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I'm learning about how to account for the fact that we can't really model (to a perfect degree of accuracy) an Orbital system with more than two bodies - I [very, very barely] understand this as the n-Body Problem.

Now, thinking about how to build a Dyson Swarm, the best method seems to be to dismantle Mercury

My question is:

Would moving this massive amount of materials from one part of the Solar System to another, cause the Solar System's balance to be thrown off?

How would a future civilisation cater for this?

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    $\begingroup$ (1) We can model to evolution of an n-body gravitational system to any degree of acuracy we want, over as long a time interval we want. (2) What cannot be done is model its evolution over an infinitely long time. (3) Over a sufficiently long time, any gravitational system with more than two bodies is chaotic: there is no such thing as "the Solar System's balance". (4) The entire history is less than 10,000 years long; let's be generous and assume we want to predict the evolution of the system over a timespan ten times longer; that's only 100,000 years, and we can do that. $\endgroup$
    – AlexP
    Sep 9, 2020 at 7:08
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    $\begingroup$ Would Mercury's mass be enough? I'd also assume each satellite would have some means of course correction. $\endgroup$
    – NomadMaker
    Sep 9, 2020 at 14:15
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    $\begingroup$ I'm with @NomadMaker, the mass of Mercury wouldn't make much of a swarm. Some of the collected power must be used to keep the satellite in place (thrusters). You need equipment for transmitting the power somewhere useful, additional comms for diagnostics and maintenance... Even if it's self-repairing, you need someplace to store the raw mass needed for that process (and the raw mass weight), otherwise you need docking/repair facilities. Batteries... converters/transformers... And you need enough of them to make this all worthwhile. The mass of Neptune might not be enough. $\endgroup$
    – JBH
    Sep 9, 2020 at 17:37
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    $\begingroup$ @Kristian "The entire history is less than 10,000 years long" means just that, the period of time which we call "history" (by definition, the time from which we have written record of human activity) is less than 10,000 years long, all the earlier time is prehistory, literally "before history". It's just to illustrate that 100,000 years is a very long time compared to the history of humanity. $\endgroup$
    – Peteris
    Sep 10, 2020 at 0:07
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    $\begingroup$ @Anderas You'll need some serious energy to extract the gravitationally bound gas. Even if you went ahead with it, you'd just end up with a bunch of hydrogen you'll need to fuse anyway, so it's probably easier to just extract the energy directly from the sun. $\endgroup$
    – Kristian
    Sep 10, 2020 at 18:22

4 Answers 4

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Mercury is the least massive among the planets of the solar system, with about 5% of Earth mass. For comparison our Moon is about 1% in mass with respect to Earth.

The center of mass of the Mercury-Sun system is about 5 km from the center of the Sun, while Mercury is about 60 million km from it. 5 km is probably less than the precision with which we can measure the radius of the Sun or the position of a body in space.

If that mass can cause any disturbance to the solar system, we are talking about something of second or third order with respect to the effects given by the Sun or Jupiter.

There are more worrisome things than the mass of Mercury.

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    $\begingroup$ Mercury is about 1/6 millionth the mass of the sun. If creating a dyson swarm inside Earth's orbit it wouldn't really affect it at all. If creating a dyson swarm outside Earth's orbit then Earth might move 15 miles further away from the sun due to the decreased mass in the inner solar system, but the effect of the swarm could be treated as a hollow shell so it wouldn't pull the Earth out any more. $\endgroup$ Sep 9, 2020 at 15:20
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Considering Mercury is the innermost planet in our solar system, it probably wouldn't affect the stability at all.

If you calculate the gravitational attraction of any other object towards the center of our solar system (where Mercury roughly is), the contribution from the Sun is so absolutely massive that you can completely ignore the contribution from Mercury. Thus dismantling it shouldn't really change much.

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It has already been said, but here again. Mercury is the innermost planet. Compared to the mass of the sun, it's negligible. If you then move the mass around the sun, instead of a mass besides the sun, it'll make barely any difference to the whole.

It's probably comparable with the biggest cargo ship full with lead going from one side to spread around evenly around the earth. The matter will change the distribution of the Earth's matter, but it'll not matter for the balance for it or the moon. You can basically ignore it.

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Earth today is rotating slower than it should, because we lifted a lot of water to higher places, by building dams everywhere.

I guess you didn't notice. That's because the effect is small. Really small. Some microseconds every day more or less... well, the GPS system DOES notice, a microsecond equaling to something between 20cm and 1m. We have a space observation program looking at pulsars just to determine those microseconds.

Dyson habitats made from Mercury would probably lift themselves to earth' orbit for the nice temperature. So everything inside that orbit would fly around the sun a small bit slower or a little bit farther outside, everything outside that orbit wouldn't notice. Yes you can simulate the effects today already for many, many thousand years.

I guess your civilization would do so before lifting something more important than mercury, and would even have better simulations than we have.

Those habitats would probably have some kind of engine to avoid straying far from their course, or to avoid the occasional stray asteroid or comet. They would use those to counter any unwanted effect.

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