There is a tool so ordinary that almost nobody has considered how it works, and the answer turns out to be more particular than expected.
The obvious model is a…
There is a common assumption that sealing a letter was about privacy, and it misses what the object was for.
A seal provides no privacy whatsoever. Anybody determined to read…
There is a contradiction at the centre of making charcoal that explains everything about how it was done.
The wood has to be heated to a high temperature, and the…
There is a small category of materials that are not assembled from anything, and felt is the oldest of them.
Almost every fabric is made of threads. Spinning turns loose…
There is a common assumption about layered rocks that slate steadily breaks.
The assumption is that a rock which splits into sheets does so along the layers in which it…
There is an image that makes most people wince the first time they see it: a hammer driving nails into a horse's foot.
The reaction is reasonable, and it rests…