Digital storage feels permanent. It is not. Data decays — through physical degradation of storage media, through format obsolescence, through simple neglect. The dissolution of data is quieter than the dissolution of paper — there are no yellowing pages, no crumbling bindings — but it is no less real.
Magnetic media — floppy disks, hard drives, magnetic tape — lose their magnetic charge over time. A floppy disk stored in ideal conditions might remain readable for 10 to 20 years. A consumer hard drive might last 3 to 5 years. Archival-grade magnetic tape, properly stored, can last 30 years, but the drives required to read it may not survive that long.
Optical media — CDs, DVDs — degrade as their reflective layers oxidize. Manufacturers claimed lifetimes of 50 to 100 years; independent testing suggests 5 to 10 years for recordable discs. Solid-state drives, the current standard, store data as electrical charges in floating-gate transistors. The charges leak over time, especially at high temperatures. An unpowered SSD may lose data in as little as a year.
Format obsolescence is a separate problem. Even if the media survives, the software required to interpret the data may not. Files created in WordStar, WordPerfect, or early versions of Microsoft Word may be unreadable on modern systems. Proprietary formats — the native files of defunct applications — are digital fossils: the data is there, but its meaning has dissolved.