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B If Earth moves at 500,000 mph then why don't satellites stay behind?

  1. Jan 6, 2017 #1
    If Earth moves at 500,000 MPH then why don't satellites get left behind?

    The solar system is orbiting the galaxy's central black hole, so, if you push a satellite in 1 direction while it attracts to Earth it will orbit Earth but should be left behind big time still.

    Also, if we were to place something in space that doesn't move, would it be left behind quickly?
     
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  3. Jan 6, 2017 #2

    phinds

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    And I guess the moon should be left behind too. And using that reasoning, all of the planets should get left behind as the sun orbits the center of the galaxy and all of the planets moons should get left behind as the planets orbit the sun and ...
     
  4. Jan 6, 2017 #3

    A.T.

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    According to what?
     
  5. Jan 6, 2017 #4
    Guess I'm going to have to explain this deeper. Here we go.

    If you put something in space and move it, it stays moving at the same speed. Earth itself is doing so at 500,00 MPH right now. If one of our satellites were to be placed in space at a exact location and so that it isn't moving AT ALL then it would keep its location in space while it watch Earth fly away from its-self fassst. Yes the satellite is being attracted to Earth but that doesn't keep it moving with it at the same speed of 500,00 MPH gravitational pull. And yes the satellite is moving in a direction so it orbits Earth and not fall to Earth but this movement again doesn't keep it moving with that 500,00 MPH Earth. So, why doesn't it get left behind if Earth is moving so fast? Would the satellite be left behind if we placed it so it isn't "moving" in space keeping its same location? It should be left behind then.
     
  6. Jan 6, 2017 #5

    TeethWhitener

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    How fast is the satellite moving when it's on the ground, before you launch it?
     
  7. Jan 6, 2017 #6

    Vanadium 50

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    Why does this have to be a satellite? If the earth is moving at 500,000 mph, why am I not pushed right out of my chair?
     
  8. Jan 6, 2017 #7

    ZapperZ

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    If you are on a fast-moving train, and you toss a ball upwards, why won't the ball fly off and get left behind?

    Zz.
     
  9. Jan 6, 2017 #8
    Because the Earth and the air very close to it are moving at 500,00 MPH.

    While if you put something in space completely out of the atmosphere so it is-not-moving keeping its location - it will be left behind.
     
  10. Jan 6, 2017 #9

    ZapperZ

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    No, because you can do this in vacuum, and the ball will still follow the same trajectory. Otherwise, the work that I do in ultra-high vacuum will look really weird with thing hitting the walls.

    So it has NOTHING to do with the air.

    Zz.
     
  11. Jan 6, 2017 #10
    The, then........ how !

    I had wondered that for the longest time too! Will the ball hit the vacuum's wall.

    Is it gravity?

    . . . HOW ! ?
     
  12. Jan 6, 2017 #11

    ZapperZ

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    You are discovering one of the most fundamental aspect of our universe that has been described by the likes of Newton and Einstein. The concept of inertial reference frame, whereby velocity is relative, and that a reference frame moving with some constant velocity with respect to something is no different than if it isn't moving at all! The laws of physics looks no different in a moving (with constant velocity) inertial frame than another frame that isn't moving with respect to some reference point.

    This is the fundamental tenet of classical mechanics and Special/General Relativity.

    Zz.
     
  13. Jan 6, 2017 #12

    phinds

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    No, it is not. It is rotating at a good clip but the center is stationary. That's according to my frame of reference. It is also going in circles. That's from the Moon's frame of reference. It is going in a different set of circles in the sun's frame of reference. It is also moving approximately linearly according to the CMB. There is no such thing as moving except in relation to something else. This is at the heart of your misunderstanding, as the zapper has already pointed out.
     
  14. Jan 6, 2017 #13

    Nugatory

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    Some unnecessary digressions have been removed from this thread.
     
    Last edited: Jan 6, 2017
  15. Jan 6, 2017 #14

    Nugatory

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    This problem was first solved by Galileo, early in the 16th century AD.

    Indeed it would.... If you really did place the satellite in space in such a way that "it isnt moving at all". But stop and think for a moment about what it means to place the satellite in space in such a way that "it isn't moving at all".

    You are floating motionless in space watching the earth zoom by at 500,000 mph. When you say something "isn't moving at all", you're saying that it is moving at zero mph relative to you. So yes, if we place the satellite somewhere in space where "it isn't moving at all" then of course it and the earth will move apart at 500,000 mph - that's what happens when one thing is moving at 500,000 mph relative to you and the other thing is moving at zero mph relative to you.

    But launching a satellite from a planet moving past you at 500,000 mph isn't placing it in space in such a way that it isn't moving at all relative to you. The satellite was moving at 500,000 mph relative to you while it was sitting on the launchpad.... and as you have correctly said above, if something starts out moving "it stays moving at the same speed". There's no force acting on it to slow it down after it leaves the launchpad, so it keeps moving at 500,000 mph relative to you. And if the satellite and the earth are both moving at 500,000 mph in the same direction relative to you, they're both moving at zero mph relative to one another, so they don't move apart.

    Someone moving in the same direction at 200,000 miles relative to you would describe the situation differently: they would say that they were floating motionless in space while the earth and the satellite (whether on the launch pad or above the surface of the earth) were zooming by at 300,000 mph and you were moving in the opposite direction at 200,000 mph. Both descriptions of the situation are equally valid.

    Now try describing the situation from the point of view of someone who is moving at 500,000 mph relative to you. What do they say about the motion of the earth and the satellite?
     
  16. Jan 6, 2017 #15

    Janus

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    I think you missed his meaning. He was asking why the ball isn't left behind by the train. Or let's put it another way. When you toss a ball, your hand starts by carrying the ball forward. then you let go. Does the ball, because you are no longer propelling it drop straight down to the ground, or keep moving forward int he the direction you hand was moving when you let go?
     
  17. Jan 6, 2017 #16

    russ_watters

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    That's some powerful air to be able to keep me moving at 500,000 mph while I'm sitting on my couch not even feeling a breeze!
     
  18. Jan 6, 2017 #17

    berkeman

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    Hi IsItSo,

    Can you tell us a little about your educational background so far? What level are you in school so far, and what physics and math classes have you taken so far. That will help us a lot to guide you with our replies. Thank you. :smile:
     
  19. Jan 6, 2017 #18

    russ_watters

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    We've been trying to help you with logic and examples, but let's be specific: Newton's first law says an object will continue in its current state of motion (including remaining at rest) unless acted on by an outside force. So an object doesn't need any help staying "moving" with Earth.
    http://hyperphysics.phy-astr.gsu.edu/hbase/Newt.html
     
  20. Jan 7, 2017 #19

    berkeman

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    The OP has been back and read our responses. Thread is closed unless he/she contacts me by PM to re-open it.
     
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