Super duper


The full moon will be will be about 221,802 miles from Earth tonight, which is about 15,300 miles (roughly 7%) closer than average, and therefore is making its way into the popular consciousness as a "supermoon."  Wikipedia sniffs that it's really called a perigee-syzygy, and that indeed all full moons are really just plain old syzygys.  ("Syzygies," which probably is more correct, lacks orthographical style and balance.)  I don't think the snooty name is going to catch on; it's hard to rhyme and it doesn't scan worth a hoot. Although "perigee" and "syzygy" aren't bad dactylic oblique rhymes for each other, they wouldn't make a satisfying limerick.

There's been some crazy talk lately about how much stronger the tidal forces will be, or how big and bright the moon is going to look, or even what social paroxysms may be observed.  Newspapers tend to say it will be "14% bigger and brighter," whatever that means.  A disk area of 14% greater size, I suppose?  That sounds bigger than it looks to the naked eye.  Here's what a 12% increase looks like, from 2011's perigee-syzygy-superdupermegamoon:

As for tides, the effect hasn't been that great in the past.  Supermoons happen pretty often, about once a year.  The variation results from our satellite's elliptical orbit.  Although the moon's orbit has a period (obviously) of one month, the "bump" of the ellipse is out of synch with the full-new-moon-phase cycle by a couple of days, so it takes a little over a year to repeat a line-up of the full moon with the short end of the ellipse.  Solar eclipses (not to be confused with ellipses) also are affected by how close the moon is to the Earth, as well as how close the Earth is to the sun; that can make the difference between a really dark eclipse and one with a bright ring of sun peeking out all around the dark moon.  Eclipses, however, exhibit much longer cycles than supermoons, because eclipses also are affected by the fact that the moon's orbit around the earth is about 5 degrees off of the plane of the earth's orbit around the sun, a retrogressing wobble that makes the plane of the moon's orbit cross the plane of the Earth's orbit in a direct line between Earth and sun only every 18 years or so.

It's been so cloudy here that I'm not sure we're going to see the supermoon at all, but we'll make sure the guns are loaded anyway, in case of a zombie apocalypse.

15 comments:

bthun said...

Walkin' Boss is at a horse show this week so being in bachelor mode, I had a brew or trice on the front porch last evening. At around 11:00 pm noticed how nice (and a wee bit larger than usual*) the moon appeared.

Zombies? We're always at DEFCON 4. Any abnormal dog yapping allows ample time to hit DEFCON 2, or 1 should a zombie wander onto the Hun hovel patch...

*I can usually pick the correctly sized wrench or socket from a glance at the size of the bolt head... Less a talent than years of conditioning, i.e. a stupid human trick.

Grim said...

I've been watching this moon develop unusually closely, the last week or so. It's been lovely; I wasn't aware of it being larger, but I wasn't looking for that. It just caught my eye for some reason.

karrde said...

Saw the bright moon high in the sky at about midnight last night.

I wasn't able to look closely, though, as I had to keep my eyes on the road (and keep the motorcycle vertical).

Is the full moon (super perigee syzygy with extra brightness) Friday night, or Saturday night?

Texan99 said...

Saturday.

DL Sly said...

"...they wouldn't make a satisfying limerick."

He said, "The moon is so lovely
Hanging in the night sky so idly.
Don't think me a boob,
For grabbing my tube,
To check for perigee syzygy.
0>:~}

Anonymous said...

Zombies? No, no, it's werewolves you have to look out for tonight. Remember to get your lycanthrop insurance before moonrise or your policy will not become effective until the next scheduled full moon. :P

LittleRed1

Tom said...

There once was a girl named Suzy
Who loved the moon at syzygy
Afraid of collision
She risked all derision
And fled from lunar perigee

Assistant Village Idiot said...

"Syzygy" is a great word for Hangman. (So are "gypsy" and "rhythm," but you have to spread them out so that people aren't on to you game.)

bthun said...

"Zombies? No, no, it's werewolves you have to look out for tonight. Remember to get your lycanthrop insurance before moonrise or your policy will not become effective until the next scheduled full moon."

No problemo. I self-insure with Winchester Ballistic Silvertip ammo in .223, 30-06, and 7mm RemMag. The right tool for the job as it were... =8^}

Grim said...

No sign of zombies here, but it sure is a pretty moon.

bthun said...

It was a pretty moon. A little hazy, with high thin clouds, but no ghouls...

Anonymous said...

First time I've ever heard that word actually used in a sentence.
(And you know which word I'm referring to, don't you?)

BillT said...

Supermoons happen pretty often, about once a year.

Perigee moons occur at least three times a year, four in some, with almost no effect on tides.

The only significant effect a "supermoon" produces is to strike panic into the minds of people whose attention spans rival that of goldfish...

Texan99 said...

Ah, BillT, but a perigee-syzygy moon is different. It has three more syllables.

From what I was reading, the perigee effect is faintly measurable in the tides, but it's a matter of a couple of centimeters. Nothing to evacuate the waterfront properties over, unless you were already cutting it awfully close. Any self-respecting low-pressure area does more to exaggerate the local high tide.

A lot of intuitive notions about astronomical effects lose sight of the scale of the many forces contributing to the background noise -- as we already know very well from popular notions about climate change.

BillT said...

Most of the background noise associated with climate change is produced by the carbon dioxide released whenever some UN "scientific" functionary opens his yap...