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 planet like that tends to breed a special kind of person: tough enough to stay alive and smart enough to make the best of it. When that kind of person discovers he's being cheated of wealth he's risked his life for, that kind of planet is ripe for revolution.