Jeff Bezos, CEO of Amazon, has a new pet project: building a clock that runs for 10,000 years. It will be built inside a mountain, which adds to the coolness of it all. About the power source:
The main power storage for the clock is a large weight hanging on a rack gear. The weight can be wound both by visitors to the clock, as well as the solar winder. The power from this system is used to ring the chimes on any day it is fully wound. The rest of the time it powers the time- keeping mechanism, and has enough power to run the clock for many years without any human winding or sunlight.