Those thoughts have come up again and again as I read this rather awful synopsis of a research paper done in 2010 that says some metaphors, such as "time flies" cannot be translated into sign language. I feel offended very time I read it, as though they are saying the concept itself can't translate.
I think the real lesson is that metaphors cannot translate literally, not that they can't translate at all. I don't know very much Israeli Sign Language, but I've met Israelis who have no problems with ASL, and there seem to be points of similarities.
The real issue of translation is that words both denote (name a specific action/object) and connote (associate or mark specific properties of that object, both concrete and in language usage.) The Israeli sign they used had a denotation similar to "flies" as used for animals, but has a visual image and connotation best translated as as "flaps." Butterflies fly, bird fly. But I doubt that Israeli signers use a "flapping flight" sign for airplanes. Had they asked about the sign used for airplane flight, they might have found that yes, "time flies" could be translated using the airplane flight sign, or yet another sign, as in ASL. You see, sign languages have many words that denote and connotate narrower and richer meanings, just like in English.
You can't say "time flies" as "time flaps, time migrates, time hovers, time dives, time lands" in English and mean the same thing.
Which brings back to why the true ASL idiom for "time flies" is something very different-- "time zooms" {zooms, splits, disappears into the distance, like a train.} "Zoom" is a visual metaphor of motion and disappearance, which fits "time" as poorly as the idea of flight. So what do those two words have in common? What connotations are both metaphors using? How is a bird like a train? What does "time flies" mean after all?
The answer is speed. Birds fly quickly. They can vanish almost as soon as you see them. So can a plane, or a train. "Time flies" means that time is quick, it is gone before you are fully aware. That is the metaphorical meaning. Now we can look at the Israeli sign and realize that a sign showing "flapping" is wrong to translate speed-- the connotation is literal: flapping wings, above the ground. This sign applies to butterflies, not very fast, bats, also not fast, and birds. Speed is a variable connotation of this word. It is not right as a translation.
"Zoom" shows a lot of distance covered and a final disappearance in a very brief sign. Vanishing into the distance is the cardinal connotation, and the sign can be used to denotes motion either on the ground, or in the air, depending on where you put the baseline finger. "Zooms" can be applied to the rapid motion of cheetahs, planes, trains, birds, rockets, so forth- which are all very different objects. The connotation is of speed and vanishing. This makes "time zooms" a good metaphor and easily understood.
It's also interesting to me, because the sign "zooms" depends on perspective drawing, which wasn't in effect until the Renaissance, and the then-common image of train tracks, which is an Industral Age image. ASL truly developed during the 19th century through 20th century, and drew from metaphors.
English is an older language, and this idiom "Time flies" actually is translated from Latin-- Vergil wrote "Tempus fugit" (Time flees/ escapes) which was translated into English as "time flees" (Chaucer, Canterbury Tales, 1390) and later settled into the English language by 1639 as "time flies."
"Fly" and "flee" not only are similar words, "fly" in English emphasized the connotation of quickness rather than guilt or fear (as flee shows.) Time is not afraid or guilty, it just goes quickly.
So we could say that "Tempus fugit" doesn't translate exactly into English either. Maybe Vergil did mean that time flees like a thief, guilty and fearful. But as we see from the poem, he meant time escapes forever, and cannot be returned. English does not quite capture that in its translation of "time flies."
But ASL "time zooms" actually captures that meaning much better, because the denotated meaning of "zooms" is to disappear in the distance.
The paper is wrong; you don't even need sign language to analyze how metaphors work across languages. While "iconicity" and literal meaning may seem to be the reason why "flapping time" fails to succeed, the true problem was mistranslation based on matching words based on a denotation-- a narrow definition-- not actually used in the metaphor itself (i.e. "time flies" never meant "time is winged just like a bird, a bat, or a butterfly")
Interestingly, in Rome the god of travel, thievery, and business-- and the messenger to the Gods-- was Mercury, and he was routinely carved with wings on his feet and his helmet, to show that he was quick and could fly. We named the nearest planet to the sun for him because it moves so quickly.
Today if we portrayed a similar, devious god, we would use airplanes or rockets to show that speed-- that he could fly to heaven and back- and we would have different connotations of power, speed, knowledge. Vergil may have been thinking of Mercury's speed and cleverness in mind when he wrote "Tempus fugit."
Today, people in industralized cultures may see wings on feet and helmet, and we see feathers, floating, deformity-- rather than the speed the wings were supposed to show, because so many things we see and use daily, including cars, are faster than most birds. Only our cultural heritage helps remind us that people didn't always see the world like that.
But without keeping that context in mind, this image of winged feet fails to convey fugitive speed almost as badly as "Time flaps" does in Israeli sign language.