Models of the Solar System
The first model of the solar system was the Geocentric model. The Geocentric model was proposed by the Greek astronomer Ptolemy. He believed that the sun, planets, moon and the stars all orbited the Earth in a perfect circle.
Until the 1500's the Geocentric model was considered and accepted. However in the 1600's a polish astronomer, Nicolaus Copernicus, proposed the Heliocentric model. The Heliocentric model suggests that the Sun is at the centre of the solar system and everything inclusing the Earth orbited it.
As the technology has improved, it has allowed humans to discover many things about space.
e.g. the invention of telescopes has led to the discovery of new planets like Uranus.
Galilieo was the inventor of the telescope. In 1610, around the time of the Heliocentric model, Galileo observed Jupiter. He used his telescope and saw three stars lined near the planet. When Galileo looked at the stars again in the evening, he observed that the stars had moved and changed their positions. However, when he looked at the planets again after a week, he noticed that another star had appeared. He realised that the stars did not move away from Jupiter and that they were not stars but moons of Jupiter. This showed that not everything was in orbit around the Earth.