Lunar occultation of Mars (33)

Yesterday evening was, miraculously, clear! And so David dusted off his little Celestron C-90 spotting scope and trained it on the lower left edge of the full moon—where, at precisely 6:34, the planet Mars nudged up against our local satellite and then quietly slipped behind. (Well, of course it was quiet: it's outer space.)

And today, I saw some lovely imagery of this event, which was much, much better than our fuzzy, jittery view. But still, it was rather awesome to see Mars and the Moon in such close conversation, for a brief moment, in person.

Here's a couple of photos:

Photo by Ethan Chappell

Photo by astrophotographer Andrew McCarthy

My FB friend Brian Fies, meanwhile, wrote an interesting post today about such astronomical events and "ancient astronomers." And I'm just going to steal it wholesale because he says it so well.

I was trying to explain the Moon's motion to [some friends] and said something like, "The Moon actually moves from right to left (west to east), and it's going to pass Mars pretty fast." It occurred to me later how confusing that is, because the Moon obviously rises in the east and sets in the west (left to right in the Northern Hemisphere), just like the Sun and stars, so how can it also move from west to east?

     It does both at the same time.

     Because Earth spins once a day, everything rises in the east and sets in the west. But on a slower time scale, from day to day or week to week, the Moon and outer planets meander in the opposite direction, from west to east (the word "planet" means "wanderer")*.

     The Moon's motion is actually incredibly complex. Since its orbit isn't a perfect circle, from our point of view the Moon gets slightly larger and smaller, and moves slightly faster and slower, over time. Its orbit is also tilted with respect to Earth, so from month to month it bobs north or south, similar to how the Sun moves higher or lower from season to season.

     All these different motions—wheels within wheels within wheels—repeat in a 19-year rhythm called the Metonic cycle (or the more accurate 76-year Callippic cycle). Whatever spot and phase the Moon is in today, it'll be in that exact same spot and phase 19 years from today. Ancient astronomers knew all about it. The Babylonians, Hebrews, Celts, and perhaps Polynesians all built calendars around it.

     Here I'm approaching something like my point: marvel at how smart they were! Ancient astronomers didn't have Newtonian physics or what we'd call modern scientific discipline, but they were careful and brilliant observers. A civilization that can watch, track, document, and mathematically express the motions of lights in the sky over decades is working at a very high level. It was somebody's job to do that, and probably one they passed down to generations of apprentices because some celestial cycles last longer than one astronomer's lifetime.

     Never underestimate the intelligence of ancient peoples. They had the same physical brains, the same cleverness and insight and genius, that we do. They had their Newtons and Einsteins. Could you observe the Moon every day for 19 years and discover the Metonic cycle? I couldn't. But people did, thousands of years ago, in many cultures independently throughout the world.

     The Metonic cycle is an example of why I hate any ideas of "ancient astronauts"—for example, that the Egyptian pyramids are too perfect and complex to have been built without the help of aliens. Baloney. We are very clever apes who excel at finding patterns. We use language, writing, and mathematics to describe the patterns to others, who can then build on them. What an insult to all those ancient geniuses to claim they were too stupid to do it without outside help.

*Footnote: Yes, I know about retrograde motion. Go soak yer head.

The Metonic cycle depicted in a 9th-century manuscript
from St. Emmeram's Abbey in Bavaria.

Brian finished up by posting an image from a book-length science comic he was working on when fire destroyed his home and studio in 2017 (the Tubbs Fire, which experience he chronicled in A Fire Story). The working title of this page (in his head) was "Don't Be a Dumbass."

Brian is also the author of the digital comic Mom's Cancer (released in hardback in 2006) and, very recently, The Last Mechanical Monster (released in hardback in October). I need to read these. Maybe buying and reading those can count as my thanks to Brian for letting me steal his post.