In some sense you can track the progress of a technological civilization by its ability to write accurate and narrow lines. This sort of work has made the IC world possible and now we are seeing a new mechanism for accurately removing material.
Femtosecond laser machining has been around for some time - I remember discussions years ago on its use in mask defect repair. It seems to be getting much more practical these days and with megahertz repetition rate lasers on the horizon it is not unthinkable to imagine one in your dentist's office.
The interesting trick is that material is vaporized before the energy is thermally transferred to adjacent material. The energy density is also so high that it is possible to do work in transparent material (like diamond) through multiphoton ionization.
A very clever question on a physics Ph.D. prelim was "How deep can you dig a stable hole on Earth?" When you are prepared for quantum electrodynamics and general relativity questions, this throws a wrench into things.
There are a few very interesting challenges with prize money attached. The really big prize was the Longitude Prize which was won by the clockmaker John Harrison rather than the astronomers of the day.
In this century Paul MacCready cracked the human powered flight problem courtesy of the Kremer Prize and Charles Lindergh was motivated by the Orteig prize. Richard Feynman offered two $1000 challenges in a famous 1959 speech. One, a tiny electric motor, was too easy and fell in a year. The other, printing text at a density sufficient to place the Encyclopedia Britannica on the head of a pin, was very difficult.
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