One thing we learned on the most recent episode of LOST (“The Constant”) is that Desmond was not simply recollecting his past in a vivid hallucination, nor simply seeing the future, but going to the past and future (or, at least, his consciousness was doing so.
It was stated at one point in the episode is that the future cannot be changed. This seems, in terms of the show’s outlook, to be both true and untrue. Desmond managed to make changes, but “the universe has a way of course correcting”, and so in the longer-term, things follow their “destiny”.
The big question now is who the woman (Ms. Hawking) was who met Desmond in his past in the earlier episode “Flashes Before Your Eyes“, and knew that he was “unstuck in time”. Who are the “time lords” in this show? What is their connection to the Others, to the island, and to the mysteries of the show? At the very least, her name makes the importance of physics in recent developments not unexpected!