Friday, December 31, 2004

Gunfire Tonight!

One of the exciting things about living out here in the Arizona Territory is that all too many local hombres love to greet the the New Year with a hail of gunfire aimed heavenward. It adds a nice Middle Eastern touch to the Copper State.

Part of the problem is the sad state of science education in these United States. There are people who do not understand that a falling projectile poses a threat. (I have actually met such people.) They understand that they cannot catch with their bare hands a round fired at them; but they don’t understand that that same round, falling on a human head from a sufficient height, will kill the head’s unlucky possessor.

Let’s see if we can understand the physics. If I jump from a chair to the floor, no problem. Same if I jump from a table to the floor. But I shrink back from neighbor Bob’s suggestion that I jump from my roof to the ground. "Just kick away the ladder, like Wittgenstein, and jump down." Nosiree Bob! But why should it be any different? The mass of my body remains invariant across the three scenarios. And the gravitational field remains the same. But the longer I remain falling in that field, the faster I move. A body falling in the earth’s gravitational field falls at the rate of 32 feet per second PER SECOND. Thus the body ACCELERATES. The body’s velocity is ever increasing. Now the momentum of a moving object -- which is roughly a measure of the amount of effort it would take to stop it from moving -- is the product of its velocity and its mass. So a small mass like a bullet, left falling for a long enough time, will attain a high velocity and thus a high momentum, and so do a lot of damage to anything it comes in contact with, a human skull for example.