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The Solar System

The History of the Solar System.

People have used observation to find out things
about our solar system (and the rest of the Universe).
Observation just means looking at it.

In the past, people just looked out at the night sky and
saw points of light. Most of these points just stayed still (the stars)
but some of them seemed to move or wander around (the planets).
The word "planet" comes from the Greek word for "wanderer".

In the past it was believed that the Sun and the planets
orbited the Earth. This is called the geocentric model.
"Geocentric" means "Earth at the centre".
People believed this because from the Earth
it looked like everything was going around the Earth.

At the beginning of the 17th century an Italian man called Galileo
was looking out at the night sky using a telescope.
Galileo did not invent the telescope but he improved the
technology and made a new one which was three times as powerful.

Using his new telescope he saw some moons orbiting Jupiter.
He realised that some objects in the sky orbited things other than
the Earth, so the Earth could not be at the centre of everything.

He then looked at Venus and saw that it orbited the Sun!
He soon realised that all of the planets orbit the Sun.
This is called the heliocentric model of the solar system
meaning "Sun at the centre" (see picture).

Galileo was not the first person to suggest
that the Sun is at the centre of our solar system
but he was the first person to prove it
using the new technology of the telescope.
Today scientists use a range of different telescopes
to gather information about the Universe.

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