What keeps the world from falling apart?
Gravity keeps loose objects grounded. Pencils on a desk, books on a shelf, water in a pond, would all be floating free if weren't for gravity, that downward pull to the earth's center. But what keeps attached objects grounded? Why don't buildings and rocks and trees fall to the planet's core? What keeps our own bodies from falling apart? It's because gravity is a wimp. Electromagnetism, that essential friend of telephony, is 10 to the 42'd power stronger than gravity. Sky and Telescope magazine's Stuart Goldman writes that, "It's this mutual repulsion of billions of electrons that prevent . . . everything . . . from plunging to the center of the Earth." Stuart was reviewing the new PBS series, The Elegant Universe, based on Brian Greene's book of the same name. Here's a paragraph from that book, along with a link for a much longer excerpt:
"The electromagnetic repulsion [compared to gravity on the Earth] is about a million billion billion billion billion (10 to the 42th) times stronger! If your right bicep represents the strength of the gravitational force, then your left bicep would have to extend beyond the edge of the known universe to represent the strength of the electromagnetic force. The only reason the electromagnetic force does not completely overwhelm gravity in the world around us is that most things are composed of an equal amount of positive and negative electric charges whose forces cancel each other out. On the other hand, since gravity is always attractive, there are no analogous cancellations -- more stuff means greater gravitational force. But fundamentally speaking, gravity is an extremely feeble force."
http://www.wwnorton.com/catalog/fall03/
Unrelated graphic but still neat (Click for larger image 249K)