# In The Expanse, how does rotating Eros create gravity?

On various occasions in The Expanse TV series, it's mentioned that the asteroid Eros has artificial gravity.

As explained in-universe, the gravity comes from rotation. This is especially mentioned on the second season in the episode "Home".

How can rotation generate "artificial gravity"? I would guess normally it would create quite the opposite and whirl everything out into space.

• You're thinking of it upside down; on Eros and the other inhabited asteroids they live inside, with the floor being furthest from the core. See e.g. expanse.wikia.com/wiki/Ceres, which shows a map of Ceres where the "lowest" levels are closest to the surface. Apr 7, 2017 at 20:49
• Eros takes advantage of centrifugal force. Floors are placed in such a way, that when you stand inside, your feet are pointed towards space, and your head is pointing at the center of the asteroid. PS: that also means that everywhere you go is uphill on Eros. Huh. Apr 7, 2017 at 21:00
• This also means that the living space must be limited to under the equator. There won't be any artificial gravity under the poles. Apr 7, 2017 at 21:48
• @JDoe - If you rotated it along the long axis, you'd have maximum living space along the inside with the poles reserved for zero-g docking Apr 8, 2017 at 8:48
• The best way to visualize this is having a look at a washing machine. The drum rotates, laundry sticks to the inside of the drum. And yes, as @JDoe said, laundry does not stick to the axis of rotation, but rather tries to stay as far away from it (perpendicularly speaking) as possible. May 11, 2017 at 9:31

From the source novel, Leviathan Wakes, we learn that people live inside Eros. The spin does indeed threaten to spin them off into space, but the floor (really the exterior walls) prevent this from happening.

Eros supported a population of one and a half million, a little more than Ceres had in visitors at any given time. Roughly the shape of a potato, it had been much more difficult to spin up, and its surface velocity was considerably higher than Ceres’ for the same internal g. The old shipyards protruded from the asteroid, great spiderwebs of steel and carbon mesh studded with warning lights and sensor arrays to wave off any ships that might come in too tight. The internal caverns of Eros had been the birthplace of the Belt. From raw ore to smelting furnace to annealing platform and then into the spines of water haulers and gas harvesters and prospecting ships. Eros had been a port of call in the first generation of humanity’s expansion. From there, the sun itself was only a bright star among billions.

• Another question: how does it have uniform g if it's shaped like a potato? Apr 7, 2017 at 21:16
• @Gallifreyan - I assume the key would be to negate its spin entirely, pick the longest axis, then spin it along that. Apr 7, 2017 at 21:22
• Are you sure it has a uniform 'gravity'? Or does it just have a gravity that is with an acceptable range? Apr 7, 2017 at 21:22
• @Galifreyan Eros's "gravity" (centrifugal) pull is greater near the surface than closer to the core, obviously, so it already does not have uniform g. I know you meant uniform across one "level" of the station, but given the differing "gravity" between the levels I assume the inhabitants are used to minor differences across a level. Apr 7, 2017 at 21:28
• @Saiboogu I'm sure, and the peril of the author's intent is always the interpretation of the reader/viewer :D
– Erk
Jun 1, 2018 at 6:34

You are correct. It would try to throw everything into space. The only thing is, it would be throwing it into what you're thinking of as the ceiling, but is their floor.

It would work the same way the water stays in a spinning bucket. The water tries to fly away, but the bucket holds it into place.

On the spinning Eros, the people try to fly away, but the stone keeps them in place.