Subatomic Physics

Chapter 19
Nuclear and Particle Astrophysics
The most incomprehensible thing about the world is that it is comprehensible.
Albert Einstein
The marriage between elementary particle physics and astrophysics is
still fairly new. What will be born from this continued intimacy, while
not foreseeable, is likely to be lively, entertaining, and perhaps even
beautiful.
M. A. Ruderman and W. A. Fowler (1)
For millenia, the stars, Sun, and Moon have fascinated humans; their properties
have been subject to much speculation. Up to a short time ago, however, observation
of the heavens was restricted to the very small optical window between about 400
and 800 nm, and mechanics was the branch of physics most intimately involved in
astronomy. In the last century, the situation has changed dramatically and physics
and astronomy have become much more closely intertwined. In this chapter, we
shall sketch some of the areas in which subatomic physics and astrophysics are
linked.
19.1 The Beginning of the Universe
O God, I could be bounded in a nut shell and count
myself a king of infinite space, were it not that I
have bad dreams.
Shakespeare, Hamlet, Act II, Scene 2.
In 1929 Hubble observed that well-known lines in the spectrum of gases (e.g.
Hydrogen) from stars in galaxies were shifted towards the red. Hubble was able
1 M. A. Ruderman and W. A. Fowler, “Elementary Particles,” Science, Technology and Society
(L. C. L. Yuan, ed.), Academic Press, New York, 1971, p. 72. Copyright c○ 1971 by Academic
Press.
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