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PARTISAN REVIEW
just as the pitch of a train whistle falls as the train recedes. The shift
in the frequency of light, toward the red, is in a measure propor–
tional to the distance, a fact known as Hubble's Law . Third , the
universe is found to have a remnant of an explosion at the beginning
of the universe , the big bang, that set off the expansion-a small but
uniform background radiation, a noise underlying every human
signal measuring 2.7 degrees above absolute zero.
This discussion recalls the challenge at the opening paragraph
as well as related challenges . A major unanswered question is
whether the mass of the universe is great enough that the force of
gravity will eventually stop the expansion and cause a contraction
resulting in a big crunch. The alternative is for the universe to con–
tinue expanding forever. One possibility, if the big crunch is our
fate, is that we are a part of an infinite cycle of bangs and crunches .
Another especially interesting idea, proposed by Ed Tryon of
Hunter Colege, is that the universe is a state created out of nothing.
The evolution of the early universe, then, has been explained
on a qualitative level by big bang cosmology, which supposes an in–
itial explosion of a singular configuration signaling the beginning of
the universe. We would like, though, to understand more specifical–
ly the formation of galaxies , the distribution of elements and the
nature of the elementary particles in the universe . We are interested
not only in why there is something rather than nothing, but also in
why there is the specific something that we see around us . An idea
that has been vital in our approach to this question, an idea that ap–
pears vital to much of physics , is that of symmetry .
Many problems that might at first seem intractable can be
dealt with by making use of the available symmetry . For example,
one might ask if there is a stable point for a marble on a merry-go–
round. By symmetry , there can be only one possibility : the center.
If
the marble goes anywhere else , the configuration plus merry-go–
round will change as the merry-go-round turns ; the process of
rotation does not leave the confiEWration invariant.
If
the marble is
placed at the center, however, thei>configuration is left invariant by
rotations .
It
therefore possesses rotational symmetry. That is to say,
the invariance of the configuration under rotations implies a rota–
tional symmetry . Symmetry considerations have reduced the
calculation to a trivial observation.
The notion of symmetry is at the heart of many of the matters
discussed here. It is crucial not only to the understanding of physical
laws, but also to the philosophical setting we have suggested.
