Astrophysics

The twenty-fifth entry is a zona habitável, and English has two names for it where Portuguese has one. The formal one, « the habitable zone », matches the Portuguese word for word. The other comes out of a nursery tale. « The Goldilocks zone » is what a newspaper, a television programme and a good many textbooks will call it, after the child in the story of the three bears who tastes the porridge and finds one bowl too hot, one too cold and one just right. That is the whole argument in three bowls: too near the star and the water boils away, too far and it freezes, and only a band in between leaves it liquid, which is what the sentence on this page says. The figure has since walked out of astronomy. « A Goldilocks economy » is one growing neither fast enough to overheat nor slowly enough to stall, and « the Goldilocks principle » names any rule of thumb that asks for the middle of three. Portuguese tells the same tale and has built nothing on it: a zona habitável is named for what it allows, not for a child at a table.