Two oranges and a flashlight

A little astronomy is a dangerous thing

The much ballyhooed total eclipse came and it went, more than a third of a world away. I didn't pay it much attention at the time, though I did marvel at some of the photographs of totality, while also staying aware that I had no way of knowing whether they were, in fact, of this totality rather than some previous event. A couple of people I know were there that I know of, and their accounts were terrific in a detached way. I also saved "Annie Dillard's Classic Essay: 'Total Eclipse'", which The Atlantic generously made available "until the end of August". But I didn't read it.

Then we had a discussion with some friends after a delicious dinner, and one of them was puzzled about why the eclipse moved from west to east, while the sun moved from east to west. Poor benighted fool, I thought, and did my best to explain that although it seemed to us down here that the sun was moving from east to west, in actual fact, seen from the sun, we were moving from west to east, and so of course the eclipse did the same. Because, of course, I knew with absolute certainty that during the eclipse the sun and the moon were to all intents and purposes stationary relative to the earth.

My friend refused to budge.

I went to get a piece of paper, and as I drew what my words had failed to convey, I realised with horror and, frankly, delight, that I was completely and utterly wrong. A quick check confirmed it.

The reason the eclipse moves from west to east is because the moon's shadow is moving from west to east as the earth rotates beneath it.

If only I had read that essay of Annie Dillard's, I wouldn't have been so dead certain I knew what I was talking about. She writes:

What you see in an eclipse is entirely different from what you know. It is especially different for those of us whose grasp of astronomy is so frail that, given a flashlight, a grapefruit, two oranges, and 15 years, we still could not figure out which way to set the clocks for daylight saving time. Usually it is a bit of a trick to keep your knowledge from blinding you. But during an eclipse it is easy. What you see is much more convincing than any wild-eyed theory you may know.

My grasp of astronomy is not that frail. And I do actually remember seeing a partial eclipse as a child, though I have no idea how old I was. But now, all I want to do is experience a total eclipse for myself.


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