Aristotle

Viviana I. Chaparro Barriera

The word physics comes from the word phusis that is nature. For Aristotle phusis is the internal activity that makes anything what it is. Aristotle held that the universe was divided into two parts, the terrestrial region and the celestial region. In the realm of Earth, all bodies were made out of combinations of four substances, earth, fire, air, and water. The fundamental assumption in Aristotelian physics was that the natural state of sublunary matter is rest. Earth, air, and water must seek their natural place at rest in the center of Earth unless stopped by an impenetrable surface like the ground or a table. The natural place of rest of the element fire is somewhere above us. The air we see around us is a mixture of the elements air and fire, so its behavior is complicated by the competition between the tendency for fire to rise and air to fall. Except in very complicated situations such as when air and fire were mixed together, motion was not a natural state of affairs.       

Aristotle was born in the small Greek town of Stagiros. His father, Nicomachus, was a physician who had important social connections, and Aristotle's interest in science was inspired by his father's work. His first’s years are not clear, but at the age of 17 Aristotle joined Plato's circle at the Academy in Athens and stay there for 20 years. On Plato's death in 348-347 B.C. Aristotle left for Assos in Mysia. Aristotle married Pythias. He traveled to Mytilene and stay there for 2 years. Aristotle returned to Athens in 335-334. He established a philosophical school of his own. Members of this school took meals in common, and formalities were established to the members. The lectures on the school were divided into morning and afternoon sessions, the more difficult ones given in the morning and the easier and more popular ones in the afternoon. After ledding the school he went to Chalcis, where he died the following year of a gastric ailment.

 

Aristotle is the author of a great number of writings, but only few have been recognized. His earliest writings were produced under the influence of Plato and the Academy. Most of these are lost but these were exoteric works written for the public, and they deal with popular philosophical themes. The dialogues of Plato were the inspiration for some of them. 

Aristotle's model provided a simple, compelling explanation for falling rocks, rising flames, and the circulation of the air. However, it was less successful in explaining "violent motion" such as when an object is hurled from a catapult. Their theories are simplified in two laws: 

1. The speed of falling is proportional to the weight of the object.

2. The speed by which an object falls depends inversely on the density of the medium it is falling through. 

The Aristotelian theory of gravity was a theory that stated that all bodies move towards their natural place. For some objects, Aristotle claimed the natural place to be the center of the earth, wherefore they fall towards it. For other objects, the natural place is the heavenly spheres, wherefore gases, steam for example, move away from the centre of the earth and towards heaven and to the moon. The speed of this motion was thought to be proportional to the mass of the object.