Okay, for the purposes of the Clarke Rule of No Moving Parts in "City
and the Stars," we should define a "part" as condensed matter the
size of an atom or larger. Subatomic particles and plasma don't
count. Also, atoms can move when they undergo fission or fusion.
Some people including the inimitable Stewart Brand, editor of the
Whole Earth Catalog, are trying to make a 10,000-year mechanical clock. See:
http://www.longnow.org/clock/
This has moving parts galore and it is huge. If I were making a
10,000-year clock, I would make it the size of a wristwatch, and I
would have it activate and register once per day, or once per year,
triggered by and powered by sunlight. Sort of like Stonehenge. I do
not know if any photovoltaic devices will last for centuries. I
believe some camera light meters from the 1930s still work fine. PV
cells last around 15 years but they are exposed to direct sunlight
all day, and placed outdoors. The gadget I have in mind would be
protected. It would be difficult to ensure that sunlight still
reaches it if it is left unattended for centuries. It might be best
to put it in orbit or on the moon.
- Jed
