Gravity and magnetism follow the inverse square law. Do some research on the inverse square law and which other physical phenomena follow the inverse square law. http://www.youtube.com/watch?v=JW3tT0L2gpc

The force of gravity depends on three key factors which are: the mass of the larger object, the mass of the smaller object, and the distance between their two geometric centers. To learn the details of this relationship and how they work as a formula, read this link.

And if you're still not convinced that gravity is important, click here (don't worry, clicking the link won't make you float away).

Using the universal law of gravitation, determine the force of gravity between a typical person and the Earth. Do research to find the appropriate constants and values. http://www.universetoday.com/34824/force-of-gravity/
Here is a video showing an experiment conducted on the moon. It's the famous Hammer and Feather experiment devised by Galileo. http://www.youtube.com/watch?v=4mTsrRZEMwA