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BB Theory vs. Theory of Evolution - which is more thrustworthy?

  1. Mar 24, 2009 #1
    Personally I regard the ToE as a fact, but is the BBT just as much of a fact? Can we trust both theories 100%, or are there gaps that need to be filled first?
  2. jcsd
  3. Mar 24, 2009 #2
    The big bang theory successfully explains empirical observations such as Hubble's law, and made very accurate predictions with regards to (for instance) the abundance of primordial elements or the cosmic microwave background fluctuation spectrum, which beautifully agree with the observations. There is no serious evidence to doubt the general ideas presented by the big bang theory, although some details of the specific implementation into models are not fully clear. The way I see it, this is the case with most scientific models : they will powerfully simply encode a wealth of observed trends in just a few ideas, but when you go to the tiny structures, you will also always find specific examples which we do not understand well enough yet.

    For both theories, there are quite a few things to work on, but it does not imply that the principles are wrong, it is just an expected feature of such general models.
  4. Mar 24, 2009 #3
    What is it exactly that is certain, and what is not? Is it for instance not worth doubting that the universe expands?
  5. Mar 24, 2009 #4
    Nothing is ever "certain", and the general question is extremely vast.

    First, not questioning the theory part, there is a likelihood for its parameters to be within certain error bars given comparison with data. For instance (a very elementary example), there is a very high likelihood that the Sun will rise tomorrow (calendar date) between 5 am and 10 am (silly example), and there is a very small likelihood that it will rise between 7:00:01 am and 7:00:02 am (GMT), if you integrate this over all Earth. Those likelihood being what they are, there still is negligible doubts that the Earth will still orbit around the Sun tomorrow. So a theory, even if not proven false, at best only has a domain of validity with a range of possible values for its parameters.

    Second, there is no such thing (or we do not know of such a thing) as "the absolute likelihood for a theory given data". That from a pure logical point of view forces one to give up on the possibility to have an objective measurement of validity of a theory given data, only because we have no clue as to what the set of all possible theories is, even less how we could "measure it". For instance, it still is possible that the world out there is just a set up designed to test the development of intelligence, and how long it will take us to figure it out. To make it short, there is a likelihood for an agreement between data and theory, but not for a theory itself given data.

    The above two points are just fundamental statistics. The points below are more related to the applications of classical and quantum statistics.

    Third, you have two sorts of intrinsic randomness beyond those two first points, even given the perfect theory and the data with its error bars. One is classical chaos the second is quantum indeterminism. Classical chaos lets us know that Nature can conspire to ruin our models any point in time. If only the positions of the 8 (or more) planets run into an unstable configuration point, it is possible that the Earth be ejected from the system, and although we know by simulation that this is reasonably unlikely, we also know that we could not predict it on very long scales. Classical chaos would go away if we could have data without error bars and perfect computational power (which in classical physics is not possible in practice, but still possible in theory). However, quantum indeterminism finally lets Nature do really crazy things, with even less likelihood, but way wilder in principle. We may be talking about negligible probabilities over time longer than the age of the Universe, and volumes larger than its volume, but remember, once it has happened it does not matter anymore that it was unlikely ! And it happens constantly at small action scales, like inside nuclei, or at very short distances for very light objects.

    Most probably it is not worth, this being a personal opinion given with all the above commentaries ! There has been numerous attempts, and there are still some, to alternate theories to the big bang expansion, but none of them had the simplicity and the elegance necessary. The evidences for the big bang make it really difficult to build an alternative model.

    Is it worth doubting that the Earth orbits around the Sun ? It was worth searching for alternate theories of gravitation before Einstein, and it can arguably bring questions as to "who orbits around whom ?", but that was not obtained by questioning the motion of the Earth itself. By the same token, it seems to me that were we to find a new theory significantly different from the big bang model and superseding it, it would not come to us by questioning the big bang itself, but maybe by questioning more fundamental question, such as "what is the correct theory of quantum gravity ?". Even maybe progress in this last question will come from somewhere else too actually !
  6. Mar 24, 2009 #5
    Then shouldn't it be FoE?
  7. Mar 24, 2009 #6
    Lol, I don't buy that.
  8. Mar 24, 2009 #7

    I hope you were being funny, as anyone who uses the phrase 'Fact of Evolution' with conviction should be taken to a hole in the ground and have a building dropped on them.

    I really really hate how people mistake facts and theories.

  9. Mar 24, 2009 #8
    Well, its only called a theory as it is the highest form of proof possible without use of mathematics, i.e. the definition of theory. Hence, it isn't too far off to say fact of evolution.

    After all, at a cellular level, evolution has been *observed* directly. Its just that at the large scale of human beings and complex animals the timescale of evolution is much, much slow.
  10. Mar 24, 2009 #9
    When people say Fact of Evolution they mean to imply that


    Theories explain facts therefore it cheapens them to say 'fact of anything that is a scientific theory'.

    In that case why is it not 'fact of gravity' 'Atomic Fact'.
  11. Mar 24, 2009 #10
    Oh I see what your trying to say. Thats fair enough then why you think fact and theory should be distinguished.

    But all in all, just because evolution is called a 'theory' doesn't disprove that it *does* happen.
  12. Mar 24, 2009 #11


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    Staff: Mentor

    Slight correction: you can't regard a theory as a fact. Evolution is an observed fact. The theory of evolution is not.

    This may help answer the question....
  13. Mar 24, 2009 #12


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    Staff: Mentor

    No, people say "only a theory" when they are trying to cheapen it. No one is trying to cheapen it here, they are only accidentally mixing the very real issue of the fact of evolution (which is observed) vs the theory of evolution (which is the explanation of the fact).

    This would be like confusing the fact of gravity with the theory of gravity.
  14. Mar 24, 2009 #13
    Evolution is a fact and a theory.
  15. Mar 24, 2009 #14
    Is the expansion of the universe an observed fact?
  16. Mar 24, 2009 #15
    Yes I know its both and that's not what bugs me. When used in the correct context its fine. Its when people use the phrase:

    'Fact of Evolution' combined with a phrase like "i've never seen in textbooks..." "why isnt it called..."

    Its either deliberately (in in some cases a lack of understnding) coming to the misleading statement that 'theory' is akin to 'crackpot idea'

    I also really hate it when people mess up lend and borrow.
  17. Mar 24, 2009 #16
    Does it make sense do believe in both evolution and creationism?
  18. Mar 24, 2009 #17
    I recently saw a chemist on the telly who didn't believe in evolution. I understand him to some degree, as the ToE didn't get along well with his personal faith personal experience. What I don't understand is that people can ignore evidence just because thwy don't want it to be like that.
  19. Mar 24, 2009 #18


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    Staff: Mentor

    Yes, it is. But if you are meaning to imply that the expansion of the universe is the big bang, well....

    The expansion of the universe implies a big bang but it is not the big bang. The big bang is a single event that happened a long time ago and cannot be directly observed. It is a prediction of a theory, not a fact.
  20. Mar 24, 2009 #19


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    Staff: Mentor

    That depends on what interpretation of "creationism" you use. What the word typically implies is wholly incompatible with evolution. You can, however, consider the creation story as an allegory (or something else), which would allow compatibility.
  21. Mar 24, 2009 #20
    So, in the same way as observed micro evolution suggests that humans have evolved from lower species, the expansion of the universe suggests that there was a big bang once?

    You can believe that God guided evolution.
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