Sounds very similar to Arthur C. Clarke's assertion that any sufficiently advanced technology will be indistinguishable from magic to a less developed species. To an extent I can believe that. Those that remain logical though will theorize that there is a scientific explanation as for why that technology exists, but may not know what that explanation is. I doubt the term 'magic' would be used, but we would definitely be in awe and unable to explain it.
Science fiction stories are best related to when they're still couched in the same basic scientific laws that we understand in the present. There are two terms I keep coming across amongst Science Fiction writers. AM and FM. Actual Machinery, and F^*#ing Magic. Actual Machinery gives off noise, needs regular maintenance, breaks, needs lubricant, rusts, etc. FM is a dangerous thing to use in Science Fiction because it's indistinguishable from the kind of Magic you'd read about in Fantasy novels. (Magical Teleportation vs. the Enterprises' Teleporter)
Einion is right that we can imagine force shields that a super-human in power armor can carry which will absorb the kinetic and thermal energy of an Orbital Bombardment of Plasma Missiles. It could run for 30,000 years on a single battery charge and turn homing missiles back at their target with the precision of a sniper. Thermal energy from the sun will be admitted through the barrier, but it will deflect the thermal energy from a Lasgun. HE explosive rounds will simply rock the Marine back on his heels while he can accept a hug from an orphan. The shielding will conform perfectly with his legs and feet so that he can maintain mobility and keep traction.
But unless it's based in theories we can comprehend then it loses all credibility of being possible. I'm not saying Warhammer 40k is the most believable setting, but when FM overwhelms the presence of AM in a setting it's just turned to arbitrary crap. The trick is finding the right blend to make it seem fantastic, and plausible. Improbable is fine as long as it can sound plausible. Objects that defy the laws of physics as we know it that are commonplace? It needs at least a pseudo-explanation. The fact that we're even trying to discuss the merits or plausability of the setting implies that it has at least some merit to it.
Please note: I don't mean to come across as hostile. This is just a subject I enjoy and am enthusiastic about.
Very true, but Warhammer 40k has as much AM as FM. The problem is one of image. Even in setting the Actual Machinery (AM) is presented as F%*#$ Magic (FM), due to a severe downturn in society and how we understand technology. A pitch which, really, is becoming all the more believable as I go through life. A vast amount of technology is presented as magical, and is treated as such in the setting, but it is still maintained like Actual Machinery. Amongst the incense and chanting they're also pushing buttons, oiling and lubing machinery, and doing the normal activation process of their machines.
To most of us that just sounds like utter stupidity, but have you ever watched someone talk to a computer to get it to work faster? What about someone with a specific ritual to get a malfunctioning machine working?
This makes it especially hard to explain the technology behind it because of the mystifying jargon of the people who build and maintain the machinery. Not only that but the complicated process of explaining significantly advanced technology that requires a familiarity with lesser technology that is itself unfamiliar.
For instance, if you were to try explaining the Land Speeder, you'd have to explain how the anti-gravity is generated, then you'd have to explain the mechanism behind it, then the mechanism behind that, and regress past several dozen scientific theories and principles to explain even the simple parts of it.
Alright, so it's a little more complex in the explanation because we
don't have any idea exactly how it works. However, an easier mental scenario would be to pick any 18th century scientist, and show him/her an iPod or (gods forbid) an iPhone, and explain it to them. Most of us would probably give up with "It plays music" and pray that they don't ask how. The technology leap makes it seem almost impossible, and the leap in understanding of science makes it seem like nonsense. Perhaps "magic" is a problem of grammar rather than reality, the word is steadily slipping out of it's more common "fantastical" usage and into a set "fantasy" definition, so perhaps Clarke's quotation could use an updated word choice.
However, on the other hand, there is a lot (
a lot) of technology that was only written about in the past that is now becoming a reality, and it's all based off of these vague utterances in great Sci-Fi that had almost no explanation to them. Things like powered exoskeletons, mind-machine interfaces, AI, space elevators, the internet.
Neuromancer alone set a lot of very reachable bars in science fiction that are shaping how we reach science fact.