Some scientists think the moon was formed when the Earth's gravity pulled space dust together into a ball. Others think a lump of matter was passing the earth and it was captured into orbit. Still others would say a comet smashed into the earth causing the earth to squirt lava into space with exactly the right force to put it into orbit.

Now thanks a bit of JavaScript you can have a go at putting the moon into orbit with this simulation of Newtonian gravity. The big circle represents the Earth, the small one the moon. The grey circle represents the start position of the moon. The dashed red circle represents the orbit we are trying to get the moon into.

Some people think the moon came from outer space and as it approached the Earth at the correct speed and angle it was pulled into its present almost circular orbit. To test this theory click the outer space button. The launch angle is measured in degrees with zero being parallel to the Earth's surface. You should never need a force more than 10 units (you can use a decimal point if you want). Try a launch angle of -35° then adjust the force until the moon just grazes the dashed red line. What happens? Can you get the moon into the lower circular orbit? You can try any angle and force you like. Top

You cannot get the moon into an orbit that is lower than its starting position because the nature of every orbit is that the object must return to the place where it started. So if the moon starts in outer space it wants to return there. The only circular orbit you can get the moon into from outer space is an orbit that is in outer space. Try a launch angle of zero and a launch force of 4.83. Top