Thursday Throughput: Arrakis, New Caprica, and Us

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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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  1. Avatar Oscar Gordon
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    Re: Planets. I like the idea of planets in the habital zone of a star that are tidally locked, so you get a thin strip of livable space all along the day/night terminator.

    Also, my orbital mechanics is a bit rusty, but you could have a planet in the same orbit on the opposite side of the sun. The key thing to remember about orbits is that orbital distance and speed are related. Two planets in the same orbit will be moving at the same speed, so as long as they are far enough apart that the Gravity Equation is a very, very small number, things will be fine. And if something causes one planet to change speed, it will also change orbit, so a collision would be unlikely. Although that doesn’t mean bad things won’t happen if the change is small, because eventually one planet would catch the other and even if they don’t collide, their orbits could destabilize.Report

    • Avatar Will Truman in reply to Oscar Gordon
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      says:

      When I was young we were taught that Mercury had a tidal lock, though now we know (and maybe we knew then it just didn’t filter down to the textbooks yet) that’s not quite the case. Which is a pity because even just “not quite” ruins that whole terraforming and colonization plan!Report

  2. Avatar Oscar Gordon
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    says:

    ThTh5: Step one, stop subsidizing people living near water.Report

  3. Avatar Will Truman
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    says:

    Thanks!

    I had forgotten about that aspect of Arrakis (I audiobooked the first Dune book, but that’s it). I mostly remember it being a desert. Such a planet does not need to be a desert (as in no surface water), correct? From a quick look around most are suggesting it was caused by something else (asteroid impact).Report

  4. Avatar Jaybird
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    says:

    We did the egg thing in elementary school.

    We couldn’t get it to work.Report

  5. Avatar Mike Schilling
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    says:

    ThTh2: The Trojan points are stable if M1 is sufficiently bigger than M2, as the Sun in to the Earth. Is there a constraint on the mass of the object at the Trojan point? All the real-life example I know of are small like asteroids or even smaller like spaceships.Report

    • Avatar Oscar Gordon in reply to Mike Schilling
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      says:

      Dr. Siegel might correct me, but the only constraint is that the gravity equations balance. So if you have a star and gas giant as the primary gravity relationship, you could have any two planets at the L-points, as long as they are about the same mass and not more massive than the gas giant.Report

    • Avatar veronica d in reply to Mike Schilling
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      says:

      Yeah, I was going to post thing. The stable Lagrange points emerge when you find the extrema of the two-body Lagrangian system absent any other bodies. So the Lagrangian points of the Earth-Sun system would look very different if you plopped an Earth-sized body down into one of them.Report

  6. Avatar George Turner
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    says:

    The most reliable indicator of sea level changes is, oddly enough, the Earth’s rotation rate, which can be measured with insane accuracy – because astronomy. Since we’re spinning, any increase in sea level manifests as an outward mass shift, slowing the rotation due to conservation of angular momentum. If the cause of the sea level is polar melting, the effect is even more pronounced because mass is shifting outwards from near the axis of rotation.

    Thus, the Earth’s spin provides a hard-physics reality check on otherwise squishy sea-level measurements, because it turns out that sea level is actually pretty tricky to measure and easy to fudge quite a bit because they’re trying to measure wave heights across a huge service with sub-centimeter accuracy, which is really well below the error bars of the available techniques.Report

  7. Avatar George Turner
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    says:

    ThTh1: Polar regions can be tricky depending on axial tilt, wobble, precession, nutation, and orbital eccentricity, all of which will combine with to make the high latitude climate shift dramatically over time. Even on a nice planet like ours, the climate in the Scandinavian regions has dramatically changed five times just during the current interglacial.

    Holocene climate variability – Part A (There are 10 parts to that series)

    I would expect that polar climates would always be a lot more sensitive to orbital variations than equatorial regions, though I haven’t done the math on it. Near our equator, the sun can swing all over the place but it’s still high overhead. Near the pole such a 30 degree shift is the difference between a nice day and perpetual night.Report

  8. Avatar dragonfrog
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    says:

    ThTh4 – y’all don’t to Autumn where you live?

    We don’t really do much of an Autumn here either – the forecast for this coming weekend includes overnight frost, so anything one was hoping to leave out in the garden to ripen only gets one week of “Autumn” to do it in. We’ve brought in all the potted perennials that we hope to overwinter, and will shortly be finding out which ones are overrun with aphids that suddenly have no predators or cold nights to keep them in check.

    ThTh8 – is there anything Millenials can’t kill?Report

  9. Avatar George Turner
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    says:

    ThTh5: The IPCC report that the ocean’s are warming faster than expected cites a paper that got retracted the same day the report hit.

    Retraction Watch story. The story’s linked update points out that the IPCC was citing the retracted paper for their report.Report

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