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Red Shift = Expanding Universe?

  1. Jan 20, 2008 #1
    Has anyone ever considered the possibility that the perceived Doppler effect of light from distant stars/galaxies is not caused by movement of the emitting bodies, but rather a side effect of light traveling extraordinarily long distances under the week gravitational force of the entire universe?

    I have no basis to make such a theory, but intuitively I feel it is plausible. It has been proven that light is bent by gravity. Could it not also be possible that under certain circumstances it could also affect light resulting in a Doppler-like effect?

    Whether the universe is expanding or not is not the nature of my inquiry, simply I wonder if the measurement method is 100% reliable, because even a slight deviation from absolute perfection in measurement could have huge consequences.

    Any thoughts?
     
  2. jcsd
  3. Jan 20, 2008 #2

    russ_watters

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    Yes, I'm not real up on the specifics, but there is an idea called "tired light" that is generally discounted. I'm not quite sure if it is based on gravitational redshift, but gravitational redshift is a very real effect. It is a well proven, but to be the cause of the redshift we see, the universe would need an enormous density.
     
  4. Jan 20, 2008 #3

    cristo

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    Here is a page from Ned Wright's website which puts forward criticisms in tired light theories.
     
  5. Jan 20, 2008 #4
    Thanks for the information. I did not know about the tired light theory.

    Best regards
     
  6. Jan 30, 2008 #5
    I have the same feeling. Not very happy with the red shift = expanding universe assumption. OK, there may not be enough mass to account for the observed shift, but what about the waves themselves? I mean all of them. If our redshift measurements of the universe are based on these specific ubiquitous spectral lines, then it seems like we are floating on a sea of these waves. I wonder that, if in the billion years it has taken the light waves to reach us, that there could be interference effects with all the other sources of that light (including whatever existed a billion years ago where we are now). Such effects as could cause a shift in the observed wavelength. Even though this notation may seem silly, I still say the existing explanation is lacking . . . .
     
  7. Jan 30, 2008 #6
    Im not sure intereference between photons would create a redshift affect, in in analog senario it would just create a new wave with properties of both, in the particle physics arena my beleif was that photons do not interact with each other under any of the primary forces (thought im probably wrong)
     
  8. Jan 31, 2008 #7

    Chronos

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    Other independent indicators are remakably consistent with the expansion hypothesis. Time dilation in supernova light curves, for example, is a compelling example. The expansion hypothesis is not refuted by theories that accept objects are at distances commensurate with their redshifts. To defeat the expansion hypothesis, you must provide irrefutable evidence of a 'rogue' object with properties [size, velocity, etc.] forbidden by physics as we know it. A nobel awaits the first successful applicant. Arp has been trying to do this for half a century without success.
     
  9. Jan 31, 2008 #8
    Hmmm, I didn't know there was more evidence piling up to support the theory. That does get the wheels turning.

    It is an intriguing idea, I guess. Does the current theory imply that space expands at a rate that is a function of its extent (i.e. local space is not observed to expand because it has, almost by definition, a negligible extent)? Likewise does the space between us and the most distant object expand at the greatest rate?

    If so, thats not too far off from the observed effects of gravitation. I am going out on a limb here (after all isn't that the best place to contemplate gravity?), but anyway, doesn't this sound a little like gravity: where space CONTRACTS at a rate that is a function of its extent?
     
  10. Feb 1, 2008 #9
    Well, yeah, EVERYtime I try and consider the alternative...which is that the ENTIRE universe started out as a micro-dot.

    ....and the fact that this rule doesn't apply in our local universe.

    But it would take an GIGANTIC amount of evidence to convince the cosmology community of this. As they would be forced to admit that everything they have believed in and formed conclusions by for the last 100 years was all false. :O :)
     
  11. Feb 1, 2008 #10

    marcus

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    According to current cosmology (based on Gen Rel) our local space does NOT expand and that includes the entire Milkyway galaxy and even our local group of galaxies. These form a gravitational bound system and are not receding. Only much more distant things recede. Only much larger distances expand.

    For large distances the current rate is one percent every 140 million years.
    Or 1/140 of a percent every million years.

    You ask does the space between us and the most distant object expand at the greatest rate? and the answer if you mean percentage rate is NO. It is always the same percentage increase in distance (at least with minor differences aveaged out).
    But if you mean the milesperhour rate or km/second rate then the answer is YES because one percent of a large distance is a larger increase than one percent growth of a small distance.

    Where you always misjudge the community, and go wrong, BoomBoom is that you don't realize that people would LOVE to have a new, better theory of gravity to replace GenRel!
    And people are always proposing revisions of GR, and if they are proposed by smart people they get eagerly examined. And a big research effort is always going on trying to find faults with GR. They would LOVE to find somewhere it gives a bad prediction, say out at the 5th or 6th decimal place.
    We have been using GR for 100 years and we would love to find a flaw with it and get a better theory of gravity (and spacetime geometry) to replace it! Then that would totally change cosmology, which is based on classical GR.

    The trouble is GR is an extremely accurate theory of gravity, which has passed tests over and over again with extraordinary high precision and flying colors.

    In the context of cosmology Gen Rel predicts that distances change dynamically and to the extent that it shows a uniform patter then it has to be expanding or contracting. So if GR is the correct theory of gravity, then we have to be seeing either redshift caused by the stretching of distance, or we have to be seeing blueshift due to the shrinking of distance.

    And it happens the universe is clearly not collapsing, at least for now.

    So GR tells us to expect redshift caused by the percentage increase in largescale distances And that is what we SEE.

    So if you don't like this, what you need is to find a new theory of gravity. And if it gets as rigorously tested and has superior precision to classic GR then you will be a HERO and everybody will love your theory.

    Then we can see if your improved GR ALSO predicts that distances should be percentagewise increasing, or whether it has some other explanation for redshifts and some other history of the universe.

    BUT FIRST IT HAS TO BE AS PRECISE AS GENERAL RELATIVITY, OR BETTER. The car has to run, or people will not be interested in buying it.
     
  12. Feb 2, 2008 #11
    It would seem this also only really applies locally though....

    When they find a huge contradiction in GR (such as galaxy rotation and movement, or a perceived acelleration of expansion, etc.), then instead of revisiting the previous assumptions to find the apparent flaw, it seems as if they assume the previous assumption is still correct and invent new parameters to make the math fit the new observation. In the process, introducing a whole new assumption to pile on top of the old ones so that we get to where we are now: 90+% of our universe is made up of some mysterious undetectable "dark" matter and energy.

    Black holes is another one where the math breaks down...perhaps there is some very fundemental way in which we misunderstand the very nature of how BHs and SMBHs effect their surroundings.

    I don't know and don't claim to be any sort of expert in any way in these matters. I was just trying to convey to the OP that he is not alone..... :)
     
  13. Feb 2, 2008 #12

    marcus

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    You misrepresent how the scientific community operates. Maybe it looks to you as if they just blithely stuck in DE and DM and proceeded uncritically. Not so. A lot of effort has gone into imaging and mapping clouds of Dark Matter and it has been successful. So it is a good thing the model predicted Dark Matter. Another point for Gen Rel.

    The initial arguments for DE and DM were treated with skepticism and much effort went into exploring ALTERNATIVE laws of gravity which would explain them away. A number of people are also still studying ways to explain the acceleration which don't require a cosmological constant or any form of DE.

    You say instead of revisiting the previous assumptions but the previous assumptions, namely the basic theory of largescale geometry, GR, is precisely what has gotten revisited! Repeatedly, assiduously, by many people in a multiprong effort, over the past decade.

    Look BoomBoom, you apparently don't follow the literature. So you don't know how the community operates or what it has been doing. Before you criticize something find out something about it.

    What you can, I think, criticize responsibly is popular science journalism because the journalists have not kept you informed about all the work being done on alternatives to GR and alternative explanations of the data.
     
  14. Feb 2, 2008 #13
    Thanks Marcus, that was an interesting read. So GR predicts that large distances change with time, ok. That makes me wonder, does GR also predict that if one were observing a variable star at large distances, that the star's observed period (or even luminosity) would be different than the actual period due to the dilation across such large distances?
     
  15. Feb 2, 2008 #14

    marcus

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    Thanks for the kind word Shotgun. All signals get stretched out by the same factor, the factor by which distances got expanded while the light was in transit. Several people here are hands-on astronomers. I hope they respond to quantitative questions like this.

    The lightcurves of supernovae ARE affected by the expansion of distance to them. the schedule of the flash gets stretched out just like light gets redshifted. So that effect is taken into account.

    You are talking about ordinary variable stars, not supernovae. The lightcurve from a Cepheid variable should also be stretched out by the same factor (z+1) that the lightwaves are stretched out. So that is probably also taken into account. Should be, unless z is negligibly small.
     
    Last edited: Feb 2, 2008
  16. Feb 2, 2008 #15
    What does `stretch-out` mean scientificly?

    What does it mean that lightcurves are stretched out? Please explain it scientificly!
     
  17. Feb 2, 2008 #16

    marcus

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    Lightcurve is a scientific term for the recorded brightness as it changes over several hours or days.

    Certain types of supernovae have a characteristic shape to the lightcurve. Just as an example, say it rises for 1 day and reaches a peak and then takes 3 days to die down.

    if something is observed at redshift z=1, that means that everything is stretched out by a factor of z+1=2

    So the wavelengths of the light are stretched by a factor of 2.

    And the lightcurve is stretched by the same factor, namely 2.

    Instead of taking 4 days to go through its flash it takes 8 days.

    this is not a Doppler effect. it is not what is usually called "time dilation" either.
    it is the effect of the whole message getting stretched out as it traveled thru space where distances were getting stretched out. Space got stretched by a factor of 2 while the signal was on its way, so it got stretched too.

    You asked "please explain it scientifically" but I think I already explained. Lightcurve is a technical scientific term already. Hope that helps.
     
  18. Feb 2, 2008 #17
    According to General Relativity, every where and each time the physics is the same. Therefore the event at factor 2 is the same event that would happen in Milky Way.
    The two-todays or two-hours spanned short-period events can be affected by large-scale cosmological expansion? It is hard to understand. Would you give me the right references?
     
  19. Feb 2, 2008 #18

    marcus

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    http://arxiv.org/abs/astro-ph/0608639

    Here's a reference on the lightcurves of type 1A supernovae

    very roughly speaking they take 10 days to rise to peak brightness
    then they stay near peak for around 10 days
    and then they take about 20 days to get back down to near what they were

    the curve is actually smoother, and kind of pretty
    you can find a smoothed out version graphed in the paper towards the end

    if it is at z=1
    whatever it takes 40 days to do, in its restframe, that signal will get stretched out by a factor of 2
    so it will take us 80 days to watch the whole show

    whatever takes the star 10 days, like ten days to rise to max brightness, that will take 20 days for us to watch.

    because the signal gets stretched while in transit, just like the wavelengths of the light itself

    But Jin He you are the author of these papers:
    6. arXiv:astro-ph/0605213 [ps, pdf, other]
    Title: The Faulty Assumptions of the Expanding-Universe Model vs. the Simple and Consistent Principles of a Flat-Universe Model -- with Moving Pisa Tower Experiment which Tests General Relativity
    Authors: Jin He

    7. arXiv:astro-ph/0604084 [ps, pdf, other]
    Title: Einstein Field Equation: the Root of All Evil? Prediction on Gravity Probe B, Quantum Gravity and Solar Application
    Authors: Jin He
    Comments: Gravity Probe B prediction is corrected

    8. arXiv:astro-ph/0512614 [ps, pdf, other]
    Title: The Possibility of Curved Spacetime, Black Holes, and Big Bang is Less than One Billionth
    Authors: Jin He

    I doubt that I can explain anything satisfactorily to you,
    maybe someone else can explain things to you better
     
    Last edited: Feb 3, 2008
  20. Feb 3, 2008 #19
     
  21. Feb 3, 2008 #20

    marcus

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    ===============
    I am guessing on the order of 10-100 megaparsecs---dont think it can be pinned down. Wallace, if he sees this, may choose to correct or make this estimate more precise

    BTW I was speaking very loosely about space expanding and not expanding. I used those phrases because that is how everybody talks.

    But if you want to be really precise you might want to read an article about this that Wallace and some other astronomers wrote.

    I'll get the URL
    http://arxiv.org/abs/0707.0380

    space is not a material.
    distances between things can increase in an approximately systematic way, but only approximately
    there is no sharp cutoff where distances below a certain length do not and all distances above that length do

    the nearby galaxies form a gravitationally bound system with us, distances in a gravitationally bound system, a cluster, are not part of the largescale systematic increase of distances.

    how large a patch of space around you is occupied by a gravitationally bound system of galaxies depends on who you are and where you live. some clusters are larger than others, some clusters belong to superclusters
    the whole thing is irregular

    all you know is that if you go out far enough things vaguely and gradually begin to look like a systematic expansion
    how far you have to go depends on where you start and what the local neighborhood is like.

    http://arxiv.org/abs/0707.0380
    Expanding Space: the Root of all Evil?
    Matthew J. Francis, Luke A. Barnes, J. Berian James, Geraint F. Lewis
    8 pages, accepted for publication in PASA
    (Submitted on 3 Jul 2007)

    "While it remains the staple of virtually all cosmological teaching, the concept of expanding space in explaining the increasing separation of galaxies has recently come under fire as a dangerous idea whose application leads to the development of confusion and the establishment of misconceptions. In this paper, we develop a notion of expanding space that is completely valid as a framework for the description of the evolution of the universe and whose application allows an intuitive understanding of the influence of universal expansion. We also demonstrate how arguments against the concept in general have failed thus far, as they imbue expanding space with physical properties not consistent with the expectations of general relativity."
     
    Last edited: Feb 3, 2008
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