Number 379 (Story #3), June 25, 1998 by Phillip F. Schewe and Ben Stein THE MOON WAS THE FIRST OBJECT OF PURE SCIENCE, according to Martin Gutzwiller of IBM (gutzwil@watson.ibm.com). The Babylonians (c1000 BC) recordedthe comings and goings of the Moon arithmetically without understanding the geometry. The Greeks (c200 BC) went further; they viewed the solar system as sitting in an immense vacuum surrounded by the fixed stars. But even the clever Greeks knew nothing about the underlying physics of the solar system. This fell to Newton (1687) in the "Principia," and the 18th century mathematician/physicists such as Laplace. These thinkers proposed the principle of universal gravitation and tried to check it out on the complicated Moon-Earth-Sun system. The study of this oldest of three-body problems is the true subject of Gutzwiller's article in the April 1998 issue of Review of Modern Physics. In many physics problems, the dynamics of two interacting bodies (a planet and a star or two electrical charges, say) is easy. Add a third body and things get complicated, indeed chaotic, which is why Newton and his 18- century followers were largely stumped in their efforts to nail down the Earth-Sun-Moon dynamics. Gutzwiller compares the study of this problem with the history of particle physics: the amassing of cross sections, branching ratios and other particle properties (the kinds of things published in tables) corresponds to the "Babylonian phase," while the advent of the standard model represents the "Greek phase." The third, or Newtonian, age, in which the masses of the quarks and fundamental parameters such as the fine structure constant will be explained, has not yet arrived. (For a study of the 3-body problem with ions, see Update 372)