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I am writing my first short story in science fiction and am struggling with the issue of gravity.

TLDR:

  • What would it take to make a planet match Earth's gravity (e.g. Titan (yes, it's a moon but for the sake of argument it's settleable ergo a planet), Mars, or beyond)?

  • Conversely, what would it take to make a long-term inhabited space station match Earth's gravity?


Gravity is a tricky subject in sci-fi. Do we assume that, without explanation, we can walk on a foreign world the same as we could on Earth (or whatever the central planets are called). Or do we make changes to world, via terraforming or assume like there would be issues with gravity.

Some examples of the above would be Star Wars - Return of the Jedi. Luke seemingly has no problem with gravity when he goes from Tatooine to Endor to Yavin 4, etc. While, on Firefly - they make ready mention of worlds being terraformed to "Earth-that-was" standards, they don't mention how they overcame the issue of gravity. More recently on the show The Expanse, the issue of gravity is front and centre with it having such an effect on some people in some cases it is used in torture for people not from Earth.

My question lays here! What would we need to do in two aspects of space colonization to ensure that we as a people can move freely from one settlement to the other (at least anatomically - if that is the right word).

  • What would it take to make a planet match Earth's gravity (e.g. Titan (yes, it's a moon but for the sake of argument it's settleable ergo a planet), Mars, or beyond)?
  • Conversely, what would it take to make a long-term inhabited space station match Earth's gravity?

Please feel free to cite our works in science fiction, hard science, anything to back up your argument except magic. It is important to my story to have something to back this up, so as to not just rely on an attitude of "Meh, it just works."

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  • $\begingroup$ For a hard sci-fi treatment of this issue (and planetary colonization in general) you could do worse than Kim Stanley Robinson's Red Mars trilogy, which touches on a number of useful techniques: centrifugal gravity for starships and habitats, personal mobility equipment, special exercises, and the like. $\endgroup$ – Cadence Sep 19 at 23:09
  • $\begingroup$ The second half seems like a duplicate, or at least a close relative, of this question. Its first answer is practical (and used by a lot of science fiction writers), its second is uses some hard-sci-fi level handwavium $\endgroup$ – Punintended Sep 19 at 23:10
  • $\begingroup$ Are you asking only about real gravity due to mass, or are you including "artificial gravity" due to the centrifugal force felt by observers in a rotating system? $\endgroup$ – Hypnosifl Sep 19 at 23:31
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    $\begingroup$ I apologize, but this question is either simple (to the point of insensibility) or asking for patentable answers. The only way we humans know of (OK, that I know of, but I'm betting...) to create gravity is to put mass beneath your feet (toward the center of an object) or put you in a hula-hoop (toward the perimeter of an object). Both are so well documented that the question seems to fail the basic research requirement of Stack Exchange. The question might also be too broad. Are you asking how to modify Titan? How to build a space station? That's two very different questions. Too broad. $\endgroup$ – JBH Sep 19 at 23:51
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    $\begingroup$ On small worlds with low gravity, you can combine spin gravity with existing gravity by putting people on the slops of an upside down spinning cylindrical frustum. The gravity will pull them down, as will the centrifugal force of the spin (technically, centrifugal force does not exist, but it feels like it does or something like that). $\endgroup$ – Richard Smith Sep 20 at 2:03
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There are some interesting ways in which gravity has been talked about in sf without the magic of "Grav Plating" ;-)

First, there is artificial gravity created by motion/spinning a hollow object on its axis. Probably the best examples of this perhaps the hollow metallic tube of Rama.

More recently The Expanse gave everyone a glimpse into space ships that are designed with decks stacked like buildings, so they get simulated gravity when under acceleration / deceleration. There's a nifty article on Forbes which shows a scene from the Expanse TV series showing the effects of gravity simulated by spin.

In terms of "real" gravity, we know that it is a result of attraction one object to another proportional to its mass. If you wanted to create 1g on a planet, it would need additional mass to create that gravity: A pretty big ask! ;-)

Alastair Reynolds, in his book "House of Suns" got around this by placing a small singularity (yes, a black hole!) at the center of a small planetoid to create enough mass/gravity so as to create a 1g environment on an object far smaller than an Earth-sized planet.

Short of devising a special "gravity wave manipulator" (aka Grav Plating) that can change a very weak force like gravity into something more substantial you either have to a: Create constant acceleration; b: Spin an object (centrifugal force) or; c: Find a way to increase mass to the point you have 1g of attraction

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