How could an aquatic alien race develop a technologically advanced civilization?

I was thinking more generally but let's say they posses both gills and lungs.

The funny thing there is that when you start postulating amphibian species that go on land to discover fire and metalworking and electricity and such, you're basically replicating the path of evolution on Earth. You no longer have a purely "aquatic alien species". Now, if they became sapient underwater and migrated to land later, that's a significant enough departure from Earth to make them "alien", but their technology is still recognizable.

One thing I will note is that having both gills and lungs (or more generally, being able to get around equally well on land and in water) is less efficient from an evolutionary standpoint; there would have to be some comparative advantage gained by retaining this capability. Developmental energy is precious and developing dual systems for breathing and locomotion is wasteful.

Tossing this around in my imagination, I picture a society whose strata are divided among those who dwell only in the water, those who dwell only on land, and those who go between them. The water-dwellers would probably be traditionalists, dissing those rebellious and intransigent folks who breathe air and wield fire.

Edited by Fighteer on Sep 6th 2018 at 9:49:55 AM

I was thinking more along the lines of them possessing lungs and gills but are still completly aquatic and can't leave the water without mechanical aid, as for why they'd have both, perhaps they are designed to be very adaptable and can survive in a wide range of underwater environments include oxygen poor and freshwater ones where lungs would be more useful.

Whether your alien race will live mainly in water or on land is principally a function of their body structure and that in turn of their history. The ability to make fire on land probably won't be of much decisive value in determining their habitat especially if they aren't sedentary.

Of course, on an alien planet the water can be as oxygenated as you want it to be.

Not without some major bending of the laws of physics and of logic in many instances.

But what chain of technology would give rise to that "mechanical aid"? How would a purely water-dwelling species even conceive of, never mind construct, the sort of machines needed to allow them to move on land? You have a chicken and egg problem.

Adding on to what Septimus said, while you can certainly envision different chemistry in their water, you still have to obey the overall laws of chemistry (and the underlying physics), and water that's oxygenated enough to sustain combustion is pretty much pure fantasy. Or at least if such a thing were possible, I don't see how life could exist in it.

Edited by Fighteer on Sep 6th 2018 at 12:19:50 PM

Im not a chemist, so I dont understand why an amount of free oxygen suspended in water violates the laws of chemistry. Can someone explain that?

Free oxygen in the atmosphere and dissolved oxygen in the water maintain a concentration equilibrium, so the percentage in each body is going to remain at about the same level in the long run. If there's excess oxygen in the water, it's going to diffuse out into the atmosphere and vice versa. The difference is that dissolved oxygen in water is, well, dissolved, and subject to strong intermolecular forces with the surrounding water molecules, so there's a lot of energy to overcome; it's not going to just float freely towards a body undergoing combustion like atmospheric oxygen would. Unless the oxygen saturation on your planet is so high that the water isn't really water anymore and the air is on fire all the time, that is.

There are chemical mixtures in real life, like thermite, that provide their own fuel in the form of decomposing oxides and give out so much energy at such a rate upon reaction that they could burn underwater, but I don't see a way for our underwater race to develop such a thing without first being exposed to above-water fire on the regular.

Edited by eagleoftheninth on Sep 7th 2018 at 6:37:24 AM

"Unless the oxygen saturation on your planet is so high that the water isn't really water anymore and the air is on fire all the time, that is."

Now there's a planet worthy of a story! Lets see life evolve there.

So the main barrier isnt a fire under water, its thinking to ignite the thermite or magnesium, and having a source of ignition?

Well, you need a way to generate enough energy to ignite the fire - either by mechanical friction or a chemical reaction - and you need a source of oxygen to sustain the oxidation. Fire in the atmosphere can draw oxygen from the surrounding air to react with its fuel, but obviously you can't do that with dissolved oxygen underwater. Thermite brings its own fuel in the form of highly reactive aluminium powder, which is oxidised by iron oxide in a violently exothermic reaction. Though both components are metals, so producing it underwater obviously poses a bit of a chicken-and-egg problem.