Never judge a book by its cover, we are told from a very young age. (Marketers know better—consumers always judge a book, or anything else for that matter, by its cover.)
MIT’s Media Lab, in conjunction with the Georgia Institute of Technology, has developed a technology that will decipher text printed on the pages of a closed book. PBS has more:
This scanner exposes the contents of the concealed pages by relying on terahertz radiation. Terahertz waves mimic X-rays and soundwaves by being able to penetrate surfaces. Moveover, different chemicals — ink on paper for example — absorb terahertz radiation in different amounts. By beaming terahertz waves at a book, the MIT Media Lab device can skip through pages, but also tell the difference between blank and ink-filled parchment.
The gadget shoots these waves in short bursts, a portion of which bounce back whenever they encounter the small slivers of air between the pages. Meanwhile, computer scientists at Georgia Tech developed a sophisticated algorithm that deciphers these reflections when they return to the scanner.