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Direction of rotation in our Solar System

  1. Jul 11, 2009 #1
    Why do all of the planets revolve in just one direction? Is it due to the stability of the system?

    Do the satellites revolve arround earth in all possible directions, or there are only a few?
     
  2. jcsd
  3. Jul 11, 2009 #2

    physicsworks

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    1. I Think it is due to the features of the http://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System" [Broken]. Since any peace of dust initally had defined angular momentum (and thus defined directon of rotation) than, moving in the field of central force, this momentum had no chance to change its direction and length.
     
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  4. Jul 11, 2009 #3

    HallsofIvy

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    The direction in which artificial satellites revolve around the earth depends on how they were initially put into orbit. Although, because the earth itself rotates from west to east, it is MUCH EASIER to put a satellite into orbit going from west to east, using the earths rotational speed rather than fighting it.
     
  5. Jul 11, 2009 #4
    But the same effect may be caused as a result of collision in space two protostars - giant gas-dust balls. As a result of this impact their dense cores are stored as single objects, and shells dissipate. As a result create the binary system. In addition to two protostar formate a gas-dust protoplanetary disk. Balls of time condensed in the Sun and Jupiter. From dissipated shells are formed planets.
     
  6. Jul 11, 2009 #5
    Current theory is that a solar system starts as a lot of dust and maybe the occasional rock floating around here and there. The probability that a given area of dust in a galaxy has zero angular momentum is extremely small, considering all the fun things that happen among the stars and dust in a galaxy. So there will be some general swirling and non-zero angular momentum. The minority of rocks and dust that do happen to be moving against this general swirling and angular momentum will experience resistance that tends to cause them to go with the flow, so to speak. Sprinkle some floating dust on the surface of the water in a bucket, randomly stir the water briefly (not necessarily in a circle), and most of the time you'll eventually see the things settle down to at least some degree of general rotation (although certainly some of that is helped considerably by the round sides of the bucket, gravity plays a similar role in solar system formation).

    As was said by others, since the Earth rotates from west to east, launching a satellite west to east adds an extra ~800 miles per hour to the orbital velocity (assuming its launched from Cape Canaveral, for example) and launching it east to west subtracts ~800mph. So it takes a bigger launch vehicle to get a satellite orbiting east to west. So if it doesn't matter which way a particualr satellite goes, they will launch it west to east so they can use a cheaper launch vehicle. Where it does matter, they launch them in the direction as needed and pay extra for a bigger launch vehicle. For example, some satellites designed to take pictures of the Earth are even launched north-south so that they go over the poles. This is also one reason Florida was chosen for the main US space port--its closer to the equator and thus gives the satellite more initial velocity.
     
  7. Jul 11, 2009 #6

    DaveC426913

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    There are plenty of polar-orbiting satellites.
     
  8. Jul 11, 2009 #7

    D H

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    Several (most) of these are in sun synchronous orbits: inclination ~ 98.2 degrees (i.e., retrograde). The US launches such satellites from Vandenberg rather than the East coast because a south southwest launch places the trajectory over open water.
     
  9. Jul 11, 2009 #8


    really? why wouldn't it be the same?

    wouldn't they be like saying it's easier to run from west to east than it is to run from east to west?
     
  10. Jul 11, 2009 #9

    DaveC426913

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    It's easier to run from west to east if you start by jumping off a train moving from west to east, yes.

    If, instead, you jumped off the train to run east to west, you'd have lost all the momentum the train could have given you - you'd have to jump much harder to reach the same speed.
     
    Last edited: Jul 11, 2009
  11. Jul 12, 2009 #10
    but velocity is relative, and using your analogy, the train in this case is the earth. if you jumped on the train, you should be able to jump in any direction equally becuase your velocity is relative to the speed of the train. So even though you are jumping backwards, you're actually still moving forwards due to inertia, but relative to the train, you have moved farther back.
     
  12. Jul 12, 2009 #11

    Chronos

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    Agreed, velocity is relative. If you jump off a car in the direction of travel, the velocity is additive [your jump velocity plus the car velocity]. If you jump opposite the direction of travel, it is your jump velocity minus the car velocity. It will appear, from your reference frame, that you jumped a much larger distance from the car if you jump backwards, but that is an illusion. To a stationary observer, you appear to be a contender for long jump champion of the world if you leap in the direction the car is travelling.
     
  13. Jul 12, 2009 #12
    ok so i still don't understand how a satellite being launched from west to east is easier, given that like you said, it's all based on the frame of reference, and the frame of reference is the Earth. In that, it doesn't actually matter to a static observer which velocity the satellite is going, only that it is moving slower than the Earth is spinning to achieve the effect of it going east to west.

    Could it maybe a weather thing? Winds to go eastward?
     
  14. Jul 12, 2009 #13
    ok so i did a bit of research and i got this explanation.
    http://answers.yahoo.com/question/i...SLR.klgjzKIX;_ylv=3?qid=20081130121636AASe5jg

    however, my question now is, ok fine, it's got the 1000mph head boast, but isn't this figure irrelevant because once it's in orbit, it HAS to keep a 1000mph just to stay stationary.

    1000 mph in effect becomes the new 0 MPH. If it goes less than that it's traveling west, if it goes faster than that it goes east.
     
  15. Jul 12, 2009 #14

    DaveC426913

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    What you're missing is that "the required speed of the satellite" (to stay in orbit) is not "relative to the moving surface of the Earth". It is "relative to an external frame of reference".

    Whether the Earth were non-rotating, or the Earth spun at 1 rotation per hour (25,000mph at the equator), the satellite must orbit at the same speed: ~18,000mph - as seen from an external POV. i.e. once in orbit, the Earth's rotational speed is irrelevant to the satellite's orbital speed.
     
  16. Jul 12, 2009 #15

    russ_watters

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    ....So when orbiting from west to east, a satellite appears to an observer on the ground to be moving at 17,000 mph, but when orbiting from east to west a satellite appears to be moving at 19,000 mph.
     
  17. Jul 13, 2009 #16

    ideasrule

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    Yes, Newton's laws only apply to inertial reference frames. Earth's surface is not inertial; it's accelerating towards the center.
     
  18. Jul 13, 2009 #17

    russ_watters

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    How is that post useful? It doesn't seem to me to have anything to do with what Dave said.
     
  19. Jul 13, 2009 #18

    DaveC426913

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    Thank you. I thought it was just me. :tongue2:
     
  20. Jul 15, 2009 #19

    Chronos

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    Footnote for ideal: It dont matter after you leap, but, is hugely important when you leap. This is physics 101. If you fall out the door of a car going 60 miles per hour, it will hurt more than falling out of a car going 0 miles per hour.
     
  21. Jul 15, 2009 #20
    Hello,

    Thankyou every body for your valuable comments. I have been reading along since then but got the feeling that the matter is getting more difficult. The most interesting answer was that any turbulence on water surface in a round utencil gets into circular motion, uniform and unidirectional. I am thinking over it. How the gravity could perform the similiar role? Am I not on side of being mislead by an anology?
     
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