The GravityLight is basically an LED bulb packaged in a housing, and by attaching a bag that comes with the lamp, all the user would have to do is fill the bag with about 20 pounds of dirt or rocks and let gravity do its work. According to its creators, this would be enough to generate about 30 minutes worth of power after which they’d just have to repeat the process again to keep the light turned on. The initial batch of 1,000 GravityLights will be distributed for free to villagers in Africa and India, whereby its creators claim these villagers will be able to save money by not having to buy kerosene-powered lamps.