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It would hardly be a tropical paradise as depicted in Avatar tho

Water for agriculture is what we need to worry about

Wow. Did they speculate how the decline will happen? People having less babies?

So it’s like pouring 100 gallons of fresh water into 1 gallon of salt water

Wow, great thought! Lots to think about.

I believe there are nebula made of water vapor, (or ice crystals?) that are more massive than our solar system, so we wouldn't even have to isolate the hydrogen and oxygen, but a controlled burn of H and 2O would be a source of heat energy. (Also a risk of explosion!)

Hauling around enough to make a difference for a planet, (either water or the gasses,) would be another challenge. Even if we had spaceships the size of a football stadium, that would be insignificant compared to one of the great lakes, much less an ocean. If we could haul around volumes comparable to large asteroids or small moons, then we're making progress.

Without doing any math, I am picturing spheres of water the size of Texas. It would take a steady supply of them to fill the world's oceans. Thousands? IDK

Our usual solution to clean anything is to dilute it. IE add more water to it so the parts per million of the dirty thing drops. If you're trying to do anything else the processes are a LOT more energy/resource intensive.

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and those are stepping stones for even bigger discoveries in 2023 and beyond🙌🏻

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I agree. When I was very little, I use to naively think that we can just ship snow from the poles for water. Like sending trash on a rocket to the sun. Or packing some sunshine into a box and ship it to a cold place, or vice versa.

Humans are great at solving problems. It's getting them done is the difficult part. Or sometimes, getting people to listen to start with.

For exomoons, the gas giant does not necessarily have to be in the habitable zone, due to a variety of factors such as tidally induced geological activity. I cite Titan. Imagine if it's subsurface lakes were nitrogen and oxygen (instead of ethane etc.) It would absolutely be habitable by humans, despite the parent planet being far outside our sun's relatively small habitable zone.

Also the global population is expected to peak in the next century and then start a steady decline, possibly as soon as 2064.

Desalination requires a ton of energy and money. As is with everything else on the planet, governments won't move until it hits the fan. We live in a world of over consumption of resources. I agree there is plenty of sea water in the world, and with the icecaps melting, it's a good idea to take as much of it as we can to make it into drinkable water to just maybe keep the oceans from rising. But from the stand point of 2022, we will run out of fresh water if nothing changes. They've known about this impending issue for almost a decade now and not much has been done about it. I wish it weren't so, but it is what it is.

"We" is ambiguous. Humans as we know them? Probably not. Some genetic variation / descendant of humans eons from now? Probably could visit it. Extremely advanced construct / "AI" / created being? Almost definitely could go interstellar. Artificial and biological hybrid humans (cyborgs / posthuman bodies)? Also likely if they're ever made.

Thank you very much my good man

Actually the film is interesting in subtly addressing the magnetosphere thing. A moon around a gas giant would be at risk of being fried by radiation focused by the planet's own magnetosphere. This is the challenge with Europa, and why the Europa clipper mission won't ever actually orbit Europa itself. In avatar you repeatedly see areas of massive magnetic flux, generally where the 'spirit trees' are. You can tell from large rock rings standing on end, following the contouring of magnetic field lines. This is also close to the 'flying mountains' which are suspended by such a magnetic field. The new movie was a bit different, but the original mentioned 'unobtanium' being mined which was a natural room temperature superconductor causing the magnetic fields. Generally small planets and moons solidify and a solid (ish) core like Mars doesn't produce a strong magnetic field like earth has. A small moon like Pandora flying free would solidify and lose a magnetic field, then have it's atmosphere stripped by solar wind, again like Mars, but an exo-moon would have massive gravitational tidal flexing to keep it's core active just like Io and to a lower degree Europa.

So kinda, outside of the magic 'unobtanium' it could exist

It would take less energy to re-hydrate a entire planet than it would to go to another star and pick up the water there and bring it back, especially if you do it in a reasonable amount of time. So yes a lot of alien invasion sci-fi is just dumb.

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>It’s not going to pass through into some fantasy dimension

Is that a commonly accepted model of a black hole?

I do have another question, why is it so difficult to clean water

So I’m an engineer for a cruise line that uses desalination from Reverse Osmosis, the issue with doing it on a massive scale is the amount of brine waste it produces. It’s extremely concentrated brine (nasty salt water sludge byproducts). We would have to figure out how to dispose of huge quantities without damaging the ecosystems.

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Could we just “collect” it for the galaxy

First off you would have to have a gas giant orbiting in the habitable zone for a terrestrial type planet. I consider that to be highly unlikely