May 22, 2004

On the Weakness of Gravity

Living in our so-called biophilic universe I like to think about its particular physical parameters. The anthropic principle suggests that we should think of our universe as one of an ensemble of universes -- ours having the special characteristic of producing intelligent observers. Thus, it's worthwhile to think about the factors that had to come into play in order for our specific universe to be able to produce life.

One major player in the makeup of our universe is the force of gravity. Gravity, of course, is responsible for particles coming together, giving form to such structures as galaxies, suns, and planets. It's also responsible for one of the most powerful objects in the universe: black holes.

That being said, the force of gravity itself is exceptionally weak. In fact, compared to other physical forces, it's a total wimp. Take electromagnetism, for example. The gravitational attraction of protons is approximately a factor 10X36 weaker than electromagnetic repulsion. That's a crazy difference! This weakness can be demonstrated with the simple experiment of using a magnet to pick up a small metal object. One small magnet has greater attractive force than the entire planet below it.

The exact characteristics of gravity, however, may not be arbitrary. Even a minor deviation from its current value would have resulted in a vastly different universe than we see now, one that may not have been able to foster life. As an interesting analogy, cosmologist Alan Guth notes how one second after the Big Bang the mass density of the universe must have been at the critical density to an accuracy of fifteen decimal places in order to counterbalance the expansion rate and produce the flat universe we observe today.

So remember just how weak gravity really is the next time you fall flat on your face and maybe you won't feel so bad. Or maybe not.

No comments: