Gravity Shield

Background

In an extremely fanciful conversation with someone recently (and no, no one was stoned), I brought up the idea of moving Venus further from the Sun so it could cool and perhaps we could then find a way of making it habitable.

Mars and Venus are close to the Earth. Mars' gravity is about 38% that of Earth, enough for us to hope that the low gravity won't be a health risk. Venus's gravity is about 90%.

So I looked it up- it certainly IS a concept...

On Quora, a few people listed reasons why gravity shielding isn't possible. On the other hand, Rubins Guitars noted that it's only impossible based on today's understanding of physics.

Other current concepts

Note that to deflect an asteroid, a current concept is a gravity tractor would uses its mass to pull an asteroid a bit to alter its trajectory. If this were done very far away, only a small change would be needed.

To me, it seems like putting something large enough into space would be a challenge. It seems like pushing the asteroid would make more sense. This might mean heading toward it then turning around to drift into it, then when close, firing thrusters to move away.

Using lasers from Earth is another option. To get sideways force on the asteroid, we could either set up mirrors on the moon, or on a space craft.

Neither of these would be enough to move a planet, of course.

What's possible tomorrow for a gravity shield

Gravity has been said to be a warping of space-time.)

Perhaps we'll find other ways of warping space-time.

Having some space-warp technology makes all sorts of new ideas interesting.

The most gravity-shield'ish idea would be to see if there could then be an un-warping technology.

But there's also just warping space on the other side of the planet, to suck it that way.

Note that the force of gravity from the sun to the earth is huge. Even in the possible space-warp technology, it takes a lot of energy to warp a small area of space enough in front of a small space craft. I doubt it'd make a difference for a planet. (Note all planetary orbits are almost circular, so it's not going to matter much where in its orbit it's done.)

A non-starter, traversing and tacking

When being pulled by a force, the obvious way to resist is by traversing- digging into the surface and slowing one's descent by increasing sideways motion. This doesn't work for a gravity well because there's nothing to dig into. Unless, of course, there turns out to be some actual fabric to space that's not yet discovered.

The further problem is that a planet is already in orbit, that is, it's not actually falling into the gravity well, the gravity is just stopping it from flying away. So one could argue that it's already fully traversing.

Another solution for Venus

The problem with Venus is that it's too hot. This comes from two sources.

First, it's about 3/4 of the distance of the Earth to the Sun, so gets about twice the radiation of Earth. Besides lessening the radiation trapped by the atmosphere, we'd need to either have some kind of solar shield or move it further.

Second, it has a ton of CO2, 96%, compared to Earth's current percentage of 0.414 (June, 2019, it was 0.31 in 1958). This causes an enormous greenhouse effect, trapping more sunlight and heat on the sun-facing side of the planet than it emits on the side that faces outer space. This heats up Venus till it's so hot that on the space-facing side it emits the same amount- currently at about 864 degrees Fahrenheit (paper burns at 451 degrees.)

There are a number of kinds of solutions.

1. Moving Venus further from the Sun (the motivation for looking for a gravitational shield, above.)
2. Lessening the amount of CO2 in the atmosphere. Perhaps this would mean making carbon precipitate so there's more oxygen in the atmosphere. Or perhaps multiple CO2 atoms would bind together to precipitate.
3. Undoing the greenhouse effect. Perhaps something can be added to the atmosphere that lets light escape. This probably means some sort of chemical reaction, equivalent to lessening the CO2 in the atmosphere.
4. Bypassing the greenhouse effect. Perhaps the light that shines on the planet can be converted to another wavelength that isn't reflected by the CO2.
5. Physical solar shield. This is some kind of physical shield that shades the planet. This can be done in two ways. The first is by orbiting the planet, in which case it must be huge. The second is by being closer to the sun, in which case it has a different orbital time.

   If a shade is orbiting the sun and is closer to it, it goes faster around the sun. But if we lessen the sun's gravitational pull, a stable orbit would be slower. I wonder if there's a spot close to the planet that would effectively pull the shade toward it enough that it could orbit at the same speed... (I don't have time to do the math at the moment...)

6. A chemical shield. When a volcano erupts, the ash in the atmosphere gives us a bit of shade by reflecting sunlight. Could we purposely add something to the atmosphere to do this?
7. Reflective ground - If we make the planet's surface more reflective, it'll reflect more heat. I don't know if this could work on Venus, but it's the idea behind the White Roof Project and the problem with the white arctic sea ice declining.
8. Increasing plant life. On Earth, turning deserts green could trap more CO2 in plant matter. (Of course, for all I know, deserts reflect a lot of light...) While it's much too hot on Venus for this, an extremely far-fetched idea is to make a form of life that could thrive in that atmosphere and temperature while consuming the CO2.