The convenience is obvious: the PDF file rather than the stack of papers on the desk; the instantly viewable photo rather than the wait for prints from the camera shop; the quick keyword search rather than the need to flip through pages to find the desired passage. But this marvelously handy information is strangely transient—especially the information each of us might want to store for our own purposes, as opposed to the Big Brother–style central registries of our phone calls, credit-card transactions, and similar activities.
“The best-preserved data tends to be on stone steles and cuneiform tablets,” Billington told me when I went to the library to hear about its recent attempts to solve the “digital preservation” problem. “Papyrus, vellum, parchment—all those classical modes hold up pretty well.” Chris Weston, of the library’s Office of Strategic Initiatives, recounted what he called a typical story of old-style data preservation. “Someone in upstate New York was cleaning out the attic of an old farmhouse—and there was a letter from Benedict Arnold. It had been in a cool, dry place for 200-some years. With most things on paper, unless you throw them away or actively destroy them, they’re likely to stay around.”
It’s just the reverse, of course, with digital data. Unless you go out of your way to renew and preserve it, information on a computer will disappear fairly quickly. More precisely, it will become unusable. Several related processes are involved. One is what Clay Shirky, a media scholar at New York University, has mock-portentously called “Playback Drift: The Silent Killer.” This boils down to the idea that the physical devices for storing and then retrieving digital data succeed one another so quickly that information is in constant jeopardy of being trapped in an obsolete format.
The first files I produced on a computer, in the 1970s, were stored on Radio Shack audiotape cassettes. After that, I used a computer with eight-inch floppy disks. The book I wrote twenty-five years ago using that computer still looks fine—but the interview notes for it, which I “saved” on those big old disks, I might just as well have burned. For all practical purposes, there is no way for me to get at them anymore—nor at other information that over the years I’ve lodged on 5.25-inch disks, small archival high-density tapes, some varieties of Zip drives, and other media that my current computers can’t handle. As each new and improved storage system comes out, computers generally remain compatible with the immediate past system but not with anything older. A few years ago, virtually any new PC had a built-in 3.5-inch disk drive. Now such drives are often missing or optional, as CD-ROMs and DVDs have become standard. Eventually the small disks will be obsolete and information on them will be orphaned. Any file stored more than six or eight years ago, and not transferred to something more modern in the meantime, is on its way to doom.
The old files that I still can use—and in fairness, there are a lot of them—are the ones I’ve taken the trouble to copy from an old computer to a newer one each time I’ve bought a new system. But even those files suffer from a different form of playback drift, which is the constant change in file formats. I have word- processing files that were originally created in WordStar, XyWrite, Electric Pencil, DeScribe, and other now-extinct programs. Some can be transferred into the current standard, Word, but not all—and the problem is worse for many database, note-taking, and e-mail programs. As if that were not enough, there is another silent killer: “bit rot.” Pictures fade over time, and so, in a sense, does digital information. Both hard and floppy disks store data with tiny magnetic charges. Inevitably, the charges weaken, corrupting and finally eliminating the data. CD-ROMs and DVDs store data by etching pits in a layer of dye, which can also fade. It is as if all of our books and newspapers had been printed with disappearing ink. How long does each kind of degradation take? Some people told me five years on average, some people said fifteen—but in any case, less time than you’d hope to keep those digital pictures of your wedding. Recently I came across a box full of snapshots of my mother as a child, in the 1930s. They survived without being tended; today’s counterparts will not.