Because physics doesn't even have the language to describe the feeling of pain. Similarly, physics doesn't have a language to describe how "green" looks, it can

Because physics doesn't even have the language to describe the feeling of pain. Similarly, physics doesn't have a language to describe how "green" looks, it can only describe the frequency of green etc. Also have a look at http://en.wikipedia.org/wiki/Qualia http://en.wikipedia.org/wiki/Qualia, it's basically what I'm talking about.