Absolute movement

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  • Thread starter Ross Arden
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if you have 3 space ships on the x, y and z axis and they blast off....one of them must be moving in an absolute sense.

Is it the case that if there is absolute movement then there MUST be absolute time also?
 

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  • #2
Drakkith
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if you have 3 space ships on the x, y and z axis and they blast off....one of them must be moving in an absolute sense.
No, once they stop accelerating then it would be equally true to say than any one of the ships is stationary and the other two are moving.

Is it the case that if there is absolute movement then there MUST be absolute time also?
I'm not sure, but I believe that it would imply something like that.
 
  • #3
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but an observer standing at the origin of the coordinate system would have to say that at least one of them is moving in an absolute sense

If there is absolute movement then the thing that is moving absolutely is moving a set distance in a set time
 
  • #4
Drakkith
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but an observer standing at the origin of the coordinate system would have to say that at least one of them is moving in an absolute sense
The observer would say that all of them are moving relative to them. All of the spaceships would say that the observer is moving and they are stationary.
 
  • #5
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if you have 3 space ships on the x, y and z axis and they blast off....one of them must be moving in an absolute sense.
No, they are all stationary in their own rest frame, and the other ships are moving relative to them.
There is no absolute rest frame
 
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  • #6
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but the observer would also have to say that one of the space ships is moving in an absolute sense. Im not saying he can tell which one, but one of them, including the observer must be moving
No, they are all stationary in their own rest frame, and the other ships are moving relative to them.
There is no absolute rest frame
But can anyone say they are all stationary?
 
  • #7
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one of them is definitely moving, it is not moving relative to something, it is absolutely moving
 
  • #8
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An observer at the launch site would see all of them moving.
The launch site is not in any special absolute frame though, it could be anywhere
 
  • #9
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is there a frame where the person in that frame can say they all stationary?
 
  • #10
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No, all of them are moving relative to any arbitrary spacetime coordinate you choose, other than where a ship is,
 
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so at least one of them is moving in an absolute sense, ie an absolute distance in an absolute time?
 
  • #12
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Define what you mean by absolute.
It's trickier than it might at first seem.
 
  • #13
russ_watters
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Thread locked. @Ross Arden, you should accept the answers you were given. Thanks everyone.
 
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  • #14
Dale
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if you have 3 space ships on the x, y and z axis and they blast off....one of them must be moving in an absolute sense.
No. At least one of them must be moving relative to anything. That is not the same as absolute motion.

Absolute motion is a different concept. It specifically refers to motion with respect to some single unique reference frame which is singled out by the laws of physics. It does not refer merely to a scenario where we are certain that at least one object is moving relative to any reference frame.

If it were absolute motion then there would be a physical experiment which could unambiguously and uniquely identify which one was absolutely at rest.

Edit: sorry about the late post, had to walk the dog in the middle of typing it
 
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