Aristotle, projectiles and guns

Abstract

When guns were developed in Europe in the 14th century, the theory of projectile motion was not the one we are familiar with today due to Galileo and Newton but the one taught by Aristotle approximately 1700 years earlier. In addition to Aristotle's wide-ranging philosophical concerns, his theory arose from the observation in everyday life that if an object is moving something must be moving it. This idea works very well for the horse and cart but is puzzling if you apply it to a thrown stone or spear. Problems with Aristotle's theory of projectile motion were identified by one or two people between his time and the 14th century, particularly John Philoponus (6th century AD) and John Buridan (14th century AD). An archer or a spearman does not need a theory of projectile motion, just a great deal of practice. But once the gun was invented it became important to know what angle a barrel should be oriented at and how much propellant to use, particularly as gunpowder was expensive. However, for many years afterwards the manufacturing techniques used meant that cannonballs were a loose fit to gun-barrels making cannons both inaccurate and of poor reproducibility shot-to-shot. Also air resistance makes the trajectory both impossible to calculate and qualitatively similar to theories based on Aristotle's writings. It was not until Galileo and Newton worked on the problem that a better theory of ideal projectile motion was arrived at.