*why does my cat roll on her back through the sand in my garden? Is she scratching her back? Asking attention? Removing bugs? What the hell is she doing? *how does a cat purr? *can cats see colours? *how do I turn an associal cat (she very rarely sits on my lap for instance) into a social one? Do's and don'ts? *why does a plastic bottle shrinks if I pour boiling water in it? *You've probably seen the Evanescence video "Going Under". At some point in the vid, Amy Lee (the singer) dives under water, and sings, although her clothes and hair clearly indicate that she is under water! How do they do that? Also, on a local tv channel, commercial breaks start and stop with girls swimming under water, while opening their mouth! Same question.