Alan Lightman - When a traveler from the future must talk, he does...

When a traveler from the future must talk, he does not talk but whimpers. He whispers tortured sounds. He is agonized. For if he makes the slightest alteration in anything, he may destroy the future. At the same time, he is forced to witness events without being part of them, without changing them. He envies the people who live in their own time, who can act at will, oblivious of the future, ignorant of the effects of their actions. But he cannot act. He is an inert gas, a ghost, a sheet without soul. He has lost his personhood. He is an exile of time.