It's common for people to say that if a time traveler or an alien displayed advanced technology to ancient or medieval people, that they'd assume it was magic, and either worship him as a god or burn him as a witch.
But if aliens visited the Earth tomorrow and had technology hundreds of years in advance of anything humans have yet invented, I'd think few if any would suppose it was magic. You might say, "Yes, but we are technologically sophisticated people, unlike those medieval people." But people in the Middle Ages built complex clocks and other mechanical devices, and cathedrals and other buildings at least as grand as anything we build today. Ancient people built the Coliseum and the pyramids. The Greeks built complex mechanical devices -- like the Antikythera machine. Would the ancient Greeks have assumed that, say, a flying machine must be magical? Or would they have said, "Ah, like Daedalus built"?
So my question is, Is there any evidence that ancient or medieval people would be unable to distinguish advanced technology from magic? For example, are there documented historical examples of, say, 19th century Europeans encountering a primitive tribe and the primitive people thinking the European's machines were supernatural?
My intent here was not to get into a discussion of whether there really are supernatural forces in the universe. Whether there really is a God who performs miracles, or ghosts, or people with psychic powers, doesn't affect what I was driving at with this question. You may think that people are foolish and gullible to believe in religion, but even if you're right, it's not a matter of confusing technology for the supernatural, it's a debate about whether the supernatural exists.
I admit I may be splitting hairs here, but I think it's a fundamentally different idea. Suppose a con man tries to convince people that he can read minds. The issue isn't that people are confusing technology with magic, but that they are being duped by a con man. Odds are he isn't using any particularly advanced technology, but simple stage magic tricks. Very little stage magic depends on high tech gadgets: it's almost all slight of hand, a box with a hidden compartment, smoke and mirrors. I know some mind-reading tricks, and none of them involve high technology, they're all about having an accomplice who uses code words to pass you information and that sort of thing.
Very Late Update
I see a number of posters here have made comments on the order of, "If you don't understand it, it's the same as magic." No, it's not. It's true that people use the word "magic" colloquially to mean "stuff I don't understand" or even "stuff that's really impressive", as in, "we talked via the magic of cell phones" or "wow, this new cleaning product works like magic!" But my intent with this question was that I meant "magic" in the literal sense: something supernatural, ghosts, psychic phenomena, etc. I'm sure 90+% of the population of America and Europe don't know how cell phones or computers work. But they don't suppose they are literally evil spirits captured in a box.