From boingboing this morning
"The slums of the Philippians are getting an extreme home makeover in the form of two liter bottles in their ceilings. The bottles function as 60-watt lights powered by 100% solar energy. Refraction is an amazing thing, if you drilled a hole in your ceiling light would drop directly through the opening in a straight line casting a shadow on the ground in the shape of the hole. By placing a bottle filled with water into the hole, the light is refracted by the water and emitted at 360 degrees like a light bulb. Light bulbs are taken for granted in America, yet are luxury item for the Philippians slums. The two liter bottles filled with water and a small amount of bleach to keep algae from growing, act as a light in the often-unlit slums.…"