To quote myself: "Referring to judgments of the
plausibility of the rationalizations as realism (or "hard") science fiction is a bottomless well of argument. Does plausibility mean probability or possiblity? Does the current state of knowledge or that when written serve as the standard? Does the scientific education of the writer or the reader matter most?"
The private creation of a space flight industry was always absurd, from the day anyone closed Verne's From the Earth to the Moon, and thought: "A gun club?

" Private creation of space flight was never plausible, because spaceships aren't sailing ships or airplanes.
And yet, Jules Verne was right. He only made one small mistake; the fuel and power in real life was put on the craft, not the firing mechanism. But when you come right down to it; it's a bullet that is fired up.
And sorry, but spaceships ARE sailing ships or airplanes, they just go a little higher and faster. Exactly the reason why there are private institutions seeking privatized space flight today. If the vision for these things had occurred sooner, or the vision of going into space as a national endeavor had occurred much later, private spaceflight would have been first.
The supposed nuclear threat from the Soviet Union was Cold War propaganda. Even at the time of the Cuban missile crisis, nuclear war would have largely meant the annihilation of Soviet Union. The real threat of nuclear war dissipated rapidly when the Soviet Union actually acquired an effective nuclear deterrent, and each reheating was due to US efforts to reacquire a massive superiority making nuclear attack "feasible." The threat to the US was never any more plausible than the nuclear threat from Iraq or Iran or North Korea or Israel or Pakistan or India.
Again, if you know some of the horror stories of the cold war, you know that we came damn close on more than one occasion of getting burned in nuclear fire. The simple fact is, that whether or not your country gets blown to bits by the counter strike, has never stopped idiots from making scenarios of doing it. Besides which, if you think the nuclear strike has already been launched by the other guys, you have nothing to lose and push the button.
Even in the Thirties, the idea that the calendar (which had orginated in the days of the Roman Empire,) would be replaced was implausible in the extreme. Further I submit to you that it was never intended to be realistic, i.e., true to life, but a deliberate exaggeration intended for satiric effect. (Satire is not a subgenre of humor, which means, I did not say Huxley was joking.)
Nope, the Julian calendar originated in the days of the Roman Empire, named after Julius Ceasar. The Gregorian calendar we use today originated in sixteenth century.
I picked those examples in hopes that time would have worn away customary suspension of disbelief in implausibilities. Nonfiction is not realism. Realism is things like Turgenev and Flaubert, Ibsen and Strindberg. They are fiction and they do no contain implausibilities or impossiblities of the sort science fiction and fantasy do.
Uh, sorry, but the moment a story contains a person that didn't exist, it's not real, and pretty much according to you, not realism.
In any event, the insistence that there is somehow realism of any sort in science fiction also runs into problems with outright impossibilities. Wells' Invisible Man has Griffin able to see. How can light be captured by invisible eyes? If it is, where are the shadows cast when light is somehow absorbed by the invisible retina? Invisible Man is still science fiction.
And this would be a case of it not being realism. Doesn't mean that all Science Fiction has no realism.
Science fiction is a work that has some fantastic, i.e., nonrealistic, element that is explained as somehow natural. The "explanation" may be the tacit assumption that the reader has read previous science fiction using some of the same tropes, in which case the name of an imaginary phenomenon may be all that's actually written. The example of "telepathy" comes to mind. Why do we have a name for something that doesn't exist?
Which, of course, has got nothing to do with anything.
Alternate history stories presume the reader has some vague notion of many worlds or multiverse floating around but they don't even trouble to explain it any more.
Nope, not at all. An Alternate history story is just that, an alternate history, an exploration of "what if"? No requirement of the many worlds theory required, because guess what, some of the writers of the genre didn't even know the theory existed, and I'll bet there were stories in the genre before the theory even existed.
Of course, an alternate history does not eliminate realism, quite the contrary.
So, once again, realistic doesn't mean real, it means close enough to reality it could have been/could be real. Stories with nuclear annihilation are as far removed from not realistic as you can get.
There are works of science fiction that have outright impossibilities, just as impossible as anything in fantasy.
There are also works of fiction in the mainstream that have outright impossibilities and are just as impossible as anything in fantasy. Doesn't mean that all works of fiction are by definition unrealistic. To boot, I've rather been arguing that if and when such things occur, and these happens very often, and they're massive; we've got bad stories and we should be avoiding them. However, this does not mean that all SF stories have them, or that all SF stories are unrealistic.
This dates back to Jules Verne and H.G. Wells, and if those guys are science fiction, then nothing is.
You're wrong, especially Jules Verne spent his time meticulously keeping within science.
[quote\None of the currently acceptable speculations as to an end run around special relativity (permitting "FTL"/time travel,) are practically possible. One solar system is not going to produce the energy of a small galaxy. That's not close enough to reality to be realistic.[/quote]
You're wrong. There's a little thing called vacuum energy, or zero point energy, or Dark Energy. It's the energy stored inside of every single insignificant little point of space-time. And guess what, even the energy in one point, is enough to obliterate a planet.
And again, just because it is practically not possible now, doesn't make them impossible period, and suppositions that it can be done in the future does not make them unrealistic. Especially not when science itself endorses these options, and even comes up with things that seem even more outlandish than what science fiction came up with.
Defining realism so that it's meaning depends on when it is used (at time of writing or now,) or by whom (writer or reader/viewer whose scientific education meets an unspecified standard,) is not defining it at all. Plausibility or possibility, built into your definition of realism, are impossible to define.
Which of course means, that by your definition all fiction is by definition is unrealistic. After all, how plausible is it, than an actual Tom Sawyer existed, going through exactly the adventures he went through in his book. Or name any other fictional character from whatever genre.
Further, ALL "realism" depends on when it is used. A book that is realistic in the 80s, would be considered written by an uneducated hick trapped in the jungles in our day.
And similarly, bring a contemporary realistic book to the deepest darkest jungles and let someone who spent his entire life living there read it, and he or she'll most likely consider the book a piece of unrealistic SF idiocy.
All realism depends by definition on when it is used, who it is used by, and where it is used.
By your definition there is no realistic fiction. The only books that have a small shot at being realistic are school books, and even most of them are probably not realistic at all.
It is impossible to approximate the reality of 2050, because no one knows what it is. It is impossible to approximate the reality of longevity treatments, because no one knows what they are. It is impossible to approximate the reality of the intercourse between Neanderthal and homo sapiens because no one knows what it is.
You know, at some time, we didn't know electrons either, hell, we still might not know exactly. Yet that didn't mean we threw in the towel and gave up. We went to use our minds and imagined what it may be like, wrote equations down in mathematics and then did experiments to see if they fit.
Now, just because we cannot do any experiments on longevity treatments, or interspecies sex in the past (yet), does not mean if we go an imagine what it might be like, and do our best to keep it grounded in reality and what we do know, you can't write a very realistic story. And just because we might one day invent a time machine, go back in time, and see such for ourselves, and find out the writer's imagination got it wrong, still doesn't mean his story was unrealistic. It would have been unrealistic even he didn't even attempt to ground it in what we do know.
Fantasy, by contrast, has a fantastic element which is not rationalized as somehow natural, but is explicitly supernatural, or which is not lawful, sometimes explictly held to be chaotic or transcending quotidian cause and effect. Indeed, one of the attractions of fantasy is that it denies such basic scientific principles as cause and effect. That denial is like the fizz in soft drinks.
Actually, a fantasy that isn't beholden to cause and effect, is a fantasy that is completely random and has no internal rules of logic at all. This would be a piece of fiction that will be nearly universally derided as being bad.