"Yes," came the sarcastic reply, "it would be a most tender sacrifice—except that a person would be in no condition to give orders before he ever reached the pool, and I don’t think the robots would ever turn back to the cliff without orders. Figure it out! We’re two or three miles from the pool—call it two—the robot travels at four miles an hour; and we can last twenty minutes in our suits. It isn’t only the heat, remember. Solar radiation out here in the ultraviolet and below is poison ."