A BBC report this week about a project in the Philippines that has brought virtually free light to dark homes in some of that country's poorest neighborhoods brightened our day so much that we went looking to find out more.
It seems that taking a plastic bottle, filling it with clean water and a little bleach and then suspending it from a ceiling through a hole to the sky can bring about the same amount of light into a room as a 50-watt bulb. It's all due to the way the light of the sun refracts.
True, the bottles don't shine in the night. But in many places these are homes that are close to pitch black even during the day. And the bottles mean some of the world's poorest people don't have to spend money to get some light during the day. Plus, the bottles aren't wasted.