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Re: [Phys-L] cosmology activities



On 5/31/2019 3:09 PM, David Bowman wrote:
Regarding:

The key idea is to use /masking tape/ to construct geodesics.
You can apply tape to surfaces that have zero or nonzero
intrinsic curvature and see what happens.
This is an excellent suggestion. I would only warn that in order for the analogy to work properly the tape needs to be *carefully* laid down on the surface locally straight/even with no bunching/wrinkling or stretching/tearing of the tape material as it is laid down. If the surface has significant curvature over a length scale comparable to the width of the tape and the tape *can't* be laid down without local distortion, then the tape needs to be laid down in a way that any unavoidable stretching or binding is laterally symmetric across the centerline of the tape. (But maybe this caveat is included in one of JD's lurid details.)

David Bowman
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I suppose I had better bring the usual note of practicality to this amusing idea. Masking tape these days may be purchased in a form that can mask quite small radii. This is NOT the tape for this demonstration.

Brian W