The engineering behind impossible machines

Every impossible machine is a tolerance story. The idea is usually old; what changes is the day someone can manufacture a part accurate enough to make it real.

Fusion reactors need magnetic fields shaped to millimetre precision around plasma hotter than the sun's core. Bucket-wheel excavators move mountains while distributing load across ground that should not hold them.

The pattern repeats: materials, metrology, and control systems arrive first, and the impossible machine follows a decade later.