Most writers will know that there's a difference between 'hard' and 'soft' science fiction. Hard sci-fi utilizes scientific accuracy and grounds itself in chemistry, astronomy, and other practical sciences that actually exist. Soft science fiction is more flexible in what's logical, more or less it relates to social sciences, relaxing the realism element. Basically, hard science fiction typically follows scientific realism, where soft sci-fi does not.
I like describing my writing as "Hard Science Fiction, Low-Fantasy", since I have fantasy elements in my book, but the hardline is the science. For me, I've always found science fiction intriguing if the concepts could apply to reality. In Einstein's theory of relativity, it's possible for wormholes to exist, and thus to our understanding of technology and physics, this would be the closest to traveling intergalactic distances in a human lifetime. Already, our world doesn't need magic to be interesting; science on its own is already so complicated and fascinating in itself.
In using hard science fiction, if you also choose to go down the fantasy route like I have, I think it's essential to understand that a world like this more than likely has a hardline system of magic just as complicated as the science. Like any good magic system, they're complicated, flawed, and not every little of magic is known. With these two writing styles converging, I enjoy calling it a 'World of Two Sciences', since one is grounded in reality, and the other is flavored as the world demands it. As a result, magic should never be used as a one-fix all type of situation. Some problems require science to solve; others require magical knowhow. If you can balance both the science and the magic system, that's how you know you have a solid system. If magic can just do everything science can and more, that's a more fantasy-like story, potentially in medieval stasis.
Maybe there's a reason behind why science might not work the same way it does in reality; as such, a story could still be just as, if not more, interesting. I'm not saying you should reinvent physics itself, but I'm sure the few authors who have done so have an immaculate attention to detail. In a future novel, I might try something similar, but no promises. We'll see how difficult it is to make a dimension where nothing makes sense.
I suppose one reason I always found hard science interesting was because I found space interesting. When I watched sci-fi shows as a kid and could point out how little inaccuracies existed, I often thought the creators were doing the real, interesting science a disservice. With the idea that advanced science is indistinguishable from magic, the ideas have gotten so carried away with that saying that they turned into soft science fiction. Whether we realize it or not, it's quintessential to the future of humanity to promote scientific minds. After all, some scientific concepts started out as fiction at some point. The most notable instance of this was when JFK, at the beginning of the 1960s, gave the US the ambitious mission to land men on the moon and bring them home. 1969, just later that decade, it happened.
Sometimes, scientific ideas come from fictional concepts, and these concepts become integrated into the real world once their substance has been explored. Leonardo Da Vinci designed countless unique inventions that, hundreds of years later, were adapted to the real world (one of the most notable being the tank). Even if it’s long after the work of art is completed and the artist is no longer around, their work continues to live on inside the human consciousness. In a sense, the writer Homer has been alive for thousands of years by this metric.
Back to scientific realism, I love this philosophy since it gives scientific answers to fictional narratives. Even with elements that are currently commercially unobtainable that exist in the real world (like Francium), there may yet come a day that we can use Francium hydroxide for scientific purposes. That day may be far in the future, but the fact that it’s possible and could be used in a fictional narrative makes it hard science.
Chemistry is only one piece of the puzzle, of course. While some other writers propose mechanical engineering, with astronomy being a popular point of sci-fi, I think one piece of science that might be overlooked is biology in writing. Not just from DNA, RNA, and creating unique or mixed animals, I also mean it from the standpoint of life synthesis. Relating back to space, every organism on Earth is a carbon-based lifeform, but an element that is just as complex as carbon and could potentially also give rise to life is silicon. In such a case, solvents need to be like how water is a solvent for carbon-based life. Nevertheless, fictional biology and especially astrobiology might be the most interesting pieces of science, since it’s not just about the scientific concepts anymore; it’s about creating a brand new organism.
Though science is still in its early infancy, humanity is on its way to the stars. The road is tumultuous, but the ultimate destiny is to expand beyond this terrestrial cradle of civilization. We will one day look back on the times when we knew the geography of the Earth, but barely knew much about the geography of the stars. After all, mapping out every individual world takes more than just using a satellite; it takes an explorer with a dream.
Until we meet again,
Dustin