If you're me, you're in the process of turning a giant garbage ball into a massive sphere that will eventually become a paper mache planet Earth.
If you're Tim Noble and Sue Webster, your ball of garbage is distinctly less spherical and more ........ abstract. But of course, shine a light behind a seemingly random trash pile and you can end up with some pretty amazing silhouettes.
Here is their art
According to weburbanist.com, Sue and Tim collect their trash from the streets of London and through some combination of miraculous intervention, talent, and patience, they come up with the perfect shadow.
Here is the link: http://weburbanist.com/2008/06/04/recycled-art-from-trash/