Today brings up a question I’ve long had about many calendars that have notes for important dates.
So far this month my calendar has shown: Labor Day (US & Canada), Grandparents Day, Mid-Autumn Festival (China), Independence Day (Mexico), Autumnal Equinox, various phases of the moon, and, today… “Mercury goes retrograde until October 15th.”
Who finds this a useful entry on a calendar? It seems like this information would be interesting to only a handful of people, all of whom would already know it. But I’ve seen it quite a bit.
Mercury doesn’t go retrograde on a specific day each time - people who are interested in it need to look it up. And it’s nice to have on a calendar so that when you’re scheduling say, a house closing or an employment interview, you can casually be “busy” that day.
ETA: I speak of astrological interest, of course. I assume the astronomical interest is obvious.
I’d imagine most people who are interested already know when Christmas and the Fourth of July are, too. I’d imagine anyone interested in astrology or backyard astronomy might be interested in knowing when Mercury goes into retrograde. I can’t imagine why they’d have the date memorized, though - they’d probably want to mark it on a calendar.
I’ve only rarely seen that sort of thing on a calendar, BTW. But if I’m choosing between two calendars I like, I’ll usually choose the one with more items on it, just because I like trivia. There’s no harm in having the movement of the planets marked, and who knows, maybe it’ll come up in conversation someday!
The part that puzzles me is that Mercury doesn’t go retrograde-- That’s a phenomenon that only occurs with planets further than the Earth from the Sun. My best guess is that they’re referring to its maximum separation from the Sun.
I have to say, as a former backyard astronomer, that I appreciated having the dates of some of the garden-variety planetary configurations marked on a calendar–opposition, conjunction, greatest elongation of Mercury and Venus.
But even at my backyard geekiest, I don’t think I ever assigned any importance to knowing when a planet went retrograde. That is really trivia of the highest order.
That’s not true- inner planets still appear to go retrograde when they’re at closest orbital approach* to Earth. Relevant Wikipedia article.
*Orbits can be assumed to be circular here.
Gilded Lily, objects in the sky like planets normally move in one direction (eastward relative to the stars) when you look at where they appear to be night to night. However, sometimes they move the other way (westward relative to the stars) because one planet is passing another in their orbits. It’s like when you pass a car on the freeway and the car appears to be moving backward relative to you, even though we all know it’s moving forward. It’s a trick of relative motion.