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“The problem of having a life-possible temperature over a fair part of area for a fair part of the time has been solved by Earth by a deep inclination (25° 27' to the perpendicular of the plane of orbit) to give the seasons, by a rapid rotation to give reasonable days and nights, and by an orbit that is only slightly eccentric to act as governor. This latter is very tricky: ask any demiurge who is in the business of making and positioning planets.”