no additional stretching will occur.

Once the lightwave is stretched, the stretch cannot be reversed
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I can not see how it could not be reversible. Clearly, if the expansion of the universe would for instance stop and turn into a collapse, we should (eventually) see a blueshift rather than a redshift, i.e. the photon wavelength is reduced again in accord with the now shrinking space. And since there is no way for the photon to tell whether this shrinking is a global or just a local effect, it should adjust its wavelength also if it just travels from a region of expanded into one of unexpanded space.

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 />Clearly, if the expansion of the universe would for instance stop and turn into a collapse, we should (eventually) see a blueshift rather than a redshift<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Yes, a new, independent action on the lightwave can change it to any wavelength. My exclusion referred only to the original expansion mechanism.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">since there is no way for the photon to tell whether this shrinking is a global or just a local effect, it should adjust its wavelength also if it just travels from a region of expanded into one of unexpanded space.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">I'm not getting your picture. "Global" vs. "local" is irrelevant. Get rid of the counterproductive notion of "photon" and all its associated baggage, most of which is misleading. Propagating light always acts as if it is a pure wave. If a set of ocean waves passed over a region where new water was being added (say, from a pump under the ocean floor), the water waves would get longer in wavelength, and that would not be reversible when the wave left the region where new water was being added. -|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>
...I'm not getting your picture. "Global" vs. "local" is irrelevant...
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Tom, I think he means "not gravitationaly bound" vs. "gravitationly bound" or "expanding space" vs "non-expanding space".

JR

<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 />Clearly, if the expansion of the universe would for instance stop and turn into a collapse, we should (eventually) see a blueshift rather than a redshift<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Yes, a new, independent action on the lightwave can change it to any wavelength. My exclusion referred only to the original expansion mechanism.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

So just to clarify this point: what happens then if a light wave is sent out from a distant galaxy in an expanding universe, and half-way through its journey the expansion suddenly stops and turns into a (symmetrically reversed) contraction (so that the size of the universe at reception of the light signal is the same again as at the moment it was sent out)? What would then the redshift be when we observe the light?

Thomas