Amazing invention: using a water bottle to provide sunlight into slum housing

This is a great low-tech idea.

An ingenious update of the 19th century ship deck prism: http://www.scientificsonline.com/deck-prism.html

I remember coming across this a few months ago. It's a great way to get some affordable solar light into a space, and seems like it would be great for poorer communities and places where electricity isn't readily available - so long as there's an available supply of bleach (though I suppose you could just regularly change the water).

My grandfather used to do this for lighting in a couple of storage sheds and part of the barn on his farm.