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Moon's Bulge Explained

Posted by ryuzaki0 on from the put-some-cream-on-that dept.

anthemaniac writes "The moon has an unexplained bulge that astronomers have been trying to find a source for since 1799. Finally, an apparent answer: The equatorial bulge developed back when the developing moon was like molasses (and you thought it was cheese!) and, rather than today's nearly circular orbit, it 'moved in an eccentric oval-shaped orbit 100 million years after its violent formation.'"

26 of 204 comments (clear)

  1. no by GigsVT · · Score: 5, Funny

    It's just happy to see you.

    --
    I've had enough abrasive sigs. Kittens are cute and fuzzy.
  2. Uh huh by Anonymous Coward · · Score: 4, Funny

    Its nothing more than a little baby fat.

  3. Come on people, give the moon a break... by Bamafan77 · · Score: 5, Funny

    Everyone knows your metabolism slows down after a certain age. Still though, a half hour a day on the treadmill probably wouldn't hurt either.

    1. Re:Come on people, give the moon a break... by Anonymous Coward · · Score: 5, Funny

      30 minutes a day on the treadmill? The fucker goes 1km/sec ALL DAY LONG!

      YOU do that, fat-ass!

    2. Re:Come on people, give the moon a break... by isellmacs · · Score: 5, Informative
      http://en.wikipedia.org/wiki/Luna_(moon)

      http://en.wikipedia.org/wiki/Selene

      I'd say "Her" would be appropriate, as the name Luna (the name of our moon) comes from the Roman Goddess of the Moon.

    3. Re:Come on people, give the moon a break... by 19thNervousBreakdown · · Score: 4, Funny

      (Wait, the moon IS a chick, isn't it?)

      Hmm. So beautiful it inspires poetry, so attractive it pulls the sea, and men feel compelled to spend more than they can afford just to walk all over it. Oh, and let's not forget, every 28 days it swells and causes dogs to howl.

      I think you're on the right track.

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    4. Re:Come on people, give the moon a break... by gkhan1 · · Score: 3, Interesting

      If that is true, it is a baaad mythology. The moon has always in the human mind been female, for basically every known religion. It was a good long while since I studied this, so I apologise if I make any mistakes.

      In most (almost all I think) mythologies there exists a goddess that is identified with the moon (and a god that is identified with the sun, although he is rarely as important). For instance in greek mythology, it's Artemis, the goddess of the new moon. See, it has everything to do with phases. That's a funadmental theme in many religions, the cycle of birth-life-death-rebirth. The moon is the perfect symbol for this, first being very small (new moon), to becoming brilliant (full moon) to eventually dying (dark moon), and then being reborn (new moon again). This is closely tied to another classic mythological motif (a favourite of mine), that of the descent to the underworld. This one is everywhere in mythology and literature, Inanna does it, Jesus does it, Gandalf does it (when he fights the Balrog), frickin' Harry Potter does it. The motif is basically where a "hero" (Inanna/Jesus/Gandalf/Harry!) descends to the land of the dead (sumerian underworld/hell/beneth the mines of Moria/the Chamber of secrets), on the way he/she gets "undressed", either metaphorically or literally (Inanna loses her armour i think/Jesus is whipped and put on a cross/Gandalf skipped that part of the mythology/Harry loses both Ron and Hermione), faces the dark side of himself/herself (Erishkigal/the Devil/the Balrog/Voldemort), dies and is reborn (Inanna comes back/Jesus gets resurrected/Gandalf becomes Gandalf the white/Harry is resurrected by the Pheonix). Anyway, this is a tangent, back to the point.

      This montly cycle does not only symbolize life and death, but also a decidedly more feminine cycle (if you can't guess what it is, I ain't gonna tell ya). While this connection is rarely explicit, it is certainly present. The moon also symbolizes many aspects that we as humans connect with femininity, such as darkness, magic, mystery and death, wheras the sun symbolizes typically male attributes such as ligth, reason, strength and life (it's so sexist that I can barely type without gagging, but that is the way the archetypes work). Therefore, the moon is often assigned to a female deity. Infact, because of the phases thing, it is sometimes assigned several. Artemis is the virgin goddess of life, the hunt and rebirth, and is the goddess of the new moon. Hecate, the dark witch-queen of sorcery is essentially the dark side of Artemis, is the dark moons goddess. One interpretation of this is that once a month, the beautiful, lively, and wonderful goddess (=a woman) turns into a raging witch-queen (=a bitch). (I'm telling you, this is so god-damn sexist, I want to vomit!) This female connection with the moon is the reason that many dark and mysterious concepts are frequently connected to women, such as intuition. You never hear anyone mention male intuition, do you? This is also why there are much more witches than warlocks in mythology and literature.

      Anyway, I've been rambling on for a while now, and I should stop. The point is, if Tolkien chose to make the moon male, he made the wrong choice. In the human mind the moon is, and has always been, female.

    5. Re:Come on people, give the moon a break... by Shadow+Of+The+Sun · · Score: 4, Informative

      In the Norse mythos, the moon is masculine and the sun is feminine.

      And almost everything that Tolkien wrote is based off of the Norse mythos. For example, the Norse term for the Earth is Midgard. Midgard means "Middle Earth."

    6. Re:Come on people, give the moon a break... by Chr0nik · · Score: 3, Interesting

      In ancient Arab and Sumerian religions, the moon was a Male god, and was considered the King of gods. You can see the crescent moon on much of the period coins etc. Harran was the literal city of the moon god and was named after him. Long before Muslims undertook Haaj to Mecca, it was a center for a religion of this type. The Kabah actually pre-existed Islam. In Babylon there were two distinct versions of this polytheism one in which the moon god was a man, and the other in which it was a woman. The Male versions of the moon God when by many different names, Sin(pronounced seen), Allah, Haran, Aksum, Yerah... Probably many others. In Egypt, Greece, and later, Rome it was always a woman, because by that time, it had been determined to be a smaller body than the sun, although closer. Since it was smaller, it could obviously not be male... Oh yeah, and saying that mythos regarding rebirth is related to the mentral cycle is like saying that my paying bills every thirty or so days is related the wife's cycle. That's simply rediculous, because if that was true, the fucking bills would come at a much better time of the month.

      --


      ... what did you expect, something profound?
  4. The answer is apparent. by BoBathan · · Score: 5, Funny

    Bulge at the equator, violent formation, clearly the Moon is American.

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    EOF
  5. sometimes... things come to mind... by CarnivoreMan · · Score: 3, Funny

    Well... perhaps the man in the moon was thinkin about some of them women from Venus....

  6. Excellent... by Quaoar · · Score: 4, Funny

    Now when I have to explain the bulge in my pants, I'll say it's because I'm eccentric! /Badump bump

    --
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  7. scientific explanation debunked by peektwice · · Score: 4, Funny

    It's a codpiece.

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  8. Monolith? by wingfoot · · Score: 4, Funny

    There wouldn't happen to be a strong magnetic field at the bulge would there....? How about a black monolith buried beneath the surface causing the bulge....?

  9. Missing energy by Harmonious+Botch · · Score: 4, Interesting

    So how did the eccentric orbit become so nearly circular? That takes a lot of energy ( and a little coincidence )

    1. Re:Missing energy by Jazzer_Techie · · Score: 5, Informative

      Actually, circular orbits are the lowest energy state. Thus, tidal forces cause the system to gradually lose energy until it settles into a circular orbit. When you add up the 1/r potential of gravity and the repulsive 1/r^2 centrifugal potential, you get a function with a nice minimum which is the radius of a circular orbit. The reason that elliptical orbits occur is because the period of the orbit exactly matches the period of oscillations around the minimum potential. Thus when you go around once, you end up right back where you started and get a closed, elliptical orbit. (Note that this is true only for Newtonian mechanics. Once you take General Relativity into account, the periods aren't the same and orbits precess. We can directly observe this in the orbit of Mercury as a perhelion shift of 43 arcseconds/century.)

    2. Re:Missing energy by gardyloo · · Score: 3, Interesting

      Whoa. What's the repulsive 1/r^2 "centrifugal" potential? At first I thought you were including G.R. with the talk of tidal forces, but then I realized (via the 1/r potential) that you're talking about regular old Newtonian gravity. That's fine. But where's the repulsive potential?
            The only tidal forces I can see in this problem are evinced in the deformation of the earth or the moon, their atmospheres, and the ocean of the earth. Wikipedia has this to say about tidal locking:

      There is a tendency for a moon to orient itself in the lowest energy configuration, with the heavy side facing the planet. Irregular shaped bodies will align their long axis to point towards the planet. Both cases are analogous to how a rounded floating object will orient itself with its heavy end downwards. In many cases this planet-facing hemisphere is visibly different from the rest of the moon's surface.

      The orientation of the Earth's moon might be related to this process. The lunar maria are composed of basalt, which is heavier than the surrounding highland crust, and were formed on the side of the moon on which the crust is markedly thinner. The Earth-facing hemisphere contains all the large maria. The simple picture of the moon stabilising with its heavy side towards the Earth is incorrect, however, because the tidal locking occurred over a very short timescale of a thousand years or less, while the Maria formed much later.

          I'll have to try to work out how tidal forces within one astronomical body might lead to a circular orbit. It might be a well-known effect, but it's not obvious to me.

  10. Re:Wait a minute... by Kelson · · Score: 3, Informative

    The radius at the equator is slightly longer than the radius at the poles. It's not quite a perfect sphere.* Sort of like if you took a rubber ball, set it on the floor, then pushed down slightly.

    The same is true of the Earth, though I believe it's generally attributed to the Earth's rotation.

    * Yes, I know that craters and such interfere with it being a perfect sphere too. No need to get pedantic, people of Slashdot. Well, no more than usual.

  11. Like a dinosaur by Namarrgon · · Score: 4, Funny

    It's thin at one end, much much thicker in the middle, and thin again at the other end.

    I have another theory, you know...

    --
    Why would anyone engrave "Elbereth"?
  12. shapes by ah247msg · · Score: 4, Funny

    I wish the bulge around my middle had as good an explanation... adam0@247msg.com

  13. mmmm.... by denttford · · Score: 5, Funny

    Space Beer.

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  14. I don't think so by npietraniec · · Score: 3, Informative

    The moon is actually a spaceship. http://www.theforbiddenknowledge.com/hardtruth/moo n_spaceship.htm

  15. Re:Wait a minute... by Mr.+Underbridge · · Score: 4, Insightful

    Right. I'd assume these guys accounted for the tendency of a rotating body to form an oblate spheroid, and that the moon's current orbit can't account for the degree of its oblacity (if that's a word). Thus it would need to have exhibited some more violent orbit in the past.

  16. Re:Wait a minute... by Billosaur · · Score: 4, Insightful

    Don't all circular/spherical objects bulge around the middle?

    If they are planets and they are spinning, yes. Just look at pics of the Jovian worlds, especially Saturn. And the Sun has a definite bulge. Of course, for most of the planets, the bulge is pronounced because they are still elastic to some degree. The Earth bulges owing to the fact that the continents are riding around on their crustal plates, which ooze on molten material, and the Moon is tugging on them as it goes aroudn us. The Moon's is more fascinating because it is a geologically dead world, so the bulge happened some time in the past and then got frozen in place.

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  17. Re:Eccentric vs. Circular Orbit by Anonymous Coward · · Score: 3, Informative

    While you have a very interesting theory, I think it is more likely due to the fact that circular orbits are the lowest energy state. Thus, tidal forces cause the system to gradually lose energy until it settles into a circular orbit. When you add up the 1/r potential of gravity and the repulsive 1/r^2 centrifugal potential, you get a function with a nice minimum which is the radius of a circular orbit. The reason that elliptical orbits occur is because the period of the orbit exactly matches the period of oscillations around the minimum potential. Thus when you go around once, you end up right back where you started and get a closed, elliptical orbit. (Note that this is true only for Newtonian mechanics. Once you take General Relativity into account, the periods aren't the same and orbits precess. We can directly observe this in the orbit of Mercury as a perhelion shift of 43 arcseconds/century.) . . . more or less.

  18. Fondue by fattybob · · Score: 3, Funny

    Mollases is more of a textural camparsion, but it must be remembered that this occured as the moon cooled, cooling from molten to solid cheese, so perhaps a better explanation would be that the bulge occured during cooling while the moon was like Fondue.