Could This Planet Physically Exist?

The ocean could be shallower than the Ice VI layer, or you could have volcanoes and mountains sticking out of it.

If the depth is close to the Ice VI depth, you could have plains of the stuff, with highlands above it.

If you mined down through it, you might have to excavate faster than new Ice VI could form in the excavations, or keep it warmer in the mines so it wouldn't form. But the farther down you go the hotter you have to keep it. Or you could fill the mines with a different liquid, like oil. Makes it dangerous to be a miner, since you have to bring a source of oxygen with you.

yes. But are these mountain peaks and volcanoes still below the surface of the ocean? Because I can't have the bottom dwellers climbing the mountains to anywhere near the surface of the ocean

Your world's premise is vaguely similar to a world in the STOS episode 'For the World is Hollow and I Have Touched the Sky'.

In that episode their world was actually a spacecraft, a Noah's Ark, if you will, whisking their civilisation away from a certain fate. One of its denizens, an old man, scaled one of the mountains - an illegal act under their law - and discovered that their sky, which was supported by the mountains, was solid. As punishment, an implant in his neck activated and killed him, but not before he told Kirk and McCoy of his discovery.

Unbeknowst to the ship's inhabitants, their world had gone off-course due a malfunction in its master computer, but none of the inhabitants were even aware that they were actually on a spaceship, one headed for disaster. Great episode.

A number of science fiction stories come to mind with that general theme of "our world is not what we thought it was", when the big reveal comes to light. Always a great adventure!

I was envisioning them as stopping far below the surface. Like I said, the hot water rising from them could serve as rising thermals to allow them to float upward. On the ohter hand, if you are using a Goldilocks zone, even if they rose to the surface they may not be able to climb them. It might be like trying to climb a mountain that sticks out of the atmosphere. The challenge is not the climb but the low pressure.

And I appreciate everyone else's input and comments as well. Voda is becoming a community built world.

We are the builders of worlds!

It is hard to imagine an advanced civilization without some form of land. Most creatures in the wild are hunter/gathers whether it is in water, land, or the air.

The movie Waterworld was pretty weird, like civilization gone haywire. But you need a crisis that only becomes apparent early in your story.

You might want read "What if the Moon didn't exist". It has about 6 or 7 different interesting concepts that makes you think.

In a recent documentary on dolphins and communication between them, a statement was made something like "These particular dolphins finally found some humans intelligent enough to work with them in catching fish." This is still going on somewhere in South America on the Atlantic side and has been going on for the last 200 of years or more. The dolphins actually signal the men when to throw out there nets. The way we fish on earth now endangers the species. But for a few hundred years, the ocean was fully of bounty.

I think it is interesting that we are just beginning to realize how difficult it is to communicate with another intelligent species. What do those sounds mean?

What we seem to have in common with other species is food and survival and effects on our environment. The way of most life seems to be hunt and gather or civilization of some type. Rules for that civilization gets into philosophy. Sleeper material.

I read a story a long time ago, I think by Larry Niven, about life in a small nebula. It was too small to condense into a star, but large enough to condense so that it had decent air pressure. There were spherical trees that grew there, and you could fly space ships right into it. It was lit up and heated by neighboring stars.

I'm wondering if a small nebula like that could condense water that would collect into an ocean at the center. It could have a rocky bottom, too. If the nebula were spinning, you could have many lakes or oceans that orbited the center of gravity, and they could collide or split apart. Putting the ocean in a nebula would avoid the problem of having the atmosphere evaporate away.

Correct. The 500 mile depth of the ocean was completely arbitrary, as was the diameter of the planet and the core. I don't know enough about that subject 2 be stubborn about any of those distances. I just wanted the distance between surface and ocean floor to be vast. So vast that the bottom dwellers could conceivably think that their entire universe was liquid, and so vast that the two civilizations discovering each other would not be able to happen without some level of technology. Those are the basic points I would like to keep intact. I would preferably like some combination of diameter and depth that would avoid both ice on the top surface, and ice VI on the ocean floor, if at all possible. Those are variables I'd rather not have to work with if there was some combination of factors that could eliminate them. Hero, you mentioned using an even larger planet. Perhaps that is the way to go. Canary, your nebula idea sounds interesting but I worry that it may be a little too complicated for me to write about and fully understand. If I write this story, at some point I'm going to have to understand everything about my planet well enough to be able to answer my own questions. I can't keep asking you guys the answer to every single detail throughout the whole process of writing a story.

but keep in mind that this is fiction, and every minutia does not have to be 100% accurate. There is some literary license that can be taken. I just don't want any glaring major flaws that are completely contrary to known science. but a little bending of reality is acceptable, if it serves a purpose and is not outrageous.

Mt. Everest is only six miles high. If measured from the ocean floor, Mauna Loa's height is only slightly greater, at 31,000 feet. Challenger Deep, in the Marianas, is seven miles deep. These are the tallest and deepest features on Earth. But 50 or 60 miles' depth? That would most certainly require technology to penetrate indeed - from either direction. That much depth would be totally opaque to electromagnetic radiation at any frequency, but not to acoustic energy. Thermoclines would cause ducting that would enable long-distance acoustic communication between parts of your world's civilisation, but radio is out of the question - the conductive medium of the water prevents it.

Wouldn't it be interesting if your bottom-dwelling inhabitants *heard* explorers on the surface, but couldn't fathom the source. Not right away. Living on a water-covered world and their hearing would likely be quite acute, but their eyesight non-existent as there was never an evolutionary need for it. Otherwise normal fishes living in underground aquifers, for example, are often blind and colourless. Where there's no need, there's no evolutionary thrust in that direction. Your creatures having eyesight implies that they once lived close enough to the surface to perceive light. Were it my story? I would give them *acoustic* 'vision', akin to 3D sonar, but not eyesight unless it played into the story.

Correct. The 500 mile depth of the ocean was completely arbitrary, as was the diameter of the planet and the core. I don't know enough about that subject 2 be stubborn about any of those distances. I just wanted the distance between surface and ocean floor to be vast. So vast that the bottom dwellers could conceivably think that their entire universe was liquid, and so vast that the two civilizations discovering each other would not be able to happen without some level of technology. Those are the basic points I would like to keep intact. I would preferably like some combination of diameter and depth that would avoid both ice on the top surface, and ice VI on the ocean floor, if at all possible. Those are variables I'd rather not have to work with if there was some combination of factors that could eliminate them. Hero, you mentioned using an even larger planet. Perhaps that is the way to go. Canary, your nebula idea sounds interesting but I worry that it may be a little too complicated for me to write about and fully understand. If I write this story, at some point I'm going to have to understand everything about my planet well enough to be able to answer my own questions. I can't keep asking you guys the answer to every single detail throughout the whole process of writing a story.

but keep in mind that this is fiction, and every minutia does not have to be 100% accurate. There is some literary license that can be taken. I just don't want any glaring major flaws that are completely contrary to known science. but a little bending of reality is acceptable, if it serves a purpose and is not outrageous.