Gravity




Cruise your radio dial today and try to  nd any popular song that

would have been imaginable without Louis Armstrong. By introduc-

ing solo improvisation into jazz, Armstrong took apart the jigsaw
puzzle of popular music and  t the pieces back together in a dif-
ferent way. In the same way, Newton reassembled our view of the
universe. Consider the titles of some recent physics books written
for the general reader: The God Particle, Dreams of a Final The-
ory. When the subatomic particle called the neutrino was recently
proven for the  rst time to have mass, specialists in cosmology be-
gan discussing seriously what e ect this would have on calculations
of the ultimate fate of the universe: would the neutrinos’ mass cause
enough extra gravitational attraction to make the universe eventu-
ally stop expanding and fall back together? Without Newton, such
attempts at universal understanding would not merely have seemed
a little pretentious, they simply would not have occurred to anyone.

a / Johannes Kepler found a
mathematical description of the
motion of the planets, which led
to Newton’s theory of gravity.

This chapter is about Newton’s theory of gravity, which he used

to explain the motion of the planets as they orbited the sun. Whereas