Monthly Archives: May 2010

Sit Down, Big Guy

Posted on by

Foul trouble

Observers of the NBA know that the direct effect of fouling out actually has less impact than the indirect effect of “foul trouble.” That is, if a player has a dangerous number of fouls, the coach will voluntarily bench him for part of the game, to lessen the chance of fouling out. Coaches seem to roughly use the rule of thumb that a player with n fouls should sit until n/6 of the game has passed. Allowing a player to play with 3 fouls in the first half is a particular taboo. On rare occasions when this taboo is broken, the announcers will invariably say something like, “They’re taking a big risk here; you really don’t want him to get his 4th.”

Is the rule of thumb reasonable? No!

The strategy of sitting a player with “foul trouble” seems to be tied in with the notion that points scored late are worth more than points scored early, so if a player can play N minutes before fouling out, you want to have some of those minutes available at the end of the game. But if (after sitting the player longer than the normal rest rotation dictates) the player doesn’t foul out, you haven’t maximized his minutes. The article also discusses some of the caveats on this approach.

I think there’s an interesting undercurrent to all professional sports coaching, where it’s more acceptable to lose if you follow the conventional wisdom approach than if you go maverick. Bill Belichick was lambasted last fall for “going for it” on 4th down instead of punting — it doesn’t matter so much that you could justify the decision as being the better one, from a risk analysis standpoint. The strategy was not the normal one, and it failed. Ergo, it was wrong.

Added: IOW, “Conventional wisdom” seems to linger longer than than the rules and strategies that gave birth to it.

Lucky 13

Posted on by

13 Things That Saved Apollo 13

Part 1: Timing

If the explosion happened earlier (and assuming it would have occurred after Apollo 13 left Earth orbit), the distance and time to get back to Earth would have been so great that there wouldn’t have been sufficient power, water and oxygen for the crew to survive. Had it happened much later, perhaps after astronauts Jim Lovell and Fred Haise had already descended to the lunar surface, there would not have been the opportunity to use the lunar lander as a lifeboat.
…
But this was not the first time the crew had been ordered to stir the tank. It was the fifth time during the mission.

Links to the other 12 things are in the post.

Touch-a Touch-a Touch-a Touch Me

Posted on by

I just got a new iPod Touch. My old iPod — purchased before the touch was on the market — is suffering from rapid battery depletion, and isn’t going to serve its purpose of distracting me for a long period of time on an upcoming trip to the left coast. So I decided to buy myself a present. It’s my birthday, and besides, I’m good enough, I’m smart enough, and, doggone it, people like me! Even after playing with it for only a short time, I found myself thinking that the whole web-surfing experience would be so much better with a larger screen and omigod. I’ve just purchased a gateway gadget, and addiction is imminent. I expect I’ll be jonesing for an iPad before long. But not before I rant a little.

Which brings to mind a number of articles I’ve read over the years, usually appearing in bunches whenever a new product has hit the market, which have tried to convince me that Apple actually sucks, and I’m just a victim of a slick marketing campaign. Yeah, right. The hypnosis must be very good, because I keep buying, which makes me a fanboy in the mind of many critics, in whose world there are two types of people: those who loathe Apple, and fanboys who unquestioningly buy the products, despite the fact that they suck. And I just don’t get it.

I bought a sports car because I wanted a sports car and is (for all practical purposes) a two-seater. Trying to convince me that I’ve been duped, and that I don’t love my sports car — and I couldn’t possibly enjoy it, because it has insufficient seating — seems pretty stupid. If I had wanted or needed a car that seats four or eight, I would have gotten a sedan or a minivan. If I had purchased a sports car knowing that I needed more seating capacity, I would be an idiot. But if you think I bought it because I was taken in by some glitzy ad, I think you have misjudged things. Sucky products suck because they don’t work the way they are supposed to, and good products do. That’s the dividing line. My car doesn’t have a trailer hitch, but that’s because it’s not designed to haul a trailer, not because it’s a shoddy product.

Cheat Sheet

Posted on by

How Scientific Papers Get Retracted

The peer-review process, where editors and scientists vet the research and conclusions of scientific papers, is an important one. But even bastions of good science can be duped by an ethically impaired scientist. Studies suggest that the pressure to publish, especially in support of a hypothesis, can motivate even the most brilliant researchers to plagiarize, fudge data and play lose[sic] with their methods. And on the rare occasions that they do, it’s a quick trip to retraction and banishment from the science community.

In principle, cheating should be at a minimum. If you falsify data and the result is unimportant, there will be little effect but little notice paid. If the result is important, then other researchers will attempt to duplicate the result and/or build on them, and those experiments will fail. That will be important news, and eventually you will have to explain the anomaly.

The Dictionary is not a Technical Resource

Posted on by

QUT physicist corrects Oxford English Dictionary

Dr Hughes said the Oxford English Dictionary (OED) since 1911 had incorrectly stated that atmospheric pressure was the operating force in a siphon when in fact it was gravity.

“It is gravity that moves the fluid in a siphon, with the water in the longer downward arm pulling the water up the shorter arm,” he said.
Now the illustrious Oxford English Dictionary’s editors are moving to have the definition corrected, after receiving an email from Dr Hughes.

Atmospheric pressure is actually smaller at the short end of the siphon, so it should be obvious that pressure is not the main effect. When the liquid in the long arm drops due to gravity, the cohesion of the particles pulling the remaining water along, and while this is the main effect it isn’t the only one that is present. If the pressure in the tube drops low enough, you would form low-pressure voids, but these are prevented by the atmospheric pressure on the fluid. Siphons have been shown to work in vacuum, but I would guess this is under some limited set of circumstances. Fill a tube, then turn it upside-down and put the end in a pool of the same fluid, and you will get a void at the closed end if the tube is tall enough — you’ve made a barometer. A siphon is going to run into this problem, and the height at which any given fluid will do so depends on the atmospheric pressure.

Infinity Can Be Mind-Boggling

Posted on by

The Hilbert Hotel

[T]he Hilbert Hotel doesn’t merely have hundreds of rooms — it has an infinite number of them. Whenever a new guest arrives, the manager shifts the occupant of room 1 to room 2, room 2 to room 3, and so on. That frees up room 1 for the newcomer, and accommodates everyone else as well (though inconveniencing them by the move).

Now suppose infinitely many new guests arrive, sweaty and short-tempered. No problem. The unflappable manager moves the occupant of room 1 to room 2, room 2 to room 4, room 3 to room 6, and so on. This doubling trick opens up all the odd-numbered rooms — infinitely many of them — for the new guests.

It’s the end of the From Fish to Infinity series to which I had previously linked.