20 years ago today, the very first episode of Star Trek: Deep Space Nine aired on American television. And Star Trek would never be the same again — but Deep Space Nine also had a lasting impact on all genre television. The grittiest of Star Trek series helped to give us a lot of the things we take most for granted on science fiction and fantasy television today — and here are just a few of the ways.
Those long, sweeping arcs. It seems like a weird thing to mention now, because every random cop show or space adventure has storylines that carry on from episode to episode, more like serialized novels than collections of self-contained stories. But back when Deep Space Nine started, the idea of following "arcs," especially ones that went on for more than one season, was still more unusual on TV. For a Star Trek show, especially, it was considered weird to have so many continuing storylines.
As writer/producer Ron Moore said, in an interview at TrekMovie:The Enterprise, like I said earlier, could pull up to a planet and have an episode and keep going. With Deep Space Nine, anything that took place on the station, well guess what? Next week you are still on the station. And Bajor is not going anywhere. So really you had to keep playing those stories. You couldn't make a big change in Bajor's political structure in one week and then ignore it then next. You had to keep it going. Kira's story with his relationship with Bajorans had to keep evolving and so did Sisko's and they had a long-term mission. They had a mission about Bajor into the Federation. That alone meant that it was going to be serialized at least on that front.
Anders goes on to identify multiple other legacies of the best Star Trek--the place given to religion, the exploration of the ethics of terrorism, and so on. While commenters who point out the similar role of Babylon 5, I'm inclined to think that these two shows of the 1990s often worked in parallel to each other without imitating each other.