I marvel at the body's pickiness. We are comfortable when the temperature is between 68 and 75 degrees Fahrenheit. Drop below 68, we get cold and must move around or put on jackets. Rise above 75, our pores sweat to cool us off. From the near absolute zero of deep space to the sun's fiery core, the universe spans 30 million degrees, and our range of flexibility is 7 degrees? Philosophers complain that the cosmos is harsh and inhospitable, but are we not astonishingly particular in our demands? We are like a beggar pleading to be fed with any of 7 specialty foods.

Amazingly, the universe obliges us with a tolerable if not ideal climate—provided we do not venture five miles above or below this planet's surface, our narrow safe zone. At a picnic on a perfect spring day, there is boiling magma beneath the thin dirt floor we stand on. Meanwhile the air overhead, where planes are flying, would frostbite our skin and quickly kill us with hypothermia.