By that logic almost all time-travel and FTL stories are fantasies. The Time Machine, Foundation, Ringworld... all magic-based fantasy.
Yes. (Though it's been too long since I read Foundation, in my teens, to remember if it contained violations of physics, and I don't know Ringworld.) But all FTL and time travel stories are fantasy.
Taking an absolute position that "if it's not proven science it's crap" is problematic at best.
Where have I ever said that?!?!? I've said over and over that I LIKE fantasy. I just want it to be called what it is.
... That approach means that Star Trek style communicators were once fantasy, but then they transitioned to SF as we entered the Information Age, and then they became just plain old reality after we built them.
Again, not at all what I said. In fact, practically the opposite of what I said. Small radios never violated the laws of physics. I've never said that a technology must exist today to be sci-fi. I said that it must not violate well-established laws of physics. FTL travel violates the laws of physics. Small wearable radios do not.
I'm not trying to put words in your mouth, or imply that you don't like fantasy. I was attempting a joke based on 'if it's not Scottish it's crap' is all. Please read the statement as 'if it is not proven science it is fantasy' instead.
"Small radios never violated the laws of physics."
They certainly did. To someone in 1802 a hand held device for long distance communication was fantasy powered by magic. There was no scientific foundation for radio. Heck, electricity was barely a thing. One might have imagined a magic mirror that could contact other magic mirrors, but this was outside known physical law.
But by the 1820s experiments exploring the relationship between electricity and magnetism began. Could that magic mirror be science fiction at that point? Or after 1873 when Maxwell's work triggered research into radio communication? Maybe the magic mirror became scifi in the early 1900s when radio was demonstrated to made practical?
I'm not saying your approach is wrong. I'm just pointing out that it has problems, because the established body of scientific knowledge changes over time. I suspect this is the inspiration for Clarke's "any sufficiently advanced technology is indistinguishable from magic."
Right now physics has some interesting gaps, and a spotty understanding of spacetime. FTL is ruled out by GR, but we know GR is not perfect, because it does not integrate with quantum theory. Which is also not perfect because it does not integrate with GR. I doubt that a grand unified theory of everything Will give any indication faster than light travel is possible, but I'm not going to that possibility out completely. Maybe one day FTL will be conclusively ruled out. At that point pretty much all of science fiction will be retrospectively incorrect. I might still think of it as SF that was incorrect as opposed to fantasy, however.