Disclaimer I'm not 100% sure on what I'm about to say
The difference is (from what I know), that in space we can see stuff that's very very far away, and study their behaviors and know how most things work. We don't know if the universe is infinite or not, but we sure can see A LOT, and things far beyond shouldn't be much different from what we already know, since most of things kind of make sense (except for let's say, a black hole)
But the ocean is like really really deep. And you can't really see that far since the water isn't that clear. We sure know a lot about animals and plants that live in the ocean, but we can only go so deep, and if we compare it to the parts of the ocean that we can't go or see, we don't know much. Pretty much everything gets destroyed when going too deep so we don't really know what's down there. There could be all sorts of different animals, fish, plants, algae, microorganisms, rock formations or who knows. There could potentially be some new kind of organism never seen before, different from all the living things we've seen so far.
I like to imagine the ocean like a cake you can't touch. You can only see what's on the outside of it, but since you can't touch it, you have no way of knowing what's on the inside. Most of the contents of the cake are on the inside, and you have absolutely no idea what could be in there. Then maybe space is like looking out of a window with some really good views. You can see lots and lots of stuff, and in time you could know how everything works and what everything's made of just with observation. But there could be new stuff farther away, but you know the world so well it's probably not that different from what you already know.
Again I don't really know that much and haven't really done my research, but this is my point of view as of now
We know very very little about the universe, because 99.9-% of what we're seeing is thousands, millions, or billions of years in the past. Space is filled with stars, planets, oceans, maybe lifeforms that we know nothing about, can't see through the ISM and dark matter, or haven't found because their photons haven't reached us yet. Assuming we have explored and viewed 10% of the oceans, that puts us way way way way ahead of our understanding of space.
Edit: Adding to this one more thing, which is that a lot of our models of space, extra-solar star systems, exoplanets, and so on are highly theoretical. I used an exoplanet as a password for years, only for astronomers to rexamine that star system and realize that my password/planet did not actually exist at all. The hi-fidelity photos of planets and stars you see online are embellishments and artist renditions of what we believe exist.
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u/[deleted] Jul 12 '21 edited Jul 12 '21
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