The Half-Life of Facts

True Today, False Tomorrow

People used to believe that the more meat you ate, the healthier you would become. Later, they believed that meat was bad for you; later still, they again believed that meat was good for you; now it’s all a matter of conjecture. The debate over red wine’s health benefits or detriments continues to the point of utter confusion. Everyone used to believe that all the stars in the universe – including the sun – orbited the Earth.

All of this proves one unshakeable truth: Knowledge is mutable. Like a radioactive substance, every known “fact” has a half-life. Scientists can “measure the amount of time” it takes “for half of a subject’s knowledge to be overturned.” They can determine the rate at which new facts develop, how fast they spread and how often they change. Facts – your “individual states of knowledge awareness” – fall into three categories:

1. “Fast-changing facts” – These data are always in flux, like the weather report.
2. “Slow-changing facts” – Some facts shift over great time spans, like the “number of continents” on Earth.
3. “Mesofacts” – Certain facts change...