Coventry: You're talking about changing the past, and I know damn well we can't change the past! It catches up to us, and changes us!
Louise: Well, we haven't changed much. We're all still dying, this place still stinks, and you are still as ugly as ever!
Sherman the Robot: It is not the end. It is not the beginning of the end. It is the end of the beginning.
Bill Smith: [Louise and Bill have gotten into Louise's sports car; Louise rockets out of the parking space] Tower clear you for that take-off?
Louise: Sherman, come with us!
Sherman: There is no place for me where you are going. Go now.
[Solemly stays behind to close up the time portal and is vaporized in the timequake]
Louise: [the escalator on which Louise and Bill are riding has just stopped] Well, we could be stuck here for hours. Maybe we'd better get acquainted.
Dr. Arnold Mayer: We scientists should get out of the lab more often; we might learn something!
Dr. Arnold Mayer: [Addressing a lecture hall audience, possibly at the United Nations] We've talked about quarks and anti-neutrinos. But, what about people? It's quite a step from demonstrating that sub-atomic particles can travel backward through time to saying that people can. What would be the result of people traveling in time? For one thing, paradoxes become possible. Say you build a time machine, go back and murder your father when he was ten years old. That means you were never born. And if you weren't, how did you build the time machine? It's the possibility of paradoxes that make most people rule out time-travel by human beings. Still, why not? If you were careful, you could do it. You would not go back to kill Adolf Hitler, much as you might like to, 'cause it would change history. A time-traveler would have to be careful, but he could do a surprising number of things. He could observe, for one. He could find out once and for all who was on the grassy knoll that day in Dallas. And he will know what we can only guess at... that we are destroying the planet we live on by complacency. He will have to live with our legacy of pollution & acid rain. Our negligence today is producing a world in which our children's children will be barren, and the human race heading towards extinction. He could also take things, providing they wouldn't be missed: a cup of water from the Pacific Ocean, a stone from the Grand Canyon. This may sound pointless, but sometimes very small differences can be crucial. The difference between a dead man and a man who's alive can be very small. What about a man who's about to die... a man no one will ever see alive again? This is the hard part about looking for time travelers: they don't want to be found. You must look for them in places where no one is. Or where there are people no one will ever see alive again.
Bill Smith: [Doesn't speak, but his eyes narrow]
[Louise is driving like a maniac; Bill is marveling that she has not killed them both in a wreck]
Bill Smith: How long have you had this thing?
Louise: A few months.
Bill Smith: You must be the luckiest woman in the world.
Bill Smith: [to Louise, an undercover time-traveller] The rule is: Never sleep with anyone who's crazier than you are.