Set for Life

The Exquisite Design of Earth's Internal Thermostat

With global attention fixed on Earth's surface temperature and the relatively narrow range required for the existence and preservation of life as we know it, perhaps we may be excused for failing to appreciate the significance of Earth's just-right internal heat flow. The fact that this heat flow happens to occur within the ideal range to produce two of our planet's unique life-sustaining features seems every bit as improbable—dare I say miraculous?—as Earth's present 9,500-year window of extreme climate stability.

Recent research shows Earth to be the internal heat flow champion among rocky planets of its size and age. Earth's size and age would lead scientists to expect negligible heat transfer...