There is in Euclid the contempt for practical utility which had been inculcated by Plato. It is said that a pupil, after listening to a demonstration, asked what he would gain by learning geometry, whereupon Euclid called a slave and said "Give the young man threepence, since he must needs make a gain out of what he learns." ... No one, in Greek times, supposed that conic sections had any utility; at least, in teh seventeenth century, Galileo discovered that projectiles move in parabolas, and Kepler discovered that planets move in eclipses. Suddenly the work that the Greeks had done from pure love of theory became the key to warfare and astronomy.
Bertrand Russell, The History of Western Philosophy