Above Our Heads

Our planet is not just the ball of rock and water that we stand on. It is also the thin layer of atmosphere that we cannot see, but which all life depends on. The oxygen we breathe, the carbon dioxide and nitrogen that sustain the plants, the cycle of evaporation and precipitation—it may not be what you think of as “the earth,” but without it there would be no earth as we know it.

What things that are essential to your health and happiness tend to escape your notice?