Night after night, last August in the Wind River Range, I had a fantastic sky full of stars, and it set me to thinking. One question that came up was the difference between stars and planets.
Modern astronomy has one answer, and the old astronomy has a completely different one.
Every schoolchild knows the modern answer. Planets—of which the earth is one—orbit the sun, which is a star. Planets emit no light and little or no heat. Stars, in contrast, are insanely bright and hot. Though many times bigger than planets, they (except for our sun) look tiny because they are so far away.
Few schoolchildren know the old answer. Not many highly educated adults do either. One really smart friend with multiple degrees in sciencey fields said it was completely new to her when I explained how the times of moonrise and moonset cycle through the 24-hour day in lockstep with the moon’s phases. Used to be, everyone knew that.
For thousands of years, in nearly all cultures, the following difference between stars and planets was pretty universally known, because anyone can figure it out by diligently observing the night sky with the naked eye and noting its patterns over time.
(They had one big advantage over us moderns. Before 100 or even 40 years ago, the typical naked eye saw a lot more stars than it does now, due to urban light pollution.)
Stars—the overwhelming majority of those dots of light in the night sky—are rigidly, perpetually fixed in relation to each other. That’s kind of amazing: the same pattern, century after century. (It turns out they actually do move, as higher-tech astronomers have learned, but it’s imperceptible at human time scales.) At the same time, this rigid panoply is in perpetual motion as a whole relative to the horizon, on both nightly and yearly cycles. Nightly, it wheels around a center point near the North Star. The panoply we see at any one moment is a hemisphere, but the entire panoply must be much larger, as new portions of it continuously unfurl at one horizon while equal portions sink beneath the opposite horizon.
Planets, in contrast, are the five visible dots of light that differ by slowly moving about across the panoply—“wanderers,” the Greeks called them, planetes. The other celestial bodies in motion are very different: sun and moon are huge discs; shooting stars dart ephemerally; comets turn up in slow motion every once in a very long while.
Comparing the new and old astronomies in terms of quality, I decided that modern astronomy is more interesting; deeper; more satisfying if you’re looking for explanations. I’m in awe of the remarkable intellects who figured it out.
The old astronomy, on the other hand, is more factual and more useful.
Factual, in that its facts (outlined above) survive intact as they have for millenia. In contrast, any given fact of modern astronomy, from basics like the number of planets to esoterica like the abundance of dark matter, stands a serious risk of getting deposed during your lifetime.
Useful, because it provided the basis for measuring time, as well as the basis for navigating around the earth. (Down here on earth, we no longer need stars to navigate by, but our spacecraft still use them.)
For sheer utility, has anything come directly out of post–Copernican astronomy that can bat in the same league as those two things? I couldn’t think of any, but my friend Chris Leger pointed out a foreseeable use that could one-up the old astronomy: predicting and averting an asteroid collision.
So. The old astronomy is truer and (so far) more useful, yet we’ve gone and dropped it from the curriculum of being human. What’s up with that?
To me, it’s one of many ways of being out of touch with the real world.
After stars vs. planets, I moved on to jetliners. Later than approximately midnight, they cross the Wyoming sky only from west to east, and after a while of doing that they cease. I think I can explain that one, too.