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Inflation and Element Formation: Irreconcialble?

  1. Nov 7, 2013 #1
    I write this in the hope that somebody reading this can explain to me, a laymen, in non-mathematical, plain English terms, why my thinking is wrong regarding the calculation of the age of the observable Universe and the formation of the elements in the Periodic Table given the (short) age of the Universe.

    I watch the TV series dealing with the Universe where astronomers say that the universe is about 14 billion years old. In the same breath, they also say that the light we see today coming through our telescopes on earth left a distant galaxy just shy of 14 billion years ago. (let us assume for simplicity sake about 13.5 billion years ago). I will call that distant galaxy "Galaxy X". If my understanding of what they are saying is correct, this would suggest that the plasma/energy/ matter (or whatever label the scientists want to call it and which I will call "Stuff" for simplicity sake) which became Galaxy X and the Stuff that ultimately became the Earth (which, for simplicity sake, I refer to as "Earth-Stuff") both came into existence at the same time and from the same starting gate -- about 14 billion years ago.

    Question #1: Assuming my understanding just discussed is substantially correct, how is it possible that the light we see today coming from Galaxy X took 13.5 billion years to reach us when the light which left that distant galaxy already had reached Earth-Stuff billions of years ago? It seems to me to be impossible for an observer on earth to see the light from Galaxy X twice: the first time is when the (hypothetical) observer located on Earth Stuff observed that light about 14 billion years ago; the second time is when a present day observer on earth saw that early light coming from Galaxy X while peering through a telescope.

    Question #2: I understand that Expansion?Inflation of the Universe may answer my first question. As somebody on this Forum explained, the effect of Inflation/Expansion of the Universe is that even though Galaxy X and Earth-Stuff came into being at the same time about 14 billion years ago, Inflation/Expansion caused Galaxy X and Earth Stuff to become instantly separated (at an apparent speed faster than the speed of light) by a distance so great that it has taken the light from Galaxy X about 14 billion years to reach us today. But then how is it possible that the Earth today possesses all the elements in the Periodic Table? I ask this question based upon Cosmologists and physicists telling us that many of these elements came into existence through the death of earlier stars. If that is so and given that the age of the earth is about 4 billion years old, it seems to me that there could not have been enough time for those earlier stars to come into existence and then die within a time frame that would allow the four-billion year old earth to have the elements it has today.

    I hope I have stated my question in a manner that does not cause many of the readers of this forum to throw their hands up in despair. I would appreciate those who have a far greater understanding of this to provide answers.
     
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  3. Nov 7, 2013 #2

    marcus

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    Hi Aboro,
    I remember our earlier thread where you were thinking it is impossible for light from a star to take 13.4 billion years to get to us. I know you asked for a NON-MATH explanation, but I want to try something that is basically just arithmetic. No equations, no algebra.
    I want to encourage you to learn to read this table:
    (It has a lot of extra stuff you don't need to understand. Don't let that scare or confuse. I'll suggest what to focus on.)

    [tex]{\scriptsize\begin{array}{|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|r|} \hline a=1/S&S&T (Gy)&R (Gly)&D_{now} (Gly)&D_{then}(Gly)&V_{now} (c)&V_{then} (c) \\ \hline 0.091&11.000&0.4726&0.7105&31.447&2.859&2.18&4.02\\ \hline 0.106&9.469&0.5920&0.8894&30.231&3.193&2.10&3.59\\ \hline 0.123&8.151&0.7414&1.1130&28.920&3.548&2.01&3.19\\ \hline 0.143&7.017&0.9284&1.3922&27.509&3.921&1.91&2.82\\ \hline 0.166&6.040&1.1621&1.7401&25.990&4.303&1.80&2.47\\ \hline 0.192&5.199&1.4542&2.1728&24.357&4.684&1.69&2.16\\ \hline 0.223&4.476&1.8185&2.7087&22.602&5.050&1.57&1.86\\ \hline 0.260&3.853&2.2723&3.3685&20.721&5.378&1.44&1.60\\ \hline 0.302&3.317&2.8355&4.1732&18.711&5.642&1.30&1.35\\ \hline 0.350&2.855&3.5313&5.1413&16.574&5.805&1.15&1.13\\ \hline 0.407&2.458&4.3851&6.2820&14.316&5.825&0.99&0.93\\ \hline 0.473&2.116&5.4225&7.5870&11.954&5.650&0.83&0.74\\ \hline 0.549&1.821&6.6657&9.0202&9.516&5.225&0.66&0.58\\ \hline 0.638&1.568&8.1292&10.5121&7.046&4.494&0.49&0.43\\ \hline 0.741&1.350&9.8148&11.9676&4.596&3.406&0.32&0.28\\ \hline 0.861&1.162&11.7095&13.2878&2.224&1.915&0.15&0.14\\ \hline 1.000&1.000&13.7872&14.3999&0.000&0.000&0.00&0.00\\ \hline 1.162&0.861&16.0138&15.2745&2.081&2.417&0.14&0.16\\ \hline 1.331&0.751&18.1309&15.8712&3.784&5.036&0.26&0.32\\ \hline 1.524&0.656&20.3179&16.3092&5.321&8.110&0.37&0.50\\ \hline 1.746&0.573&22.5554&16.6216&6.693&11.686&0.46&0.70\\ \hline 2.000&0.500&24.8287&16.8396&7.910&15.820&0.55&0.94\\ \hline \end{array}}[/tex]

    For starters let's just talk about the FIRST ROW of numbers
    the earliest stars I've heard about were very massive so they burned their fuel fast and had short lifetimes and then went supernova. Lifetimes on the order of a million years or a few million. they were from a time when distances were about 1/11 what they are today. That is why the label S=11 on that row. that top row is "first stars" and first puny little fuzzy blobby galaxies called "protogalaxies".

    So try reading the first row. It tells you that the YEAR was year 473 million. Right? Do you see where it says what year it was? We can round off. Maybe it was 400, or 450 or 500 million. Precision is not important, just get a rough idea. TODAY by contrast, is year 13.8 billion. Do you see that down in the S = 1 row? S=1 means distances are exactly the size they are today, so it mean the present era.

    What the table means by Dthen is the distance BACK THEN when the star emitted the light we are just now getting today. It is the socalled "proper" distance that astronomers use, which you would have measured if you could have gone back to that time (year 473 million) and stopped the expansion process long enough to measure by whatever conventional means e.g. radar. and then when you had measured you could have let expansion continue.

    Do you see where it says that the distance from our matter, back then, was 2.86 billion LY?

    This is Thing One. You are interested in the very earliest stars, that we are today getting light from.
    They formed and sent us their light around year 470 million (the U had been expanding from its much more dense condition for about 470 million years, by then).
    And when they formed and sent us the light we are getting today, they were at a distance of about 2.86 billion LY from the matter that eventually became our galaxy and our solar system, and us. That's how far they were from here, if you could have stopped expansion at that moment, long enough to measure by radar ranging or a long string or yardstick or whatever.

    Let's stop here. Assimilate this much, just from the top row of the table. Let us know if you have any questions about the top row. does anything not make sense. Notice that there are speeds given, showing how fast the now distance and the then distance were growing. That could be thing two.
     
    Last edited: Nov 7, 2013
  4. Nov 8, 2013 #3

    cepheid

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    Sure, the matter was there from the start. Galaxy formation happened later, but it began to happen fairly early on in the 13.7 billion year history of the universe.

    It hadn't already reached "Earth stuff" billions of years ago. The light from the most distant objects that we can see has only just arrived (for the first time). It has had only just enough time to reach us given the age of the universe.

    He didn't. There is only one "first" arrival time for the light, and at all subsequent times, light is continuously arriving.

    Again, why do you think that this happened? It didn't.


    Just call it expansion. In cosmology, "inflation" refers to something else very specific.

    Yes.

    How is 10 *billion* years not enough time for earlier stars to be born, live, and die?

    Perhaps you are thinking of the fact that since the estimated lifetime of our sun is 10 billion years (5 billion of which have already gone by), this would allow for, at most one generation of stars prior to the present one? There are a few things to keep in mind:

    - one generation of stars would still have produced heavy elements
    - there was, in fact, more than one generation of stars prior to the present one. Not all stars have the same lifetime. Stars more massive than our sun live for much shorter times (hundreds of millions of years or less). And these more massive ones are the ones that explode as supernovae, producing the heaviest elements and spreading them out widely.
    - The first generation of stars, which astronomers refer to as "Population III" stars, would have been different from the ones that are forming now. Because they would be made from raw materials that have *no* heavier elements (only hydrogen and helium), it is actually expected from theoretical models that they would be able to achieve higher masses and hence be much shorter lived.

    http://www.universetoday.com/24776/what-were-the-first-stars/
     
  5. Nov 8, 2013 #4

    Chalnoth

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    Why would you think that an observer sitting near the matter that would eventually form into the Earth would be able to see that galaxy that long ago? Galaxies that far away would have likely been outside of our horizon 13.5 billion years ago, and would only become visible much later.

    For some real numbers, see here:
    http://www.astro.ucla.edu/~wright/CosmoCalc.html

    An object whose light we're seeing today has taken 13.5 billion years to reach us would have a redshift of about z=21. Its distance when it emitted the light we're seeing today would have been about 1.64 billion light years, but we would have only been able to see about 0.44 billion light years out at that time, due to the very fast expansion rate back then. So the light from this galaxy did not reach us early-on, and we only became able to see the galaxy later due the fact that the expansion rate has slowed considerably in that time.
     
  6. Nov 8, 2013 #5

    mathman

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    Earliest stars were formed about 500 million years after the big bang. They were big and burned out fast. They gave rise to all the elements other than those created immediately after the big bang (H, He, Li). 9 billion years (time between first stars birth and solar system birth) is plenty of time for element formation.
     
  7. Nov 8, 2013 #6
    Marcus, Cepheid, Chalnoth and Mathman, I am fortunate indeed to receive your replies. While I have read them, I need time to comprehend them as well. Please give me some time to do that. Thanks to all of you.
     
  8. Nov 8, 2013 #7
    Hi Aboro, et al.

    Your question seems to me to be a very good one, Aboro.

    Would I be correct in summarizing it thusly:

    If all in the universe today started from the void with a big bang, AND started from a single point exploding matter into existence outward from that point, then wouldn't it be necessary that either the sky would be dark (because no outward motion could exceed the speed of light) or there must be either motion or universe expansion at a rate faster than the speed of light?

    Does that reasonably explain your question? (It sounds like a good question to me.)

    If it does, then it seems the key follow up question is what is the difference between an expanding universe and the motion of an object in that universe - that we could say one of these could exceed the speed of light yet the other could not exceed the speed of light? It seems to me that there must be a phenomenological difference (including a verifiable description of the mechanism) for a) an expanding universe and b) for motion in a universe, before it would be reasonable to accept an argument based on differentiating such two suspect ideas. Since I am not a physicist, but am interested in these concepts, I wonder if the physicists might help me as well with Aboro's question, by explaining the two mechanisms for a) an expanding universe and b) for motion in a universe, and provide the empirical evidence relied on with regard to such a phenomenological differentiation.

    By the way, Aboro, I have read some very recent alternative explanations for Hubble's observation that dimmer stars have more optical frequency shift (which seems to be the basis for the expanding universe conjecture). One comes from Yijia Zheng's research at the Chinese Academy of Sciences (arXiv:1305.0427 and arXiv:1306.1015, and perhaps others), where Zheng refers to empirical observations of photons losing energy by coupling with plasma (being absorbed into an electron and then re-emitted at every-so-slightly lower energy). Of course lower energy is lower frequency, so another way of looking at what Zheng is considering is as a simple frequency conversion as is done in every single radio device (cell phones, am/fm radios, satellite television, they all use frequency mixing to accomplish frequency downconversion). Then, redshift of dimmer stars can be explained simply because the dimmer (further) stars encounter more plasma mixing on their way from their origin to Earth. In this scenario, there seems to be no need of an expanding universe ... although monetary inflation seems to be unavoidable, at least for now!
     
  9. Nov 9, 2013 #8

    cepheid

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    This is exactly the wrong way to think about the big bang (and is a common misconception, because of the name). The big bang was not an explosion of matter outward from a single central point into a pre-existing space. Rather, the big bang marked the beginning of the existence of space and time itself, and the expansion of space outward. There is no single central point, but rather every point expands away from every other point in a way that appears completely isotropic and homogeneous (which is consistent with our observations of the universe on the largest scales). We have a cosmology FAQ thread on this:

    Where did the big bang occur? (Hint: everywhere at once)
    https://www.physicsforums.com/showthread.php?t=506991 [Broken] (third and fourth paragraph especially)

    You might also find our (enormous) thread on the balloon analogy helpful, although it is a bit unfocused:

    https://www.physicsforums.com/showthread.php?t=261161

    Superluminal expansion is not inconsistent with special relativity, because no object is moving faster than light in any observer's inertial reference frame. No one is "catching up to a light beam." There is a dicussion of this in this paper:

    http://arxiv.org/abs/astro-ph/0310808

    AND we have an FAQ thread on this:

    Can the expansion of space be faster than light?
    https://www.physicsforums.com/showthread.php?t=508610 [Broken]


    This is not a new idea, it is just a variant of the old "Tired Light" hypothesis, which is easily shown to be false by observational data:

    http://en.wikipedia.org/wiki/Tired_light

    We also have a couple of cosmology FAQ threads somewhat related to that:
    Could redshift be intrinsic rather than due to expansion? (Hint: no)
    https://www.physicsforums.com/showthread.php?t=506994 [Broken]

    What evidence is there for the big bang model? (hint: it's much more comprehensive than just redshift alone)
    https://www.physicsforums.com/showthread.php?t=506993

    EDIT: Also, saying that "dimmer stars show more optical frequency shift" and that "this is the basis for the expanding universe conjecture" is wrong for two reasons:

    1. Cosmological redshift only applies to very very distant objects, i.e. other galaxies. So you should really be saying that galaxies appear redshifted, not stars. Every star that we can observe *individually* is within our own galaxy, and none of these are expanding away from us, because our galaxy is a gravitationally-bound system

    2. Redshift alone is not the sole basis for the "expanding universe conjecture" (which is way more than just a conjecture at this point). Expansion of the universe is predicted/explained by General Relativity and supported by a whole host of observations: the existence and the blackbody spectrum of the CMB, the abundance of the light elements (produced by big bang nucleosynthesis), to name just a couple. See the last FAQ above.
     
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  10. Nov 9, 2013 #9
    That's a lot of information : ).

    So the big bang is a bit like Hilbert's Hotel? Even though all space is already occupied it can still fit more?

    The point Aboro made that caught my attention is the apparent incongruity between conjecturing expansion as causing the observed frequency downshifting vs. what seems a necessarily concomitant superliminal velocity -- if ever "H" is positive in the equation v = HD. No matter if one conjectured the big bang as suddenly appearing at one time and throughout all space (Hilbert's Big Bang, say) or if one conjectured the big bang from a single point in time and space, that apparent incongruity seems to be one that continues to need attention. There appear to be a number of reference papers which seem to consider the issue far from closed on the side supporting expansion, and the frequency downshifting of the Pioneer 6 spacecraft's telemetry when the telemetry path was near tangential to the Sun's surface seems to be a remaining problem of explanation that so far has better explanations by such as Zheng's soft-photon process, no? I am just beginning to get a feel for these issues. But I am always reluctant to buy in to a decided theory when there are many dissenters (as there appear to be here), when observations are of such distant and complex phenomena, and when reports only use a few examples measurements in attempt to support a theory that one would expect to show rather universal consistency.

    I wonder if the expansion is supposed to be uniform? What mechanism would make the expansion non-uniform I wonder?

    These are the questions that come up for a newcomer to the topic like me. They have probably been well worked over by the veterans.

    The thing that strikes me as positive from the soft-photon theory of Zheng is that it would permit for a great variance in the v = HD behavior (and I have seen some charts which showed such variance, but it doesn't seem easy to find the raw data by just googling around). Do you know where a lot of good raw -- totally unfiltered, or nearly unfiltered -- data might be? So much becomes clear by just looking at data.

    I have seen an article about twin (or is it binary?) stars, making the relatively obvious point that they should have the same average cosmological redshift if that is what was occurring (perhaps that was Zheng too, but maybe someone else), but the average redshift is different for each of the two stars. That makes no sense to me if it were primarily cosmological (i.e., expansion based) redshift involved. I wonder if others have found any good review papers on that topic?

    I did find one review paper -- but I haven't really been focused on this topic too much, and there are surely many more. But the first one I happened into (arXiv:0707.1350) did little to impress that things were anywhere near as settled as I infer some profess. But I wonder if that's really such a big deal that there is a bandwagon orthodoxy effect ... I mean, without some degree of certainty expressed (even if overcertainty) it would probably be hard to justify the largest sums to invest in experiments. I suppose the main risk is that the experiments might look at the wrong thing (from not having duly considered all the angles ... found something there recently w.r.t. the DST mistake in space physics, which frankly relates to the redshift issue potentially, because the soft-photon process may involve the type of plasma interactions which Zwicky had proposed might exist, but which appear to be rather complex affairs to study).

    Thanks, Mentor (whomever individual/s that may refer to), for some initial pointers. If you had any further points on where to find evidence that easily disproves the two papers by Zheng I referred to, that would be nice to know about, because his papers look pretty sound on an initial read. Zheng uses the phrase "reasonable tired light theory" -- so I infer he is aware that some tired light theories are unreasonable. I wish Zheng had been more explicitly to differentiate what he felt was reasonable vs. unreasonable (any guesses anyone?).

    I'll be interested to try to understand your assertion that, "Superluminal expansion is not inconsistent with special relativity, because no object is moving faster than light in any observer's inertial reference frame. No one is "catching up to a light beam." There is a dicussion of this in this paper:", because as I think of it, my reference frame extends to infinity as does yours (is that true? maybe my assumption is false), and if so then surely any galaxy at a distance of c/H or greater away from me (where c is the speed of light and H is the Hubble constant) will -- according to the expansion theory -- be going faster than light in my reference frame, no? That seems like some rather simple math that would be hard to get around with some fancy theory ... but I am probably missing something, and I haven't yet read your references on that, which I look forward to doing (but if you could manage a simple explanation for your statement, rather than needing to go to the references, ... or is it too complicated to put in a paragraph or two? Thanks!).

    The Hilbert Hotel image on the Big Bang is a new one for me, that I'll have to see what others have said about it. Many people take issue with the Hilbert Hotel "paradox" because it seems to permit adding more to infinity ... which on the face does seem a bit problematic ... and I would suspect that people would have made similar objections to the Big Bang theory then along the same lines (have they?) ... that if the universe suddenly came into being at the time of the big bang and already filled all space, that it wouldn't have any room to expand into!!!!

    Your help is immense, Mentor, thank you. Do you happen to recommend which research scientists or theoreticians or papers presenting the strongest case against big bang or expanding universe? It's sometimes good to look at various perspectives to see which portions of the argument of each seem to have the greatest integrity. So much to learn. So little time!
     
  11. Nov 9, 2013 #10
    Marcus, I do have questions regarding the Table.

    Question 1: If I understand the Table correctly, Row 1 says that Galaxy X (“GX”) and Earth Stuff (“ES”) were separated from each other by a distance of 2.6 Gly when the U was just 473 million years old. Is it accurate for me to say, therefore, that when T = 0, the distance between GX and ES also had to equal zero?

    Question 2: Assuming your answer to Question 1 is yes, is it also accurate for me to say that within a mere 473 million years, a phenomenon cosmologists call “Expansion” caused GX and ES to become separated by a distance of 2.6 Gly?

    Question 3: Assuming your answer to Question 2 is yes (and Reed, this may be germane to your post as well), is it correct for me to conclude that the rate of expansion between GX and ES is not the result of these two objects moving away from each other at a speed greater than c but by the creation of space (“Space Creation”) between these two objects such that light traveling at c takes longer to get from one point to another? I believe that you or somebodies like you who loves to teach others analogized the concept of Space Creation to a jogger who is able to run at a constant speed of 10 miles per hour. Even though the distance between the points of start and finish is 20 miles, it nevertheless took the jogger 24 hours to get to the finish line because he was required to spend time running (at 10 mph) on a tread mill resulting in him needing 24 hours to get to the finish line whereas he would only have needed 2 hours to do that if he was not hampered by the tread mills.

    Question 4: Assuming I am understanding the Table correctly, the rate of expansion between GX and ES went from 2.6 Gly when U was 473 million years old to 5.8 Gly when U was 4.4 billion years old, i.e., an increasing rate of expansion. Am I correct in concluding that a deceleration thereafter occurred as shown by the following row which says that the distance between GX and ES was 5.650 Gly when T = 5.4225?

    Question 5: Assuming your answer to Question 4 is yes, can you please explain what phenomenon caused the deceleration?

    Question 6; I know that I may now be off-topic but if your answer to Question 4 is yes, I was under the impression that the Universe was expanding (perhaps caused by the presence of dark energy). If that is so, how can the deceleration discussed in Question 4 be reconciled with an observed rate of an expanding Universe?

    Marcus, I have other questions but before I get too far afield, it would be great if you answer the ones I have framed.

    I am still assessing the posts given by Cepheid and others to this tread.

    Thanks!!!!!!!!!!
     
  12. Nov 9, 2013 #11

    Drakkith

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    I prefer not to think in terms of "new" space being added, but instead think of it in terms of increasing distance between everything.
     
  13. Nov 9, 2013 #12
    I am aware of no mechanism ever observed with such capability. Can you help me there?

    Whether or not augmented space comes diffusively or at the perimeter, conservation of space seems at issue with big bang (Hilbert Hotel). But that doesn't mean there is a problem if space isn't conserved. Is there a mechanism or evidence where space is not conserved?

    There has been one line of thinking surrounding the various levels of physical observations being emergent from other levels (with infinities in between) whereby recursive mathematical forms (fractals, more or less) may populate all levels of space. If mechanisms were all dependent on such relationship, then any oscillation in the underlying generator functions could be imagined to produce spatial nonconservation. While I have read some theories of fundamental fractal physics, they are likely far from any mainstream physics, and I am not sure where either has offered any mechanism description for expansion (but I am suspecting there are mechanistic descriptions somewhere, I have not spent very much time at all looking). Unless one gets to either mathematical theory or mechanistic description (the two can be rather equivalent, especially once at a small enough scale) it is hard to imagine any reasonable differentiation between space expanding and objects moving -- the effect then perhaps being indistinguishable, there has not been any dealing with the issue of big bang conflicting with faster than light motion, no?
     
  14. Nov 9, 2013 #13

    Drakkith

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    The two effects are indistinguishable as far as I know. And no, FTL due to the expansion of the universe doesn't conflict with anything. The recession velocity of an object can be anything, even far beyond c, as there is no global speed limit in GR, only a local one.
     
  15. Nov 9, 2013 #14
    What doesn't make sense to me about that is that local and global are a continuum in the sense that there is no definitive defining point beyond which the state "local" is no longer "local".

    So to me it does not compute to say that "around here things can't go the speed of light" but that "over they they can go the speed of light", because over there is really no different than around here, because "around here" is in this place (0) or a step away (1), or n+1 for any n already in the set, so "around here" extends indefinitely in any direction.

    It seems a false pretext to posit speed limits nearby but no speed limits further away, or to posit that far away and nearby are somehow different in their fundamental potentiality for certain phenomena (all other things being equal). Could you fill me in on how to get around that without inconsistency? Else one is left with the conflict, it would appear, that Aboro has asked about, no?
     
  16. Nov 9, 2013 #15
    Cepheid, you say that "It hadn't already reached "Earth stuff" billions of years ago. The light from the most distant objects that we can see has only just arrived (for the first time). It has had only just enough time to reach us given the age of the universe."

    --- it seems to me that your response can only be understood if one assumes that an expansion of the Universe occurred which therefore caused the light from Galaxy X, i.e., the galaxy we recognize today as the most distant object, to reach us today. Without the concept of expansion coming into play, it seems to me that the first light from Galaxy X reached Earth Stuff about 13.5 billion years and therefore out telescopes would not be able to capture that first light since it is now billions of years past us. Am I missing something?. that "first light" is now billions of light years beyond us and is not capable of being seen by our telescope agoexplaination nt objects had to have reached Earth Stuffthe instant the Universe came into existence. Without expansion at inception,

    You also say "How is 10 *billion* years not enough time for earlier stars to be born, live, and die?
    Perhaps you are thinking of the fact that since the estimated lifetime of our sun is 10 billion years (5 billion of which have already gone by), this would allow for, at most one generation of stars prior to the present one? There are a few things to keep in mind:

    - one generation of stars would still have produced heavy elements
    - there was, in fact, more than one generation of stars prior to the present one. Not all stars have the same lifetime. Stars more massive than our sun live for much shorter times (hundreds of millions of years or less). And these more massive ones are the ones that explode as supernovae, producing the heaviest elements and spreading them out widely.
    - The first generation of stars, which astronomers refer to as "Population III" stars, would have been different from the ones that are forming now. Because they would be made from raw materials that have *no* heavier elements (only hydrogen and helium), it is actually expected from theoretical models that they would be able to achieve higher masses and hence be much shorter lived."

    -- Thanks, Cepheid, for framing the issue this way. You are correct when you say I was erroneously assuming that all stars have a life expectancy similar to the sun. They don't.
     
  17. Nov 9, 2013 #16
    Drakkith, assuming that 2 objects are not moving relative to each other, what is the difference between the creation of new space between these 2 objects and the "increasing distance between everything." It seems to me that these two concepts are the same. Am I missing something from your explanation?
     
  18. Nov 9, 2013 #17
    -- Cepheid, it seems to me that Reed's comment (which I also share) begins to make sense only if we take into account the creation of new space that is forming between two distant objects such that the laws of motion and light speed are valid for conditions existing in or near that object but break down or become inapplicable when the two objects are assessed relative to each other.
     
  19. Nov 9, 2013 #18
    Drakkith, please ignore my query in post # 16. You answered that question in post # 13.
     
  20. Nov 9, 2013 #19
    ... and if the space is expanding throughout space, then 1 angstrom away could also be not local and have faster than light motion ... no? (i.e., expanding universe, to me, seems not to hold up to scrutiny without some deeper and more fundamental and described mechanism ... it seems like a story to patch up observations in physics for which no good story has yet emerged ... which is why I've been inclined to look at Zheng's work, et al., for alternative explanations without what seem to be the problems attendant to expanding universe/big bang theory ... but N.B., I am no expert in these areas)
     
  21. Nov 9, 2013 #20

    cepheid

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    I added an "ago" to your quote. Did you mean to have one there? If not, then I do not understand the sentence.

    Let's simplify the situation. Let's suppose that the universe is finite in age (13.7 billion years) but it is static, rather than expanding. Let's suppose also that that it is infinite (spatially), meaning that it has no boundaries. So all the matter (and space) in the universe somehow came into being 13.7 billion years ago, and formed into galaxies "shortly" thereafter. These galaxies are all (more or less) at fixed distances from each other (ignoring small local motions through space due to gravitational interaction). So, you're wondering, how could we only just be receiving the "first light" from Galaxy X now when it has had almost 13.7 billion years to reach us? Shouldn't the first light have long ago reached the location where Earth is now? Answer: it depends how far away Galaxy X is in this hypothetical static universe. If Galaxy X is only 3 billion light years away, then obviously its light first began to reach Earth long ago (only 3 billion years after the beginning). The light from it that is just arriving now left 3 billion years ago. So we are seeing that Galaxy as it was 3 billion years ago, not how it was when it first formed. On the other hand, if Galaxy X is now 13.7 billion light years away, then light from the clump of matter from which it formed is now only *just* arriving today. If Galaxy X is 40 billion light years away, then its light still hasn't reached us, and we cannot see it. So, in this hypothetical static universe, there is a sphere of radius 13.7 billion light years centred on us that contains everything we can see. We cannot see beyond this distance, because light from objects at those farther distances have not yet had time to reach us in the age of the universe. We call this volume the *observable* universe. And the really cool thing about it is that the farther out into the observable universe that you look (in distance), the farther back in time you are looking. You see images of nearby objects as they were recently. You see an object half-way across the distance of the observable universe not as it is now, but as it WAS at the halfway mark of the history of the universe. You would see an object right at the edge of the observable universe as it was right at the beginning of time.

    The real situation in our expanding (not static) universe is similar to what I described above, except that the radius of our *observable* universe is even larger. It's some 46 billion light years, even though the age is only 13.7 billion years. The reason for this is that the universe is expanding. So: consider light from Galaxy X that is only just reaching us now for the first time. When that light left that object, it's formational clump and "Earth stuff" were very close together indeed. But the *present* distance of that object is very large, due to the expansion. So, there is no longer as obvious a relationship between the time it has taken for light from an object to reach us (for the first time) and its distance. I think these are the kinds of ideas marcus was trying to familiarize you with with his table. Defining distances to objects in an expanding universe is tricky. At least, you have to consider the distance of the object then (when it's light first left), the distance now (when the light first arrives) and the distance you would infer from the light travel time, which is not the same as either of the other two.

    Have you read the Cosmology FAQ thread on "faster than light" expansion? It's the fourth link I put in post #8.
     
    Last edited: Nov 9, 2013
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