Earth-Centered Universe - Assignment Example

The theory and belief that the Earth is at the center of the universe/solar system, is known in astronomy as Geocentrism. Now superseded, this theory proposed that the “Earth is stationary and at the center of the universe; closest to Earth is the Moon, and beyond it, extending outward, are Mercury, Venus, and the Sun in a straight line, followed successively by Mars, Jupiter, Saturn, and the so-called fixed stars” (Encarta, 2006). Though advanced since Aristotelian times, this theory was popularized by Ptolemy, an Egyptian astronomer, sometime in the 2nd Century.

Ptolemy’s “deferent & epicycle” model proposes that each planet possesses a sphere called an epicycle, which rotates within a deferent; another sphere that rotates around the earth. The deferent’s rotation, according to the theory, causes the planet to move towards and away from the earth. This theory, alongside its supporting model, was deemed inconsistent several times (through follow-up observations of the solar system) and is described by Kuhn (1985; 105) as a “rather unsatisfactory physical mechanism.

” It was superseded in the 16th Century by the Copernican system. SUN-CENTERED UNIVERSE      His theory, which also posits that the earth makes a full rotation on its axis once every day, is most likely based on the prior work of the Greek mathematician, Aristarchus.