I’m an avid sci-fi and fantasy reader and also writer; while reading the many informative answers (and questions) it reminded me of a question I’ve had before but never seem to be able to find a true(ish) answer:
Is it (would it be) possible to live somewhere that has multiple Suns or/and Moons? And what would happen to the land?
For sake of argument in one of the stories I’ve written (completely fantasy by the way) in this world there are two Suns and four Moons.
I am very curious on what the effect of four moons would do to the oceans? Would this world need more oceans(water in general) than land? Would this mess up the whole world itself? More desert perhaps, because of the two Suns? Would two Suns only burn up a planet? Or would two Suns (or even more) work out if perhaps the planet were farther away from the Suns (than, say, we are from our Sun)?
And on this same thought how would the moon phases work with multiple moons? I realize that Earth’s moon revolves around the Earth, and the Earth itself rotates as IT revolves around the Sun. Okay (please bare with me) say in this hypothetical creation of a world that this other planet has four moons (yeah, I get planets can have multiple moons… wonder why we don’t… sorry back on track) and two Suns, perhaps this Planet revolves around both Suns like the Earth does her’s and also has four moons circling the Planet. Would you always see the four moons? Like how you can sometimes see Earth’s moon even when it’s still daylight? Would you ever have night if you have two Suns? (Would it depend on how big the Planet is?)
Okay I’ll stop now just long enough so someone can hopefully give me an answer (by the by I thought that perhaps this belonged into the Cafe part of this, but then I thought ‘but I want ACTUAL answers it just so happens that the REASON I have this question is artistically in nature’ (ie: the only reason I’m asking is because I wrote about it making me wonder…okay I’m doubly done)) THANKS!
Multiple moons are not a problem – if you notice, there are several planets in our own solar system that have them. Their effects would depend on how many, how big they are, their orbits, etc.).
Multiple suns are more difficult, but not insurmountable. Again, it depends on the planet’s orbit, the size of the suns, etc.
As a writer, it doesn’t matter what the physics are. If you want two suns in a story, put two suns in the story. There’s no need to explain.
Multiple moons are easy. Each one will have phases just like our current Moon does. Depending on the size, distance, orbital inclination you could have all sorts of interesting effects.
Practically speaking what you can’t have is multiple *large *moons like ours. If they were large, they’d interact gravitationally and pretty soon they’d collide. Or almost collide & break up. If a planet has multiple moons, they’re gonna be small.
As seen from Earth, Venus has phases just like the Moon does; new, crescent, half, etc. But because it’s appears so small, it’s not obvious to the naked eye that’ws what’s happenieng. instead it just apears brighter or dimmer, or vaguely larger or smaller. With binoculars yuo can see the phases though.
Small moons, like Mars has, would be similar.
As to multiple suns: It’s pretty well believed that that arrangement won’t work, at least not for habitable-to-humans planets. There’s not a way to create a long-term stable orbit around two large bodies orbitting one another unless the plnet is waaaay out there.
Such a planet *could *exist for awhile and if you had a start ship you could go visit it. But there would be no opportunity for life to form there & get intelligent on its own. The planet would fall into one or another sun or be spit out into the void long before life got going.
Oh trust me, nothing will stop me from putting whatever I want in my stories, the reason I love fantasy. But I actually want REAL information. That’s why I gave a for instance with the Planet with four moons and two suns. I want to know what that Planet would (could?) look like? What happens with the oceans? What happens with the seasons? Etc, etc, etc… I’m not asking for the story I’m asking BECAUSE of the story.
If it helps I’ll say, the moons? half the size of Earth’s one. All mainly equal, spaced like a diamond shape, (one on top, two on the side below, and one below the two) and two Suns the same size as ours. (I realize this means to have a slightly inhabitable planet it would need to be a bit far from the suns, so I’ll say probably as far away as our fifth planet -I can’t think of the name I worked last night and I’m really too tired/lazy right now to go looking it up anywhere isn’t it Jupiter?- )
Leaffan: Awesome, I’ll have to take a little look see, thanks.
I get the moons, I wasn’t that worried (wasn’t at all actually) about those because so many of our own planets have many moons.
But I’m curious about the Suns… would the Planet have to revolve around both Suns together or could you revolve between the suns? Would that just burn up a planet though? I guess it would, if it was very close, I’m guessing the Suns would have to be millions of miles apart… would that work? Two small suns and a slightly large planet?
For multiple suns, you can either have a case where the suns orbit fairly closely to each other and the planet orbits both of them at some distance, or a case where the planet orbits one sun fairly closely and the second sun orbits the first at some distance.
In the first case, from the vantage of someone on the planet, the two suns will always appear to be fairly close to each other in the sky. They will over time appear to orbit each other, possibly with one crossing in from of the other periodically. When they do, the amount of light coming from them will dim somewhat as one eclipses the other. The two suns will rise and set at about the same time, although you can have brief periods where only one of the two is above the horizon.
In the second case, you’ll have one primary sun which will to the people on the planet behave like ours, and a much dimmer secondary sun whose position in the sky relative to the primary sun will change slowly, possibly taking months or years to make a full cycle.
In either case, astrologers on the world can be expected to devise quite complex zodiac systems based on the movements of the suns relative to each other and the background stars.
They are by Neil F. Comins, and they are amazing resources for wanna-be alternate-solar-arrangement-desiring-authors.
Basically, each book takes different possible alternate paths regarding the earth, moon, and sun: - no moon, lots of moons, two suns, big moon, moon closer, moon farther, living ON the moon rather than the planet, and writes up a little short story with specific bits inserted that reflect the changes caused by that arrangement.
Then he follows up each scenario with an explanation of what those changes will also cause to change, why he thinks those changes will happen, and what those changes may mean to the evolution of intelligent life in those locations.
Really awesome set of resources, and fun to read to boot!
Please slow down; it’s exhausting reading your ADD-like writing. Slow down and ask a really coherent question & you’ll get better, more useful, answers.
In what I write below you’ll see “day” , “year”, etc., in quotes. That’s to call attention to the point that a different planet will have the same ideas, but they will be of different lengths than Earth’s, and they may also be wildly different in relationship. There could be a million “days” in a “year”, or a “day” could be longer than a “year”. “Days” could be longer or shorter than “seasons” too.
What do you mean by what the planet could look like? It could look like anything; the configuration of moons has no specific influence on the planet. It could be all water, all dirt & cold like Mars or all dirt & hot like Venus, or have no atmosphere at all like Mercury. Or it could have both land & water like Earth but in any combination of islands, continents, & oceans. Or be 100% frozen. Or all gas with no solid core at all.
The relationship between the planet & its suns would mostly influence the temperature It would also cause the direct side effects of temperature, like whether or not there’s an atmosphere, etc. As explained several times above, it’s real unlikely to get an inhabitable planet with multiple suns.
Moons don’t affect ocean configurations. Well they slightly affect oceans via tides. Multiple small moons will mean small Moon-caused tides.
On Earth the tides are caused by both Sun & Moon. The nature of Sun-caused tides will depend on how big or close the sun(s) are.
In single-sun systems, seasons are a function of orbital eccentricity & rotational axial tilt. And the ratio between the length of the “day” & the “year”. In Earth’s case the axial tilt is by far the major influence. Your planet could have any “seasons” you want, ranging from almost none to Earth-centuries of “summer” hot enough to boil lead & Earth-centuries of “winter” cold enough to freeze the entire atmosphere.
In the case of multiple suns there would be the additional wild card of changing insolation due to the changing orbital configuration. This would probably be the most significant factor driving the equivalent of seasons. In fact the belief that most 2-sun system can’t harbor life is precisely becasue the “summer” & “winter” on each planet would be too different (and each too long) to permit any living thing to survive both environments.
Moons can’t adopt a static diamond shape’d relationship. They’ll all end up in more or less the same plane although at different distances. And if they are at different distances, then they’ll have longer or shorter orbitanl periods. The closest moon might go once around the planet in a fraction of a “day”, whereas the more distant ones would take most of a “day”, or several “days”, or about 30 “days” like our Moon does, or even longer.
When I say moons more or less in the same plane, there could easily be several degrees difference between their orbits’ inclination. Which would be enough that different moons would be “northernmost” at different times of the year. It *would *be a complicated dance which might take “centuries” to repeat. Unlike our simple Earth-Moon relationship which repeats the exact same evolution every 30-ish days.
One thing moons will NOT do is maintain a fixed relationship to each other against the background of the sky.
It IS plausible to have small bodies settle for awhile (thousands of years, but not the entire lifetime of the panet) at the LaGrange points. The effect as seen from the planet would be bright star-like objects seen near both the “eastern” & “western” horizon seen at every dusk & dawn. Viewed through a telescope they’d always appear to be half-lit & half-dark, just like a half-Moon does here.
When you say you want 4 moons *1/2 the size *of Earth’s Moon, do you mean half the visible apparent diameter, half the physical diameter, or half the mass? Those are very differnet things. IMO, you’re not going to get multiple moons which look much bigger than tiny disks of light. That is, each will look itty bitty in the sky compared to our Moon. If we say for comparison that our Moon appears as big in the sky as a dime held at arm’s length, then the largest moon in a 4-moon system might be this big at arm’s length: o
or maybe this big: O
Lizzyerd, you should probably ignore this comment, your posts are completely comprehensible, not exhausting and not ADD-like.
I frequently throw out lists of questions when brainstorming or trying to give someone enough examples of the types of question’s I’m interested in, perfectly reasonable.
On a planet with multiple moons that is orbiting a single star (or both stars of a binary pair), all the moons would alway appear to be in the same phase I believe. So they’ll all be full, or half or whatever all at the same time, because the light is coming from the same direction. I think. Someone will correct me if I’m wrong :).
You’re wrong :). The light is coming from the same direction, but the moons are in different positions. If one is near the star’s apparent position, it’s a new moon, and if one is on the other side of the planet it’s a full moon.
Not an answer to the question, but a suggestion…the OP should read Flying Sorcerers by Larry Niven and David Gerrold. Some of the references are outdated (the symbol of the God of Sheep is a horned box, and today it would have to be a cable dish), but overall, very funny. It can be read as science fiction OR fantasy. And the planet has two suns, one red and one blue.
LSL & Raft: Yeah, sorry, I tend to go multiple directions when I get thoughts and ideas. And I do like brainstorming better, wasn’t really sure exactly what ‘add-like’ writing was. But no worries.
Anyways. Thanks the second info was so much better, perfect in fact LSL. Let me ask you this, also: Would moons normally revolve around each other then? I think that’s what you said with my example about the diamond shape formation, that basically at one point they may have this shape in the sky but they would not remain this way. I just want to make sure I got it correctly.
Oh, and I meant half the size of earth’s moon as in half the physical size, half of everything really, half diameter and half in circumference. And as for what the Planet would look like, I know the moons wouldn’t really have anything to do with the planet, maybe a very small amount (wouldn’t more moons cause bigger or longer tides? and if tides are Sun and moon, which I never knew, if there were multiple suns and moons wouldn’t it do something as well to the moons?) Sorry… there I go again, on tangents.
Anyways. I meant more about what multiple Suns would do to a planet. If there were many suns it would hurt the planet if it wasn’t far away from those Suns correct? I’m thinking a Mercury like planet if there’s many suns.
The climate depends on the distance to the stars (and their type), but it could be hotter or colder than the earth.
The moons would normally orbit the planet independently. There are orbits where two of them swap places regularly, for example, but this situation is not too stable. Normally they would all orbit in the same plane, so a diamond shape would not occur, and it would be temporary in any case.
As for the tides: If your moons have half of our moon’s diameter, they have only 1/8 of the mass, so the tides would be weaker depending on their distance to the planet. But according to their current position, their influence will cancel out or amplify by a lot, so you get a situation like with spring and neap tides on earth, only a lot more complicated.
Helliconia was mentioned upthread. I never found the books (I had the omnibus edition) worth re-reading, but the interesting practical effect of having one nearby sun and one that was sometimes far away and sometimes near was that the planet had mini Ice Ages on a cycle of centuries, so they’d have long warm spells for a while, then long freezes, and both the planetary ecology and the humans themselves adapted to cope.
For instance, as “spring” draws near, lots of humans get sick and die from a disease that causes the survivors to become much thinner and better adapted for the hot years to come. Then as the second sun recedes several generations later, a related sickness causes the survivors to bulk up and become cold-adapted. And there is also a non-human race, rather like minotaurs, that are much better adapted to the cold and become dominant during the ice ages, but end up helping humans to survive until the warmer weather returns.
