We humans have done a lot of efforts to make production of light cheaper and ECO friendly. Almost every abundant natural source has been tested to obtain energy. Most popular are water, wind and solar energy. But we never happened to see any work on gravity. Two London based designers Martin Riddiford and Jim Reeves came up with an idea of using gravity as a source of energy.
Their aim is to provide safe and cheaper lights to replace the kerosene lamps, which are being widely used in remote areas of Africa. The total cost of a single unit is $10 but it has absolutely no running cost. So it means it will save a lot of money in the long run. The principle to run gravity lamps is very simple. All you have to do is hang the weight filled with rocks, sand, or mud in it. The light will illuminate for 30 minutes. Moreover you can have other tasks performed as well which includes powering lights and charging batteries. So in short, gravity light is the best alternative against kerosene lamps. Currently developers need funds to raise their project and shorten the cost per unit. To see gravity light in action watch the video below.