Thursday Throughput: Io Edition


Michael Siegel

Michael Siegel is an astronomer living in Pennsylvania. He is on Twitter, blogs at his own site, and has written a novel.

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10 Responses

  1. Avatar Jaybird

    The experiment that I heard about that, now that I’m thinking about it, must not have worked.

    Imagine, if you will, an octogon mirror box. In the style of a cylinder.

    Now imagine two mirrors, at a 90 degree angle, a mile away. These mirrors are set up in such a way that if you shoot a laser at the cylinder at a 90 degree angle to it, offset by a few inches, the light travels a mile to hit the angle bounces 90 degrees to hit the other mirror, then bounces back and hits the cylinder again on one of the other mirrors two sides away and go in the exact same spot as if you were shining the laser without the cylinder there in the first place. That same exact spot is where you have the measuring device. It just needs to be something that says “yep, I’m being hit with a laser!”

    With me?

    Then start rotating the cylinder. When you find the speed at which the cylinder can turn and the initial flash of light bounces off of the first mirror and goes two miles, comes back, and hits the mirror only one side away (instead of two) and you’ve got the speed of light.

    As a kid, I thought that that was elegant.

    And *NOW* I’m thinking “that requires a level of precision that makes sense in comic books but they’d never be able to pull that off in real life.”

    And the planet example is elegant as hell. And it predates Watt’s steam engine.Report

    • Avatar Michael Siegel

      That experiment works just fine. We did it as undergraduates. You shine a laser onto a spinning mirror. The beam goes to a second mirror and comes back, at which point the mirror has moved slightly and creates a dot offset from the original. That was done in the late 19th century to try to characterize the ether.Report

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