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The story takes place in our future, during the 25th century. I'm looking for a scalable technology that could allow something as small as a cyborg or personal vehicle to fly, or something as big as a massive spaceship to land on Earth safely. While a lot of the technology in this story is fairly realistic, I am prepared to use as much handwavium as required for this particular technology ; all I require is for it to be internally consistent.

The idea is that this technology would allow the user to manipulate gravity around them in order to "pull" them into the sky or the direction they want to move, or to make them light enough to land delicately. The technology is widely spread in society, so it can't be something too difficult and costly to produce in large quantities.

Since current scientific knowledge offers no way to do this (as far as I could find), I'm thinking about introducing undiscovered materials or forces that could be used, or maybe harnessing the effects of dark energy and dark matter in a useable way. As an example, I quite like the "Element zero" idea from the Mass Effect games (a new element which can increase or decrease gravity when it is subjected to an electrical current).

This is my first post here, I hope the question is appropriate.

EDIT : If it's not possible to justify movement with gravity fields alone, it's possible that the technology would only lower the mass of its vehicle enough that low power thrusters would produce movement. The question of how gravity could be manipulated in such a way remains.

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    $\begingroup$ Gravitation is only attractive. There is no repulsive gravitation. By manipulating gravitation you can reduce your weight, potentially to zero, but it will never push you up. $\endgroup$ – AlexP Apr 4 at 13:18
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    $\begingroup$ I was thinking about creating a gravity well ahead of you that would pull you towards it, not creating negative gravity to push you. Apologies if I didn't explain it clearly. $\endgroup$ – Vincent Apr 4 at 13:27
  • $\begingroup$ And the machine which goes ahead and creates the gravity well, how did it get there in the first place, and what keeps it there? Gravity is an attractice force. It attracts things to the source of the gravitational field. $\endgroup$ – AlexP Apr 4 at 13:35
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    $\begingroup$ See edit in my initial post. $\endgroup$ – Vincent Apr 4 at 13:47
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    $\begingroup$ ... You should not take my comments as saying that the setup would not work in a story. It just doesn't fit with reality-check and physics. But then, many famous stories, starting with Homer's Iliad and Odyssey, through Kafka's Metamorphosis up to Charles Stross's Laundry Files don't fit with reality-check and physics. If your story features a machine capable of creating anti-gravity than that's perfectly fine. $\endgroup$ – AlexP Apr 4 at 13:49
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Unfortunately, we still don't really know what gravity is.

There are many theories out there regarding gravity - however the general consensus is that we haven't yet got to the bottom of it and figured it out.

There are two main generally-preferred (as of 2020) theories:

  1. Gravity is a bending of spacetime, caused by the presence of Mass. We have seen evidence of this in the macro-scale, however have not at the nano-scale. (General Relativity)
  2. Gravity is a force carrying field similar to other bosons we have detected, such as electrons and photons. This would be called the Graviton. But we haven't discovered this yet. (QFT - Quantum Field Theory)

They, unfortunately, contradict each other and are irreconcilable. The quest for a unifying theory of Gravity has concerned most physicists for almost a whole century and we haven't solved it. Dark Energy and Dark Matter are terms to describe perplexing observations that don't line up with either of these theories.

So perhaps to resolve your conundrum you need to 'pick one'. Lets give some options for each:

  1. If General Relativity is true, and you want to manipulate gravity:

    • As all matter is 'at rest' and trajectories are altered by spacetime bending under mass, you need therefore a 'negative mass' to have a reverse effect.
    • Alternately, as mass and energy are interchangeable, energy can be used to distort gravity, however you need a way for distortion to de-bend spacetime.
  2. If through Quantum Field Theory:

    • Let's say we discover a Graviton, then we would now know that the Graviton mediates the Gravity Force similar to the strong, weak nuclear and EM fields. Knowing this perhaps we can figure out how to manipulate this field.
    • If we can figure out how Gravitons decay, we could build a 'reverse path' to reconstruct them, but perhaps with properties that we prefer.
    • An alternative interpretation could be time-reversal. A positron is an electron travelling back through time. If we could create a negative Graviton, perhaps we could reverse certain properties of a Graviton (possibly).

Altogether it is rather complicated, and many Sci-Fi's use the 'handwave' technique (antigravity plating, antigravity field) precisely because we don't know enough about gravity yet.

Edit: (BTW: Dark Energy and Dark Matter don't necessarily have anything to do with 'Gravity'. They are just indications that there is something missing that causes a difference in our observations. For instance, Dark Matter could be particles that are not detectable yet that cause galaxies to hold together, and does not mean Gravity can be manipulated. Nor Dark Energy, being the accelerating expansion of the universe, means that Gravity is negatable).

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Welcome to worldbuilding SE! This is a really great question because there are so many ways to go about it. I think there is one really good way that sounds believable (for sci-fi that is). There are other ways to go about it which will no doubt be shown in other answers. Here's a list:

  • magnets
  • antimatter
  • new elements
  • dark matter/energy (what I will showcase)

Now since we don't know much about dark matter and dark energy we can make up almost anything. You could say that there is a way to capture dark matter using [antimatter/new elements/magnets] and use dark energy to lessen the pull of gravity by adding it in another direction, or you could say when you combine matter with dark energy it makes negative mass. You can really do anything with dark matter/energy. (but in reality no it wouldn't work)

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