M ACHINES AND C LASSICAL M ECHANICS
There are four known types of force in the universe: gravitational, electromagnetic, weak
nuclear, and strong nuclear. This was the order in which the forces were identified, and the
number of machines that use each force descends in the same order. The essay that follows will
make little or no reference to nuclear-powered machines. Somewhat more attention will be paid
to electrical machines; however, to trace in detail the development of forces in that context
would require a new and somewhat cumbersome vocabulary.
Instead, the machines presented for consideration here depend purely on gravitational force and
the types of force explainable purely in a gravitational framework. This is the realm of classical
physics, a term used to describe the studies of physicists from the time of Galileo Galilei (1564-
1642) to the end of the nineteenth century. During this era, physicists were primarily concerned
with large-scale interactions that were easily comprehended by the senses, as opposed to the
atomic behaviors that have become the subject of modern physics.
Late in the classical era, the Scottish physicist James Clerk Maxwell (1831-1879)—building on
the work of many distinguished predecessors—identified electromagnetic force. For most of the
period, however, the focus was on gravitational force and mechanics, or the study of matter,
motion, and forces. Likewise, the majority of machines invented and built during most of the
classical period worked according to the mechanical principles of plain gravitational force.
This was even true to some extent with the steam engine, first developed late in the seventeenth
century and brought to fruition by Scotland's James Watt (1736-1819.) Yet the steam engine,
though it involved ordinary mechanical processes in part, represented a new type of machine,
which used thermal energy. This is also true of the internal-combustion engine; yet both steam-
and gas-powered engines to some extent borrowed the structure of the hydraulic press, one of the
three basic types of machine. Then came the development of electronic power, thanks to Thomas
Edison (1847-1931) and others, and machines became increasingly divorced from basic
T HE LEVER , LIKE THIS HYDROELECTRIC ENGINE LEVER , IS A SIMPLE MACHINE THAT
PERFECTLY ILLUSTRATES THE CONCEPT OF MECHANICAL ADVANTAGE .