As we know, "Any sufficiently advanced technology is indistinguishable from magic" (Arthur C. Clarke). Conversely, many magical events in older fiction can be duplicated today by mainstream technology. A century and a half ago, someone who witnessed a translucent human figure floating in midair and emitting eerie moans would unquestioningly recognize it as a ghost. Now we'd respond with, "Cool special effect. I wonder how they did that?" Just such an apparition appears in Jules Verne's 1892 novel THE CARPATHIAN CASTLE, on the cusp of the shift between the two probable reactions. The local people think the vision of a dead opera star at the titular castle is her spirit, when it fact it's produced by a sound recording and a projected photograph.
In George du Maurier's 1894 novel TRILBY, the villain, Svengali, uses hypnotism to transform an ordinary girl who's tone-deaf into a famous singer. She can produce exquisite melodies only in a trance. When Svengali dies, she instantly becomes unable to sing. At the time of the novel's publication, little enough was known about hypnosis that this scenario doubtless looked scientifically plausible. Now that we know hypnosis doesn't work that way, Svengali's control over Trilby seems like magic, and to us the story reads as fantasy.
Several decades ago, I read a horror story about an author who acquires a typewriter that's cursed, possessed, or something. He finds that it corrects his typos and other minor errors. Gradually, this initially benign feature becomes scary, as the machine takes over his writing to an ever greater extent. He narrates his experience in longhand, since if using the typewriter he wouldn't even be able to demonstrate an example of a misspelling. At the time of publication, this story was an impossible fantasy. Now it would be merely a cautionary tale of a word processor with an excessively proactive auto-correct feature. From the beginning of J. D. Robb's Eve Dallas science fiction mysteries, set in the late 2050s and early 2060s, almost everybody carries a handheld "link," a combination communications device and portable computer. When the earliest books in the series were published, that device was a futuristic high-tech fantasy. Now the equivalent has become commonplace in real life. But another tool Lt. Dallas uses in her homicide investigations still doesn't exist and remains problematic. Police detectives employ a handheld instrument reminiscent of Dr. McCoy's tricorder to gather data about murder victims. One of its functions is to pinpoint the precise time of death to the minute. That capability would seem to run counter to the intrinsic limitations arising from the nature of the decomposition processes being analyzed. Therefore, the exact-time-of-death function strikes me as irreducibly quasi-magical rather than scientific, something the audience has to accept without dissecting its probability, like the universal translator in STAR TREK.
The distinction between science and magic can get fuzzy when nominal SF has a fantasy "feel." Marion Zimmer Bradley's Darkover series takes place on an alien planet inhabited partly by descendants of shipwrecked Terran colonists. Strict "hard science" readers might not accept psi powers as a real-world possibility, however, and the common people of Darkover regard laran (psi gifts) as sorcery. Anne McCaffrey's Pern series, also set on a planet colonized by migrants from Earth, features fire-breathing, empathic, teleporting, time-traveling dragons. Although these creatures have an in-universe scientific explanation, they resemble the dragons of myth and legend. Robert Heinlein's novella "Waldo" blends SF and what many if not most readers would consider fantasy. The title character lives on a private space station because of his congenital muscular weakness. Yet he overcomes his disability by learning to control his latent psychic talent under the guidance of an old Pennsylvania hex doctor who teaches Waldo how to access the "Other World." Incidentally, "Waldo" offers an example of how even a brilliant speculative author such as Heinlein can suffer a lapse of futuristic imagination. Amid the technological wonders of Waldo's orbiting home, Heinlein didn't envision either electronic books or computer games; a visitor notices paper books suspended from the bulkheads and wonders how Waldo would manage to play solitaire in zero-G.
I've heard of a story (can't recall whether I actually read it) whose background premise states that, in the recent past, the wizards who secretly control the world revealed that all technology is actually operated by magic. The alleged science behind the machines was only a smoke screen. If such an announcement were made in real life, I wouldn't have much trouble accepting it. For non-scientists, some of the fantastic facts science expects us to believe—that we and all the solid objects around us consist of mostly empty space; that the magical devices we used to communicate, research, and write are operated by invisible entities known as electrons; that starlight we see is millions of years old; that airplanes stay aloft by mystical forces called "lift" and "thrust"; that culture and technology have advanced over millennia from stone knives and bearskins to spacecraft purely through human ingenuity—require as much faith in the proclamations of authorities as any theological doctrine does.
Margaret L. CarterCarter's Crypt