1) Why does the moon orbit the earth?<br />If gravity attracts 2 objects like the earth and the moon then why don't they crash into each other like humans would crash into the surface of the earth if running out of a helicopter?<br />I've tried the bowling ball/sheet experiment. I roll a tennis ball towards the bowling ball; it either immediately crashes into the bowling ball if my aim was perfect, otherwise it takes a small spin around the bowling ball before inevitably crashing. I've visited every website I can find about General/Special Relativity and Warped Space-Time, but none of them seem to explain it properly (neither does Hawking's book).<br /><br />2) As an astronaut is lifted away from the earth's surface does the pull of gravity have the same value whilst inside the earth's atmosphere? Once the astronaut is outside of the atmosphere why does he suddenly experience weightlessness and is no longer being pulled towards the earth? Or is all this a gradual process? <br /><br />3) One of the four forces of nature includes Electro-magnetism, but isn't electricity and magnetism both separate forces in their own right, albeit unified with mathematical equations? So instead of 4, shouldn't there really be 5 forces in total?