One Enlightenment aspiration that the science-­fiction industry has long taken for granted, as a necessary intergalactic conceit, is the universal translator. In a 1967 episode of “Star Trek,” Mr. Spock assembles such a device from spare parts lying around the ship. An elongated chrome cylinder with blinking red-and-green indicator lights, it resembles a retracted light saber; Captain Kirk explains how it works with an off-the-cuff disquisition on the principles of Chomsky’s “universal grammar,” and they walk outside to the desert-­island planet of Gamma Canaris N, where they’re being held hostage by an alien. The alien, whom they call The Companion, materializes as a fraction of sparkling cloud. It looks like an orange Christmas tree made of vaporized mortadella. Kirk grips the translator and addresses their kidnapper in a slow, patronizing, put-down-the-gun tone. The all-­powerful Companion is astonished.

 “My thoughts,” she says with some confusion, “you can hear them.”

The exchange emphasizes the utopian ambition that has long motivated universal translation. The Companion might be an ion fog with coruscating globules of viscera, a cluster of chunky meat-parts suspended in aspic, but once Kirk has established communication, the first thing he does is teach her to understand love. It is a dream that harks back to Genesis, of a common tongue that perfectly maps thought to world. In Scripture, this allowed for a humanity so well ­coordinated, so alike in its understanding, that all the world’s subcontractors could agree on a time to build a tower to the heavens. Since Babel, though, even the smallest construction projects are plagued by terrible delays.

Translation is possible, and yet we are still bedeviled by conflict. This fallen state of affairs is often attributed to the translators, who must not be doing a properly faithful job. The most succinct expression of this suspicion is “traduttore, traditore,” a common Italian saying that’s really an argument masked as a proverb. It means, literally, “translator, traitor,” but even though that is semantically on target, it doesn’t match the syllabic harmoniousness of the original, and thus proves the impossibility it asserts.

Translation promises unity but entails betrayal. In his wonderful survey of the history and practice of translation, “Is That a Fish in Your Ear?” the translator David Bellos explains that the very idea of “infidelity” has roots in the Ottoman Empire. The sultans and the members of their court refused to learn the languages of the infidels, so the task of expediting communication with Europe devolved upon a hereditary caste of translators, the Phanariots. They were Greeks with Venetian citizenship residing in Istanbul. European diplomats never liked working with them, because their loyalty was not to the intent of the foreign original but to the sultan’s preference. (Ottoman Turkish apparently had no idiom about not killing the messenger, so their work was a matter of life or death.) We retain this lingering association of translation with treachery.

The empire of English has a new Phanariot class, and they are inventing the chrome light-­saber apps of the utopian near-­future. They are native speakers of C++, and they reside in our midst on semipermanent loan from the Internet. On the plus side, they are faithful to no sultan. The minus is that they are not particularly loyal to any language at all.

Google Translate is far and away the venture that has done the most to realize the old science-­fiction dream of serene, unrippled exchange. The search giant has made ubiquitous those little buttons, in email and on websites, that deliver instantaneous conversion between language pairs. Google says the service is used more than a billion times a day worldwide, by more than 500 million people a month. Its mobile app ushers those buttons into the physical world: The camera performs real-time augmented-­reality translation of signs or menus in seven languages, and the conversation mode allows for fluent colloquy, mediated by robot voice, in 32. There are stories of a Congolese woman giving birth in an Irish ambulance with the help of Google Translate and adoptive parents in Mississippi raising a child from rural China.

Since 2009, the White House’s policy paper on innovation has included, in its list of near-term priorities, “automatic, highly accurate and real-time translation” to dismantle all barriers to international commerce and cooperation. If that were possible, a variety of local industries would lose the final advantage of their natural camouflage, and centralization — in social networking, the news, science — would accelerate geometrically. Nobody in machine translation thinks that we are anywhere close to that goal; for now, efforts in the discipline are mostly concerned with the dutiful assembly of “cargo trucks” to ferry information across linguistic borders. The hope is that machines might efficiently and cheaply perform the labor of rendering sentences whose informational content is paramount: “This metal is hot,” “My mother is in that collapsed house,” “Stay away from that snake.” Beyond its use in Google Translate, machine translation has been most successfully and widely implemented in the propagation of continent-­spanning weather reports or the reproduction in 27 languages of user manuals for appliances. As one researcher told me, “We’re great if you’re Estonian and your toaster is broken.”

Warren Weaver, a founder of the discipline, conceded: “No reasonable person thinks that a machine translation can ever achieve elegance and style. Pushkin need not shudder.” The whole enterprise introduces itself in such tones of lab-coat modesty. The less modest assumption behind the aim, though, is that it’s possible to separate the informational content of a sentence from its style. Human translators, like poets, might be described as people for whom such a distinction is never clear or obvious. But human translators, today, have virtually nothing to do with the work being done in machine translation. A majority of the leading figures in machine translation have little to no background in linguistics, much less in foreign languages or literatures. Instead, virtually all of them are computer scientists. Their relationship with language is mediated via arm’s-length protective gloves through plate-glass walls.

The problem is that all texts have some purpose in mind, and what a good human translator does is pay attention to how the means serve the end — how the “style” exists in relationship to “the gist.” The oddity is that belief in the existence of an isolated “gist” often obscures the interests at the heart of translation. Toward the end of the marathon, I asked a participant why he chose to put his computer-­science background to the service of translation. He mentioned, as many of them did, a desire to develop tools that would be helpful in earthquakes or war. Beyond that, he said, he hoped to help ameliorate the time lag in the proliferation of international news. I asked him what he meant.