h a l f b a k e r yA riddle wrapped in a mystery inside a rich, flaky crust
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A clear disc is spun at near light speed. This means that light passing through nearer the edge travels further in the glass than light passing nearer the centre. The disc thus behaves like a concave lens.
Adjusting the speed of rotation will affect the focal length.
Penrose-Terrell rotation
http://en.wikipedia...se-Terrell_rotation
It's just an affine transformation in Minkowski spacetime [lurch, Jul 14 2011]
[link]
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I'm not sure about holding this up to my face to take pictures if it's spinning that fast ;-) |
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The light is travelling perpendicular to the direction of motion. Is there actually any effect? |
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Hmm. Very interesting thought. |
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Why would the spinning glass bend the light? |
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As I remember (from Sagan's "Cosmos" videos), as an object in relativistic motion passes a point perpendicular to the observer, that object will appear skewed, or rotated, such that the leading edge will appear to be farther away from the viewer than the trailing edge. |
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(That's the Terrell effect, see link) |
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While spinning a glass disc to relativistic speeds would certainly be impossible outside of a thought experiment, it might be possible to develop a similar effect inside a free-electron laser cavity, with the electrons being magnetically accelerated in a circle, perpendicular to the length of the laser, using a betatron-like apparatus. |
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Anyway - besides the effect of Penrose-Terrell, you've got the Fitzgerald contraction to deal with as well, and I'm certain that will have an effect on the geometry, but my brain is getting melty (right-left artistic-logical smackdown) so I can't imagine quite... |
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OK, this was a stupid idea. |
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I disagree. It might be dangerous (in terms of aneurysms for theoretical physicists) but I think it's fun. |
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This is vaguely baked, in that ordinary refraction is interaction between light and the material's electrons (which are sorta-kinda spinning around in circles). |
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I thought this was going to be about spinning an elastic transparent object so that centrifugal force influences the shape and controls the focal length. Using this principle, a short-sighted person could achieve clarity by looking directly up and spinning in circles very fast. |
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//I thought this was going to be about spinning an elastic transparent object so that centrifugal force influences the shape and controls the focal length//
Very half baked. |
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I originally thought this idea was going to be about spinning a lens so that dust and distortions don't show up, which is also baked. |
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Spinning a pool of mercury at far less than relativistic
velocities makes a good parabolic reflector. |
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I expect similar forces would destroy the glass plate
long before it got to any measurable fraction of c. |
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