Plunging to earth

I skydived solo once. After a few drinks, friends often find me willing to give an elaborately detailed account of my experience. My narrative continues until I notice my audience drifting away, as they invariably and unaccountably do. My dive was from a small plane about 3,000 feet high, with no more than ten seconds of free fall. It's a hard experience to forget.

A gentleman named Felix Baumgartner is also planning to "skydive." Not from 3,000 feet, however. From a balloon, 120,000 feet (about 23 miles) up in the stratosphere. He will find himself in free fall for about 5½ minutes, long enough to mull over the joys and sorrows of his life to date. Within the first 30 seconds, he will have reached a speed of 600 miles per hour.

The point of his endeavor is to "see what happens" when a human body, virtually unprotected except for a pressurized suit, breaks the sound barrier.

Felix isn't a completely crazy cat. Serious scientists and science are behind his stunt. Actually, an Air Force pilot did something similar, from 100,000 feet, back in 1960. Unfortunately, he went into a spin of 120 rpm and blacked out, not waking up until his chute automatically deployed near the ground.

My first reaction to reading all about this in the New York Times was to wonder how Felix would be able to exceed the terminal velocity for a human body, usually put at around 120 mph. But that figure assumes the falling body's arms and legs are extended. Terminal velocity increases if the diver pulls his extremities in and up close to his body, and falls head down. Also, the customary figure for terminal velocity assumes normal atmospheric pressure. During much of his fall, Felix will be plunging downward through an extremely tenuous atmosphere, almost a vacuum. As you fall, terminal velocity decreases one percent for every 525 foot loss of altitude. With this information, terminal velocity at 120,000 feet can be readily calculated. The calculation is left as an exercise for the reader (as my math books used to so frustratingly put it).

Also fascinating -- to me, at any rate -- is the meteor effect, although the scientists must have reasons for believing this not to be a problem. The atmosphere protects those of us on the earth's surface from having to dodge a daily shower of space debris. The friction through the air as rocks fall towards earth causes them to vaporize long before they reach the surface.

Even tiny rocks, not much bigger than a grain of sand, can be clearly observed as meteors as they heat and burn. Why wouldn't the same happen to a human body? It would be an awesome way to go, if you had to go. Streaking across the sky, a ball of fire, observed by millions. Almost worth it.

At least better than having a heart attack while tending your virtual garden on Farmville.