Steampunk is what you get when Science reaches the end of knowledge circa 1899 or so. I know most people imagine zeppelins and goggles and top hats with clocks in them when they think steampunk, but I would prefer to think of the state of scientific knowledge and energy source.
- Steampunk design is stuck with coal or wood as its energy source.
- Dieselpunk adds gasoline and oil.
- Rocketpunk includes nuclear fission.
Here's the thing I got to wonder about. Through simple extended and aggregated monkey empiricism, humanity was using technologies not at all theoretically understood. Wootz steel, for example, was being manufactured in large quantity centuries, or perhaps millennia, before modern materials sciences in the 1930s quantified the exact properties that made the steel desirably functional.
Why didn't the Romans have steam power and railroads? They certainly had the ability to build high pressure vessels out of bronze or even iron, and most of the principles utilized by Oliver Evans and Richard Tevithick were understood by the ancients. So why not?
Why didn't James Watt power his stationary steam engine with an atomic pile? Some old-fashioned curiosity, coupled with good British graphite and natural thorium ore, should have resulted in a nice house-sized fission reactor in or around Manchester.
Clearly, the answer was, they hadn't figured it out yet, or, if they had, they didn't need it. Respectively, muscle (slave and animal), wind and water power, or wood and coal power, were sufficient for the Romans and English. But still... once you see how easy it is to make this shit....
Still and all, I'm glad I don't live in a steampunk or dieselpunk world, or at least, not entirely. We still do, as evidenced by all the soot, and dirt, and pollution, and fucking up of our water supplies.
Give me a rocketpunk world, in fact, give me a world populated with a specific kind of breeder reactors, and I really don't have a problem with that at all. I really don't.