Johannes Kepler's theories of the universe were notable for hypothesizing that the universe was created on April 27, 4977 B.C. and that the planets orbit in an elliptical pattern rather than a circular pattern. His theory superseded previous theories which postulated that planets move in circular orbits at constant speeds.Know More
Kepler based his theories on the ideas of Copernicus, who had previously proposed that the sun, rather than the Earth, was the center of the solar system. Working from this perspective, Kepler began to carefully observe the motion of the planets, particularly Mars. After obtaining a telescope from Galileo Galilei and improving its design, he realized that the orbit of Mars did not fit into a circular pattern. From this observation, he began to formulate his theory that the planets moved in ellipses rather than circles.
This theory led to his later theories of planetary motion, which stated that the speed of a planet's motion is determined by its distance from the sun. Although his theory about the origin of the universe has been discredited by modern astronomy, his laws of planetary motion have proven widely influential in the development of later scientific theories, including Isaac Newton's law of gravity.Learn more about Universe
The achievement motivation theory of John Atkinson and David McClelland is one of the most highly cited theories of motivation in contemporary psychology. This theory was proposed as the result of their research that focused on motivators for cognitive processes, like the expected or perceived value of the results of an action. The achievement motivation theory was published in 1953.Full Answer >
The belief of early astronomers that the Earth was the center of the universe stemmed from limited astronomical tools and geocentric attitudes. The Ptolemaic Model, developed around 100 A.D., presented the Earth-centered solar system in which most early Roman astronomers believed.Full Answer >
Ptolemy's model of the universe was geocentric, containing the Earth at the center with a series of circles, called deferents, moving outward from the Earth, containing the moon, Mercury, Venus, the sun, Mars, Jupiter and Saturn. Ptolemy placed fixed stars and the Primum Mobile in the spheres after Saturn.Full Answer >
Gravity holds the universe together by keeping the large bodies that make up the universe together. It keeps the Earth in orbit around the sun, the sun in orbit around the center of the Milky Way and the Milky Way bound to other nearby galaxies known as the Local Group.Full Answer >