While models are certainly important to software architects, the idea of modeling isn’t a new one and
in fact has been with us since classical times. The ancient Greek astronomer Ptolemy taught that a
central Earth was orbited by the sun, moon, planets, and stars. We now know that Ptolemy’s model
was wrong, but it was good enough to predict the motion of heavenly bodies to reasonable accuracy.
In Renaissance times, the Polish astronomer Copernicus created the more accurate heliocentric
model, in which the Earth revolved around the sun. One hundred fifty years later, Sir Isaac Newton
set forth his laws of gravity and motion in Principia Mathematica. Newtonian mathematics survived
unchallenged until Einstein published his general theory of relativity in 1916.

Ptolemy, Copernicus, Newton, and Einstein were all trying to describe the same phenomenon—the
apparent motion of the sun, planets, and stars. None of their models were entirely correct, but each of
their models could be considered good enough for the purposes to which it was put.1 Indeed,
Newtonian mechanics is still adequate for all but the most specialized applications even today. The
lesson from these famous attempts at modeling the physical world is that no model is perfect, but even
an imperfect model can provide us with useful information about the reality it is modeling.