Cultural effects of living in a binary star system

[gestaltist]

Noice, that raised another question: when exactly will those cultures tell apart one star from another, if they are similar in size, luminosity and appearance? If there are two stars, cultures will probably try to give names to both of them, but if they're just two glowing spots dancing on the sky, then how do they tell which one is which...

This is something I am trying to decide for my conworld at the moment. I kind of like the idea of twin suns that people see as equal and can’t tell one from the other.

[Keenir]

Noice, that raised another question: when exactly will those cultures tell apart one star from another, if they are similar in size, luminosity and appearance? If there are two stars, cultures will probably try to give names to both of them, but if they're just two glowing spots dancing on the sky, then how do they tell which one is which...

This is something I am trying to decide for my conworld at the moment. I kind of like the idea of twin suns that people see as equal and can’t tell one from the other.

very cool.

question - does this mean that, instead of being seen as mutually orbiting objects, the suns might be seen (at least (equatorially?)) as two objects that slam into one another, get thrown back, and then charge at one another again?

[Canis]

Noice, that raised another question: when exactly will those cultures tell apart one star from another, if they are similar in size, luminosity and appearance? If there are two stars, cultures will probably try to give names to both of them, but if they're just two glowing spots dancing on the sky, then how do they tell which one is which...

This is something I am trying to decide for my conworld at the moment. I kind of like the idea of twin suns that people see as equal and can’t tell one from the other.

very cool.

question - does this mean that, instead of being seen as mutually orbiting objects, the suns might be seen (at least (equatorially?)) as two objects that slam into one another, get thrown back, and then charge at one another again?

That's a fantastic concept, like drops of fiery dew, merging and separating!

[gestaltist]

Noice, that raised another question: when exactly will those cultures tell apart one star from another, if they are similar in size, luminosity and appearance? If there are two stars, cultures will probably try to give names to both of them, but if they're just two glowing spots dancing on the sky, then how do they tell which one is which...

This is something I am trying to decide for my conworld at the moment. I kind of like the idea of twin suns that people see as equal and can’t tell one from the other.

very cool.

question - does this mean that, instead of being seen as mutually orbiting objects, the suns might be seen (at least (equatorially?)) as two objects that slam into one another, get thrown back, and then charge at one another again?

That’s exactly what I have been thinking. Or they could even be seen as one object splitting and merging. They would have to explain why the world gets colder every time they slam together, though.

Although I also have an idea for a culture that thinks that the Moon is the old father (hence the dim light) of two unruly twins. The Father has to stay up all night to make sure that the twins are safe at home. When he finally falls asleep, exhausted, they go out to play.

[bbbourq]

I realize that this thread is a little old, but I find it relative in that I, also, am creating a conworld in which the planet revolves around a binary star. I read all of the posts and I am grateful to have found this treasure trove of information.

Aside from cultural effects a binary star would have on a particular community or civilization, what evolutionary effects would a binary star have on life? My main question is this: how would a binary star affect the development and evolution of eyesight given that there might possibly be an abundance of double shadows?

If they are relatively close binary stars, then wouldn't any surviving planets orbit the gravitational center of both?

Thus, the twin suns would more or less occupy the same portions of the sky during the day.
There would be one shadow, then, in that case.

I agree; however, I think this only applies when the binary star is high in the sky. I am sure with the atmospheric refraction at sunset that both suns will be visible. There might be, then, double shadows during these phenomena. Given this case, I can visualize a culture holding sunrise and sunset especially sacred. There is also the possibility that a civilization lives in an area where the suns never get past sunset or sunrise; therefore, during this period one would only see double suns.

[sangi39]

Presumably you could calculate this.

Let's take Kepler-47, a binary star system with a planet orbiting around both stars within the habitable zone of the system.

Kepler-47A radius: 96.4% of Sun
Kepler-47B radius: 35.06% of Sun
Distance between A and B: 0.0836AU
Semi-Major Axis of Kepler 47c: 0.989AU

Angular Size of Kepler-47A: 0.51372 degrees
Angular Size of Kepler-47B: 0.186824 degrees
Angular distance between Kepler-47A and B: 4.7871 degrees (so about 9 times the apparent size of 47A)

From what I can understand of the maths in the regard, but it means that should the stars be as far apart as they can in the sky, the centre of the ends of two shadows that are each 1 metre in length will be 8cm apart. For every extra metre that the shadows grow in length, the centres of the ends of those two shadows will become 8cm further apart.

So, for example, if the Kepler-47A and B were 45 degrees high in the sky, casting light down on a mountain as tall as Everest (8,848m), the two shadows of the peaks would be 740m apart. The two shadows cast by the tree Hyperion (115.7m tall), would be 9m apart at the same time.

Stars that are closer together and/or further away will cast shadows closer together while starts further apart and/or closer to the planet will cast shadow that are further apart. The stars orbit each other, so they get closer and further apart over time (in the case of Kepler-47, the two stars orbit each other once every 7 days) so the two shadows will get closer together, then they'll cross, then they'll get further apart again, and back and forth as the planet orbits the star.

What any of this means for evolution and the evolution of vision I have no idea, but I suppose you could work from that sort of maths and go from there.

[Keenir]

Aside from cultural effects a binary star would have on a particular community or civilization, what evolutionary effects would a binary star have on life? My main question is this: how would a binary star affect the development and evolution of eyesight given that there might possibly be an abundance of double shadows?

Well, most of the stages of eye development wouldn't care - their goal was just to tell light from dark, sun from shadow. Then teasing out basic shapes or movement - again nothing that double shadows would interfere with.

I would think that double shadows would make it easier for herbivores to spot their predators, once eyes can resolve images and start to see details...after all, with two shadows, stuff like countershading gets harder. (though would that apply to herbivores, or would they just opt for armor?)

So perhaps, if the double shadows means camouflage has to be extra good to be effective, then eyes might become even sharper (at picking out color/movement/something else)

And that doesn't touch on whether it would be color vision (like humans, fish, birds) or black and white (like most mammals) or some color and UV (like octopi and bees)

I hope this helps at least a little.

[Imralu]

As far as I'm aware, camouflage is no less effective in artificial lighting from multiple sources.

[Keenir]

As far as I'm aware, camouflage is no less effective in artificial lighting from multiple sources.

what of just countershading? it'd be trickier with two light sources, yes?

[qwed117]

Most hypothetical binaries that are inhabitable are two small stars orbiting each other with the barycenter in between the two. The planets orbit the stars well outsidea of the two, essentially orbiting a síngle barbell shaped star. The other system, where planets orbit within the barycenter and the two stars would be extremely unstable, and planets would be shot out of the center. But if it somehow remained stable, the planet would be extremely hot.

If you go with the interesting option 2, then crystal eyes might occur, just because of the heat. Option 2 might imply large eyes, due to low light visibility, along with cold weather adaptations.