Moore's Law

In the world of computer hardware, Moore's Law refers to an observation made by the cofounder of Fairchild Semiconductor (and Intel), Gordon Moore (RIP), that the number of transistors in an integrated circuit tends to double every two years-ish.

Moore actually originally posited that an annual doubling was likely for a long while, but after a decade of running companies that made these things—which are fundamental components of microchips—he adjusted his assessment, saying that a doubling every two years made more sustainable sense.

This law is interesting in that it's not a law at all, but an observation made by a man who was in the position to notice likely long-term trends before most other people, and who's anecdote was thus taken seriously by other industry contemporaries, and by people who entered the industry later.