Four-Day Planet Four-Day Planet . . . where the killing heat of a thousand-hour "day" drives men underground, and the glorious hundred-hour sunset is followed by a thousand-hour night so cold that only an Extreme Environment Suit can preserve the life of anyone caught outside. Fenris isn't a hell planet, but it's nobody's bargain. With 2,000-hour days and an 8,000-hour year, it alternates blazing heat with killing cold. A...