[Nukapei]

Good way to explain it, SPM! Yes, the basic rules of physics must apply. And, if they're broken, a reason must be given. Like you said, Legolas never would be able to walk on snow in our world; but in Middle-earth, it's just a property of the Elf species, just as much as walking upright is for real humans, or breathing through gills is for a salmon. And Galadriel's mirror, as well as other forms of "magic" such as the palantiri and magic doors, etc., are just forms of technology. Otherwise, again like SPM said, the whole story wouldn't be believable. However, these "rule-breaking" incidences give the story an air of fantasism and other-worldliness that it wouldn't have otherwise. And that's why we love it so much -- it's an escape from reality!