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Stupid Space Dragon's Tail

  1. Oct 10, 2014 #1
    Last week's Dr Who episode "Kill the Moon" infected me with stupid, and now I am compelled to try to calculate the speed at which the dragon wags it's tail.

    Observational data:
    1) Earth's moon had grown to have Earth gravity at this point, so I am assuming that it was also the size of the Earth when it turned into a puff cloud and vanished.

    2) The dragon took about 1 second to flap it's tail half the distance that appears to be equal to the diameter of the Earth.

    Looking up the size of Earth, I get (13000/2)/1= 6500 kps.

    Obviously I've never tried anything quite like this before, how badly did I do?
  2. jcsd
  3. Oct 11, 2014 #2


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    That's probably the most accurate description ever of the Dr Who phenomenon.

    I haven't seen that one. So the Moon has grown in size?
    I presume the internal composition hasn't changed, though. This'd mean it needs to be larger than Earth for the same gravity, due to lower density. From memory, the density ratio is something like 3/5, so the Moon radius would need to be 5/3 times larger than Earth's. That's about 10000km. So by this estimate it's 10000km/s.

    However, it's *cough* unreasonable to assume the Moon wouldn't get compressed under its, now higher, gravity, so its denisty would be higher than originally. How much it'd compress is something I can't fathom, but by pulling a number out of my behind I'd give it a 10% increase in density, leading to 10% change in radius = 9000km. And the tail swing is at 9000km/s.
  4. Oct 14, 2014 #3
    Dr Who has some Spock's Brains in it, but other episodes can be very thoughtful and creative. "Hide" a few weeks ago was very good. I gather that the next one is getting good reviews - It is about creatures from the second dimension.
  5. Oct 14, 2014 #4


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    I've only watched Eccleston's and Tennant's incarnations. Skipped Smith altogether, and I can't get my head around Capaldi - after seeing him in "The thick of it" I keep expecting him to be spouting streams of invectives every five minutes.

    But yeah, most of the series seems to be balancing on the fine line between plain silly, and the brilliant moments like "Midnight" or "Blink".
  6. Oct 14, 2014 #5
    Weeall...he has got his moments...

    *Yeah that’s the TARDIS’s swear filter...
  7. Oct 14, 2014 #6


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    I guess you haven't seen the very first Dalek episodes. I'm not sure which was sillier: the old Dalek implementation (with Morris Minor indicator lights on their domes), or Barbara's 1960's hairstyle. :D

    BTW, (speaking of "stupid space dragons"...), can anyone recall which episode had a "space whale" as an energy source. Was that Dr Who or Torchwood?
  8. Oct 15, 2014 #7


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    I remember that one. A quick peek at wikipedia reveals it was "The Beast Below", and that I have actually watched quite a good bit of Smith's episodes. Huh.
  9. Jan 3, 2015 #8
    There was also a Torchwood called "Meat" where this whale-sized alien was captured and the bad guys kept cutting parts of it away and selling it to restaurants and grocery stores. (It had fast healing so it grew back, but was in pain.)
  10. Jan 25, 2015 #9
    What's stupid about space dragons? They're probably more feasible than time travel, faster-than-light and transporters.
  11. Jan 25, 2015 #10


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    They're not very intelligent.
  12. Jan 25, 2015 #11


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    Signed away the residuals?
  13. Jan 26, 2015 #12
    Not stupid at all. It's just horrible to be raped by a dragon's tail, I may get the true meaning of penetration.
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