Today, you buy a house and get a deed on paper. It will probably still be readable a couple hundred years from now. But more and more records--legal, government, and corporate--are being created as digital information that never exists on paper, and doesn't last nearly as long. If deeds become digital-only documents, will people still be able to prove they own their homes two decades after they buy them?
Digital documents have a variety of limitations, some of them severe. In the case of computer hard drives and tape, the magnetic charge that distinguishes a one from a zero gradually degrades and can turn into gibberish in as little as 10 years. Similarly, physical changes affect compact disks, although more slowly. Some have lifetimes pegged at 30 to 100 years.
Then there's the playback hardware. Even if the storage medium remains in good shape, it may not be readable by modern equipment. The digital tapes containing the 1960 U.S. Census Bureau, for example, can be read by only one machine in the U.S.--in the Smithsonian Institution. Or the data may have been recorded using software that, like the CP/M operating system that preceded MS-DOS and Windows, is all but forgotten.
One common solution is to regenerate data periodically, rerecording it on modern media with current systems. But even this has a hitch: When transferring data, there's always the risk of a hiccup that causes a zero to be copied as a one. The best policy, according to the National Institute of Standards & Technology: Keep digital media at 65F and 40% humidity, and most will last for several decades at least.
By Otis Port