The most effective way to find and destroy a land mine is to step on it.

This has bad results, of course, if you're a human. But not so much if you're a robot and have as many legs as a centipede sticking out from your body. That's why Mark Tilden, a robotics physicist at the Los Alamos National Laboratory, built something like that. At the Yuma Test Grounds in Arizona, the autonomous robot, 5 feet long and modeled on a stick-insect, strutted out for a live-fire test and worked beautifully, he says. Every time it found a mine, blew it up and lost a limb, it picked itself up and readjusted to move forward on its remaining legs, continuing to clear a path through the minefield.

Finally it was down to one leg. Still, it pulled itself forward. Tilden was ecstatic. The machine was working splendidly.

The human in command of the exercise, however -- an Army colonel -- blew a fuse.

The colonel ordered the test stopped.

Why? asked Tilden. What's wrong?

The colonel just could not stand the pathos of watching the burned, scarred and crippled machine drag itself forward on its last leg.

This test, he charged, was inhumane.