During a 2004 cleanup operation at the Hanford nuclear site in Washington state, personnel digging through a trench uncovered a safe containing a glass bottle. And inside the bottle, white sludge. Tests identifying the substance as a type of plutonium gave way to more tests until, in the Spring of 2009, scientists from the Pacific Northwest National Laboratory revealed what, exactly, the crew had uncovered: A 1944 artifact from the fledgling nuclear weapons program—the oldest existing sample of bomb-grade plutonium from a nuclear reactor, with a half-life of 24,110 years. Although this sexagenarian sludge isn’t dangerous to touch—its particles are too large to penetrate skin—it’s poisonous if swallowed or inhaled and will be for centuries to come. Yet it was housed in a flimsy receptacle that should rightfully contain nothing more toxic than bleach. In the rush of nuclear discovery, the mid-century scientists never paused to consider that a trespasser might happen upon the safe and crack it open.

Since that time, “deep geological disposal” has replaced shallow trenches as our preferred nuclear-waste-storage technique. a proposal to make Nevada’s Yucca Mountain the site of a national repository for nuclear waste and has yet to submit an alternative plan. Meanwhile, Republicans in the Senate have called for the construction of 100 new nuclear reactors by 2030, and the Senate climate bill introduced in late September endorses the “continued development and growth of a safe and clean nuclear energy industry.”> But another, more abstract problem—raised by the Hanford message in a bottle—remains unsolved: not how to store waste but how to label it. Not what container to use or where to bury it but how to explain the long-term dangers of what’s inside to a trespasser. This seemingly simple conundrum (just use a radiation hazard symbol!) is complicated by the fact that such a trespass would prove lethal if it took place not only in 60 years but in 10,000 or 100,000. China, the planet’s oldest continuous civilization, stretches back, at most, 5,000 years. And the world’s oldest inscribed clay tablets—the earliest examples of written communication—date only from 3,000 or 3,500 B.C. It’s impossible to say what apocalyptic event might separate 21st-century Americans from our 210th-century successors. Successors, mind you, who could live in a vastly more sophisticated society than we do or a vastly more primitive one.

Communicating the dangers of nuclear waste to unfathomably remote descendents may seem like a topic best left to third-drink philosophers in dorm rooms. It’s actually been left to the most humdrum of all Cabinet-level departments after commerce, agriculture, and the interior: the Department of Energy, which oversees the disposal of radioactive trash at the Waste Isolation Pilot Plant near Carlsbad, N.M. According to government guidelines, DoE must plan for the continuing safety of the site over the next 10 millenniums. According to some scientists (PDF), the government uses the shorter time span as a bureaucratic convenience”>

So in 1991, the department (through Sandia National Laboratories) hired 13 linguists, scientists, and anthropologists at a cost of about $1 million to devise a conceptual plan for a 10,000-year marker system. DoE has yet to hash out the practical details, and probably won’t until just before the pilot plant closes in the 2040s. Expert Judgment on Markers To Deter Inadvertent Human Intrusion Into the Waste Isolation Pilot Plant,” is a bizarrely fascinating read. Since its publication in 1993, there have been sporadic flurries of media interest in its existence—notably in 2002, after the Senate voted to authorize Yucca Mountain as a permanent waste repository—but few considered assessments. The paper takes seriously the quixotic goal of warning far-off civilizations and ultimately proposes a system as elaborate as it is futile.

The academics dismiss, out of hand, a “Keep Out” sign—a woefully lacking solution, since nuclear waste will remain dangerous much, much longer than such a message would remain intelligible. David Anthony, author of The Horse, the Wheel, and Language, argues that “very few natural languages, those that are learned and spoken at home, remain sufficiently unchanged after a thousand years to be considered the ‘same language.’ ” Case in point: Although modern English grew out of Anglo-Saxon, Americans need either a translation or special expertise to make their way through the Anglo-Saxon epic, Beowulf. Radiation-hazard symbols, as well as other icons immediately recognizable to 21st-century observers, are similarly insufficient. A red circle with a diagonal slash, the report notes, could look like a pictograph of a hamburger if knocked on its side. In a telephone interview, Harvard historian of science Peter Galison—who has lectured on the permanent-markers project—added that a skull-and-crossbones is also too ambiguous: Even today, it connotes danger only to some. Latin Americans may associate it with the Catholic Day of the Dead holiday—during which celebrants wear skull masks and bring sugar skulls to graveyards. An intruder who happens to be familiar with pirate lore might assume the image signifies buried treasure.

Even if future trespassers could understand what keep and out mean when placed side by side, there’s no reason to assume they’d follow directions. In “Expert Judgment,” the panelists observe that “[m]useums and private collections abound with [keep out signs] removed from burial sites.” The tomb of the ancient Egyptian vizier Khentika (also known as Ikhekhi), for example, contains the inscription: “As for all men who shall enter this my tomb … impure … there will be judgment … an end shall be made for him. … I shall seize his neck like a bird. … I shall cast the fear of myself into him.” It’s possible that the vizier’s contemporaries took Khentika at his word. But 20th-century archaeologists with wildly different religious beliefs had no reason to take the neck-cracking threat seriously. Likewise, a scavenger on the Carlsbad site in the year 12,000 C.E. may dismiss the menace of radiation poisoning as mere superstition. (“So I’m supposed to think that if I dig here, invisible energy beams will kill me?”) Hence the crux of the problem: Not only must intruders understand the message that nuclear waste is near and dangerous; they must also believe it.

The report’s proposed solution is a layered message—one that conveys not only that the site is dangerous but that there’s a legitimate (nonsuperstitious) reason to think so. It should also emphasize that there’s no buried treasure, just toxic trash. Here’s how the authors phrase the essential talking points: “[T]his place is not a place of honor … no highly esteemed deed is commemorated here.” Finally, the marker system should communicate that the danger—an emanation of energy—is unleashed only if you disturb the place physically, so it’s best left uninhabited.

As for the problem of actually getting these essentials across, the report proposes a system of redundancy—a fancy way of saying throw everything at the wall and hope that something sticks. Giant, jagged earthwork berms should surround the area. Dozens of granite message walls or kiosks, each 25 feet high, might present graphic images of human faces contorted with horror, terror, or pain (the inspiration here is Edvard Munch’s Scream) as well as text in English, Spanish, Russian, French, Chinese, Arabic, and Navajo explaining what’s buried. This variety of languages, as Charles Piller remarked in a 2006 Los Angeles Times story, turns the monoliths into quasi-Rosetta stones. Three rooms—one off-site but nearby, one centrally located, and one underground—would serve as information centers with more detailed explanations of nuclear waste and its hazards, maps showing the location of similar sites around the world, and star charts to help intruders calculate the year the site was sealed. According to 1994 estimates, the whole shebang would cost about $68 million, but that’s just a ballpark figure based on very incomplete data.

Proposals for the “earthworks” component demonstrate that the whole project of communicating with the future is really a creative assignment, more dependent on the imagination than on expertise. What’ll really scare off 210th-century tomb raiders? The report proposes a “Landscape of Thorns” with giant obelisklike stones sticking out of the earth at odd angles. “Menacing Earthworks” has lightning-shaped mounds radiating out of a square. In “Forbidding Blocks,” a Lego city gone terribly wrong, black, irregular stones “are set in a grid, defining a square, with 5-foot wide ‘streets’ running both ways. You can even get ‘in’ it, but the streets lead nowhere, and they are too narrow to live in, farm in, or even meet in.”

The Sandia panelists were not the first to devise a several-thousand-year warning system. In the early 1980s, the semiotician and linguist Thomas Sebeok wrote a paper for the U.S. Office of Nuclear Waste Management titled “Communication Measures To Bridge Ten Millennia,” which proposes a folkloric relay system to pass along information: “The legend-and-ritual, as now envisaged, would be tantamount to laying a ‘false trail,’ meaning that the uninitiated will be steered away from the hazardous site for reasons other than the scientific knowledge of the possibility of radiation and its implications; essentially, the reason would be accumulated superstition to shun a certain area permanently.” Sebeok further suggested a Dan Brown-like “atomic priesthood” of physicists, anthropologists, semioticians and the like who would preserve the “truth.”

Sebeok’s concept for an artificial myth is, in a word, silly. Indeed, he acknowledges the shortcomings of the system himself: “Folklore specialists consulted have advised that they know of no precedent, nor could they think of a parallel situation, except the well-known, but ineffectual, curses associated with the burial sites (viz., pyramids) of some Egyptian Pharoahs.” Given that even organic religious movements have trouble imparting site-specific information—scholars continue to debate whether Moses parted the Red Sea or the Reed Sea, a large lake close by—it’s unlikely that eggheads could devise a myth haunting enough to turn the Carlsbad site into a permanent no-man’s land.

We’ve seen this before—or, at least, we have on screen. In Alien, the crew of the Nostromo picks up a transmission from a derelict spacecraft. Only after deciding to investigate do they realize that the transmission is a warning signal. But by then it’s too late; the Nostromo is well on its way to becoming a maternity ward for extraterrestrials. All the attention paid to the site seems as likely to encourage unwanted visitors as to ward them off, since surely future anthropologists, or just Mad Max dystopia types, will be curious to explore a spike field in the middle of the desert. The proposed systems are imaginative, but that’s all. They depend, necessarily, on the intruders’ willingness to decipher messages laboriously before simply acting—drilling to find oil, say, or precious metals.

There’s also something oddly short-sighted about this far-sighted project. Radioactivity causes cancer and a host of other medical problems—that much is certain. But the report fails to note that we may find cures for these ailments in the next century or, perhaps, even earlier. In that case, should the EPA convene a new panel to communicate the most advanced chemotherapy technique? Ultimately the option of doing nothing—of leaving the site devoid of markers— seems like the most elegant solution of all. It may at first appear callous, lazy, and irresponsible, but at the very least, this relaxed approach is cheaper than erecting spiked granite monuments and building fancy information centers—not to mention commissioning additional panels to work out all the details.