Luna nobis custodit
September 17, 2017 6:05 AM Subscribe
Moon Phases 2017 [5 relatively soothing minutes] This 4K visualization shows the moon's phase and libration at hourly intervals throughout 2017, as viewed from the Northern Hemisphere. Each frame represents one hour. In addition, this visualization shows the moon's orbit position, sub-Earth and subsolar points, distance from the Earth at true scale, and labels of craters near the terminator. Production music provided by Killer Tracks.
My favorite part is the diagram in the upper left showing the relative positions of the earth, moon, and sun. (The sun is implied by the direction of the light--the distance would be too great to show it in the same scale as the earth & moon.) I think it's the clearest demonstration I've seen of how the phases happen.
posted by Weftage at 7:27 AM on September 17, 2017
posted by Weftage at 7:27 AM on September 17, 2017
I don't really understand how the near side apparently rotates clockwise (watch how Copernicus -- the big whitish crater in the dark blobs -- rotates around).
Anyway. Great!
posted by notyou at 7:39 AM on September 17, 2017
Anyway. Great!
posted by notyou at 7:39 AM on September 17, 2017
notyou, I was also interested in the wobble. The explanation I found is that because the moon's orbit is elliptical, it speeds up and slows down during its orbit, which causes slight changes to what portion of the lunar surface is directly facing Earth. Here is one (not very detailed) explanation:
From Nasa's website
posted by Pistache at 7:56 AM on September 17, 2017 [1 favorite]
From Nasa's website
posted by Pistache at 7:56 AM on September 17, 2017 [1 favorite]
And the Earth just sits there spinning along as if that was just a normal thing to do for forever..
posted by Mei's lost sandal at 8:00 AM on September 17, 2017 [3 favorites]
posted by Mei's lost sandal at 8:00 AM on September 17, 2017 [3 favorites]
Pistache: From your link I learned that the wobble is the "libration" mentioned in the fpp.
Thanks!
posted by notyou at 8:08 AM on September 17, 2017 [1 favorite]
Thanks!
posted by notyou at 8:08 AM on September 17, 2017 [1 favorite]
Also, notice:
-that on the spinning Earth globe in the upper-left corner, the shadowed part changes with the seasons. At the equinoxes, the shadow crosses the North Pole; during summer solstice the North Pole is quite uncovered, and by the winter solstice, the shadow covers the Pole all the time
-that the long line across the middle of the screen keeps the Earth-Moon axis horizontal; since the Moon actually travels in an orbit whose plane is not in line with the Earth's spinning axis, the Earth appears to wobble back and forth as it spins.
Really cool!
posted by notsnot at 8:16 AM on September 17, 2017 [1 favorite]
-that on the spinning Earth globe in the upper-left corner, the shadowed part changes with the seasons. At the equinoxes, the shadow crosses the North Pole; during summer solstice the North Pole is quite uncovered, and by the winter solstice, the shadow covers the Pole all the time
-that the long line across the middle of the screen keeps the Earth-Moon axis horizontal; since the Moon actually travels in an orbit whose plane is not in line with the Earth's spinning axis, the Earth appears to wobble back and forth as it spins.
Really cool!
posted by notsnot at 8:16 AM on September 17, 2017 [1 favorite]
I often wonder what sort of content I'd have if I had a fully programmable large hangable wall display dedicated to a slow cycle of earth and space data. This, preferably as an app that ran in real time, would definitely be on it.
posted by Devonian at 9:01 AM on September 17, 2017 [2 favorites]
posted by Devonian at 9:01 AM on September 17, 2017 [2 favorites]
Mei: Like flight, the Earth's rotation is something that I understand from AP Physics and algebra but which still makes no sense. Much less the idea that the rotation is what generates little-g gravity.
posted by radicalawyer at 9:20 AM on September 17, 2017
posted by radicalawyer at 9:20 AM on September 17, 2017
Best Apple Watch face yet!
(Seriously, that was really cool!)
posted by TedW at 10:29 AM on September 17, 2017
(Seriously, that was really cool!)
posted by TedW at 10:29 AM on September 17, 2017
the rotation is what generates little-g gravity.
Say what now?
posted by Mei's lost sandal at 10:43 AM on September 17, 2017
Say what now?
posted by Mei's lost sandal at 10:43 AM on September 17, 2017
I find it tragically beautiful how many times the surface of the Moon has been pelted by huge space debris. Makes you wonder what would have happened if any of that made it to Earth.
posted by hairless ape at 1:26 PM on September 17, 2017
posted by hairless ape at 1:26 PM on September 17, 2017
Just beautiful. I could watch that for hours. Actually, I think I did just sacrifice an hour to it. Wonderful.
posted by Purposeful Grimace at 1:32 PM on September 17, 2017
posted by Purposeful Grimace at 1:32 PM on September 17, 2017
For our readers in the southern hemisphere, allow me to translate pracowity's mysterious comment:
C O D
posted by Wolfdog at 1:52 PM on September 17, 2017
C O D
posted by Wolfdog at 1:52 PM on September 17, 2017
Much less the idea that the rotation is what generates little-g gravity.
I may be misunderstanding what you're saying here, but I can say I've run across this notion before. If so, I think you may be conflating the ability of a centrifugal force to mimic the effects of gravity, with the actual force of gravity. They aren't the same thing though. Earth's spin has nothing to do with its gravity, that is instead a function of its mass.
For centripetal/centrifugal force to mimic gravity, you'd need to be on the inside of a spinning object, say the inside floor a spinning tire-shaped object, a la John Varley's Titan, Niven's Ringworld, Banks' Orbitals, or Bungie's Halos.
On Earth, any centripetal force we're feeling is effectively flinging us away from the surface, not holding us down. Thankfully, at Earth's rotational speeds, the effect is negligible, and the gravity generated from the sheer mass beneath our feet easily overcomes any such proclivity of the mass of our bodies to flee into space—and thank goodness, otherwise the implications get uglier and uglier the closer you get to the equators.
Please do forgive the pedantic tilt of this—even though it's what MetaFilter excels at, I cringe to think how I sound here. But I actually have run across this notion several times in people, often enough that it seems to be one of those concepts that sometimes gets crosswired in childhood and then later not reexamined because it's simply not that important to everyday life. I can actually distinctly remember my own confusion as a child when I ran across the idea of spinning forces mimicking gravity, and was trying to work out the implications in a 3D environment.
On a side note, if you've ever been confused about the distinction between centripetal and centrifugal forces, this little bit breaks it down nicely.
posted by los pantalones del muerte at 7:16 PM on September 17, 2017 [3 favorites]
I may be misunderstanding what you're saying here, but I can say I've run across this notion before. If so, I think you may be conflating the ability of a centrifugal force to mimic the effects of gravity, with the actual force of gravity. They aren't the same thing though. Earth's spin has nothing to do with its gravity, that is instead a function of its mass.
For centripetal/centrifugal force to mimic gravity, you'd need to be on the inside of a spinning object, say the inside floor a spinning tire-shaped object, a la John Varley's Titan, Niven's Ringworld, Banks' Orbitals, or Bungie's Halos.
On Earth, any centripetal force we're feeling is effectively flinging us away from the surface, not holding us down. Thankfully, at Earth's rotational speeds, the effect is negligible, and the gravity generated from the sheer mass beneath our feet easily overcomes any such proclivity of the mass of our bodies to flee into space—and thank goodness, otherwise the implications get uglier and uglier the closer you get to the equators.
Please do forgive the pedantic tilt of this—even though it's what MetaFilter excels at, I cringe to think how I sound here. But I actually have run across this notion several times in people, often enough that it seems to be one of those concepts that sometimes gets crosswired in childhood and then later not reexamined because it's simply not that important to everyday life. I can actually distinctly remember my own confusion as a child when I ran across the idea of spinning forces mimicking gravity, and was trying to work out the implications in a 3D environment.
On a side note, if you've ever been confused about the distinction between centripetal and centrifugal forces, this little bit breaks it down nicely.
posted by los pantalones del muerte at 7:16 PM on September 17, 2017 [3 favorites]
I didn't realize we could see so much of the surface (the libration is more than I'd imagined).
posted by bonobothegreat at 9:03 PM on September 17, 2017
posted by bonobothegreat at 9:03 PM on September 17, 2017
The way it only labels craters and other surface features of the moon at the terminator is artistic genius, keeping the view of the moon mostly uncluttered and labeling those features right at the moment that the low angle of the sun makes them most distinct and visible. Beautiful.
posted by straight at 9:50 PM on September 17, 2017 [1 favorite]
posted by straight at 9:50 PM on September 17, 2017 [1 favorite]
Somehow I had never come across the word libration until this thread. Now, like a child with a shiny new toy, I can't wait to show it off the first chance I get.
posted by TedW at 5:46 AM on September 18, 2017
posted by TedW at 5:46 AM on September 18, 2017
Sky at Night fans of a certain age - I stand with you - will have memories of Patrick Moore explaining it to them. And once Patrick Moore explains something to you, it stays explained.
posted by Devonian at 7:36 AM on September 18, 2017 [1 favorite]
posted by Devonian at 7:36 AM on September 18, 2017 [1 favorite]
"Spirit boating" is the best one.
posted by runcibleshaw at 9:07 AM on September 18, 2017
posted by runcibleshaw at 9:07 AM on September 18, 2017
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