There is a security feature in almost everyone's pocket that has been doing its job for over three hundred years, and almost nobody knows what it is for.
Look at…
The useful way to read a lock is as a question about what the key is proving. Every mechanism below tests something slightly different, and the differences are the history.…
Almost every unit of time you use is a measurement of something physical.
The day is the Earth turning once. The month is roughly the Moon going through its phases.…
Blood Types Were Discovered Over a Century Ago and Nobody Has Established What They Are Actually For
Most people know their blood type, treat it as a fixed personal fact like eye colour, and have never wondered what it is.
It is a molecule. Specifically, blood type…
The mechanism is usually the same: a word is used loosely, the loose sense becomes common, and the precise one falls away. Here are fifteen that travelled unusually far.
1.…
The useful way to read these is as solutions rather than as homes. Each one is addressing a specific physical problem, and the structure follows from the problem rather than…