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Redshift = expansion?

  1. Jan 16, 2004 #1
    Redshift = expansion??

    I'm not a physicist so I'll probably be laughed at for asking this.

    I understand the concepts of redshift and the Doppler effect being used to substantiate the hypothesis that the universe is expanding, indeed accelerating, since the farther an object is the higher its redshift.

    This fits.

    But, please tell me there is more than this to say that the universe is expanding and accelerating.

    I mean, there may be some undiscovered property of space that shifts the wavelength of light proportional to the distance traveled. I'm not invoking any ether theories or anything. I just mean, there has to be other data besides redshifting to confirm the expansion of the universe. I'd hate to know that so much theory is built on one type of data point.

    Can someone educate me?
  2. jcsd
  3. Jan 16, 2004 #2


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    The Cosmic Background Radiation is also taken by many to be evidence of universal expansion. CBR is a radio signal that comes from everywhere in space at once. Back when radio comunication was in its early stages, some guys were setting up a cone-shaped antenna for some purpose (telephone signals I think) when they found that the antenna picked up a low-energy interference. The signal seemed to come from everywhere, no matter what direction they pointed the antenna. At first, they thought it was radation from the decay of bird-droppings inside the horn. But after cleaning, the signal persisted.

    It was eventually determined that the signal was coming from space. Later someone found that just such a signal was predicted by the Big Bang Theory, as a left-over "glow" from the heat of the original explosion.

    Personally, I'm a bit suspicious of the BB theory, for the same reasons you mentioned. From my cinical perspective, the CBR would not be seen as support of the BBT if that theory were not already established.
  4. Jan 16, 2004 #3


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    Re: Redshift = expansion??

    There is more than just observed redshifts that supports the idea that the U is expanding.

    It is good to be skeptical and question prevailing ideas and ask for more than one kind of evidence---so seem like very fair questions you are asking.

    The main equation of Relativity has two kinds of stable solutions---space expanding and space contracting----and it goes back to 1915, well before extragalactic redshifts were systematically observed.

    The first test of General Relativity (GR) was in 1919, measuring the bending of light as it passed the sun. It passed that test and thereafter it has passed every test anyone could think of performing. Recently two pulsars (radiosource neutron stars) were found orbiting each other and this provided a stringent test which the theory passed ("with flying colors", said Ned Wright, who posted the news on his "News of the Universe" page)

    The first reason IMHO to think that the universe is expanding is that GR has been tested now for over 80 years in a lot of different cases and it works really well. The GPS system depends on using GR formulas to adjust the time signal from the satellite---if those formulas werent right the system would give the wrong coordinates. So the main equation of GR has been confirmed in many ways over 80 years.
    And this main equation says the universe should be expanding (unless it is collapsing).

    So far nothing here about redshifts or about the CMB.

    You can see that the evidence for expansion is not ONLY redshifts.
    Because of GR one would expect to see either a whole bunch of redshifts (meaning expansion) or a whole bunch of blueshifts (meaning contraction). Well, as it happens, we see redshifts rather than the reverse. So since expansion was one of the two possibilities it seems reasonable to put two and two together and explain the redshifts by the expansion.

    The CMB was an extra bonus. It was first predicted in 1945 IIRC, based on the General Relativity idea that the universe is expanding.
    If you follow that expansion back you come to a time when a flash of light is released. Since things are sparse enough that there is not much to stop the light, it must still be flying in all directions thru space. The 1945 guys (Alpher and Gamow?) predicted that the wavelength of the original flash of light would have been STRETCHED OUT by the expansion of space by a factor of around 1000 and therefore that the light would now be radiowaves.

    (if you start with visible light and stretch the wavelength out by 1000-fold you get microwave/infrared.) They predicted a certain frequency band or wavelength band to look in.

    This was a pretty radical thing to predict. It was a bold test of General Relativity and the expanding space idea----nobody had detected those Background Microwaves. They would only be expected to be there if the expanding picture was correct----no other theory had predicted anything like the CMB.
    If the astronomers looked for signal in the band that those guys predicted from GR considerations and the signal HAD NOT BEEN FOUND that would have been discrediting for GR. Scientific theories have to risk falsification---make predictions that could prove them wrong---in order to be meaningful. GR was meaningful and said look for the CMB, and the CMB was found: they found the signal right where predicted.

    I guess what Im saying is that the expansion thing is just one aspect of GR----one facet of what GR predicts. That one equation can be applied to a lot of things and used to predict different kinds of things (timechange, lightbending, spaceexpansion, neutron star orbits,....)
    By now that one equation (the GR equation) has been thru so many tests and predicted so many things that have turned out that it would be difficult to replace it with a substitute that would handle all that stuff anywhere near as well.

    (People try to develop alternatives but so far it hasnt worked out too well. Someday no doubt.)

    So ultimately I tend to believe in space expanding because it is part of what that model of gravity predicts---and the model works---AS WELL as because a whole bunch of foreign galaxies have redshifts that increase with distance. It isnt just the redshifts.
  5. Jan 16, 2004 #4


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    IIRC, the full story of the CMB and the Big Bang is somewhat richer than either LURCH or marcus have described; yes it was predicted, but the theorists didn't know how to look (or was it that they didn't really believe their predictions?); the engineers (let's hear it for engineers!) who found it worked for AT&T, and were completely unaware of the cosmic implications of their data - 'a sticky white substance of uncertain dialectric constant' seemed a more likely explanation.

    The BB has a third pillar of evidence - the primordial abundance of nuclides. It's not only that the amount of H and He in the universe is just what the BB theory says it ought to be, but also 7Li, 4He, 3He, and 2H (and the absence of anything else primordial - apart from the hydrogen we're completely a star-made product).

    The acceleration of the expansion was a surprise, and isn't well characterised yet. AFAIK, the signal is seen only from distant Type 1 supernova data, though it can be seen in the CMB (through models).
    Last edited: Jan 23, 2004
  6. Feb 7, 2004 #5
    Shurmeo, all of the light that is used in all of these measurements, is light that has travelled the distance, and arrived here, at the Face of the Earth, that is why we can observe/see it, hence, what is really happening "out there" no one really knows...the Universe could have turned back upon itself (contraction) several thousands, or millions, or (1 or 2 or more) billion years ago, and we would/will not know that till that light arrives here at the face (or 'near' face...satellites) of the planet...

    But don't think that that really means anything with respect to it happeneing today, or tomorrow, the 'evidence' (the light record) would get here before anything else happened, so we are eminantly safe!
  7. Feb 14, 2004 #6
    well, I think they can safely assume that it will NOT turn back on itself if it is accelerating instead of decelerating.

    Also, I've been told that the "expansion" of the universe is expansion of space itself, not simply objects of matter moving away from each other, although it has that effect. The effect of space expanding is basically that objects will move farther apart. I guess the expansion of space has NO effect on the location of a photon with respect to another photon, since they have no mass. But, maybe it does, maybe "separating" photons, or at least stretching the wave, could have an effect of increasing the wavelength (redshifting) of the light. So maybe the double effect of Doppler and stretching light by expanding space makes it look like the universe is accelerating?

    Also, if space itself is expanding, every particle of matter would have to expand as well(?) since, say, a proton takes up some volume, then it would also have to be expanding along with the space it occupies(?). If it didn't would electronic orbitals destabilize or something? since, the electron can be visualized to be "moving" with some momentum with respect to the proton.

    You see why I'm so confused by this seemingly simple concept.
    I think if I took some classes on GR then this might all make sense to me.
  8. Feb 14, 2004 #7
    that's kind of what i was saying, maybe there is some other undiscovered property of space (stupid aether theory) that stretches light more the farther it travels.

    I think the CBR is from the annihilation of matter/antimatter when the U was cool enough for that to happen, I think it was about 1 second old. I assume the CBR is mixture of similar wavelengths. That would mean that the annihilation event "released" a mixture of very simlilar wavelength photons? Does this mean that there was pretty much ONE type of matter particle and ONE type of antimatter particle. If there were a mixture of different kinds of particles, wouldn't the energy of their annihilation vary? Wouldn't we see a broad background spectrum or at least a few different regions of the EM spectrum to look at?
  9. Feb 14, 2004 #8
    shrumeo gravitational redshift, our local star does it...the farther away a luminous gravitational object is, the more time/distance the gravity of the source star would have to work on stretching out the emitted light, or the space in which the emitted light is traveling, in...
  10. Feb 21, 2004 #9
    Redshift created aging light!

    The redshift results from expansion of the structure of light as it travels for a long time from the distant galaxies, according to Eugene Savov’s theory of interaction. It is all one interaction that occurs at different scales and thus accounts for the great puzzles of our time.
  11. Feb 21, 2004 #10
    Re: Redshift created aging light!

    Sounds (really) nice, but there isn't any available proof...nor disproof, sooo....sounds nice...
  12. Feb 22, 2004 #11

    A complete picture of "firework universe" that nicely explains many big puzzles, presented in Eugene Savov's book Theory of Interaction,
    looks like a convincing proof.
  13. Feb 22, 2004 #12
    Re: Proof

    Your other post mentions;
    so, inasmuch as no one has been anywhere nears the outside of this solar system, to take MEASUREMENTS, or this galaxy, no one knows that with any kind of EVIDENCE, hence NO PROOF... but it sounds good...understand?
  14. May 19, 2004 #13
    The BB has a third pillar of evidence - the primordial abundance of nuclides. It's not only that the amount of H and He in the universe is just what the BB theory says it ought to be, but also 7Li, 4He, 3He, and 2H (and the absence of anything else primordial - apart from the hydrogen we're completely a star-made product).

    <<I realize that this is an old thread that may get no responses.>>

    I've heard this before, that at first when atoms started to form in the early universe that the only atoms were hydgrogen atoms, period. Where were all the neutrons? So stars are making He from H, where are these neutrons coming from? I think this can be simply answered if I just had an intro nuclear physics course, something about electron capture or something like this. O wait, der!, just read it quickly. Electron capture is one electron plus one proton makes a neutron and a neutrino. Got it. :redface:

    Well, another thing that's puzzling, that just came to mind as I type this. Unless I'm wrong, which may very well be the case, according to Electric Charge Theory, all charge should be balanced. There can't be an excess of electrons to protons in the universe, or vise versa. Isn't that strange? So, the universe has EXACTLY the same number of protons and electrons?? Every proton that formed from the quark-gluon soup, if you will, had an electron associated with it presumably. Were the formation of protons and electrons coupled somehow? :confused:
  15. May 20, 2004 #14


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    just to drift further from the point, the net energy of the universe must be assumed to be zero [entropy rules]. positive energy [matter] must be balanced by negative energy [force] to maintain equilibrium. but matter is so dense [m=e/c^2], it takes a huge amount of negative energy [think dark energy] to balance the equation. dark energy, therefore, is actually potential energy [like a rock on top of a mountain]. that is why we cannot directly observe it. predictions regarding dark matter and dark energy are merely an attempt to balance the equation using gravity as currency, imho.
  16. May 20, 2004 #15
    I find this extremely interesting. If there is no alternative but that a universe exist, then the probability of its existence is 100%. There is zero Shannon information contained in the universe. Furthermore, that the universe exists is always a 100% certainty. Whatelse is the case after that may be subject to some doubt, but we know that the universe does exist with 100% certainty. So we might suppose that the change in entropy is zero for the entire universe.

    But even if there were a less than 100% probability of this particular universe to exist, wouldn't that still remain the case throughout all of time? So isn't it the case that at least there is no change in information/entropy of the universe throughout all of time.

    I'm trying to convince myself of this. Do you know of any more official studies in this regard?

    It could be that this is the key to understanding many aspects of reality.

    First, it may be that some information involved with the curvature of space may need to equate to the information contained in the sum of particles. So the expansion of space may be linked to the creation of particles.

    Secondly, it may be possible to link the expansion of the universe with the creation of life. The expansion may represent a increase in entropy, and life may be a mechnism to decrease entropy as a balance.

    Third, you may even be able to calculate whether there is life on other planets if you could calculate the decrease in entropy associated with life, even intelligent life.
  17. May 20, 2004 #16
    What is Shannon information? And why do you somehow equate or relate entropy to "information"?

    Do you mean the creation of particles from nothing, or from "dark energy"?

    This kills me every time I see it. LIFE IN NO WAY DECREASES ENTROPY! Nor does it involve a decrease in total entropy (maybe in some cases for open systems like anything else, but not in any special "life" kind of way.) People think this because the hear in school that entropy = disorder, which is absolutely does not. Here is a nice website: http://www.entropysite.com/
  18. May 20, 2004 #17

    I reead up on it. The "entropy" in Information Theory would not necessarily, or probably not at all, the same "entropy" of thermodynamics. Maybe one could analogize them somehow, but I don't think the 2 words really mean the same thing.

    Looking "entropy" up at Dictionary.com you get:

    1. Symbol S For a closed thermodynamic system, a quantitative measure of the amount of thermal energy not available to do work.
    2. A measure of the disorder or randomness in a closed system.
    3. A measure of the loss of information in a transmitted message.
    4. The tendency for all matter and energy in the universe to evolve toward a state of inert uniformity.
    5. Inevitable and steady deterioration of a system or society.

    #2 is totally misleading BTW, but I kinda like #4, but it's more the effect of entropy than entropy itself.
  19. May 22, 2004 #18


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    Mark2, a very elegant and profound insight into the implications of a zero net energy state universe. the fact it cannot standstill [quantum theory] and must also be expanding or contracting [GR] requires a universe that is doomed to become increasing complex as well as simple. i especially like the apparent need for sentient life in the universe. expansion created additional entropy burdens that could not be 'burned off'. by conventional random creation and annihilation of particles. so the universe was forced to evolve and create more efficient 'entropy dumps'. that is sentient life, and the more aware it becomes, the more efficient is serves as an entropy 'exhaust'.

    you may be amused by some papers written by Cahill of Flinders U. i think process physics is more intuitive than scientific [at this time, anyhow]. but it does inspire a more comprehensive view of why there is force and counter force, as well as matter and anti-matter. btw, information is the densest form of entropy in the known universe.

    clarification. entropy is commonly thought of as disorder.. randomness. i prefer to think of it as balance, hence entropy has a plus [order] and a negative [disorder] quality. information is a very highly ordered state [+ energy]. we need a new description of reality to equate that. i dont object to the thermodynamic explanation. i just think it is inadequate. if this universe must exist [and i believe it is forced to exist under quantum theory], then it must become increasingly complex and simple over time. expansion is therefore required. sentience is an unavoidable consequence in such a universe.

    is this particular universe necessary? no. but it is absolutely required for a universe to exist. pure non-existence would violate quantum physics. such a universe would have a perfectly fixed position and velocity [0,0], and this is forbidden. therefore, it is 100% necessary for a universe to exist. it is also necessary for it to behave in a causal manner.

    for a universe to exist, it must be closed in the sense that it forbids observable features that would prohibit it from existing [infinity being one]. it must also include causality and be perfectly balanced [zero state] to have space-time dimensions. [i could elaborate on that but i am tired] quantum theory places a lower limit and GR places an upper limit on how such a universe must behave in order to meet these restraints.

    why do we only perceive 3 spatial dimensions and one time dimension? because that is the minimum required to explain it. there is a probability the universe has many more dimensions than we can perceive. but they are not necessary or important enough to predicate our existence.

    any reality beyond our ability to observe has no consequences in this universe. all the universe demands is that we exist to wonder why it does. [btw, i have a rough idea how to calculate the life form density necessary to perpetuate this universe].
    Last edited: May 23, 2004
  20. May 23, 2004 #19
    I suppose that at some point efficiency requires a deliberate and purposeful effort, which requires beings aware of their surrounding and mindful of that purpose who can manipulate matter to that end.

    I'm not sure that you can impose quantum mechanics on the universe as a whole. Perhaps that is a phenomena that can only be described within a universe. If the universe must absolutely exist, and there is no uncertainty about that, then the uncertainty principle would seem not to apply. Otherwise, you would be presupposing alternative times and sites where space-time itself first began. If it hadn't begun yet, then there are no alternatives as to where and when it can begin.

    Right, everything must be consistent with everything else.

    I'm comfortable with that on an intuitive level. For if the first point of space-time can arise out of nothing, then this proves that it is possible for other points to arises as well, and there you have causality (or at least logic) producing expansion.

    I'm presently reading a book by Eric J. Chaisson, Cosmic Evolution, where he expounds on how ordered states can be created only as a means of more efficient ways to dump entropy. This got me thinking about how entropy fits into quantum mechanics where one state is chosen from a superposition of many. So the nature of quantum interactions or observation reduces the number of available states and would therefore reduce entropy. Does that sound right?

    I'd like to see that.
  21. May 24, 2004 #20
    I know you two aren't listening to me but I don't care:

    I see where you are getting this anthropomorphic view of this.
    I have not read Cosmic Evolution. But I read the cliff's notes. or at least someone who read it and sounds like they know what they are talking about.
    Here are a few clips from: http://www.2think.org/cosmicevolution.shtml

    "I'm not sure if I buy everything in Cosmic Evolution. The author may be trying to use a hammer for everything and not just for the nails they were intended for."

    In another book review, on the same site:

    "Many of us already know that "we habitually inflate the impressiveness of coincidence in order to make a good story" (p. 149)."

    It sounds like you are trying to use the tendency of all heat (thermal energy) to disperse into more places than it started in (entropy) to build that into "order" and "complexity" which are not too much more than conceptual constructs in most circumstances. If he is using entropy to MEASURE complexity, or somehow detect it, well that's nice if he spells out how he does this scientifically, as opposed to just comparing 2 things, making a judgment, and saying Thing 1 is more complex Thing 2 cuz it sure looks that way to me.

    Here is an exerpt from the cover blurb in Cosmic Evolution:
    "Guided by notions of beauty and symmetry, by the search for simplicity and elegance, by the ambition to explain the widest range of phenomena with the fewest possible principles, Chaisson designs for us an expansive yet intricate model depicting the origin and and evolution of all material structures."

    Sounds great except to Einstein who said: "Elegance is for tailors."

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