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Does cosmology have the answers?

  1. Feb 21, 2009 #1
    Armed with a mass of observations and mathematical equations cosmologists tell us that the universe started with a big bang and that its ultimate fate is,as yet,unknown.Fair enough but now the ordinary person in the street is starting to believe the big bang theory and that we will soon have a theory of everything, many blindly accepting this because they are told it is so.
    Do the cosmologists,physicists and mathematicians who put this information into the public domain really believe that they have the absolute immutable truth or do some of them, occasionally,suffer from niggling doubts?
    The big bang theory and every other theory we have are just that ,theories only and not necessarily truths and shouldn't this message,also, be passed more effectively into the public domain?
     
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  3. Feb 21, 2009 #2

    HallsofIvy

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    Of course. And what's really terrible is that the government hasn't warned people that the "theory of gravity" is onlythat and they might start floating off the planet at any moment!

    I think the difficulty here is with your interpretaton of the word "theory".

    I can't imagine anyone thinking that cosmology has "all the answers". It hasn't even asked all the questions!
     
  4. Feb 21, 2009 #3

    Fredrik

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    I suggest that this thread be moved to the philosophy forum. The OP's questions and misunderstandings have little to do with physics.

    Dadface, you don't seem to understand how the word "theory" is used by physicists. They wouldn't ever use the phrase "just a theory" except as a joke. A theory is a set of statements that can be used to predict the results of experiments. "The Earth is flat" and "The Earth is spherical" are both theories. It doesn't make sense to think of some theories as "true" and some as "false". They are all "false", but some theories are better than others, in the sense that they do a better job of predicting the results of experiments. Some theories are really good (e.g. general relativity), and some are really bad (the earth is flat), but none of the theories that have been discovered so far make predictions that agree exactly with experiments. (That's why I said they're all "false").

    It's also important to understand that experiments can only tell us is how accurately the predictions of the theory agree with the results of experiments. The only "facts" in science are statements of the form "Prediction A of theory B agrees with experiment C with accuracy D".

    When you understand the above, you will understand why the phrase "just a theory" is so silly. There's no higher form of understanding than the kind you get by finding a theory and determining the accuracy with which it predicts the results of experiments. A theory doesn't stop being a theory at some point when there's sufficient evidence to support it.

    One thing that isn't emphasized often enough about "the big bang theory" is that it's not really a theory. It's a set of predictions made by a theory. The theory is general relativity. We could be more specific and say that the relevant theory here is the assumption (supported by the observed large-scale homogeneity and isotropy of the universe) that the large-scale behavior of our universe can be described approximately by an exactly homogeneous and isotropic solution of Einstein's equation. Either way, the big bang should still be thought of as a set of predictions about the behavior of the universe at times in the past, present and future.

    We obviously can't test the predictions about the past directly (since we can't go back in time), but we can certainly test the accuracy of the predictions about the present. We can also indirectly test the predictions about the past. For example, if the universe was extremely hot and dense in the past, getting hotter and denser the further back we look, then there must have been a time when atoms couldn't exist for very long (because they kept getting smashed to pieces by high-energy collisions). At some point, the universe must have expanded and cooled to the point where atoms could remain intact, and at that time the universe must have become transparent to light. (When free electrons got tied up in atoms, they couldn't stop light as effectively as before). If that's what happened, then this light should still be flying around all over the place, and guess what, it is. See e.g. the Wikipedia article on WMAP.
     
  5. Feb 21, 2009 #4
    Frederick I have no misunderstandings at all regarding the thread I started and I am using the word theory as it is understood by the lay person and not the physicist.If you think this thread has nothing to do with physics then what else is it about?Why dont you read my question properly?
     
    Last edited: Feb 21, 2009
  6. Feb 21, 2009 #5

    Fredrik

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    You're asking if physicists believe that a specific theory is the absolute truth or if they have doubts. I don't see why you would ask that if you understand that a theory is never the absolute truth.
     
  7. Feb 21, 2009 #6

    atyy

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    "...the very early universe is not yet directly accessible to our instruments .... Any theory framed in a homogeneous, isotropic model must be treated cautiously. .... inhomogeneous models, but this is a very active field of research today." Schutz, http://books.google.com/books?id=qhDFuWbLlgQC&printsec=frontcover#PPA322,M1

    "In the times of Hubble (1920s and 1930s), these were the galaxies. In later times, ... the galaxy clusters took over. ... According to current beliefs, the elementary units of the universe should be groups of voids. These changes in the definition, adopted in order to save the assumption of homogenity ..."
    Plebanski and Krasinski, http://books.google.com/books?id=uG9sDiUZJ94C&printsec=frontcover#PRA11-PA235,M1
     
  8. Feb 21, 2009 #7
    Frederick I agree that every physicist should be aware that a theory is not necessarily an absolute truth but in my experience this is a message that is not ,in general, getting through to the layperson.
     
  9. Feb 21, 2009 #8
    As far as the field of cosmology is concerned, this statement should really be switched around, shouldn't it?

    Cosmology observations only deal with the past and there is no way whatsoever to observe the present. So the predictions (or assumptions rather) are really about what the universe is like in the present since there is no way to know for sure. The closest things we can observe (outside our local galaxy) are millions of years in the past.
     
  10. Feb 21, 2009 #9

    russ_watters

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    Then the laypeople need to pay better attention in middle school science class. If "the ordinary person on the street" wants to understand science, the basics of the scientific method are pretty straightforward - it's their choice to learn it or not. It isn't the professional scientist's responsibility to expend effort to teach people who have no interest in learning. That's not what they are getting paid for.
     
  11. Feb 21, 2009 #10
    There are plenty of people,in fact probably the majoritity, who simply do not have the time or the inclination to study the subject at the necessary level of sophistication and amongst that majority there are those who like to keep in touch with what is going on by reading popular ,non specialist magazines,or watching popular T.V. programmes.Are you telling me Russ Watters that those people should be told that they should have studied more whilst at school?
     
    Last edited: Feb 21, 2009
  12. Feb 21, 2009 #11

    russ_watters

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    Yep. But don't fret - if a 7th grader can learn it, so can an adult. It isn't hard. But they have to choose to learn it. No amount of effort from scientists can force someone to make that choice. If this was 7th grade, maybe we could force people to learn, but not for adults. For adults, they have to make the choice themselves.
     
  13. Feb 21, 2009 #12
    So you would tell an adult that he should have studied more whilst at school and if he doesn't get it your response would be that even a 7th grader can learn it.Nice one.
     
  14. Feb 21, 2009 #13

    russ_watters

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    Someone who half-reads newspaper articles about science is not coming in here making a serious attempt to learn. But yeah, when we occasionally get people here who make quarter-hearted attempts, I slap them. That's what they need. I'm not going to sugar-coat and spoon-feed it to someone who isn't going to put in the necessary effort, especially since the necessary effort is so very small. My time is more valuable than that and they get more benefit from the slap anyway.

    A quick anecdote: My dad is 65 and has two engineering degrees and a business degree. But he decided he wasn't getting enough out of our conversations about astronomy because his knowledge of the subject was a little thin. So for Christmas, he asked me for an astronomy textbook and now he's reading it cover to cover. That is effort. That is to be respected.
     
  15. Feb 21, 2009 #14

    atyy

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    Are you thinking about eg. the difference in tenor between Carroll's and Schutz's comments?

    http://blogs.discovermagazine.com/cosmicvariance/2006/08/21/dark-matter-exists/

    "However, general relativity is simply a theory of physics, and it must always be tested against observation. ...... The book is certainly not closed on new theories. If the dark matter particle is detected, much of the motivation to look at ideas like these will disappear. But if dark matter searches show that the required particles are not there, then scientist will take these theories much more seriously." Schutz, http://books.google.com.sg/books?id=...over#PPA404,M1 [Broken]
     
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  16. Feb 21, 2009 #15

    cristo

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    I disagree somewhat with Russ's opinion here, and I don't think that anyone slightly interested in science should be told to go and learn about it from textbooks. I believe that professional scientists should be, to some extent, responsible for disseminating their research to the average layman; or at least to those interested.

    I don't, however, see how the average layman would think that we knew the answers to everything as mentioned in the OP, since if we did there would be not point in continuing research, would there?

    That certainly is effort, but most people who are slightly interested in science are either unable to learn, or don't have the time. For example, I know a lot of non-scientists who are interested in cosmology and other theoretical physics, but don't have a hope in hell of being able to study it. I think it should not be forgotten that the average mathematics skills of a layperson amount to arithmetic, and most people have little to no knowledge of physics. This doesn't mean that they shouldn't be able to read about science, since most things lend themselves nicely to qualitative descriptions. They will never be able to perform calculations, of course, but they will get a general feel for what's going on, and the "wow" factor. I come across a lot of people who find out what I do and then go on to talk about a programme they saw on tv, or an article they read in the newspaper. They are never going to study a subject, but know enough to ask qualitative questions, some of which are pretty interesting. I don't think we should put such people off, in fact the opposite: we should encourage good popular science that reaches out to the average person on the street.
     
  17. Feb 21, 2009 #16

    russ_watters

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    I didn't mean to imply that we should be telling everyone to read from textbooks - otherwise there would be no point to this forum! Most people here have a genuine desire to learn, which is why they come here. And most people who don't have a desire to learn half-read news articles and don't come here anyway. But we do get a few people here who make such a small effort as to be unworthy of our time.

    Yes, threads like this really irritate me.
     
  18. Feb 22, 2009 #17
    It should probably not be within the remit of a forum like this to point out the limitations of theories unless specifically asked but it is something that science popularisers should consider more.It would be nice to hear occasional comments of the type referred to by atvy in his post above.I have known many people for whom big bang clashes with their personal beliefs but when I have stressed that it is a theory only they have gone away happy.
     
  19. Feb 22, 2009 #18

    cristo

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    What do you mean by "only a theory"? This just sounds like you're brushing it off. The standard cosmological model agrees with observations to an outstanding degree, and isn't "just a theory" in the same way that, say, string theory is a theory. I don't see why it matters what people's "personal beliefs" are. The laws of nature aren't going to abide by what someone does or doesn't believe in!!
     
  20. Feb 22, 2009 #19
    I don't understand why they'd go away happy. A theory in science is placed on a much higher pedestal than mere personal belief. I guess ignorance is bliss, right?
     
  21. Feb 22, 2009 #20
    Cristo I am not "brushing off" the theory and of course there is excellent agreement between theory and observations otherwise it wouldn't be a widely accepted theory at all.Remember that theories are informed by observations and that they must conform to observations and remember,also, that observations are severely limited, so what do we really understand?Are you telling nature what she should or should not abide by?
    matt.o.who placed science on a "much higher pedestal " than "mere personal belief".Could it be that some scientists have arbitarily elevated themselves as being sole owners of the truth?With the people I referred to previously I discussed the physics with them and made it a point to never get involved with what they believed in.I did ,however,respect that they had beliefs and I think they went away with some respect for the theory.
     
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