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Tuesday, October 06, 2009

On seeing the Moon one Monday morning

Monday morning I needed to stop for some supplies at the local supermarket. Grapes, oatmeal, diet cola, cat food. Nothing special, but all necessary.

My shopping only took a few minutes, but I was tired from having been on my feet and constantly moving for twelve of the last thirteen hours. As I pushed my cart back to my car I noticed a white circular object nestled among the white clouds low in the west. It was the Moon, just past full.

It looked huge. This is a psychological effect; we always overestimate the apparent size of the Moon in the sky, which can be easily blocked by an eraser on the end of a pencil held at arm's length. But this is especially pronounced when the Moon is low in the sky and is easily visible alongside houses and trees and mountains. To me, the Moon looked huge.

The Moon is a body of matter so massive that it has pulled itself into a spherical shape, I thought. It was formed in a collision billions of years ago between the Earth and a Mars-sized impactor. It hit, was demolished, stripped off a large portion of the Earth's surface, and formed a cloud of debris which eventually coalesced into the Moon. (Those are the broad details. Somewhere along the line there was a second impact, either with the initial body or the proto-Moon.) It hangs in the sky, but is actually in orbit around our planet, held there by mutual gravitational attraction. It is massive, so massive that if you were to stand on its surface you would feel a pull of gravity 1/6 as strong as that on the surface of the Earth.

I moved my foot. I am standing on a parking lot, on solid matter. (The reflectivity of the Moon is about the same as that of an asphalt parking lot, yet it appears bright in our sky. Whenever I hear this fact, I always think about the parking lot that I happened to be standing in in that moment.) The solid matter of the parking lot is made up of atoms and empty space. Mostly empty space. I stamped one foot. Yet it is solid. I do not fall through. The atoms and empty space that make up me do not slip through the atoms and empty space that make up the ground.

I breathed in, breathed out. The air is also atoms and empty space. Nitrogen, oxygen, carbon dioxide. I breathe in, and the air fills the alveoli in my lungs. Blood flows through my lungs and exchanges carbon dioxide for oxygen. I breathe out again, and the air is slightly richer in carbon dioxide, slightly poorer in oxygen. I go on.

I looked down. I had a cart full of groceries to load into my car. The clerk who had checked me out ran into the parking lot to give me the club card I had left at the register. I had to pack the car, head home, unload, pick a rose to put on Gretchen's grave, feed the cats, feed myself, and get to bed so I could get up for work again in a few hours.

I turned my back on the Moon and got started.

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