Galileo is known to most people as the first people to use a telescope to look at the skies.

His observations resulted in him being one of the first people to challenge the ideas about the Sun and planets that had been around since the time of the Ancient Greeks.

He also discovered two things about how things fall:

1) Different sized objects would fall the same distance at the same time. To see what we mean by this, have a look at this example.

2) When you drop something, it speeds up as it falls!

As well as dropping balls from a height, he performed experiments with rolling balls and discovered that balls of different weights also rolled at the same speed and they speeded up as they rolled.

Then he put this apparatus on a table and painted onto the balls. He then let them drop off the table.

Galileo was one of the first people to do carefully set out experiments and to measure and analyse everything he saw.

Here's what Aristotle would expect to see:

Here's what Galileo saw and measured.

Galileo spotted that there are basically two forces acting on the ball - a horizontal and a vertical one.

His great insight was to see that forces change the motion of objects. Left alone, things would travel in a straight line forever. Other forces that we now know as friction and gravity slow them down.

Galileo published this work on"projectiles" and this is where he fits in with launching a Moon rocket. How do we escape the force that pulls things back to earth?

Unfortunately for Galileo publishing his ideas about the Sun being in the centre of the universe got him into trouble with the church. They weren't too happy even though Galileo had convinced quite a number of them that what he had observed and discovered was the truth!

The church threatened him with torture and so he took back a lot of what he said.

But it was Galileo's ideas along with those of Kepler after him that led to Isaac Newton making his great discovery and it was his maths that enabled NASA to get Apollo 10 to the moon and back.

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