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Question on Saturns rings

  1. May 21, 2004 #1
    Many people who believe the Earth is 6,000 years old, claim that Saturn's rings would fall onto the planet or lump together or somthing in less than 10,000 years, "proving" that the universe is less than 10,000 years old. I told on that, to the best my knowlege that Titan and Saturn had a tug-of-war going and that keeps the rings intact. Am I correct, or is there another reason? :confused:

    Please don't turn this into a religon bashing fest.
     
  2. jcsd
  3. May 23, 2004 #2

    Nereid

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    Hi Oochy, welcome to Physics Forums!

    Saturn's rings are indeed fairly 'young', but more like hundreds of millions of years than tens of thousands. :eek: In my experience, the enormity of time is so hard to grasp that to many people '10,000 years' is effectively equivalent to '1 billion years'. However, once you've got some physics and maths under your belt, it becomes easier to get a feel for such immense timescales.

    There's a lot still to be learned about Saturn's rings, and the Cassini probe now approaching the system will help a lot. The outer edges of the rings are kept in place by a set of small moons; the F ring, which is very narrow, has a pair of 'shepherd' moons that keep it that way; the A ring (the main one) also has its edge kept sharp by a moon or two (I'd need to dig out some links to check; there's a nice site - Nine Planets? - with lots of info and plenty of links). The main divisions in the rings are also kept (mostly) clear by small moons.

    Did you know that Jupiter, Uranus and Neptune also have ring systems? Much is understood now about how they were formed, and how they will change over the next billion years or so; an over-simplified summary is: the shape, structure, and evolution of ring systems is closely tied to the many small moons at comparable distances from the parent planet; orbital resonance(s) plays an important role too.
     
  4. May 23, 2004 #3

    Janitor

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    I too have heard that the shepherd moons help keep the rings together.

    Even if it could be shown that rings are short-lived, the leap in conclusion to "the Universe is young" is not valid. The rings probably formed from the collision of bodies, and that collision could have occurred billions of years after the Universe got started, in which case any particular rings we see now are transient phenomena, and we just happen to be living at the same time the rings are in existence.

    Oochy, what do Young Earthers say about the scarring of the faces of most of the moons in our solar system? The density of craters suggests an awful lot of impacts of meteors on the moons, yet the currently-observed rate of meteor impact is so low that at such a rate, a mere 10,000 years worth of impacts would result in the moons being almost perfectly pristine at this time if the moons were only that age.
     
  5. May 23, 2004 #4

    Hurkyl

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    The flaw in this type of reasoning is this: why is it more reasonable to assume that moons were originally pristine instead of pitted?


    And to go slightly off on a tangent, does it even make sense to have a "pristine moon"? Surely they'd have plenty of time to absorb impacts while they were still forming...
     
  6. May 24, 2004 #5

    Janitor

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    And some Young Earthers say that the fossils of dinosaurs and such were placed by God or Satan as false evidence of things that never actually lived. So could God or Satan have built impact cratering into the moons at time-zero 10,000 years ago? I don't see why not.
     
  7. May 24, 2004 #6

    Phobos

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    As Nereid indicated, shepherd moons help keep the rings' material in place. The "Nine Planets" website (http://www.nineplanets.org/saturn.html) mentioned doesn't have much about it. IIRC, there is an inner and outer moon to a particular ring. As the inner moon swings by, it accelerates the ring material toward it and then the outer moon swings by and pulls the material back. That way, the material is prevented from spiraling into the planet. And we should learn more about it as the Cassini mission proceeds.

    And as Janitor said, even if rings can only last 10,000 years instead of 100,000,000, that tells little about the age of the universe - - hardly more than the age of the egg salad sandwich in my fridge - - since the rings are known to have been formed long after the beginning. The age of the rings places a lower bound (minimum) age on the universe, not the upper bound (maximum).
     
  8. May 24, 2004 #7
    Wow, thanks all! I'm not one to diss my fellow Christian, but I need stuff to realign their "scientific" reasoning.

    And yes, although I have never seen it used, the moon's surface is a thing I have used before.
     
  9. May 25, 2004 #8

    Phobos

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    A noble cause. Science and religion need not be at odds.
     
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