Plastic bottles jut from the roofs in a Manila slum neighborhood. But these bottles have an important purpose: they contain bleach and water and are placed snugly into a purpose-built hole in the roof. Designed by students at MIT, they reflect sunlight, spreading 360 degrees of 55-watt-light through the room beneath. Using the simplest of technologies, these bottles brighten dim and dreary shanties, emitting clear light for about five years. The invention is part of a project called "Isang Litrong Liwanag," which means A Litre of Light, and helps some of the poorest Philippines residents save money and live better -- in a renewable way.
