Introduction

Imagine if you could float in the air, leap over your house into your back garden or cycle your bike above the sea to Wales !

You cannot do these things because a force called gravity pulls things towards the Earth. Gravity is a very useful force – it holds everything together. It keeps us on the Earth, and keeps the Earth and the other planets revolving around the Sun. Without it everything would float around. That is why it has been described as ‘The Universal Glue’.

To get an idea of what it would feel like without gravity, imagine astronauts walking around in space.

Astronaut in Space

Mark Lee's spacesuit allowed him to fly freely away from the space shuttle during this test of the SAFER backpack.

Courtesy of NASA

Astronaut in Space
Courtesy of NASA

Astronaut in Space

Mark Lee's spacesuit allowed him to fly freely away from the space shuttle during this test of the SAFER backpack.

Courtesy of NASA

Enlarge image

The astronauts appear to ‘float’. However, this is not because the spaceship is outside Earth’s gravity –  otherwise it would just float off into the Universe! It is because of ‘Weightlessness’ inside the spaceship, something we will look at later.

Every object has this pulling force of gravity, and the bigger the object the greater the force. Earth is so big and heavy that its force of gravity is very great. The nearer things are to each other the greater the force of gravity between them.