He chose this model because observational evidence of the time supported it. In this theory of motion things naturally move to the center of the Earth and the only way to deviate from it was to have a force applied to the object. So a ball thrown parallel to the ground must have a force continually pushing it along. This idea went unchallenged for 2000 years until Galileo came along and threw a spanner into that particular theory.

Aristotle also taught that the Earth was unique in the Universe, with its own set of physical laws that were different from how things worked up in the Heavens. He stated that the Earth was a World filled with change, death and decay while the Planets, Moon and Sun were perfect, unchanging and more or less ornaments on the sky, not Worlds that could be explored.

He believed that there were 4 main elements or compounds that made up the Earth: earth, air, water and fire. He also held that all the heavens, and every particle of matter in the Universe, was formed out of another, fifth element he called 'aether' (also transliterated as "ether"), which was supposedly weightless and "incorruptible".

Heavy substances such as iron and metals were considered to be primarily consisting of the "element" of earth, with a limited amount of matter from the other elements. Other, less heavy and/or dense objects were thought to be less earthy, and composed of a greater mixture of the other elements. Humans were created with all of the substances, with the exception of aether, but the relative proportion of elements was unique to each person, and there was no standard amount of each within the human body.

 

Gravity

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, moving away from the center 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 ie. steam and smoke are light so they drift upwards.

There were 7 planets, or wandering Stars, because they had a course through the zodiac in addition to traveling around the Earth: the Moon, Mercury, Venus, the Sun, Mars, Jupiter. Beyond that were the fixed Stars.
The physical elements, according to Aristotle moved vertically, depending on their ‘heaviness’ or ‘gravity’; the celestial bodies were not physical but a ‘fifth element’ or ‘quintessence’ whose nature was to move in perfect circles around the Earth, making a daily rotation. Aristotle envisioned the Earth as the true center of all the circles or ‘orbs’ carrying the heavenly bodies around it and all motion as uniform and unchanging.

 

Aristotle through the years

Aristotle dominated scientific thinking for many years. His views on motion were widely accepted because they seemed to support what people observed in nature. For example, Aristotle thought that weight affected falling objects. A heavier object, he argued, would reach the ground faster than a lighter object dropped at the same time from the same height.

After the death of Alexander the Great, Athens was taken over by people who didn't like Alexander. They suspected Aristotle of sympathizing with Alexander, and he was exiled from Athens. Aristotle died in 322 BC at the age of sixty-two in Chalkis on the island of Euboea, which had granted him refuge when he was exiled from Athens.

 

End of a long era

The first big blow to Aristotle's ideas came in the 16th century when Nicholas Copernicus published his sun-centered model of the Universe. Copernicus proposed that the planets of the solar system revolved around the Sun, not the Earth.
Copernicus observations revealed the vulnerability of Aristotle's science. Galileo went on to finally upset Aristotle's whole theory, see the Galileo Page on this site.

 

Contact me at the following :

the.universe.ie@gmail.com

SITE MAP

Share |