Supposing that a human like civilization evolved on a moon orbiting a gas giant...

Not all moons are tidally locked to their planet. In fact, it's not all that common. If a moon was going to be habitable, it couldn't be locked to the planet because month long nights and days would boil seas on the day side of the planet and deep freeze them on the night side, causing mountain grinding storms all around the globe.

It seems like the real core of the OPs question is what cultural changes would there be in a people raised on a moon. In that case, I think it's fair to say that geocentric notions would fall apart pretty quickly in favor of a heliocentric world view. This COULD produce a society that pursues a space program much earlier in their history than ours did but only if they were able to learn the requisite technologies faster as well. That's not all that likely.

As far as climate is concerned, I'd guess that a moon orbiting a planet in the "goldilocks" zone would experience broad shifts in climate in fairly short cycles. The distance from the sun that the moon would be at "full-planet" As compared to "new-planet" would make for some pretty dramatic temperature shifts. There may be snow a few days a month every month and summer heat a couple weeks later. Storms would be big and frequently but it would just be part of life. Most life on the globe would likely have adaptations to help it survive the temperature shifts and storms. (The encouragement for weather sealed houses may help drive orbital tech earlier, as I think on it.)

All in all, it would be a dangerous world to live on and that might drive a culture of innovation and reckless exploration but it's just as likely to build furtive cultures build on the philosophy "stand steadily within and let the wind blow without".
/ramble

'Hot' gas giants, meaning they are close to their star, are very much a thing. In fact there's a whole class of them called Hot Jupiters, which are planets very similar to Jupiter but which only have an orbital radius of 0.015 to 0.5 astronomical units, with 1 AU being the distance from the earth to the sun. So having a gas giant existing in the 'goldilocks' zone is very plausible

Don't think so, but it's very probable.

Though user here seems to be doing fantasy, so...

It' worth mentioning that even if tidally locked you'd have phases, like the moon has for earth.

>heliocentric world view
Not necessarily. Why would a star be center of their world and not a giant ruling their sky?

Another thought - what would be of double-star system planets?
Or double planets (can these even possibly exist?)

All you have to do is read this.

As another user noted earlier, the orbital distance would be pretty great, meaning the actual apparent size of the planet wouldn't be all that big. Maybe a little bigger than our moon but not by much. So yeah, a prominent figure in the heavens but it would be pretty clear that the sun would be where MOST of the life giving heat and light came from on the moon.

Factoring this in, it's likely that there would be cultures at some points in the world's history that regarded the planet as an enemy of life.

Or if the moon is tidally locked, leading to phases of the parent planet, they could see it as some sort of ferryman who carries the dead to the star when the planet enters its 'new moon' phase and 'disappears'. This could mean major funerary and burial rites would take place in a cycle, either on the 'new planet' or the 'full planet'

Sure there are double planets. We are on one now.
(the definition of a "double planet" isn't set in stone, it basically means the satellite has a significant mass relative to the planet. Moon is what, 1/6 of Earth?)

Moon's surface gravity is 1/6th, mass is much smaller.

>Or double planets (can these even possibly exist?)
Yes, they can. But usually it's an unstable constellation.

Just looked up the actual numbers, the moon's mass is about 1.2% of Earth's.

I do like Bank's stuff, but I marathoned about 5 of his books in a row and am currently burnt out on anarcho communists.

OP here, just back from work

So it looks like general concensus is that the climate is going to be pretty extreme. Possibly even forcing a nomadic lifestyle.
Sun worship wouldn't be totally gone, but the giant would feature fairly significantly as well.
Auroras would be all year round and might be even more significant than the gas giant itself.
It depends on how far the moon is from the giant, but it might not even be much bigger than the moon in the sky, although it would be visible most of the time.
Tidally locked moons aren't good because they create too much heat on one side and too cold on the other.

So is the OP pic or this one entirely unrealistic for distance?

Supposing a normal gas giant without anything as spectacular as the Red Spot on Jupiter, do you think the inhabitants of the moon would use the bands and storms as a kind of divination tool? Like astrology.

Would the light reflecting from the giant interfere with seeing stars at night?

Forgot my pic

As with the moon, Star watching would be a little less easy on full planet nights but that wouldn't be an insurmountable problem.
Personally, I think the size of the planet in is pretty good. I'd expect that size of a heavenly body to cast a LOT of light in the night sky. If you consider the fact that lunar surface is actually grey or charcoal in color and the silver light we recieved is just the tiny, reflected light of a whole body, it stands to reason that a planet with a broad spectrum would be flippin' magical to see at night.
Also, it's possible that seeing the sunset in the atmosphere of the planet would make them realize their own world had an atmosphere, further advance their understanding of planets, and give them a horizon to work towards. All things that would advance their tech faster than ours.

>As far as climate is concerned, I'd guess that a moon orbiting a planet in the "goldilocks" zone would experience broad shifts in climate in fairly short cycles.

I'm not so sure. I think climate would be pretty normal. Because if you want moody climate:

First, you need parent planet with very very low eccentricity. Saturn, for instance, has eccentricity of 0.0556, and difference between aphelion and perihelion is 130 times semi-major axis of Titan. Earth has eccentricity of 0.0167 which is pretty good, and difference between aphelion and perihelion is still 13 times semi-major axis of Moon.

Second, you need huge orbit for moon. Conservative estimate for habitable zone of the Sun is ~0.5 AU wide. So the orbit must be at least a significant portion of this distance. Farthest moon in solar system is Neso, with semi-major axis 0.33 AU, but it is around Neptune. I'm not sure but I don't think this is possible when closer to the Sun.

But it is fantasy, I suppose. You can do what you like.

I might be stupid but wouldn't there be a week or more of solid darkness on the moon every rotation cycle as the moon passed around the side of the planet opposite the sun?
Like obviously this doesn't happen on earth because the moon isn't as huge as a gas giant.
But gas giants are like 50x the size of the earth and larger, and the moon is going to be even smaller than the earth is.
Wouldn't frequent periods of extended darkness have serious impact for life on the planet?
Like plants would need to be able to go into hibernation at the drop of a hat so as to save energy during the dark period.
And the moons temperature would drop during this period like how it does every single night on earth except to a much more considerable degree because of the extended absence of the suns warmth.
I imagine a world like this would probably have much larger ice caps and probably exist in a period of perpetual ice age like climate.
The cultures in this world would probably have traditions pertaining to the "long dark" and legends about horrible monsters that only came out during this time.

Binary star systems are extremely common. So common, astronomers think they might be the norm.

Well, I did some googling (astronomy.stackexchange.com/questions/6635/is-earths-orbital-eccentricity-enough-to-cause-even-minor-seasons-without-axia) and you need diameter of only about 0.075 AU to make same temperatures as our seasons now. Semi-major axis of 0.038 AU is within Hill sphere of Saturn-mass planet at 1 AU from the Sun (about 0.045 AU radius), so actually it is perfectly plausible. If you combine it with temperature difference caused by axial tilt and orbital inclination of moon, I think you can have some fun with it.

There's no particular reason why a gas giant should have strong radiation belts. Neptune and Uranus don't.

Orbits are huge, so eclipse would only be a regular occurrence if the orbit of the moon was on nearly the exact same plane as the orbit of the planet—like, less than 3 degrees difference.

Also, one orbit (again, orbital radius 0.038 AU around Saturn mass) would be 160 Earth days.

>As another user noted earlier, the orbital distance would be pretty great

Not necessarily. The Moon is about 338,000 miles from Earth, but, for example, Europa is 414,000 miles from Jupiter. So it's not that much further out. But Earth's radius is only about 4,000 miles, while Jupiter's radius is about 43,000 miles. Jupiter appears to be nearly 11 times bigger in Europa's sky than Earth appears to be in the Moon's sky.

Check out the pic. The first image is the famous picture of Earth from the Moon. The second picture shows Earth blown up to ten times the size it is in the first pic. That's more-or-less what Jupiter looks like from Europa.

Idea

The Sun is the Trickster god that weaves in and out of your life providing warmth and leaving mortals with the secret of fire after having stole it.

Speaking of gas giants, is it at all possible to have a station like the one in Mass Effect 2's shadow broker DLC? How big would it be able to be?

>It might not even be a decent source of reflected light at night like our moon

Actually, if it's a planet like Saturn it would be a lot brighter than the moon.

The moon reflects about 10%of the sunlight while Saturn reflects 50%

A "full Saturn" would practically be daytime.

bumpinio

What about seas? Would tidal forces be significantly different?

Depends on the distance to the parent planet
I doubt that it will have a large influence
Which would be problematic IIRC according some theories which state that the tidal influence was necessary to create life

That, at least, should be a hard "yes". The tides are caused by the moon's gravity, and that gravity is only 1/6th Earth's. Having said that, the fact that a gas giant is mostly gaseous certainly works out to prevent things from getting crazy.

Using Jupiter and Europa again, since they're about as far away from each other as Earth and the Moon (what's 76,000 miles between friends?), Jupiter's "surface" gravity is about 2.4 times that of Earth, while the Moon's is 1/6th, which I believe would mean that its effect on Europa's "tides" is about 144 times stronger.

*Actually it's somewhat more than 144 since Europa's gravity is much lower than that of Earth, however that should still be roughly the effect of an Earth-sized moon for a Jupiter-sized planet.

Tides would get...interesting.

Thanks to you I started reading about celestial bodies reflecting light
Full Saturn would reflect about 40%, so I would guess it would be practically dawn/dusk
Full Jupiter would reflect even more, around 50%
Fun to know, Enceladus, a moon of Saturn reflects about 99% of all the sunlight

To further the question of OP
What influence would it have if the parent planet in question would also have rings comparable to Saturn?

even more space trash falling from the sky

Yeah, but very little of it would hit the ground. Saturn's rings are made up of water ice particles ranging in size from micrometers to just a few meters. They'd all evaporate in entry long before hitting the ground.

>That, at least, should be a hard "yes".
Only if the moon isn't tidally locked to the planet.

Yep. Still, perhaps the planet would become larger with time... higher mountians, higher hills, deeper dungeons...

So you would have some truly spectacular meteor showers on a regular basis?

I'm imagining a culture of sky worshippers even more intense than earth. Constantly looking at the sky and seeing omens and gods with their actions playing out and stories evolving constantly.

Attempts to reach the heavens start early and are a constant feature in their history, although they won't necessarily succeed until they're at the same tech level as when we did it

Depends on the size of the moon. If its smaller than Earth, the gravity will be less. That would make it easier to get into space, though I'll admit I'm not sure how much easier and whether it would be enough of a difference that it could be achievable with an earlier level of technology or if it just means less fuel when they DO get around to it.

What would an early tech level space fairing race even do up there? I can't imagine anything less than age of sail would make it, regardless of gravity.

>I can't imagine anything less than age of sail would make it, regardless of gravity.

Oh god.

"We got some good winds today, boy! Set a course for home, and we should be there a whole two days ahead of schedule."
"Yeah, we are setting better speed than I have ever see- whoa. Did you feel that?"
"Yeah. What was- SHIT. There it is again."
"Are we running on- oh my god, LOOK OVER THE SIDE."
"Are we FLYING? How is this happening? HOW IS THIS HAPPENING?"
"Get us down!"
"I DON'T KNOW HOW!"

The space between the moon and the gas giant is littered with bodies and wooden debris, because under the right conditions a sailing ship can achieve the moon's paltry escape velocity.

These lost ships are usually blamed on storms or sea monsters, the true fate of them and their crews a mystery.

The gas giant would be literal Hell in the eyes of the people living on the moon.

It's a giant sea of storms that periodically blocks out the Sun.

If people did worship it, it would be more akin to the Aztecs making human sacrifices so the Sun will come back.

Additionally, I'd be interested in how they view the other moons in the planetary system, along with what ever other planets they can see in their night sky.

THe planets were very important in our developing understanding of the universe. One of heliocentrism's strongest suits was it's clean explination and prediction of the movment of the planets.

I can only imagine how confusing it would all be, a veritable army of visible 'wanderers' compared to our paltry five.
And imagine if any of the other moons came with in visual distance of the planet, even if it's with a telescope!

I can only imagin that their first steps on another world would take a lot more planning than our excursion to the moon, But perhaps a early stage of their stellar exploration would have multiple nations trying to race for each moon, perhaps even establishing bases and trying to claim the rocks bit by bit. Their 'inner 'steller neighborhood is a little more crowded than ours, a little more inviting.

Bows, Atalatals, Catapults and other such launchign devices are very hard to use, but when done right become un powered ICBM's, Arcing over the horizon. There would be legends of a great archer hero who was unmade when he challenged the God's to a contest of skill. all parties kept hitting bullseye on a normal range, and when they moved to hitting somthign on the island over the horizon, a few of the gods missed and dropped out of the contest. the contest went on for days, with the gods and the hero choosing an island farther than the last, farther than the last, Until, with out the hero noticing, they had reached around the globe and shot at their own island. the gods, realizing this, Stepped aside after they let loos their missiles. The hero, taking this to be an admission of defeated turned to accept their formal admission. he is interrupted as the missiles whistle in, his own arrow catching his larynx and snatching the words out of his throat, Muting him forever.

the results of the contest very based on who's telling the story, some of them have the gods smugly accepting defeated, satisfied in the punishment for vainglory, And others have the Hero both mute and defeated, the monarch deity's arrow having made it a full foot farther than the hero's.

Get a low enough gravity and a simple kerosene-based rocket should be able to do it. By "low enough", I mean roughly Mars (about .6 that of Earth). However, with low gravity comes an attendant problem, namely, that the planet's gravity might not be high enough to keep its atmosphere from being stripped away by solar winds.

perhaps very active volcanism 'tops it off' as it's stripped away... Though I wonder if the Magnetic field of the planet would protect the moon

or it's the dark, stern and strong half of a celestial binary. Moody, Violently shifting and changing on it's face but significantly more steady in it's arc in the sky than the capricious and magnanimous sun.

>I can only imagine how confusing it would all be, a veritable army of visible 'wanderers' compared to our paltry five.

Seven. The Sun and the Moon are considered planets in the classical sense.

Ah, Missed that. Thanks Annon!

I wonder what kind of constelations they'd have, and how they'd feel abotu the darkest of nights. I could see their night sky being a bit brighter more often than ours.

In addition, How easy would it be to notice that their home planet is orbiting their gas giant, and that it (and theus they) is also orbiting the sun?

Volcanism would solve the thickness issue but present another problem, namely that volcanic emissions aren't exactly breathable; though you're right that the gas giant's own field should protect the planet, though there's a delicate balancing act in also making sure the field isn't so strong as to irradiate the planet.

Mind, part of what stripped Mars' atmosphere beyond the low gravity was also its extremely weak magnetic field. As long as the giant's moon has the "dynamo" that Earth has, you could probably have a Mars-sized planet, with the .6 gravity, maintain its atmosphere (especially if the giant's own field protects it).

You can't travel space before you have the technology to create sealed ships, the technology to create air tanks and the technology to purify air. And that's the bare minimum.
With just these techs they are still going to die because they aren't protected from their star's radiation, because they suddenly find themselves in the gravity well of their parent planet or just because the reentry process is a bit more difficult than it should be.