I know you hung up my line--Star 69

[cyrano]

This is a request for advice from my science-smart friends. Please take a moment, help me get a reality check on the setting for my FireFly OryCon one-shot.


The planet is covered in water--about 15 meters deep, in general. I think this means an old planet. If so, what are the general qualifications of a planet of that age? I'm thinking high salinity in the water, and good sized waves that travel the surface of the planet. The installment on the planet is a mining colony, sunk into the ocean floor and surrounded by large metal breakwaters to protect it from the waves.

The social economy is standard Victorian Empire--there are the lower classes who work in the mines, on the docks, in the desalinization plants, eat the fish poisoned by the byproducts of the mining and live nasty, short brutish lives. The upper classes exploit the lower, live high above in the towers and eat kittens because they're so evil.

Comments

para sacarse de mi burro

[eyelessgame.livejournal.com]

What they said, maybe plus some additional stuff.

A planet doesn't need to be old to be all water. But it needs to be old (and its core cold) to be as smooth as you first describe.

I believe Trip is right about magnetic fields. No magnetic field -> no ozone -> too much UV -> no water. Unless the star is a red dwarf and therefore puts out next to no UV (and this might go along with the 'very old planet' idea).

A magnetic field does avoid nasty radiation, though. Which implies a dynamic core (unless you go Venuslike and have a great hungus atmosphere -- despite a cold core, Venus has a magnetic bowshock field caused by its 90-bar atmosphere -- but this is bad for the planet being vaguely earthlike, or indeed having liquid water), and a hot core implies tectonic activity, which implies that while some areas might be only 15m deep, if you want not to have continents, then a lot of the planet must be deeper than that (basically you're living on the top of a submerged mountain range).

A lot of the metals in Earth's ocean are only there because they keep getting refreshed by flux from the continents; left to themselves they'd settle to the ocean floor. So you might not have a bunch of the metals that are fairly common in Earth's oceans if there's no continents to provide runoff from. But salt is a good bet. It doesn't get increasingly salty over time, though; the planet has the salt it has, and you can probably choose the salinity fairly arbitrarily for story reasons. For it to have metals (like aluminum) in the ocean, though, something would have to keep it churning more than our oceans do.

If it works for the story, you could go the Europa route. Vacuum planet, thick ice cover with liquid water underneath. Active core (in Europa's case because it's under constant tidal bending force from being next to a great honking gas giant). The heat to keep the oceans liquid comes from volcanoes under the ocean, rather than from sunlight.

Atmospherics/weather: The 30-60-90 rule seems to happen to planets besides Earth (that's air, but it applies somewhat to oceans too). As far as major currents, they'd be largely affected by the deeper areas: to get a good current, you want deeper waters, and they'll be pushed around by the shallows (and potentially flow *very* fast over the shallows when the current's right -- hey, that's a fairly cool effect. Waterstorms as analogue to windstorms.)

Is there a moon? With a moon you'd get major tidal mojo, with no continent for the tide wave to break against. Huge pair of standing waves that flow around the planet daily. (Lessened somewhat if you have variable depths for the water; shallows work as "virtual shorelines", and just get battered twice a day by the top wave shooting across.) Without a moon, there's the problem that some people seem to think Earth still has a hot core only, or partially, because of the moon's tide (since Venus and Mars don't have hot cores).

Most living matter on earth is single-celled organisms, and all of it was single-celled for 90% of the planet's history, but multicelled organisms are much cooler than single-celled.

(There's one other water world in our solar system besides Earth and Europa: Uranus appears to have a huge liquid water ocean over its core. And God's wackiest magnetic field. But that's really not a place for humans to be.)