UC to space is 100% possible, and this is my complete explanation to prove it
Background: I am a senior chemistry major at a tier 3 research university and I will soon have a published chemistry paper in a chemistry journal. After undergrad, I will be pursuing a PhD in atmospheric chemistry.
Step 1: Underwater Civilization (Medieval-like)
Most agree that before fire and metalworking, underwater civilizations with animal/plant domestication, some complex building, and large cities are 100% possible.
Step 2: Writing
Writing is actually really easy because it’s so broad. Any method of recording information is writing. Ancient Sumerian Civilization just used impressions in clay, and you can even buy underwater pens and paper now. All you really need is a hydrophobic surface and hydrophobic ink, which are both really easy to make. For example early UCs could use seaweed as the surface and any dye suspended in oil as the ink.
Step 3: Metalworking
Notice that the first two steps are out of order with the history of humans. This is because I agree that metalworking underwater would be harder to discover than in air, but definitely 100% possible and almost inevitable with generations of hundreds of thousands of individuals spending curious lives thinking and exploring the world. For how this would work, please see my forum post (A Chemist's Perspective: Underwater Metalworking). I personally think the most likely reaction to replace fire would be the reaction of organics with hydrogen sulfide (https://doi.org/10.1021/jp011713m) but there are so many good contenders that the possibility of metalworking is guaranteed (I also think floating forges might be possible, but I won’t talk about that because I’m taking the chemistry perspective). Most agree that metalworking is the critical technology that is impossible for UC, which is why so much discussion focuses on it, so with that out of the way most of the remaining path to space exploration is just restating history.
Step 3 counter arguments:
“Why wouldn’t energetic molecules have already burned before the species could use them?”
“Why do energetic molecules exist when they could be in a less energetic state?” Is one of the fundamental principles of chemistry. The answer is kinetics, which is the fact that special conditions must exist for molecules to react. Molecules do not just magically change until they are in their least energetic state, they respond to the conditions around them in predictable ways. Hopefully some thought will intuitively bring you to this conclusion. Our atmosphere has tons of oxygen, and our continents are filled with burnable wood, but most of it remains unburned because it needs initial heat to begin the reaction. It’s the same for the case of hydrogen sulfide and sulfur dioxide- they need some initial energy to get them to react to become elemental sulfur and water. This could come front sparking rocks together, or from, I dare say it, the heat of a hydrothermal vent.
I will try to add more counter arguments if I see them.
Step 4: Industrial progression
Metalworking will naturally lead to the development of advanced tools and further surpluses and development for UCs. A printing press equivalent for whatever writing system is being used can be developed. The spread of ideas will bring rapid development in theoretical and applied physics, mathematics, chemistry, politics, and economics. Soon the industrial revolution will come with assembly lines and electricity.
Step 5: Electricity
Any of the reactions used for metalworking could be used to heat up water enough to boil it, creating a steam generator. Other methods also exist. About now any UC should be easily able to pump air in from the surface and keep it in closed containers to do anything that requires air.
Step 6: Electrical Insulation
In modern society we have almost no uninsulated electrical components because it is very easy to insulate them. It would be no different for underwater civs. I only include this because “short circuiting” is a common electricity counter argument.
Step 7: Computation
Computation is just an application of electricity, no further technology is needed.
Step 8: Space Travel
At this point all of the metalworking, electrical technologies, chemistry, and computation needed for space travel have been developed.