But that's the result of later creators falling short of the original intent. Roddenberry's goal was always to make it plausible, and the fact that it was more plausible than the likes of
Lost in Space and
Space: 1999 was critical to its popularity. TNG was more plausible than its near-contemporaries too, thanks to the efforts of folks like Rick Sternbach and Mike Okuda, and that helped pave the way for the other, relatively plausible SFTV that we take for granted today. (The most hard-SF show on the air right now,
The Expanse, is show-run by Naren Shankar, who got his start in the business as TNG's scientific advisor.) Later showrunners and especially filmmakers have been more lax, but the foundational intent of
Star Trek has always been to keep one foot in reality, and that's important to its basic character and influence as a franchise, no matter how badly it may have eroded over the decades.
So it's overly simplistic to reduce ST's scientific accuracy to a single unchanging value. There's always been a back-and-forth between those Trek creators who cared about science and those who didn't. Even in the Kelvin films, Roberto Orci was concerned with scientific plausibility and did his research to try to get things right, even if he was overridden by J.J. Abrams's preference for a more fanciful approach. And I know that my friend and colleague Kirsten Beyer is doing her part on the
Discovery writing staff to keep the show's science grounded and logical, because she understands that that's a fundamental part of Trek's creative philosophy, what it has always aspired to even though it's often fallen short in practice.
The only times in its history that
Doctor Who ever aspired to anything of the sort were in its very early years. It started out as an educational show meant to teach science and history to young viewers, but it was always better with the history than the science, and its SF episodes were highly fanciful, their science lessons cursory and flawed at best and undermined by the microscopic budget. In 1966-7, they brought in Dr. Kit Pedler as a scientific advisor and tried to make the science more grounded and authentic for a while -- "The Moonbase" is a pretty good example of a story where they made a decent effort to get the science right, though the budget still got in the way and some aspects (such as a gravity beam on the Moon used for weather control on the Earth) were still highly fanciful. And it was still a show about a guy whose spaceship could travel anywhere in time and space at the touch of a button and was bigger on the inside, so it was never going to be all that grounded. The era of concern for science only lasted for a couple of years at best, and has been over for just about 50 years now. And the modern series under Steven Moffat has treated the show as a straight-up fairy tale.
Right. They're radically different shows and always has been. It's bizarre to pair them as if they were equivalent in any way besides their iconic status relative to their countries of origin. It's like having a discussion of police procedurals and comparing
Law & Order to
The Flash (although at least those have Jesse L. Martin in common).
Also, it's wrong to mistake labeling for analysis. Placing shows on some kind of linear spectrum between "hard" and "soft" SF, as if they were minerals on the Mohs scale, is not truly understanding them. Those words are overly simplistic generalizations, and at best are descriptions rather than definitions. A single four-letter word won't tell you anything worthwhile about the
specific thinking and goals of a show's creators, the perspective they had on the universe they were trying to build, the multiple parameters they were considering, the constraints they were placed under in their efforts to achieve that goal. Too many people treat sticking a label on a thing (like "hard/soft" or "canon" or "Mary Sue") as if it were the end of the discussion. No. It's barely the beginning. It's the initial thesis that needs to be justified and fleshed out by an analysis of the individual details -- which often reveal that the differences outweigh the similarities.
Not to mention that there isn't really a universal consensus on how "hard" and "soft" SF are even defined. The usual assumption is that it's about scientific accuracy, but that's not the way I learned it. What I'd call the
Analog definition of hard SF (based on the submission guidelines of the magazine known for its hard-SF sensibilities) is that it refers to stories where the science is an integral element of the plot, the source of the story's problems and solutions; whereas soft SF is something where the speculative elements could be removed without altering the basic storyline, because they're just part of the setting or are one-to-one substitutions for elements from a more standard story (e.g. doing a Western but replacing the six-shooters with ray guns, or doing a samurai movie but replacing the katanas with lightsabers). Hard SF is driven by exploring the human consequences of a scientific or technological advance, while soft SF is driven by the same elements that drive mainstream fiction -- character, social commentary, or simply action -- while using the SF concepts as symbolic or allegorical elements or merely background trappings. So in theory, one could have a soft SF story where the science is entirely accurate but just not particularly relevant or heavily explored. That's pretty much what
Star Trek always aspired to be -- a show driven by character and philosophy rather than just technical problems, a show that told the same kind of character-based drama you'd find in other genres, but getting the science at least relatively right in the process.
Here's a column where a number of SF authors discuss the "hard/soft" scale and the various different ways of defining them:
https://www.tor.com/2016/01/21/how-...tion-ten-authors-weigh-in-on-hard-vs-soft-sf/
In-story, I go with the assumption that it stands for "United [Federation] Star Ship." As a tie-in writer, I'm constrained to remain consistent with the established facts of the universe. As a fan and a viewer, though, I'm entitled to say when I think they're silly.