X-Ray Vision, For Reading Books

Right now, you’re almost reading these words on a screen, unless you’re one of those increasingly rare people who print their emails. But for generations, everything was written on paper or parchment — the digital universe we now occupy didn’t yet exist. Centuries of thought leadership, poetry, idle musings, and more are only available to us if we open up the books or unroll the scrolls they’re written in. And that’s a problem because many of those very, very old books and scrolls are delicate, and the old paper can’t be touched without risking their destruction. The ideas written inside these tomes are like Schoredinger’s cat — they probably exist, but the moment you try to access them, they cease to. Whatever the people back then would be lost,  often before they could even be read.

So for decades, scientists have been trying to find ways to read these documents without destroying them. Early attempts focused on treating the paper (or papyrus or whatever) itself, but that rarely worked and often resulted in destruction. For example, Daniel Delattre, a French papyrologist, described one such attempt to the New Yorker, and it did not go well:

Delattre explained that the two ill-fated scrolls [dating back more than 2,000 years] had been transported to Naples, where they were treated with a mixture of ethanol, glycerin, and warm water, which was supposed to loosen the folds. One scroll was peeled apart into many fragments; the other dried up and then, like a disaster in slow motion, split apart into more than three hundred pieces. “Well,” Delattre murmured, “it simply exploded.” He shook his head sadly.

The scrolls and old books are simply too fragile to work with directly. So more recently, scientists have been trying to answer the question: how do you read a book you can’t touch? And in 2016, a team at MIT came up with a solution — a radiation camera. The MIT News Office explained the team’s breakthrough:

The system uses terahertz radiation, the band of electromagnetic radiation between microwaves and infrared light, which has several advantages over other types of waves that can penetrate surfaces, such as X-rays or sound waves. [Yes, this makes my title inaccurate. Sorry.] Terahertz radiation has been widely researched for use in security screening, because different chemicals absorb different frequencies of terahertz radiation to different degrees, yielding a distinctive frequency signature for each. By the same token, terahertz frequency profiles can distinguish between ink and blank paper, in a way that X-rays can’t.

The researchers pointed the terahertz camera at some old closed books and collected the radiation data that bounced back. Using a series of complex computer algorithms, the research team was able to take that data and translate it into letters and numbers, and ultimately words, phrases, and full ideas. Without touching the book in the traditional sense, the team was able to see what was written inside.

The technology works, but (as of 2016), it was still pretty limited — but still very cool. As Gizmodo notes, “The terahertz camera can accurately calculate distance to a depth of about 20 pages, but it can only distinguish characters on a page to a depth of about nine pages. The device also requires the paper used to have some degree of transparency” so that the invisible light rays can penetrate the outer pages and reach the inner ones. And, of course, the technology is very expensive. But researchers have been trying to improve on all of that. In 2022, MIT announced that they’ve created a lower-cost version — but it’s not intended to reading old books. Rather, as their media office reported, the devices “could lend themselves to a wide array of applications, including airport security scanning, industrial quality control, astrophysical observations, nondestructive characterization of materials, and wireless communications with higher bandwidth than current cellphone bands.”

Bonus fact: If you’ve ever been near a bunch of old books and you detect an odor similar to the smell of cookies, you’re not hallucinating. The “old book smell” that you’re probably picturing in your head (smelling in your head?) right now is related to vanilla, kind of. As Smithsonian explains, “As a book ages, the chemical compounds used—the glue, the paper, the ink–begin to break down. And, as they do, they release volatile compounds—the source of the smell.” Specifically, the smell is caused by the breakdown of lignin, a polymer present in the cellular walls of wood and bark. Lignin can be used to produce vanillin, the compound that gives vanilla its distinctive flavor.

From the Archives: Untying the Not: The story of the so-called “Wicked Bible.”