TOM: I've been waiting. What was the puzzler?

RAY: I don't remember. Let me refer to my notes. Imagine, if you will, a long, long freight train, you know like the kind you always see out West.

TOM: Yeah. 750 cars.

RAY: Seven hundred and fifty cars. You can spend your entire vacation. That's why people get killed by those trains because if you get stuck waiting for one, you can spend a half a lifetime there.

TOM: And it's worth shortening your life --

RAY: It's worth it.

TOM: To take a train. Take a short at it.

RAY: Imagine that the... Imagine this. Here's the scenario.

TOM: I mean what goes through people's minds? I had to ruin my whole vacation waiting for this train. No, I think I'll just get killed instead. Okay.

RAY: Anyway, imagine this. It pulls into the train yard so that the train workers can go for a hair cut or something. I don't know. The train stopped for no apparent reason as we all know.

TOM: Yeah.

RAY: Anyway, they get back in and the engineer opens the throttle and the train starts to pull away from the yard. As it begins to pull away, somebody realizes that the caboose has a problem. No coffee. No, the brake is frozen on one of the wheels and the wheel is being dragged along and there are sparks and smoke and all kinds of nasty stuff and someone's standing in the yard, the train yard, manages to signal to the engineer and he stops the train.

TOM: Yeah.

RAY: Well, they can't fix it so they decide to just uncouple the caboose. So they remove it and they give the engineer the go ahead. "Go ahead," they say. He gives it the throttle. The train doesn't move. He gives it more throttle. It still doesn't move. In fact, the wheels are spinning.

TOM: On the engine.

RAY: On the engine. Well, the other wheels aren't spinning cause what?

TOM: They're just sitting there.

RAY: They ain't moving.

TOM: No.

RAY: Now, there's nothing wrong with any of the remaining cars and there's nothing wrong with the engine, but there is something wrong with the engineer. The question is what's happening here?

TOM: Yeah. Actually, didn't we use this puzzler once before?

RAY: No, I don't think so.

TOM: I think. I think. I think you did.

RAY: A long time ago maybe. How long?

TOM: Two weeks. Yeah. Well, give us the answer oh great wise one. See, the only reason you knew the answer was because you used this one before.

RAY: Well, I thought I had disguised it sufficiently.

TOM: Well, you did.

RAY: When a train is... When a locomotive is pulling cars, each car is attached to the one in front of it and behind it by a coupling, but the couplings aren't rigid. They're, in fact, sloppy.

TOM: Um hmm.

RAY: So that when the train stopped and it started to go. You didn't realize that something had happened before that. When a long freight train pulls into a yard, before it takes off, it will frequently back up to compress all the couplings and then when it takes off, one car at a time begins to move and it's quite a while, in fact, before the caboose begins to move.

TOM: Phew.

RAY: But in this situation, the train was stopped. He did that backing up thing. I failed to mention that in the statement of the puzzler.

TOM: Another form of obfuscation and nicely done I thought.

RAY: The train is halted because the brake is stuck and because it's stuck, the caboose is in a sense pulling the train from the other end. So, now all the couplings are all stretched out. They remove the caboose, but the guy doesn't back up.

TOM: Right.

RAY: They give him the go ahead. He says, "OK. I'll go ahead."

TOM: So, now he's going to pull all 750 cars --

RAY: At once.

TOM: At one time.

RAY: He's going to try to move the last car while he's trying to move the first car and the train is just too heavy and he doesn't have enough friction between the wheels on the track --

TOM: So, a train --

RAY: To accomplish this.

TOM: So, a train can't really pull from a dead stop all the cars that you see behind it sometimes.

RAY: If it's long enough, it can't do it.

TOM: It it's long enough, it can't.

RAY: It can't do it.

TOM: So, the little engine that couldn't. Couldn't.

RAY: Couldn't do it.

TOM: It's as simple as that.

RAY: And you have to apply the rules of incrementalism. Is you have to pull one car at a time until finally you got one car, two cars, three cars, dah-dah-dah, and you've moved them all and once it's moving, of course, you can't stop it because everyone knows trains can't stop for beans.

TOM: Yeah.

RAY: Anyway, who's going to win the new 10th Anniversary Car Talk T-Shirt, this week, Tommy?

TOM: The winner this week is Oliver Gersch. Get this. He's from Dortmund, Germany.

RAY: No kidding?

TOM: Wow! How do you say real ugly T-shirt in German, do you know?

[ Car Talk Puzzler ]