Impetus Theory
The concept of inertia was alien to the physics of Aristotle. Aristotle, and his peripatetic followers, held that a body was only maintained in motion by the action of a continuous external force. Thus, in the Aristotelian view, a projectile moving through the air would owe its continuing motion to eddies or vibrations in the surrounding medium, a phenomenon known as antiperistasis. In the absence of a proximate force, the body would come to rest almost immediately.
Jean Buridan, following in the footsteps of John Philoponus and Avicenna, proposed that motion was maintained by some property of the body, imparted when it was set in motion. Buridan named the motion-maintaining property impetus. Moreover, he rejected the view that the impetus dissipated spontaneously (this is the big difference between Buridan's theory of impetus and his predecessors), asserting that a body would be arrested by the forces of air resistance and gravity which might be opposing its impetus. Buridan further held that the impetus of a body increased with the speed with which it was set in motion, and with its quantity of matter. Clearly, Buridan's impetus is closely related to the modern concept of momentum. Buridan saw impetus as causing the motion of the object. Buridan anticipated Isaac Newton when he wrote:
- ...after leaving the arm of the thrower, the projectile would be moved by an impetus given to it by the thrower and would continue to be moved as long as the impetus remained stronger than the resistance, and would be of infinite duration were it not diminished and corrupted by a contrary force resisting it or by something inclining it to a contrary motion
Buridan used the theory of impetus to give an accurate qualitative account of the motion of projectiles but he ultimately saw his theory as a correction to Aristotle, maintaining core peripatetic beliefs including a fundamental qualitative difference between motion and rest.
The theory of impetus was also adapted to explain celestial phenomena in terms of circular impetus.
Read more about this topic: Jean Buridan
Famous quotes containing the words impetus and/or theory:
“While the white man keeps the impetus of his own proud, onward march, the dark races will yield and serve, perforce. But let the white man once have a misgiving about his own leadership, and the dark races will at once attack him, to pull him down into the old gulfs.”
—D.H. (David Herbert)
“No theory is good unless it permits, not rest, but the greatest work. No theory is good except on condition that one use it to go on beyond.”
—André Gide (1869–1951)