What Did You Know Last Week?

Or what did we know a century ago? It still amazes me to think that in 1918 we did not know that Andromeda is a galaxy outside our own. We thought that the universe was just a collection of stars. We didn’t know that we live in a spiral galaxy. Until 1953, we thought Andromeda was only one and a half million light years away. We now know it’s 2.5 (plus or minus .11) million light years away. Going further back, it wasn’t until 1610 that Galileo was able to show that the band of light in the night sky we call the Milky Way is actually a collection of individual stars. This raises a question: did the great astronomers of the past — Galileo, Newton, Halley — know anything about the stars? They were wrong about so many things! What did they really know?

The answer, of course, is that they knew a great deal. It’s just that today’s astronomers, building on everything that has been known before them, know much, much more about how the universe is organized. But I raise the issue for a reason. Sometimes I get the sense that scholars dread the prospect of writing about things they thought were true even just last week. They are worried that this knowledge is already out of date, already rendered irrelevant by some other study that someone else has done. In 1785, William Herschel drew the first map of the Milky Way (thinking it was the whole universe) and put our sun near the center of it. Two hundred years later, even a writer of light entertainment like Douglas Adams knew better,  describing it as “a small unregarded yellow sun” “in the uncharted backwaters of the unfashionable end of the western spiral arm of the Galaxy”. Herschel must be feeling pretty foolish!

Of course not! The fact that knowledge is constantly expanding (like our universe) should not make us embarrassed to claim to know anything today. Nor should we be particularly concerned with how long ago we last checked to be sure we were right. Yes, there are claims you can make about any number of things that everyone thought were true five years ago, but that someone, somewhere, working at the cutting edge of their field is just now becoming aware is wrong. Even profoundly wrong. But their discovery needs time to work itself into our total vision of the world in which we live. Until the news reaches you, you are perfectly in your rights to claim things are as you believe they are. Don’t feel the slightest guilt about it. Just sit down and write what you think and why you think it.

A good way to train this attitude is to always be writing your paragraphs about something you knew was true last week. Never try to write at the cutting edge of your own cognitive process. (That is, don’t try to write for publication at this edge; if you want to use writing to show yourself what’s on your own mind, that’s entirely your business.) Spend some of your research time there, of course. But don’t think every sentence you publish has to be “current”. It just has to accurately reflect what you knew at some reasonably recent moment before your paper was published. That’s the important thing: all published papers — most of what we read — gives us access, not to the present state of mind of one our peers, but to their past state of mind. Get used to writing about things you knew and your writing process is likely to feel less strained.

It is said that Edwin Hubble “settled” the debate about the shape of the galaxy in 1925. We’re not going to ridicule someone who weighed in on the “wrong” side earlier that year, right? Everyone was contributing to the debate, and even when they were getting things wrong, they were demonstrating how knowledgeable they were about many other things. So lighten up! You’re wrong about most things. Tell them, yes, sure … you’re as wrong Aristotle once was, as wrong as Ptolemy and  Newton! There’s nothing to be ashamed of.

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