Thanksgiving

What am I thankful for today? An essentially benevolent universe.

What am I thankful for today?  An essentially benevolent universe.

Stars perished long ago, creating the substances from which our bodies our made.  In a living star, gravity crushes hydrogen atoms into helium ones.  Hydrogen and helium are the simplest elements.  They make up most of the matter in the universe, but we are made of more complicated stuff.  As stars die, they expand and then contract.  This unique moment of contraction creates larger and more complex elements.  The main building blocks of our body, carbon and oxygen, arise in this way.  We are living proof of dying stars.

Our star, the sun, will eventually die.  But it will energize earth for another five billion years or so.  Fusion, the transformation of hydrogen to helium in its core, is the source of the energy needed by life on earth.  When hydrogen fuses to helium, it releases packets of energy, called photons, that radiate out into space.  Our bodies are attuned to photons: what we see as light, the colors between indigo and red, and what we feel as heat, the lower frequency, infrared.  Our sun's gravity holds Earth in a certain orbit, one in which we are neither too hot nor too cold. 

Thanks to the mediation of plants, the energy of the sun becomes the energy that enables and sustains our life.  The leaves of plants absorb photons, then juggle carbon, oxygen, and hydrogen to create molecules rich in chemical energy.  In this process, known as photosynthesis, the energy of fusion becomes the energy of life.  These molecules extract carbon dioxide from the air to create carbohydrates, which we eat.  When we eat animals, we are consuming the energy that they gained from plants.  We owe our lives, and our Thanksgiving feasts, to fusion and to photosynthesis.

Cross section of the root of a Buttercup.

Plants make our kind of life possible in another way.  Carbon dioxide traps infrared radiation (heat) in the atmosphere.  When plants extract it, they keep the earth from becoming too warm for our kind of life.  While converting solar energy, plants also release oxygen.  Our bodies need oxygen to transform carbohydrates and other matter into the energy that keeps us alive.  Oxygen enters our lungs when we inhale, and is passed by our blood to little power generators in each of our cells. And so we move and live.

It makes sense to thank nature for its bounty.  From the death of unseen stars billions of years ago through the life of ours for the next billions of years, from the photons of the sun to the calories on your plate, things really have been arranged very nicely for us.  One does not have to take the story of Eden literally to marvel at how the laws of physics, which seem so pitiless, arrange themselves into the regularities of chemistry and biology that we call life.

What we do with that life, of course, depends upon us.  And that is where, feasting done, I will pick up next time.