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I've just watched the first episode of The Expanse. I notice in a couple interior shots set in, I presume (by political content) Ceres, the producers/director took care to include a small bird, which flew very oddly.

This bird would flip its wings, then fold them, then flip again -- much like certain songbirds do on Earth, except that on Earth they don't hover between flips; they fly a ballistic arc. This (along with mentions of "bone density juice" and the presence of "long-bones", extremely tall folk who'd grown up in low-gee) led me to conclude that the interior gravity in Ceres must be much less than 1 G, despite the (presumably production cost driven) lack of any apparent effect on human walking, no "floating" balls in a scene with playing children, and so forth.

What level of (presumed centrifugal) artifical gravity is maintained in Ceres?

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    IIRC, in the books it is around 1/3 gee at the outermost decks, but of course, it is lower as you move inward. – dmckee Jun 30 '17 at 0:06
  • I'm not sure they ever specified in the TV show, beyond that it's much less than Earth gravity. – KutuluMike Jun 30 '17 at 1:25
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    "and the presence of "long-bones", extremely tall folk who'd grown up in low-gee". As I understood it, the Belters aren't particularly taller (nor are their bones), but their bones are notably thinner due to having grown up in a low-G environment. The only tall people we see in the show, are generally physically bulky too. I don't remember seeing any excessively tall and slender people. – Flater Jun 30 '17 at 9:27
  • The "long-bones" in the first few minutes of S01E01 (pointed out by the detective with the hat, as he explained to his Earther partner) was quite slender, and the one hanging by his armpits on Earth in a later scene same episode seemed pathologically thin (as well as obviously too weak to even lift himself off simple hooks). I got the impression "long-bones" had missed out on treatments to normalize their bone growth. – Zeiss Ikon Jun 30 '17 at 11:16
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As far as I remember, they never gave out that level of detail on the TV show. We're just told that Ceres has much lower gravity than Earth. In the novels that the show is based on, the gravity is artificially generated "spin" gravity, which does match the visual on the show: "down" is actually pointing out into space. Note, for example, that the airlocks (which should lead out into space) on Ceres are in the floor. The interior spaces on Ceres are basically built upside down from what you expect on Earth.

The novels do give an exact figure: .3g, just under 1/3 of Earth gravity, and just under twice the gravity of the moon.

At that low gravity, you would expect a bit more "bounciness" from someone who was born and raised in Earth gravity, if they were walking around unencumbered. The people on Ceres, though, were either born and raised there, or have largely adapted to it's environment. There is a scene much later in the season when a "belter" is taken to Earth, and they undergo a form of torture that merely requires them to stand up. Their muscles and bones don't have anywhere near the strength to pull this off; in order to make them comfortable, they are floated in a tank of water.

Objects like toys, though, will still fall like they do on Earth, just more slowly. See, for example, the very famous hammer/feather drop done on the moon, and imagine the objects accelerating about twice that fast.


For a good review of the artificial gravity on The Expanse there's a cool Forbes article describing how much the show got it right.

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    Note that they also show the effect of the Coriolis force; for example, when pouring a liquid into a cup, the stream appears to move in a slight curve. – Steve Melnikoff Jun 30 '17 at 9:17
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    true, that was a nice touch (though I think exaggerated for effect, given the size scales involved) – KutuluMike Jun 30 '17 at 10:09
  • I haven't seen any visible Coriolis effects yet, but the bird's behavior matches 0.3 G pretty well. It's high enough so people can walk more or less normally, but less expensive (in terms of structure, for instance) than a full 1 G. It would also explain the "long-bones" -- they grew up in ships or other habs with lower spin gravity (though we don't yet know what actual effect growing up in low or zero G would have). – Zeiss Ikon Jun 30 '17 at 11:27
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    Very early in the season Miller is pouring himself a drink, and the liquid pours sideways from the bottle into the cup. It's a very exaggerated effect but it is what would happen inside a spinning environment to a free-flowing liquid. – KutuluMike Jun 30 '17 at 12:46

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