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There is no absolute velocity, but there is absolute acceleration. And the mountaintop is accelerating more because it's in circular motion with a larger radiu

by waqf 12y ago

There is no absolute velocity, but there is absolute acceleration. And the mountaintop is accelerating more because it's in circular motion with a larger radius. However, the effect of gravity is much more significant (if it weren't, the mountaintop would be flying out into space due to centripetal force).

DennisP 12y ago
But if I'm standing on the Earth's surface, it's not accelerating relative to me. It's always at the same distance and direction. Since acceleration is change in velocity, it's impossible to have absolute acceleration without absolute velocity. You can only say that it's accelerating compared to X.
- HCIdivision17 12y ago
  It actually is accelerating relative to you, in exactly the same way that a kid on the outside of a spinny-go-round is accelerating harder than a kid on the inside. Of course, there's not a huge difference, as a couple km is spare change to the radius of the planet, but it's there. There's definitely a constant vector difference between you and Everest's peak, and that's likely what you're thinking of. But Everest itself is under a greater strain to maintain that vector compared to you. And that's actually a measurable difference (where measurable is on scales of stupefying precision not normally used in everyday life). And as another noted, it really should maintain that relative vector - if it didn't, the earth wouldn't be in steady-state and you'd have a changing position vector between you and it, and that'd imply one of you was moving... hopefully it's you. (Let's ignore all the techtonic complications, as that really ruins the simplicity of the argument :) EDIT: As noted elsewhere in the thread, Everest isn't on the equator, and - if I may be bold enough to presume - you likely aren't either. So it's not clear if you or Everest is on the outside of the spinny-go-round in the analogy. For the purposes of wondering if velocity or gravitational effects on spacetime are the dominant factors, this has no effect. If you're actually interested in the effective relative centrifugal forces between you and Everest, then it's damn near everything.

by waqf 12y ago

DennisP 12y ago

But if I'm standing on the Earth's surface, it's not accelerating relative to me. It's always at the same distance and direction. Since acceleration is change in velocity, it's impossible to have absolute acceleration without absolute velocity. You can only say that it's accelerating compared to X.

HCIdivision17 12y ago
It actually is accelerating relative to you, in exactly the same way that a kid on the outside of a spinny-go-round is accelerating harder than a kid on the inside. Of course, there's not a huge difference, as a couple km is spare change to the radius of the planet, but it's there. There's definitely a constant vector difference between you and Everest's peak, and that's likely what you're thinking of. But Everest itself is under a greater strain to maintain that vector compared to you. And that's actually a measurable difference (where measurable is on scales of stupefying precision not normally used in everyday life). And as another noted, it really should maintain that relative vector - if it didn't, the earth wouldn't be in steady-state and you'd have a changing position vector between you and it, and that'd imply one of you was moving... hopefully it's you. (Let's ignore all the techtonic complications, as that really ruins the simplicity of the argument :) EDIT: As noted elsewhere in the thread, Everest isn't on the equator, and - if I may be bold enough to presume - you likely aren't either. So it's not clear if you or Everest is on the outside of the spinny-go-round in the analogy. For the purposes of wondering if velocity or gravitational effects on spacetime are the dominant factors, this has no effect. If you're actually interested in the effective relative centrifugal forces between you and Everest, then it's damn near everything.