From: crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass)
Newsgroups: sci.physics
Subject: Re: Axiom of Physics
Date: 27 Aug 92 00:47:24 GMT
Distribution: na
Organization: University of Virginia

In article <mcirvin.714873508@husc8> mcirvin@husc8.harvard.edu (Mcirvin) writes:
>crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
>
>>In article <25781@dog.ee.lbl.gov> sichase@csa3.lbl.gov writes:
>>>
>>>Eventually, one hopes that all axioms undergo direct experimental test,
>>>verifying the fundmental assumptions of the theory by direct confrontation
>>>with reality.  At that point, I suppose they loose their status as axioms
>>>and become experimental facts.
>
>>    I am not sure that the differentiation between an 'axiom' and
>>    an 'experimental fact' (say the fact that we have never seen anything
>>    have true speed greater than c for example) is very fruitful.
>
>I think it is fruitful, but not quite in the sense Scott is using.
>Axioms live in theories, whereas experimental facts live in the real
>world, or our measurements thereof.  The constancy of c is usually
>taken as an axiom of relativity; certainly Einstein treated it that
>way.  But it's also an experimental fact, in the sense that there is
>a lot of evidence for it.  If it were proven beyond all doubt by some
>sort of experimental omniscience, that wouldn't change its status
>as an axiom of relativity.  One could still construct a completely
>different theory with a different set of axioms, though it would
>be wrong as a description of reality.

    My point was that when you are discussing the foundations of a given
    theory, the 'experimental basis' and the 'axioms' are probably
    indistinguishable (though often which axioms apply is debatable).  
    There are, in another sense, experimental facts that are not axioms 
    and axioms that are unrelated to experiment, but in the context of the
    foundation of a physical theory, an experiment that forms an assumed
    basis for a theoretical construction is an axiom.

>To speak of "axioms of physics" is to create the wrong impression
>that physics has one unified, unchanging theoretical edifice.  Axioms
>of specific theories, on the other hand, surely exist, though which
>theoretical facts are the axioms often depends on whom you talk to.

    I do not know that this is true, any more than the assumption that
    mathematics has a single unchanging theoretical edifice based on 
    its admittedly more rigourous use of the term 'axiom' (my usage:
    postulated assumption that underlies a given theory).

    I also do not necessarily think of the axiom -> theory model
    when discussing physical theories since most arise in a more
    roundabout fashion.  However, this does not necessarily invalidate
    the conception that axioms (of experimental nature or not) underlie
    all physical theories.  Though, as you have stated, the axioms
    are often not unique and can be the subject of heated debate.

                    
                                 dale bass


-- 
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926