# Spin doctors: Good pitchers know their physics

Q. What tips did the future baseball pitcher pick up in his college physics class? –N. Ryan
A. He learned that a spinning ball may curve as much as 12 inches on its way to the batter, says physicist Louis A. Bloomfield in How Things Work. Its direction depends on the axis of the baseball's rotation, tending toward the side of the ball turning toward the pitcher. A ball thrown with backspin experiences an upward lift force, enough to make the ball hang in the air unusually long and appear to "hop."

For some pitches, the trickery stems from lack of spin: a knuckleball, for instance, has almost no rotation, with the airflow over the ball's seams pushing the ball sideways and causing it to "flutter." But throwing a spinless ball requires great skill, enticing some pitchers to resort to lubricating their fingers to get the ball to slip on out.

"Like its legal relative, this so-called spitball dithers about and is hard to hit. The same is true for a scuffed ball," says Bloomfield.

Now class dismissed– with an "A" for the pitcher and a "K" for strikeout of the beleaguered batter.

Q. To see from downtown Cleveland, Ohio, across Lake Erie to Canada, you'd need an observation tower about 1500 feet high! Now I'm wondering, how far can the human eye see, anyway? –G. Galilei
A.
When we view the moon, we are seeing something about a quarter of a million miles away; the sun, 93 million miles. Under ideal conditions and with good vision, we can see the Andromeda galaxy 2.5 million light years away— each light year corresponding to about 6 trillion miles.

So there really is no "farthest distance" we can see; it's only limited by how big and bright the intended object is. Of course, looking horizontally through the atmosphere is a different matter, as weather and air quality do limit the distance. Yet under good conditions, it is possible to see 50 miles and even farther, from an airplane, for example.

Q.
Has your body really been with you as long as you think it has? –J. LaLanne
A.
Surprisingly, the vast majority of your body is younger than "you" are, such as the cells lining your gut that are replaced every five days or so, says Graham Lawton in New Scientist magazine. The outer layer of your skin turns over every two weeks, and you get a new set of red blood cells every four months.

Using a variant of carbon dating, Jonas Frisen of the Karolinska Institute in Stockholm, Sweden, has discovered that the average age of a fat cell is about 9.5 years, a bone cell 10 years, and a muscle cell 15 years. Your heart cells are on average six years younger than you are, and if you live beyond age 50, about half of them will have been replaced.

The exception in this procession is your brain, most of which stays with you for life; but even here, some cells in your cerebellum and hippocampus are younger than you are.

"All of this puts the idea of lifelong personal identity into perspective," says Lawton. Think about it.

Send Strange questions to brothers Bill and Rich at Strangetrue@cs.com

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