How can we artificially reduce gravity on a planet to live there?

Question

It is relatively simple to increase the impression of gravity by using spin, either on a low gravity planet (inside a rotating parabola) or in orbit (inside a rotating cylinder).

However, I can't figure out a way to do the opposite:

if you are on a high gravity planet, how can you locally reduce the effect of gravity?

The only solutions I see are not practical:

• We could live on a ring / train that spins all around the planet, but that requires a colossal effort to create.

• We could be immersed in a dense fluid just like when we're in water, but who would want to live there?

• We could live very deep below the planet surface (for example, around 3000km below Earth surface to have Mars gravity) but I have no idea that's even feasible.

Answer 1

Edit

I am adding new headings for each section of possible solutions.

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Centrifugal Force

Suppose that the planet is not revolving at all then the effect of gravity can be reduced by moving around the planet in a high speed train (assuming that by reducing the effect of gravity you mean the measured weight).

How?

When you move with speed $v$ around the planet then the forces acting on you are gravitational force $F_g$ and normal force $\mathcal N$ (neglecting the dissipative forces).

$$\Rightarrow \mathcal N - F_g = - m \frac {v^2}{R}$$

i.e.,

$$ \mathcal N = F_g - m \frac {v^2}{R}$$

Here $\mathcal N$ is what you measure as the effective gravity ($R$ is the radius of the planet).

Similarly if the planet is rotating then you can reduce the effect of gravity by moving in the direction of rotation of the planet.

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Free Fall

Other option is to use the concept of free-fall:

• place the stuff, on which you want to reduce the effect of gravity, in orbit around the planet (this will completely eliminate the effect of gravity) and then if neccessary increase induce some artificial gravity.

• alternatively, 0-gravity planes(Reduced Gravity Aircrafts) are now available, and you can book tickets for them and experience reduced gravity.

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Shell Theorem

Shell Theorem can be quite useful in reducing the effect of gravity. It states:

If the body is a spherically symmetric shell (i.e., a hollow ball), no net gravitational force is exerted by the shell on any object inside, regardless of the object's location within the shell.

This means that if you are inside a well then the shell of earth above you applies no gravitational force on you (obviously this is base on the assumption that planet's density is uniform).

So you can build some structure underground, in mines (...,etc), and reduce the effect of gravity on yourself.

Answer 2

The cheapest solution would be to use magnetic levitation principle as it is used in some high-speed train systems. One needs to cover a ground with a permanent magnetic field coating and to use some kind of boots with repelling magnets for levitating from the ground while walking. The only problem - stabilization. Levitating train has no such problem cause train is "attached" to a rail system. But I doubt if you would like to walk just in strictly defined paths of rails. So there's a different stabilization solution needed, otherwise when you will bend yourself over - you will change your COM position, so that it will respond to a big gravity fast and you will fall down to the ground soon or will feel discomfort at least. A couple of semi-fantastical ideas to solve that :

• You may wear some kind of powered exoskeleton which will adjust to your movements automatically, so easing your overall movement. Btw, such exoskeleton would solve your problem alone without any additional magnetic fields involved. However wearing it is a bit uncomfortable and unnatural.
• You can wear some kind of costume which would have it's own magnetic coating for repelling from the magnetized ground coating too. So magnetic boots + magnetic costume may be a solution. Wearing comfort depends on suit design. Still, given today's technologies it should be more pleasant than wearing powered exoskeleton, unless technologies for them will change too.

NOTE

This solution will not completely eliminate gravity effects, you still will feel it, for example your feets will feel same big reaction force from your boots; your heart will pump blood a way harder than in Earth. However this solution just makes some things a bit easier to accomplish, like walking, etc.

Answer 3

The only feasible way I could think of is Reduced-gravity aircrafts. These are used for training astronauts and conducting experiments in reduced gravity environments.

The following image shows the trajectory of such an aircraft:

^{Image source: Purdue University}

The path looks like a downward opening parabola. During the ascending phase, contents in the aircraft feel increased gravity (shown by $1.8\,\text g$ or in other words you'd feel roughly $1.8$ times the normal acceleration due to gravity).

At a certain altitude, the pilot pitches the nose (of the aircraft of course!) down and reduces the throttle. The engine provides enough thrust to counter the drag force. During this regime, everyone inside the plane feels weightless. Near the end of the parabola, the pilot pitches the nose up and increases the throttle to produce enough lift.

We can also experience non-zero reduced gravity by altering the path of flight i.e., slightly modifying the parabola. Typical flight plan provides about twenty seconds of weightlessness.

There are many other ways by which you could experience reduced gravity here on earth, however I think this is the one which is majorly in use and well proved method.

Answer 4

Two thoughts:

1. Reduce the mass of the planet

2. Slow the rotation of the planet

I like these way better than all the trains, planes, and magnet answers. The reason other planets have lower gravity is because they are lighter. Just like moons.

To note though: Rotation of a planet does not affect the gravity, but the rotation of a planet reduces the gravitational pull experienced by an object on the surface of that planet.

Reducing the mass seems the easiest (on a planetary scale lol). Remove trillions of tons of rock, sand, and magma and you have a lighter planet. Do so evenly, as to not look like planet pac-man.

Edit:

The question, is near impossible with our current tech. All the answers so far are, also, near impossible. You cannot have more than a couple people actually live on any heavy gravity planet with any of the answers, with our current tech. So my answer is assuming we will have the tech in the next 200 years or so. And I'm speaking specifically, reducing the mass by MOVING mass/dirt off of the planet, its possible with a shovel and a rocket technically, but 200 years from now I bet we have bigger ships.