About 60 B.C. one of the world's great poets, Titus Lucretius Carus, wrote a
long poem in Latin hexameters preaching the Epicurian gospel of salvation
through common sense. The atomic model of Demokritos and Leukippos,
proposed five centuries before, provided the bases of the description of the
universe attributed to this "common sense." Lucretius gave to his poem the
title, De rerum natura, which can be translated as, "On the Nature of the
Universe." Directed nominally to his friend the Roman statesman Gaius
Memmius, the poem was written for all educated laymen of the time.

Neither Epicurean nor Poet, but with the advantage of two millenia of
scientific progress, I am attempting to address the same kind of audience with
a similar exposition. Writing in a less heroic age, I apologize for foresaking
the hexameter form, Latin or English. But, prose though it be rather than
verse, I follow Lucretius in requesting the reader to "lay aside your cares and
lend undistracted ears and an attentive mind to true reason."

In this book I have tried to present those basic concepts of particles and
fields and of space and time, as illuminated by modern physics, very much
as a professional physicist understands them. I believe that these concepts are
accessible to the nonprofessional--that which I can't explain to an interested
layman, I must not understand properly myself. Which is not to say the ideas
are so trivial that they can be understood by physicist or layman without the
"attentive mind" to which Lucretius refers.

By and large, there is little controversy in physics and hence there is little
that is controversial in the book. The exceptions, largely concerned with the
interpretation of quantum mechanics, are addressed in a spirit of "naive real-
ism" and operationalism, which represent my own views and which I believe
are not very different from those held by most physicists.

The text is nonmathematical, though on occasion simple relations are
expressed in algebraic forms that should be known to anyone with a high-
school education. Some more complex relations that seem to be especially
interesting are presented in the extensive set of footnotes. Though few of
these require mathematical sophistication beyond that taught in the first few
weeks of a high-school algebra course, mathematical simplicity does not
translate into conceptual simplicity, and these presentations will often require
careful and time-consuming thought. Once written, a book has a life of its

-v-