There is a force of attraction between all objects in the Universe - we call this the force of gravity. To escape the`` hold of the Earth'' and get out into space, you need to go faster than what is called the Earth's Escape Speed.

Suppose that you want to launch a can of lemonade into orbit around the Earth (I am not too sure why you would want to do this but for now, let's pretend you do!). You would need to throw the can vertically upwards at a speed of about 17,500 miles per hour (about 27,350 kilometres per hour) to be absolutely sure that your fizzy pop will go into orbit. Now unless you have Superman-like strength, that's not possible and so most satellites are launched by rockets.

The rocket carries its cargo to the right height above the Earth and then releases the satellite into orbit. The satellite is still held in Earth's gravity but it now travelling around the Earth so fast that the gravitational force of attraction pulling the satellite towards the Earth is cancelled out.

If you want to know more about gravity go