in one of my long-running fantasy series, Lawful/Lawless, I add in some politics, some science and some history, and some culture. I even made up an entire language just to add some extra layers to the world. Adding history and politics must be something that makes sense within the world, but adding science is kinda tricky. Since I'm writing a fantasy novel, the science doesn't HAVE to be accurate and legit, but on the other hand, since a lot of fellow nerds are reading my stuff, I need to give them SOMETHING to not make them laugh at me and say stuff like "this guy doesn't even know basic physics" or something along those lines.
Call me bratty, but in my opinion, a good author should be smarter than the majority of their readers, or at least, know how to fake it. If you're writing a sci-fi story, then it has to have some sort of connection to real science in some way, even a small reference is enough to make the reader go "oh this guy actually knows some stuff and researched the subject"
This smart-ass attitude is even more important when writing a thriller or a tightly written story where the lil details are important and most of the established info comes into play. What I did in Lawful/Lawless was to have Mages and Humans kill each other off in the past generations and make both sides create their own falsified story to debate something interesting and add more layers and reveals. As for science, it's not real-life science, but it is similar, Mages study the History Of Magic which kinda combines the theory of evolution and the Big Bang and the law of conservation of energy with the concept of magic. I use math and trigonometry for magic circles, but I don't get too deep into it because it'll get boring, so I gotta balance things out. Explaining everything in detail is not necessary, just make a little reference. That's an easy way to appeal to people who are into that sort of storytelling.