The lack of reliable electricity in developing countries puts a damper on more than just technology use -- having to run kerosene lamps, or even those based on solar power, often involves recurring costs that whittle away at very modest incomes. GravityLight has built an LED lamp that just might lift the burden. As the name implies, a weight (usually the very bag that the lamp ships in) generates electricity through natural force: the few seconds it takes to lift the weight can generate 30 minutes of light without ever replacin
