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The Big Bang!

  1. Dec 16, 2009 #1
    I know the topic is incredibly original, but I was just curious as to how many people genuinely accept this as a feasible explanation for the creation of the universe. Personally.. I think (at least for a long time) that there is no way of knowing. I don't like how mainstream this theory has become, and think that carelessly cramming it into society just because we don't have a better explanation is pretty irresponsible.

    I think it serves as a good base to build off of, and many aspects of it are logical, but the probability of this being true is just simply way too low for me to take seriously. It is repeatedly projected as fact. A good example is when History's "The Universe", a very mainstream series, says "In the beginning, there was darkness. And then.. bang" right at the beginning. You don't know that. I love that show, but the legitimacy of this theory is a stone's throw away from that of religion. Why is it being so flagrantly spewed from every book and media outlet as scientific fact?
  2. jcsd
  3. Dec 17, 2009 #2


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    Big bang was built from straw and mud made into bricks, walls, buildings and cities. It is not trivial or contrived, rather the direction that many disparate observational parts have led over the last century. I dont know of any scientist who claims it is any more than our best guess. Nothing is certain aside from uncertainty.
  4. Dec 17, 2009 #3
    Yea, I don't have a problem with it as a general outline, but one time too many have I seen some physicist on PBS or Discovery or whatever start to go into excruciatingly minute details like "in a one millionth of a trillionth of second, the universe multiplied by six trillion billion". Just shut up old man, you're nuts.

    I'm not saying that rational people who accept the big bang as a very broad concept (myself included) are wrong to think so at all. It's just when I see crap like that, I become a little agitated.
  5. Dec 17, 2009 #4


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    It's a (very common!) misconception to take the Big Bang as an explanation for the creation of the Universe. It is not. It is part of a model for our Universe that is valid ( as in, it is supported strongly by hard data) from today, tracing back in time for about 13-14 Billion years. The theory can tell us what the Universe was like back that far in time. Beyond that we simply don't know (at least not with any certainty at this point). Maybe 'time began' not long before the further point in the past that we can know about with certainty, maybe it didn't.

    There is quite a gap between the scientific theories behind what you'd call 'the Big Bang' and some of the very very common misconceptions/misinterpretations.

    Don't be like that. You think there's no way of knowing? Why not trying and understand why we think what we do, why not look at the evidence we base this on? I'd say ignoring that because you might not like the implications is what is irresponsible!

    From whence did this 'too low' probability emerge?

    Without going into the details of epistemology, in Science nothing is a 'fact' in the way that it is used in say the legal profession. Every piece of knowledge has an uncertainty attached to it, and the more hard evidence supports that peice of knowledge, the smaller the uncertainty. There are certainly aspects of the model we have for the Universe that have very low uncertainties; The Universe is almost certainly expanding, and has been doing so for as far back as we can see. That means it must have started out from a hot dense state. We have a fair idea of what went on during this very hot dense phase, but the uncertainties about that part are somewhat larger than other parts of the theory.

    None the less, we have good evidence for our best guess about what went on in this phase. We could be wrong, but you'd need to show why a different model was better supported by the data if you didn't like it.

    I can't answer for whoever made that doco, but that description is wrong. At least its a description that is not supported by evidence. We don't know that there was darkness and then a bang. That's a misunderstanding of the theory.

    Oh please, how is something built carefully on evidence over many decades, something that has changed and morphed in response to new evidence many times, and that is still changing today as new evidence emerges 'a stones throw' from dogmatic unchanging belief in ancient mythology?

    See early comments re:"fact". But the only reason why modern cosmology theory is presented in most media outlets is because that's our best guess, well supported by evidence, that we have. What is your alternative? That we devote 'equal time' to this and some random other fairy tale in the interest of balance?

    I really don't see what your problem is here.
  6. Dec 17, 2009 #5


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    Just to clear this up, here is the scientific version (as opposed to the commonly stated pop-sci version) of modern cosmology (at least one part of it!).

    See attached image (I made this is response to a different thread a few days ago, but it's relvant to this discussion). This is a plot of the 'size' (a) of the universe, as a function of time, a(t). Note that this 'size' is a comparative, not absolute qauntity. The Universe could be infinite, in which case this a(t) tells you how much any given region expands over a given time period, in other words in makes sense in a ratio a(t_1)/a(t_0).

    In any case, this shows that starting from today (t=0) we can look back at the Universe and trace the expansion history finding that the Universe was smaller in the past, as shown schematically by the black line. As a(t) gets smaller, the Universe obviously becomes more dense. At some point, around 13-14 Billion years ago, the universe was so dense that our know physical laws breakdown and don't give us a sensible answer. At this point we don't really know how to go back any further (at least not now, but many people are working on this and progess is being made).

    This isn't really a huge problem, all it says is that our theory has a finite range of validity, it means we know an awful lot and the history of the Universe, just that we don't know everything.

    Now, a common mistake is to take the mathematical equations we have, and continue to take them all the way until a(t)=0, even though the underlying physics being those equations has stopped working. This extrapolations is shown in red. This is where the myth that 'the Universe began with a Big Bang' comes from; it's a false extrapolation that is unfounded in the scientific theory.

    On the contrary, anything could be true. The red line might be correct, but so could the aqua lines I've drawn it (for example), as could other possibilities. The point is we don't have a good theory, supported by evidence, to have any confidence in any of these. The only thing we have good evidence for is the black line.

    My hope would be that if you came back in say a decade, that there would just be a single black line on that plot. But that's not the case at this point, there is much we still have to learn about this part of the history of the Universe.

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