Earth tries to pull everything down
towards its centre.
This pull is called the force of
gravity (the invisible force).
When you lift things up you have
to pull against gravity.
If you drop a pencil, gravity pulls
it to Earth.
If you rest its mid-point on your finger, gravity
will pull down equally on both sides of the pencil
and it will balance in the air.
Did you know that there is gravity on the Moon?
The gravity on the Moon is much weaker than the
gravity that we have here on Earth.
This is why moon walking for astromauts is very