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Evidence for big bang

  1. Aug 9, 2007 #1
    I was arguing with someone who denies big bang cosmology. I presented him with the following evidences
    -Hubble's law
    -CMB
    -Abundance of helium
    -Existence of deuterium

    But apparently this did not convince him. Can someone point me in the direction of more evidences?
     
  2. jcsd
  3. Aug 9, 2007 #2

    Wallace

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    This book is a good explanation at a popular level.
     
  4. Aug 10, 2007 #3

    mathman

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    If someone doesn't want to accept the evidence for the big bang, there is not much you can do. Some people believe is the Genesis version of creation and no evidence otherwise will persuade them.
     
  5. Aug 11, 2007 #4
    His main arguments were that the laws of physics break down at t=0, so it is therefore false. Rubbish, of course. And that he is a "true atheist" since he does not believe in god or the big bang (apparently big bang is akin to genesis creation and atheists should not believe it).
     
  6. Aug 11, 2007 #5

    marcus

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    Well physicists brought this on themselves by making unclear statements to the public.

    In fact the theory of General Relativity DOES break down at t = 0.

    And it is the prevailing theory of gravity----and the geometry of space.

    that doesnt mean ALL the laws fail to apply---we dont know for sure which laws are applicable and which arent (all laws have some range of applicability)

    The classical Gen Rel theory IS NOT THE ONLY possible model for the geometry of space. There are quantized versions of cosmology which reproduce all the classical successes and also do not break down at t = 0, but they HAVEN'T BEEN CONCLUSIVELY TESTED YET.

    So your friend is right that GR breaks down. He is wrong to make a blanket that ALL laws break down. And the scientists who told him about GR breaking down SHOULD have told him that considerable progress is being made on fixing GR so that it will NOT break down. Quantizing the classic cosmological model so that it won't develop singularities.

    I tend to agree with Mathman that some people you just can't argue with.
    So you are cordially invited to hang out here at PF where there are quite a few people you can engage in reasonable discussion :smile:
     
    Last edited: Aug 11, 2007
  7. Aug 11, 2007 #6

    marcus

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    Well actually that kind of makes sense. If someone is a real stickler, he could object to classic bigbang cosmology because it breaks down at t=0.

    Reasonable people tend to forgive it for failing at t=0 because it does so remarkably well right back to, but not including, that instant. But this guy is not in the mood to be reasonable. So there is no way to satisfy him with the classic theory.

    but there IS theory in the works that goes right back to t=0 and into the timeperiod before that, and does NOT break down.

    You want something to cite as a reference. But if his objection is that the classic model breaks down then you can't overcome that just by citing more evidence that the classic model works back to but not including that time.
    You already gave plenty of evidence for it working for all t > 0.

    what you have to persuade him, I think, is that cosmological models don't HAVE to break down at t = 0, merely because the currently favored classic theory fails there.

    the failure of the laws of physics (that he talked about) is not a fact of nature, but is simply a failing of the 1915 GR theory (which predicts infinities at t = 0, infinite curvature and density---a nonsense context in which other laws cannot be applied)

    there are dozens of papers that have been published in professional journals recently about the quantized version, which does not break down but continues back (with a changeover from contraction to expansion). That is evidence that the laws of physics do not HAVE to break down.

    the fact that they happen to fail in the familiar publicized case is just an artifact
    of what model one choses to use. maybe that would make him wake up.
    if you want links to preprint copy of some quantum cosmology (QC) papers just say. much of what has been published in the past 2 or 3 years is available free online.
     
    Last edited: Aug 11, 2007
  8. Aug 11, 2007 #7
    He might just dismiss things that he does not understand. With a background in general physics, the existence of the following is not persuasive of big bang theory:
    What is so special about the CMB, abundance of helium, and existence of deuterium that he should believe in the big bang? Hubble's law may be consistent with the big bang, but by itself, it is not sufficient to reach big bang theory as a conclusion.

    I imagine that having more background in the field of cosmology would help me understand the argument for the existence of the big bang. For the time being, I can only accept it on faith.
     
  9. Aug 11, 2007 #8

    russ_watters

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  10. Aug 11, 2007 #9
    They can be understood, but the 1,000 word explanation and the typical hour long television show are not all that comprehensive. The idea is a lot to chew on. It just begs the question: Are you sure about all this? -because, on the surface it sounds a little bit crazy. It reminds me of the tribesman, completely detached from industrial society, who tried to provide an explanation for the source of tsunamis.
     
  11. Aug 12, 2007 #10

    russ_watters

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    I don't know why it would sound crazy. You have a simple choice: you can accept that people who have studied the phenomenea for decades aren't complete idiots or you can look at a concept, think it is crazy and think people who have studied it for decades are complete idiots.

    Seriously, how hard is this: The universe is expanding. So in the past, the universe must have been a lot smaller.

    It shouldn't be hard for even a layman to understand the significance of the four pillars of the Big Bang.
     
  12. Aug 12, 2007 #11

    Chronos

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    I prefer the T>0 explanation. Trying to explain time before time confuses me. The part after T=0 seems fairly simple.
     
  13. Aug 12, 2007 #12

    I will admit, I'm not in a very good position to argue with those who have studied it for decades. I might also be derailing this thread somewhat, I'm not sure.

    Back to the tribesman analogy. There are people living on remote islands in the Indian Ocean. They have no contact with industrial society. When one of these tribesman asked about the 2004 Indian Ocean Tsunami, he explained that the world sits on top of a giant tree. Something shook the tree and caused the water to roll out. The three swung back, and with it came a wall of water.

    When I think about it from his point of view, he has a very logical explanation. How could the ground shake if the world did not sit on top of a giant tree. Nothing else in his known universe can shake like that. The tree theory is also consistent with both the water rolling out, and the tidal wave that came back.

    I wouldn't stake my reputation on all this, but I have trouble discerning the quality of the logic behind the tribesman's tree theory of tidal waves and the physicist's big bang theory of origin.
     
    Last edited: Aug 12, 2007
  14. Aug 12, 2007 #13

    russ_watters

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    Even given the tribesman's access to data, there are no known trees strong enough to hold up the world. So that "theory" has a pretty obvious flaw that even the tribesman should see. His biggest problem isn't with what he doesn't know but rather with applying logic to what he does know.

    If you are having trouble following/accepting the logic, then I guess the place to start is with study of the scientific process/method, not with trying to understand actual theories.

    Still, I have trouble understanding why people can't see that Hubble expansion implies a big bang. It is such a straightforward piece of information and logical implication. Can you explain the trouble you have with this?
     
    Last edited: Aug 12, 2007
  15. Aug 12, 2007 #14
    The tribesman has reached a reasonable explanation. While you may see obvious "flaws" in his theory, there are comparable ones in the big bang theory. The problem with the tribesman's theory is that it is based on a limited knowledge of the universe. Like the tribesman, our knowledge of the universe is also limited. In fact, in the grand scheme of things, our knowledge of the universe might very well be approximately equal to his. As for Hubble's law, a 90 dimensional universe would provide for plenty of other explanations.
     
  16. Aug 12, 2007 #15

    marcus

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    two reactions
    1. what theory of gravity do you accept? for a lot of us, the evidence for GR (except where it develops singularities and does not apply) is persuasive. the precision with which it agrees with observation is impressive.

    but do you have an alternative model of gravity that you prefer?

    2. if you accept GR as a good approximation (except at the places it fails to compute) then some of what you say I find inconsistent.
    Because assuming uniformity (homog. isotrop.) seems pretty reasonable and, if you add that to GR, you get expanding universe solutions!

    So what's crazy? If you already accept GR, then you can't pretend to be in the position of a naive primitive tribesman who can't comprehend things. The expanding universe picture has to look pretty reasonable to you because it comes right out of GR.

    But you say:
    So I have to question your consistency, dimensionless. Are you who you say? You started out suggesting you have a "general physics background" and now you are shifting viewpoint and saying "think about the guy who watches an hour TV show, shouldn't he be skeptical?"

    Who are you then? Are you one of the great mass of clueless who watch science popularization TV? Or are you in part textbook-educated?
    Are you saying that an expanding universe picture seems crazy to YOU? Or are you worried about it seeming crazy to SOMEBODY ELSE?
    Could you be appealing rhetorically to the existence of a Homer Simpson, the average TV viewer, who may well find the science fare crazy but that's another issue. :smile:

    People like us at PF are obviously not responsible for whatever may be misleading or confusing on sci-pop TV, that really is a whole other issue which we can't very well address here. I for one do not watch TV and I don't have the necessary familiarity with it to respond cogently and discuss specific mistakes.

    The reason I ask you for some consistent self-definition is because we get a certain kind of anti-science termite-type visitor who uses POPULIST RHETORIC in the age-old know-nothing tradition of American politics and whose main agenda is to undermine science credibility.
    I'm not calling you one of them, I just want you to know this. I've met a bunch and their aim is not to learn but to discredit.
    And they often use a ploy of attacking the alleged HUBRIS of scientists. (whereas people in the scientific community must be humbly aware of limitations of knowledge since they deal with testable theories in a systematically skeptical way---statements are normally qualified by reference to the theory)
    The attack on science also uses the ploy of STANDING UP FOR THE unschooled LITTLE GUY, although the attacker rarely seems to be the little guy himself and it is doubtful that the little guy benefits in any way from the attack.

    So basically they come here and they engage in a subtle AD HOMINEM ATTACK against scientists in general (hubris, arrogance, egg-heads, big-brains, talking down to the little guy, pushing "crazy" ideas the little guy can't grasp, and all the faults of sci-pop TV programs...)

    It is a low-key persistent ad hominem attrition-war, and often people come in who use these ploys in a very gentle soft way---sometimes seem motivated by religion as if scientists are somehow infringing on theo-turf---often they seem to be asking US here at PF to explain or defend some vague impression that they or someone they know got from watching TV---often there is this Science is myth message which comes thru in your harping on the "primitive tribesman explaining the tsunami" story.

    I'd like to ask you to stop repeating and repeating reference to your "tribesman" story. Just forget it. If empirical science is a type of myth (which I doubt) then it is a coherent system of myths which has made thousands of fruitful predictions and is constantly being tested to the full extent possible.
    The comparison with primitive myth is propagandistic rather than informative. Instead of harping on your "tribesman" story, why don't you say what it is precisely that you want explained, and we can, if we choose, try to do our best to explain it.

    I am assuming you have a general physics background, as you seemed to indicate, and that you are NOT one of those people who consistently fan populist resentment of science.

    thanks,

    Marcus
     
    Last edited: Aug 12, 2007
  17. Aug 13, 2007 #16

    russ_watters

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    No. The tribesman knows darn well that there are no trees big enough to hold up the Earth. If he doesn't, then he just plain isn't thinking.
    Such as?
    No. He has plenty of knowledge to know his "theory" can't be right.
    I've never heard that - can you explain it?
     
    Last edited: Aug 13, 2007
  18. Aug 13, 2007 #17
    The Earth shakes like a tree
    Nothing else in the world shakes the same way that a trees does
    Therefore,
    The Earth sits on a giant tree.

    We know of no place that is large enough to contain an expanding universe. You and I both know that. If such a place did exist, one could reason that it might also have trees big enough to hold up the Earth.

    I think what he is trying to do, is come up with the best explanation he can based on the available knowledge. This is the same process by which scientists came up with the big bang model.

    If there were 90 dimensions in the universe, then our perceived 4 dimensional universe might have some kind of interaction with the other 86. It's easy for me to imagine some process in the 86 that leaks Gaussian radiation into our 4.
     
    Last edited: Aug 13, 2007
  19. Sep 7, 2007 #18

    marcus

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    the time and temperature of de-coupling?

    my understanding is that decoupling preceded the origin of the CMB by hundreds of thousands of years.

    AFAIK the Microwave Background comes from the epoch of last scattering, sometimes called "recombination", ordinarily supposed to be around 380,000 years after beginning of expansion.
    ===============

    You wrote to Martin Rees the Astronomer Royal, as I understand. Did he write back saying that your analysis was correct? Or did he simply NOT reply that your analysis was incorrect? There is some ambiguity in your post about this.
     
    Last edited: Sep 7, 2007
  20. Sep 7, 2007 #19

    cristo

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    That is exactly what I was thinking, Marcus.

    Bernard, exactly which cosmologists did you send you work to? And did any of them reply and tell you that your work was correct? I note from your webpage that you studied at QMUL (presumably for a PhD?) I presume, therefore, that you sent your work to some of the cosmologists there. Did they tell you you were correct?
     
  21. Sep 8, 2007 #20
    To Correspondents on the Hot Big Bang Theory,
    I will try and answer all the questions raised.
    Yes, according to the Hot Big Bang Theory the Microwave Background Radiation is supposed to come from the epoch when the Universe changed from being opaque to being transparent, - recombination of protons and electrons to make hydrogen (I thought that the term "de-coupling" was also used for this epoch).
    By the way, this "Recombination" should yield the energy of ionization which is 1,318,000,000 joules per kg. The energy of ionization of helium is even larger! These are enormous amounts of energy, - many orders of magnitude greater than gravitational energy, but they are completely ignored by cosmologists. The straight line graphs of the (supposed) cooling of the Universe are wrong. This is more evidence that the Hot Big Bang Theory is fallacious.
    Yes, I did study Astrophysics at Queen Mary College, London, and I sent a copy of my paper showing that the CMB ought to have a "smeared spectrum" to Dr. P. Ade there; he did not reply.
    I also sent my paper to Prof. S.W. Hawking (Cambridge), Prof. P. J. E. Peebles (Princeton), Sir Martin Rees and many more.
    My past tutor from Oxford University and one other correspondent agreed that my analysis is correct.
    None of the others replied except Sir Martin Rees.
    He replied that the "entropy is overwhelmingly in the radiation and not in the hydrogen". I did some more calculations - following his line of thought, and I showed that it did not really work. I sent my calculations to him but he did not reply a second time.
    In summary, so frequently cosmologists use "hand-waving arguments" to support the Hot Big Bang Theory without actually putting in numbers and doing the calculations.
    The point is that matter has properties, - pressure, temperature, density, internal energy, enthalpy, entropy, energy of ionization and energy of combination (atoms of hydrogen to molecules). These need to be evaluated and used in rigorous calculations; this I have done, - but cosmologists haven't.
    By the way, the original correspondent, who raised the question, and who used the helium content of the Universe as evidence for the Hot Big Bang Theory, is now on shaky ground. Latest observations show that the helium content in distant galaxies is not what the theory demands.
    Bernard R. Bligh.
     
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