# Tag Info

16

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 ...

6

This is not possible because satellites in different orbits will necessarily have different periods. They will all move across the sky in different speeds, so they will catch up to each other every now and then. Having multiple satellites in the same orbit is complicated - such arrangements are not stable on a geological timescale, and are too improbable to ...

5

The question of stability will produce very different answers depending on the exact parameters of the system, but it seems that there are regions in parameter space of stability and regions of parameter space of instability. The one example of confirmed significant non-coplanarity I know of is $\upsilon$ Andromedae A, a system containing three (and perhaps ...

4

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 ...

4

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 ...

4

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 ...

4

Yes It will not work from every spot on the planets surface, and you may catch glimpses of the other moons, but at least at the equator and tropics it should be possible. The moon I've used for this is smaller than our current moon, at 5000 metric tons. It comes much closer than our current moon, so should be about as visually noticable. Assuming Earth-...

3

I don't see any reason why this wouldn't be possible. As for the impact on agriculture, the people might have to do cyclical migration: moving closer to the equator when the tilt is more extreme & maybe back out when it's less extreme. The crops that the people would be able to grow would change in tune with the cycle.

3

You don’t even need the gas giant. It is believed that resonance effects with the moon as it recedes from the Earth can cause large fluctuations in the Earth’s axial tilt, so all you need is a planet with a large moon that’s a bit further away from it.

3

You're going to need: small, very faint moons that cannot be seen during the daytime. What we're counting on is that these small, dim moons tend to get lost in the morning/evening glare in their crescent phases. Some sort of regular orbital perturbation that advances the line of apsides of the moons precesses with the same period as the planet, so that the ...

2

There is no "Minimum to know it", the more you sample, the more accurate your orbital approximation will be. If everything was perfect: On a whiteboard, if your only input is a sensor that give precise distance and bearing measurements, you will need 3 measurements, the further apart they are in space, the better. To fit an ellipse to points, you ...

2

Chaotic initial placement of an N-body system results in everything in the sun or oort cloud. So, no. It wont be planar. I've ran a few N-body simulations trying to see what I can get to form, and randomly placing bodies (using c++'s std::normal_distribution) always resulted in a chaotic explosion. Doesn't matter if I modelled 10 bodies or 100 bodies or 1000....

1

The ramifications it would have on agriculture are the same as it would have on the ecosystem in general: life would have to be adapted for such swings. (This means that any agriculture would be based on the wild things that already are adapted.) Some plants, or even animals, might go dormant for the extreme period. (For a period this long, they are more ...

1

I do not believe this is possible. Assuming a 24 hour orbital period for the planet and 7 day period for the Moons. In a single night an observer would be able to see roughly half a hemisphere, so on average half of the moons should be visible.

1

Well first of all it depends on the viewpoint. Is this just from one side of the planet, or is it from every point? If it is just one side we and the moons have an elliptical orbit then yes. Imagine 7 moons that all have a very elliptical orbit and circle the planet once every week. On the side of the ellipse that is furthest from the planet they move slowly....

1

My answer to this question: https://worldbuilding.stackexchange.com/questions/169999/what-kind-of-lunar-orbit-would-cause-a-total-solar-eclipse-to-happen-once-a-day/170047#170047[1] May help: Another possibility is having a planet with many moons of almost totally identical size which are equally spaced in a ring around the planet. The moons all share the ...

1

Maaaybe It would require all seven moons to share the same orbit, which probably isn't a stable configuration and would have to be artificially made - there's practically zero chance that it would occur naturally. Let's suppose, for the sake of argument, that some advanced alien race made it so in the very near past, geologically speaking, and maybe added ...

1

Suppose the orbital period of the moon were exactly equal to the orbital spin of the planet. In such a case, the moon would always orbit exactly over the same spot on the planet, day and night. It would always be seen on one side of the planet, never seen on the other side of the planet, and in the same place both 'day' and 'night'. Now, slightly slow down ...

Only top voted, non community-wiki answers of a minimum length are eligible