What does it mean that the half-life of information?

Different types of information decay at different rates. Some knowledge stays relevant for centuries. Some is obsolete by lunch. Knowing which is which changes what you pay attention to.

Example: A software engineer spends Monday morning reading Hacker News comments about a new JavaScript framework. By Wednesday, the thread is forgotten, the framework's hype has cooled, and nothing from that reading session changed how she works. That same week, she spends forty minutes reading the first three chapters of Fred Brooks' The Mythical Man-Month — published in 1975. Fifty years later, Brooks' observation that adding people to a late project makes it later still governs how she plans sprints. One reading session had a half-life of days. The other has a half-life of decades. Both took the same time.

Try this: Open whatever you read yesterday — your inbox, your feed, your bookmarks. Sort every piece of content you consumed into one of three buckets: (1) irrelevant within a week, (2) useful for months, (3) useful for years or longer. Count how many items land in each bucket. If bucket one is the largest, you have a consumption problem. Identify three sources in your current diet that consistently produce bucket-three material. Move those to the top of your reading list. Identify three that consistently produce bucket-one material. Unsubscribe or mute them today.