A lot of people in digital preservation are convinced a “digital dark age” is nothing to worry about. I’ve consistently disagreed with this. The notion that archivists will replace outdated digital media every decade or two through the centuries is a pipe dream. Records have always gone through periods of neglect, and they will in the future. Periods of unrest will happen; authorities will try to suppress inconvenient history; groups like Daesh will set out to destroy everything that doesn’t match their worldview; natural disasters will disrupt archiving.
I’ve proposed the idea of a “datalith,” a data record made out of rock or equivalent material, optically readable and self-explanatory assuming a common language survives. DOTS, Digital Optical Technology System, is burned on tape rather than engraved in stone, but in every other respect it matches my vision of a datalith. It can store digital images in any format but also allows them to be recorded as a visual representation. The Long Now Foundation explains:
Unlike magnetic and optical storage solutions, which must be protected from data corruption, physical degradation, and environmental damage, DOTS physically encodes data on an archival tape coated in a phase-change alloy. The alloy is resistant to temperature extremes, electromagnetic pulses, and other common environmental hazards (though it is vulnerable to acids—including, apparently, Sprite), while the tape itself is made of archival materials.
Just as importantly, DOTS is also meant to withstand the onset of a digital dark age. The data, which may include words and images as well as digitally encoded information, is transferred to the alloy using a laser, which changes the alloy’s index of refraction. In other words, the blank portions of the tape are shiny, while the data-bearing portions are dull. The result, though written at a microscopic scale, is visible under normal magnification.
The project itself is an example of disrupted and recovered work. Eastman Kodak started the project in the 1990s but abandoned it in 2002, when testing had shown its durability to 94 simulated years. An organization called Group 47 bought the patents and resumed work in 2011. An introduction, consisting mostly of promotional material but including some technical detail, is available for downloading. (To make things confusing, the footer on every page of this publicly available PDF says “NO REPRODUCTION OR DISTRIBUTION WITHOUT CONSENT FROM GROUP 47.”)
It’s essential to have something like this for reliable long-term data archives. The people who think data will reliably be passed evermore from curator to curator are pleasantly optimistic, but history has never worked that way.