From: Hal Finney (hal@finney.org)
Date: Tue Jun 10 2003 - 23:31:09 MDT
I had written:
>>As the star passes by an observer, the field points to the current
>>position of the star. That's because the field is moving uniformly with
>>the star. In the case of a wooden framework, the beams would point
>>directly at where the star is right now, because that is how the frame is
>>built.
Damien B. comments:
> when I tried building one, my
> timber framework started to bend at the far ends, and eventually snapped
> off. I am making a serious objection here.
and later:
> As I understand it, frame dragging near a rapidly spinning black hole is
> due precisely to such a lag. And on a more prosaic level, magnetic field
> lines from the surface of the Sun get snarled and tangled as a result of
> rotation.
I'm not sure I understand your point. There is no rotation in this
example.
The "timber framework" would experience lessened gravitational fields
the farther it got from the star, so there would be no difficulty in
constructing it, in principle. It would include boards which point
radially back at the center of the star. The point of the example is
that even a moving observer will agree that the boards point towards
the star's current, and not time-lagged, position, assuming the motion
is uniform.
Hal
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