Don Marti

Mon 26 Mar 2012 10:46:34 PM PDT

Crater puzzle

Nothing to give out as a prize except some search engine juice, so I'll link to everyone who sends me a correct answer. Ready? Here goes.

You're a space explorer visiting a faraway planet, one with no magnetic field.

There are two research bases, located 180 degrees apart on the edge of a perfectly circular crater.

You land at base A, and when you're done there, it's time to visit base B. You borrow a rover, provisioned with enough fuel and oxygen to make it to base B if you drive straight across, plus a 50 percent reserve.

There's no magnetic compass, and no celestial or satellite navigation (too much space dust). But you do have an gyrocompass, which will keep pointed in the same direction so that you can steer a straight course.

You get in the rover and drive in a straight line, expecting to arrive at base B. But when you reach the edge of the crater, there's no base there. You get on the radio to base A and get some bad news.

"Ooops, we forgot to calibrate the gyrocompass. It was working, so you went straight, but we forgot to set the direction, so we have no idea what direction you went."

All you know is that you're on the rim of the crater, somewhere.

"Well, how about radio direction finding? Can base B locate me by my radio signal?"

"Nope, no directional antennas on the rover or either base. And neither base has any flares we can send up as a signal."

Then someone from base B breaks in and tells you one simple thing you can do (with no additional equipment besides what has been mentioned so far) to get to base B. What was the advice?

Answers to dmarti@zgp.org.