this post was submitted on 25 Aug 2026
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The Expanse

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With the show being one of my favorites, I'm happy to say that I'm really enjoying the novels as well. That said, it keeps bugging me when the term "thrust gravity" is always used to describe something that's explicitly Newton's 3rd law - ie, not gravity. I'm probably not understanding something, but it bugs me to see a series that makes a point to be at least reasonably scientific to use a term that seems so wrong.

Side note: How come the third law missed out on natural feeling shorthand? 1st - inertia. 2nd - f=ma. 3rd - ???. Feels like something got overlooked there.

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[–] Weirdfish@lemmy.world 5 points 2 days ago

The series talks about three different types of "gravity", being down the well, which is being on a planet and experiencing mass attracting mass, spin gravity, which is created using the Coriolis effect of being stuck to the inside surface of a spinning project, and thrust gravity, being under acceleration of a ship.

For all practice purposes, thrust and well gravity are identical, aside from hearing the engines, you would not be able to tell the difference between 1g on earth and a ship under 1g of acceleration in a straight line. The whole point of the Epstein drive in the show is "We have such a powerful engine we can just keep accelerating", get places very fast, and live with a defined up and down.

Spin gravity is distinctly different as the rotation is detectable, and depending on the radius of the ship / station / rock, can cause a dizzying effect. Belters like to distinguish themselves because the are generally immune to effects of spin gravity.

All of these effects are quite real, and in my opinion the series does a great job of being scientifically accurate.