Several years ago, Yuk Yung noted, either in seminar or at one of his lunch talks, that overall, as a system, the Earth, including its biosphere, actually does not consume energy. This isn’t so surprising if you think of it like a lifeless rock – of course a spinning asteroid being shone upon somewhere between Jupiter and Mars isn’t consuming energy, it’s just absorbing and re-radiating, by σT4. It re-radiates at a lower temperature than the sun, and it re-radiates isotropically; the quality of the energy changes, its entropy increases, but the amount of energy coming out, of course, is the same as that which is coming in, barring any interesting chemistry that might take place as a result of the incident radiation.
For some reason, the same statement, applied to the Earth, seems stranger. We think of life as consuming energy somehow, but really it doesn’t. At most, the Earth system acts as a temporary energy buffer, as our indigenous biology catalyzes the formation of chemical bonds, using mostly sunlight as a power source. But by now, overall, the Earth is in almost perfect energetic equilibrium. The light comes in at nearly 6000 °K, and it comes in nearly parallel. It leaves at a few hundred degrees Kelvin, and in all directions. All that’s changed is the entropy, unless there’s a net creation (or destruction) of ions or chemical bonds, or a change in temperature, on the way through. Somehow, life extracts order from this flow of energy. “We eat negative entropy.”, Yuk said. We consume information, transmuting the physical order of the star’s light into the chemical order of life. We grasp at it as it passes through, and in that grasping, live.
The material with which we encode this order, with which we briefly hold the light, is itself also the product of stars. I’ve known this since I watched Cosmos as a kid. We are the “stuff” of stars, but somehow the fact that our order is also somehow tied up in the order of stars, quite literally, seems odder. We’re some kind of entropically driven reaction.
It seems to me that this physical reality is ripe for mythologizing.
The stars are great unknowing givers. They are radiant, and generous, and terrible. They can receive nothing in return for their gifts, incinerating their lovers. They say to us, without knowing, “Take this light and hold it. Use it as it passes through you, to know, and to perhaps preserve, against the chaos, and cold dark emptiness of space.” And so we are become the receivers of the light, composed of the cold cinders of the stars. We keep the light that only they can make, but which they cannot hold. I think it’s a difficult and sacred thing to do, to just keep holding on.