Gravity and music

When I went to see Gravity yesterday, it was the first first-run movie I’d seen in a theater since The Hobbit last year. I don’t enjoy the movie theater experience, with too-loud sound and endless trailers, but this was a movie worth seeing in a theater. It easily has the best physics of any space movie ever made. Almost all of it is set in a free-fall environment, and everything is right, down to tiny objects floating around. If anything was wrong with the physics, it was too subtle for me to catch. Gravity poster

The story is about the ability of the human mind to cope with disaster and with its own fears. The entire cast consists of two people, not counting voices on radio. It deserves to be a Hugo nominee. Is it science fiction, though, or just a movie about current technology? Its driving premise is that the destruction of a single satellite by a missile could set off a chain reaction of careening space junk that would wreck a sizable portion of what’s up there. I’d call that a science-fiction premise.

On the negative side, the ISS is supposed to be within spacewalking distance of the Hubble and a Chinese space station just a hundred kilometers beyond. The Hubble’s orbital altitude is about 350 miles and the ISS is about 260. That’s a 90-mile spacewalk even if their orbits are perfectly lined up.* Still, it’s hard to complain when Gravity comes so much closer to being right than most “sci-fi” movies. There’s also a sequence which at first seems even more wildly improbable; it isn’t what it seems, but it undercuts the sense that Ryan Stone is solving her own problems.

In the evening I went to a concert by Symphony NH, a really high-quality orchestra right here in Nashua. Ruth Palmer joined them for a performance of the Tchaikovsky Violin Concerto. I loved the sound of her instrument and the acoustics of Keefe Auditorium. There’s even a tie-in to space movies. Conductor Jonathan McPhee told us that the main theme from the concerto was used in The Right Stuff, which won an award for Best Original (!) Score.

The concert ended with Beethoven’s Seventh Symphony. I know that symphony inside and out, but every performance is a little different, and live performances let me see the effort that goes into them. I could go on for a long time about this one, but I’ll just mention one bit of subtle humor that goes all through it, a sort of running gag with obsessive chromatic bass lines. Near the end of the first movement, the cellos and basses keep repeating a short figure while the orchestra builds to a climax. In the third movement, the horn does a G, F-sharp, G that turns into what’s been described as a “coughing fit.” In the finale, the cellos and basses just can’t keep their footing. First they’re oscillating from G-sharp to A, then they slip down to G to A-flat, to E-flat, D, and C, before finally catching themselves on alternating E and D-sharp, which they hang on to as the bass while the orchestra builds up to a big climax. If you listen carefully, you’ll notice they stay on that D-sharp even after the rest of the orchestra has placed itself firmly in A major!

Not a bad day at all.

*Update: Come to think of it, the presumed relative positions of the Hubble and ISS do imply a physics problem in the plot, apart from whether such a long spacewalk is possible. It would be too much of a spoiler to spell it out here, but if you see the movie and then think about how orbits work, you’ll probably catch it.

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6 Responses to “Gravity and music”

  1. thnidu Says:

    I haven’t seen the movie – though now I’d like to – but my first thought on reading the orbital altitudes was that they’ll be moving at different speeds, the further-out Hubble slower than the ISS. That means that not only do you have to time your departure from the one, you’ll have to match velocity with the other.

    • Gary McGath Says:

      That’s not what I was thinking of in the footnote, but yes, that too. And they couldn’t just kick off from the Hubble at right angles to its orbit, shedding its momentum, but would have to follow an elliptical intercept course, so the trip would be even more than 90 miles.

      • Paul B. =:o} Says:

        Sounds like they should have played KSP a few more times before writing the script. =:o}

        • Gary McGath Says:

          KSP? A search turns up Kerbal Space Program, “a game where the players create and manage their own space program. Build spacecraft, fly them, and try to help the Kerbals to fulfill their ultimate mission of conquering space.” Is that what you’re referring to?

  2. Eyal Mozes Says:

    Thanks for the recommendation; I might not have gone to see it otherwise, and it is an excellent movie.

    On the physics problem you’re talking about, my guess is that you’re talking about the 90-minute cycle. But that’s only a problem given the actual orbits of Hubble and ISS; if we assume the movie takes place in an alternate history in which both are in close orbit, close enough to allow a space-walk (certainly a very reasonable allowance compared to what most science fiction requires) then the physics is completely accurate as far as I can tell.

    • Gary McGath Says:

      Yes, if we posit that the two are in close orbits, then all the serious problems go away. Someone else pointed out that geosynchronous communication satellites are at a much higher altitude, so they wouldn’t have been affected by the catastrophe, but the general communication satellite blackout mentioned in the movie isn’t necessary to the plot. The astronauts lose communication with Houston, but they would have been relaying through a low-orbit satellite that could have been knocked out.


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