Many theories of the view of the solar system have changed through the years.
From our plant many people have looked upon the changing landscape of our solar system. Very careful observations of the night sky would reveal to ancient astronomers that there were five lights that did not stay put, but instead wandered around almost randomly through the constellations. The Greeks would name these objects planets.
The Greek astronomer Ptolemy described Earth as a huge ball at the center of the universe with objects circling around it. Each Planet moved in a separate circle. In his view, the moon was the lowest, then came Mercury, Venus, the sun, Mars, Juniper and Saturn. Followed by existing stars. This view of the solar system remained for thousands of years.
In the 1600’s astronomers such as Galileo began using telescopes to look at the night sky. He discovered the planets followed the sun gravitational pull with Mercury first, then Venus, Earth, Mars, Jupiter and Saturn.
As telescopes became more powerful ancient astronomers began discovering new planets.
In 1781 Herschel was trying out a new telescope and saw a light. He noticed it was a moving star. He announced he had found a comet. Upon further observations he realized it was not a comet but a new planet. Uranus was the first planet to be discovered and labeled the seventh planet in our solar system.
Astronomers believed that must have been anther planets passed Uranus. In 1846 the planet Neptune was discovered by Galle and d’Arrest using mathematical calculations first and observations second.
Due to Pluto’s immense distance from earth it was not discovered and labeled the ninth planet in our solar system until 1930 by Tombaugh.
In 2006, the International Astronomical Union created an official definition for the term planets. Pluto failed to meet all the conditional to be called a planet. It was then regrouped into the dwarf planets classification.