Light leaves every point of a subject in all directions. A lens collects some of that and reconverges it, and the entire craft is built on the properties and failures…
There is a useful principle in materials: if a substance behaves oddly in several unrelated ways, there is usually one structural feature responsible for all of them.
Wool behaves oddly…
There is a useful exercise in considering how recently an ordinary thing became ordinary, and fire on demand is the most striking example available.
Fire itself is extremely old. Reliable…
There is a way of analysing junctions that makes their differences obvious, and it is not the one most people use.
The usual way is to think about rules —…
The hard part of a clock was never the gears. It was finding something that does the same thing over and over at exactly the same rate, and then extracting…
Almost everything about how a book feels - whether it stays open, how it turns, how heavy it is for its size - was decided during manufacture rather than design.…