Thursday Throughput for July 4, 2019

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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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17 Responses

  1. Avatar Road Scholar says:

    Interesting as always, but your link for ThTh5 is borken, just the word Oumuamua.Report

  2. He said “astrophysicist”, so she named a constellation.Report

  3. Avatar Jaybird says:

    ThTh3: Has anyone been convicted due to evidence that involves mitochondria?Report

    • Avatar Brent F in reply to Jaybird says:

      Yes, mtDNA is used in cold cases, due to the greater ease in obtaining viable amounts of genetic material from degraded tissue.

      I’d consider it incredibly unlikely that anyone has been convicted due to a false match as a result of the tiny amount of paternal mtDNA in a sample though. This information would be much more likely to produce a false negative rather than a false positive match and even a false negative is quite unlikely given what the article discusses. It does throw cold water on the excessively confident 1 in a bajillion confidence forensic specialists give, because that was always premised on an unfounded belief that there was no errors in process or understanding in testing.Report

  4. Avatar Pinky says:

    ThTh5 – Sometimes a cigar-shaped object is just a cigar-shaped object.Report

  5. Avatar Road Scholar says:

    ThTh5: The article was short but I’m not seeing the rigor, just more hand-waving. I’m not saying it is an alien spacecraft, just that a natural explanation hasn’t been sufficiently demonstrated to conclusively rule it out.Report

  6. Avatar Road Scholar says:

    ThTh8: Fancy-pants spyrograph.Report

    • Avatar veronica d in reply to Road Scholar says:

      There does seem to be some energy coupling between the X axis motion and the Y axis motion, which is pretty interesting.Report

      • Avatar Oscar Gordon in reply to veronica d says:

        Are you perhaps thinking of Foucalt?Report

        • Avatar veronica d in reply to Oscar Gordon says:

          Not exactly. What I notice is, in the linear version of the 3d harmonic oscillator, each of the two horizontal axes are independent. They each oscillate at a set frequency, and that is that. Even if you use the non-linear model (where you don’t abstract out [Sin x] as just [x]), you should still see the equations decouple.

          However, in the experiment above, it appears that energy is being transferred back and forth between the X and Y axis (treating the Z axis as vertical). Specifically, about halfway through the video, you can see that the X amplitude goes down as the Y amplitude goes up, and then they reverse (although both are decreasing due to friction). That’s kind of cool.

          I assume it’s something happening in the string, or perhaps the pulley mechanism.

          I expect this has nothing to do with the Foucalt thing, which has 24 hour cycles.Report

          • If I recall undergraduate physics correctly, pendulums following a non-degenerate elliptical path do weird things. If the pendulum deviates from the ideal model, things get even weirder.

            The time for a Foucault pendulum to precess through 360° depends on latitude. At the North or South Pole, it’s 24 hours; at the equator, it’s infinite. Where I live, about 37 hours.Report

          • Avatar Oscar Gordon in reply to veronica d says:

            Could be the attachment point, or it could be the sand not flowing evenly and thus shifting the COG ever so slightly.Report

            • Avatar veronica d in reply to Oscar Gordon says:

              I would expect there are oscillations being transferred at the attachment point, but actually, it’s everything, which influences everything else.

              In math terms, the “nice” equations are something like:

              x” = -A sin x – f (x’^2 + y’^2)
              y” = -A sin y – f (x’^2 + y’^2)

              So there is some interaction between x’ and y’, via the friction coefficient (f) — but that’s always negative. It will monotonically decrease the time-average amplitude.

              What we observe is

              x” = -A sin x – f (x’^2 + y’^2) + g(x,x’,y,y’)
              y” = -A sin y – f (x’^2 + y’^2) + h(x,x’,y,y’)

              Where the g and h functions are (in a sense) moving energy between x’ and y’. It’s really cool.Report

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