Hot answers tagged

5

This answer is meant as a supplement to notovny's. I agree with their conclusions (the scenario is impossible because of the instability of this Lagrange point, and the fact that the Hill sphere is too small), and I just want to derive the "curious relation" they came up with. We start with Kepler's third law. $T_M$ and $T_p$ are the periods of the planet ...


4

Void. Light is defined by where it is not. If everything is the same brightness, nothing can be seen. Shadow is defined by the light. With no light there can be no shadow. The light magic and the shadow magic are the same magic, even if they don't realize it. They are flip sides of the same coin. The void strips the power from both of them. Void is ...


4

Two moons would make the tides more intense, not less. Also more complex. Here on earth we have "spring tides" and "neap tides" -- these are driven by the sun but there is enough of a difference that classical Greeks noticed them even though the Mediterranean is not strongly tidal. The reason the sun is of lesser effect despite its vastly greater size is ...


4

It's probably not possible for two Luna-like moons to exist around an Earthlike planet. There are two major reasons why: formation and orbital dynamics. There are two main ways that moons form. The first is similar to how planets themselves form. When the solar system was young, the material that would become the planets was essentially a huge disc of gas ...


3

This is a fascinating question! As you mentioned, the effect on the tides would be most obvious characteristic, and the only way I can think of reducing them so as not to encompass cities would be to make the second moon smaller, and to move the second moon far away. Newton's law of gravitation says that the gravitational force exerted by a moon on a ...


2

Your migration model falls in line with what is called a hot Jupiter. One possibility is that a Jupiter/Saturn like planet migrated inward disturbing the orbits of planets which had already formed. Over time two of these planets ended up getting captured by the hot Jupiter, becoming moons. Captured moons are not uncommon (see Neptune's moon Triton). Also, ...


2

Cadence's answer is very good, but it might leave you with the the sense that you can't get away with anything interesting. I think there are definitely some good possibilities. You want to imagine two moons with approximately circular orbits that have significantly different radii. If the radii are too similar, the system tends to be unstable. One way to ...


2

There are a lot of stuff that can beat them Light is movement of photons in a specific wave length, darkness/shadow is the absence of light, so they're the other side of the same coin. You can shoot a laser to me, but it will take some time to move from you to me (light is the fastest thing in the universe, but even then it takes 8 minutes for the light of ...


1

Either a mix of both or matter/energy. It is said that light and dark are two sides of a single coin (in our world one is the presence of light, the other is the absence of it), so one who controls both can easily combine them into something better than each one separately. On another point of view, you could use an extension of matter control, meaning ...


1

In you scenario the planet's recapture looks much more questionable to me. First, the space is really big. So the probability of such a massive planet to be so close to a star so that it would capture it is extremely low. Even if it happens, the most likely orbit would be very elongated, which makes life challenging by going in and out of the habitability ...


1

Not unintentionally Let us take a look at our solar system. A body in Earth orbit (ie in the Goldilocks zone where life is most likely to evolve) needs an additional 11 km/s in order to escape into interstellar space. Note that this is the best case scenario, ie where a fast-moving, sufficiently massive body ploughs into the planet from "behind" to ...


1

Alternative: the moon-to-be was gladly orbiting its star until a rogue jupiter, coming from behind, "gently" pulled it out of the orbit and wandered off. Yeah, gently is sorta relatively speaking, some tidal sloshing may have occurred in the process, their Venice wasn't quite happy about it. Ah, yes, it has been rediscovered in 2013


1

You can get rid of the tidal problem by making the two moon co-orbit, the second moon in a Trojan position. Using Earth and Moon as examples of our planet and moon, the second moon needs to be around one hundredth of the Moon's mass. It can be less dense, in order to be safely larger and therefore more visible in spite of its smaller radius. To the same ...


1

Have you see pictures or videos where Earth's Moon looks huge? I believe that the angular diameter of the Moon, about half a degree of arc, is the same as a dime held at arm's length, which is pretty small. But the Moon looks vast in many pictures and videos because telephoto lenses are used to film it. If you desire that both moons look like discs (when ...


1

A moon whose orbital period is half a day would appear to observers on the ground to go around in a day, rising in the west. Phobos is a more extreme example: its period is less than a third of a day, so it rises in the west twice a day.


1

That’s a bit of a general question to which I will attempt a general answer. The closer the Moon gets to Earth the stronger the tidal effects would be. Limit around 11,500 miles – the Roche limit at which point tidal forces would destroy the Moon and it would break up. In reality bad things would start to happen before then but that’s an absolute limit. The ...


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