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parallel through both music and astronomy. It is a bridge connecting the
two disciplines.
Twentieth-century physics also makes use of this "esthetic bridge."
In the late 1920s, shortly after the birth of quantum mechanics, a young
English physicist, P.
A.
M. Dirac, formulated an equation describing the
movement of the electron. One of the most important conclusions of his
elegant equation was that there must be a perfect symmetry between
positive and negative charges in nature. This meant that since there was
an electron which carried a negative charge, then there must perforce
exist a corresponding positively-charged particle and, furthermore, that
the masses of the two particles must be identical. However, although
there was already ample evidence at the time of Dirac's result that the
amount of positive and negative charge in nature was the same, the vari–
ous positively- and negatively-charged particles did not seem to meet the
symmetry requirements of the Dirac equation. There was enormous dif–
ference between the mass of the negatively-charged electron and that of
the positively-charged proton. For this reason, some physicists at first did
not accept the Dirac equation, but Dirac himself and many others felt
that it was simply too beautiful to discard. Several years later a new par–
ticle, the positron, was discovered, and the characteristics of this particle
accorded perfectly with the predictions of the Dirac equation - in an–
other vindication of the faith in the beauty of nature's laws. The events
surrounding the prediction and subsequent discovery of the positron
prompted Dirac to recollect:
I think there is a moral to this story, namely that it is more important
to have beauty in one's equations than to have them fit experiment..
. . It seems that if one is working from the point of view of getting
beauty in one's equations, and if one really has a sound insight, one is
on a sure line of progress. If there is not complete agreement between
the results of one's work and experiment, one should not allow one–
self to be too discouraged, because the discrepancy may well be due
to minor features that are not properly taken into account, and that
will get cleared up with further developments of the theory.
That is to say, accordance with experimental observation is not the
only standard for the value of a scientific result. It is for this reason that
physics journals do not balk at printing results that are at odds with pre–
vailing experimental evidence.
In 1954, C. N. Yang and his partner Robert Mills wrote a paper
on gauge symmetry that contained results completely at odds with ex–
perimental evidence. According to their theory, there had to exist a par–
ticle with a rest mass of zero, but
all
experimental evidence had
