Really cool–I could use one of these in Kenya.
I have a little problem with the explanation, however. Destin says “…powering a light with nothing but gravity.” This isn’t quite true: the potential energy is generated when the operator lifts the weight, and is converted to kinetic energy as gravity pulls the weight back down. The actual power comes from the operator, not gravity.
Whatever the source of the power, this is a great adaptation of a clockwork/weight mechanism to generate light where there is no cheap and reliable source of electricity.
GravityLight devices will be assembled in Kenya, providing jobs, as well as a light source that doesn’t require kerosene. You can read about GravityLight, and even donate to the cause at their website.