L.O: SWBAT describe the models of the solar system.

All other celestial objects that revolves around the Sun. The “solar system”: The Sun, 8 planets All other celestial objects that revolves around the Sun.

Humans have always wondered about the sky, the stars and the universe! Until recently, many of our ideas about the universe were wrong!

The geocentric model What do you notice about this model of the solar system

The geocentric model: Earth is the stationary center of the universe The geocentric model: Earth is the stationary center of the universe. All celestial bodies revolve around Earth.

The geocentric model made sense to people, it LOOKS LIKE the sun, moon & stars revolves the Earth! the Geocentric model explained how the sun, moon & stars moved But, It didn’t explain the motion of planets!

The word “planet” means “wanderer” in Greek The word “planet” means “wanderer” in Greek. Because the Greeks notice that the planets “seem” to randomly wander across the sky!

The planets undergo retrograde motion: first: they travel forward, then they go backwards and then they go forward again!

The geocentric model could not explain retrograde motion ( why the planets seem to “wander” randomly across the sky).

The Heliocentric model

The Heliocentric model The sun is the stationary center of the universe. All the planets including Earth revolve around the sun.

Later Johannes Kepler’s laws of planetary motion and Isaac Newton’s laws of gravity refined the heliocentric model.

All the stars in the sky are other suns! Since the Renaissance, we have learned that the universe is even bigger than our solar system! All the stars in the sky are other suns! our Milky Way Galaxy has at least 100 billion other stars in it.

Many stars have their own “family” of planets.

The UNIVERSE contains billions and billions of galaxies like the Milky Way.

Some scientist believe that there are other universes!