TBT: True Geek


Someone remembered for me, back in July 2008, when I posted this. We were talking about the station in Babylon 5.

Something seemed wrong.

We were at the Irish Well. The band was taking a break, but it was still loud. I wasn’t sure I’d heard him right. “How many tons of steel in the station?”

He told me again.

“How long?”

I was skeptical.

“And how fast does it rotate?”

“One full rotation a day. Earth gravity. Earth day.”

“That can’t be right, can it?”

We looked at each other. I grabbed a napkin. He borrowed a pen from the waitress, explaining what we wanted it for. She said to let her know the answer.

I wrote down a formula. Looked at it funny. It didn’t look right, and I didn’t think it was just the Guinness. I closed my eyes and tried to see the page from my textbook. No luck.

The band was starting again when I tried to call my ex-boyfriend. If he was home, he’d look it up. He wasn’t, but his new girlfriend wanted to know the answer too, once she could hear me over the music. She gave me the formula. I’d been close but not quite there. I promised we’d tell the ex what we found the next time we saw him.

I converted all the numbers to reasonable units and did the math. Really? I checked my work. Oops. One error here, one there. I was drinking Guinness, after all. But they cancelled each other out. The answer was still the same.

We looked at each other again and laughed. “You’re not getting me on that space station.”

“Half-millimeter steel hull? Huh-uh. Me neither.”

Then we went back to the band and the Guinness.

And if that’s not geeky enough for you, I can remember the results of the calculation, but I’m really not sure which fictional space station we were talking about.

Comments

  1. says

    One full rotation a day. Earth gravity. Earth day.

    That can’t be right. At only one rotation per day, you’d need a ship over two million miles across for rotation to produce 1 g of artificial gravity…

  2. Crimson Clupeidae says

    I’d like to see the assumptions you made for that calculation. Not that I expect the numbers from the intro of the show to actually make sense. There are sites out there with the ‘actual’ dimensions of the B5 station that you could use for an estimate of…something.

  3. says

    Indeed. Using measurements from this site, plus a density of steel of 7750 kg/m3, and the assumption that all the mass is concentrated in a single outer wall (not counting the end caps), I get a wall thickness of about 60 m. Seems a bit more plausible than half a millimeter. Also, at these dimensions, the rotational period to get 1 g would be about one rotation every 41 seconds.

  4. says

    No assumptions made except that the information my friend provided was correct. I’ve never watched the show. It wouldn’t be the first series to backfill after fans told them their big, impressive-sounding numbers didn’t work together.

  5. Crimson Clupeidae says

    I have to agree. One of the best sci-fi series made for TV. Most of the movies are pretty good too, with a couple notable exceptions.

  6. says

    Gravity is hard to get right on anything less than feature-film budgets, and I agree – I wouldn’t be setting foot on that space station either – for centripetal force to be the dominating force entails the station be ridiculously large in the absence of any other handwavium.

  7. says

    If you’re discussing the Babylon 5 station, with
    1) the assumptions for the calculation being mass, length, rotation period and apparent gravity;
    2) the mass and length correspond to the show’s stated values; and
    3) you’ve specified a rotation period of one Earth day producing 1G;
    you’re going to get a pretty strange result!

    The station spins much faster than that in the show. The station visibly rotates in all exterior shots (which wouldn’t be perceptible for a one day period). I couldn’t find any supposed “official” stats for rotation speed, but eyeballing some video clips, I’d put it somewhere on the order of a minute or so for a full revolution, which is in the ballpark of Deen’s estimate above.

    They were pretty fussy about (most of) the physics on the TV show, so I’d expect their numbers for the central element of the show to at least be on the order of believability. Not that there weren’t other subjects that might warrant scrutiny…

    I remember one episode (“Knives”) in which John Sheridan is practicing baseball on the station. It’s played straight in the episode, but I remember a discussion at the time of watching it regarding the Coriolis effect, and how bizarre a game of baseball would really get inside such a space station. You can probably find plenty of (old) arguments online about the physics involved. Still, to be fair, I think the majority of his hits were foul balls…

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