Are you making a fantastic world, or an alternate Earth? Do you like it? In the words of a wise woman: you should put a ring on it.
Well, maybe. As anyone with a non-single marital status can attest, rings have consequences. Inhabited planets are certainly no exception. Rings are beautiful whether they’re encircling your finger or your planet, but let’s explore some of the unintended consequences that come with them. We’ll be traveling to a ring-bearing alter-Earth for this sobering thought experiment. In this universe, Earth has stolen Saturn’s rings, and like any good magical ring of power, they have shrunk to fit.
Wait, how does this planet get rings in the first place? “Stole them from Saturn” is great for our alter-Earth’s mythology, but we’re going to want a scientifically plausible backstory here. How’s this: a smaller planet slams into the surface at an oblique angle, instantly liquefying both worlds and casting off a glorious spray of fiery ejecta that eventually coalesces into a ring. Except, hold on a second, this actually happened on the real Earth; the ring material eventually clumped together to form our Moon. So someone has put a ring on Earth: the ancient protoplanet Theia. It involved an unthinkable cataclysm, and the ring didn’t even last that long. At least the doomed lovers produced an offspring. The Moon is a nice consolation prize, and since Theia isn’t exactly around to contest, Earth has custody.
It all seems unfair. Everything worked out so well for Saturn; why can’t Earth have nice things? Sadly, most inhabitable worlds would be too small and too close to their sun for rings to remain stable indefinitely. Our Hill Sphere (the region of space that is gravitationally controlled by a planet, not its sun) is pretty darn small compared to distant gas giants like Saturn. Not only that, but Earth’s moon would destabilize and scatter any recently-acquired rings.
But don’t despair – our world could still have rings. Shiny rings! And it wouldn’t even require the apocalyptic embrace of one of its peers; a large comet or asteroid would do fine. It might not even need to impact the the planet directly – the world would just have to capture it and hug it really tight for a while. Or, more scientifically: the captured body would have to spend considerable time inside the planet’s Roche Limit, within which it will slowly break apart. Capturing a rogue asteroid or comet generally requires a three-body gravitational interaction. In Earth’s case, this means that the Moon would be helping out. It owes Earth that much.
As an alternate option, your planet could have an artificially created ring. All it would take is a nice big asteroid, a few nukes, and a gross disregard for humanoid lives and the biosphere in general.
Over the eons, these rings would degrade, and the particles would scatter and fall down to the surface. They would not be stable over cosmological time – that is, over millions of years. But geological time? Perhaps. And historic time? Thousands of years? You bet. Humanoid civilizations could grow up encircled by vast, luminous rings. This is where things get interesting.
Let’s skip past the part where we talk about what this would look like on Earth. That’s been done. Turns out, Saturn’s rings scaled down for Earth look ah-MAY-zing. But let’s explore the less-cosmetic implications of putting rings around an inhabited planet.
Do you enjoy mild seasons? Too bad. Rings would amplify the seasons to extremes – especially winter. When the northern hemisphere tilts away from the Sun during the darker months, the rings would be perfectly positioned to block incoming sunlight; the planet’s inhabitants would be under an enormous shadow for half the year. In the summer, the effect would be the opposite: the rings would not block the sun, but act as massive reflectors. This would have less thermal consequences than the winter shadow, but would be just as dramatic. Brilliant, ring-lit twilight would extend through most of the night. The planet’s shadow would never fully darken the rings, and its edge would be etched in red: the reflection of half the world’s sunsets. Depending on how wide the rings were, there might never be night per se during the summer months.
If the size of the particles in the ring were on par with those of Saturn, expect the recent Russian meteor incident to happen on a regular basis, as the rings slowly decayed. Except it wouldn’t affect any place so far north as Russia — the rocks would mostly pummel the equator. A consolation for this is that the equator would be otherwise mostly uneffected by the rings, except for some modest shading and cooling — which that region of the world could probably use.
During the rise of civilization, ring deities would overshadow moon deities, just like the rings would literally shade out the moon. The gods of the ring would be beautiful and fickle, punishing during the winter but blessing the summer with light. And they would randomly smite unbelievers… so long as they lived near the equator.
If the rings were more rocky and less icy (which makes sense if your world is going to be warm enough for humans), they’d scatter less sunlight, and therefore they would be less effective reflectors in the summer. More importantly: mix together rocky rings with a space-age society, and you could expect massive mining operations. Especially if the rings were formed from a torn-apart asteroid, instead the planet’s crust. (It’s easy to access the minerals in the crust, after all.) Large governments and private mining companies would be harvesting the hell out of those rings for platinum-group metals.
Rocky rings would also be easy to weaponize. Ring particle drops could be a nice, clean replacement for nukes, and individual rocks could be the perfect hiding place for satellite weapons systems. Orbital bombardment would be just another thing for the planet’s inhabitants to steal from the gods.
Any advanced civilization would have to be very careful about where it put its satellites. Launching at the equator would make the most sense economically, but it would become very risky due to the massive quantities of debris. Depending on how dense, distorted, and narrow the ring was, and how much it decayed, space travel in general might be very difficult due to the high chance of collision. An international space-race might have very different goals: “first one to run the gauntlet and survive the ring particles wins.”
Space elevators may or may not be easier. On the one hand, there’d be great anchors to use, at least if any part of the rings contained large geosynchronously orbiting particles and/or they could be moved into a geostationary orbit. On the other hand, nobody would want to be riding the space elevator when a bus-sized boulder slams into it at hundreds of miles an hour.
If the rings were at all icy – even just a few percent – then they’d be a great resource for further space exploration, since spacefarers wouldn’t have to bring water up from the surface. And if some of the ring particles were big (say, house-sized or larger), there could be refineries and small space stations anchored directly to them.
For an Earth-like planet that got a tailor-fit set of Saturn’s rings, one could assume that the package included the small shepherd moons, which would be great little platforms for building bases, refineries, resort hotels, and so on. They also create pretty ripple patterns in the rings.
Advertising via lighting up or dying parts of the ring would be a major endeavor, but possible. There could be flags of major governments, logos of major corporations, and or even giant cock graffiti from time to time – probably not permanently, due to the cost of maintaining the light show and the inevitable dispersion of any dyed particles.
These are just a few ideas for the details that you could focus on when telling stories on a ringed planet. Sure, rings make things more complicated- but that’s just another word for interesting! And if you really like your planet, you know what they say…
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