30.1

Question 1

The Earth is considered the center and everything else revolves around it. Scientists explained this model by saying that the planets, the Sun, and the Moon were embedded in separate spheres that revolved around the Earth. They thought that the stars were embedded in another sphere that also revolved around the Earth. Although Ptolemy’s model of the solar system was accepted and used for over a thousand years, it ran into many problems. One problem was the fact that the planets seemed to periodically move in a retrograde or backward motion when viewed against a background of stars. To account for this retrograde motion, Ptolemy’s model described a complicated system of circular paths that the planets followed.

Answer 1

The geocentric Model

Question 2

The Earth-centered model of the solar system endured for centuries. However, in 1543, the Polish astronomer Nicholas Copernicus proposed a different model based on the ideas of an early Greek philosopher named Aristarchus. The heliocentric model indicated that the Moon revolves around the Earth and that the Earth and the other planets revolve around the Sun. In this model, the apparent motion of the planets, stars, and the Sun is due to the rotation of the Earth. The Sun is considered the center of the solar system in the heliocentric model. Copernicus placed the known planets in the correct order in circular orbits around the Sun.

Answer 2

The Heliocentric Model

Question 3

These are planets orbiting stars other than the Sun. These planets are helping astronomers infer how planetary systems like our solar system formed. Some of these planetary systems have been discovered around stars that are similar in size, age and structure to the Sun. Most of the planets that have been found are large and massive, it is possible that there are also smaller and less massive planets like Earth. in these planetary systems.

Answer 3

Extrasolar planets