It's amazing to me that there are places where even minimal lighting is a luxury. I'm glad to see that basic physics principles are bringing a little sunlight into the dark days of some impoverished Filipinos. (Of course, if you feel like sending a donation to the cause, you can help spread the light and the love a little further.)
I've seen a lot of speculation about how, and even whether, solar bottles can light a room so well. The fact is, they do work, and they rely on some pretty nifty physics to do it.
To begin with, cutting a hole in your roof will let some sunlight in. Even a small hole in a darkened room can make a big difference. There are, however, some problems with a simple hole.
Besides letting in the rain and insects, you only get as much light as falls directly through the hole. As Solar Demi knows, you can do much better than that with some grassroots engineering. Putting a water-filled container in the hole collects more light due to two fundamental optical effects: Snell's Law and total internal reflection.