Causal Loops

You will be tampering with tremendous natural forces, Don! It is dangerous! You may unleash some awful catastrophe!

But the big puzzle: how had he—his earlier self—known that a piece of wire and a bus token would save his life? He had known, all right. Known in advance. But how? And the other five. Probably they were just as precious, or would be.

Now! Now to make a halfway decent world! Max Alben pulled the little red switch toward him.

flick!

Now! Now to make a halfway interesting world! Mac Albin pulled the little red switch toward him.

flick!

“But wouldn’t our objective reality be affected?”

He nodded. “It could be,” he said, “since, in the absence of any real passage of time, it would be in temporal ratio to our involvement in our pasts, which might force it into a different time plane altogether.”

Tel était le but des expériences : projeter dans le Temps des émissaires, appeler le passé et l’avenit au secours du présent.

translate

Such was the purpose of the experiments: to project emissaries into Time, to summon the Past and the Future to the aid of the Present.

And now I shall send you back. . . hundreds of years into the past! You will have forty-eight hours to bring me Blackbeard’s treasure chest! Do not fail!

Kyle: [to Sarah at the Tech-Noir Club] Come with me if you want to live.

It should have ended there, Gordon knew, but it did not end. Where are you, Anna? he thought at the world being swampted in cold rain. Why hadn’t shecome forward, attended the funeral, turned in the papers?

One end of this string represents your birth, the other end your death. You tie the ends together, and your life is a loop. Ball the loop, and the days of your life touch each other out of sequence, therefore leaping to one point in the string to another . . .

The T-800: [to Sarah at the Pescadero State Hospital] Come with me if you want to live.

If you can’t change anything because it’s already happened, you may as well smell the flowers.

“Slim, you should write your book,” said Annie.

“Yes! And you have to keep going for our sake,” said Annie. “For the sake of the future children of America, sir.”

I want you to bring someone from the past to the present—someone who would otherwise die only a few hours afterward. Surely that’s possible.

Hang on! That’s not possible. Ancient Runes is at the same time as Divination. You’d have to be in two classes at once.

Oh, bless my bum-flap. You’re time travelers.

So if they had gotten home five minutes before they left, like those ladies promised they would, then they would have seen themselves get back. Before they left.

Rubinrot, Begabt mit der Magie des Raben, Schließt G-Dur den Kreis, Den zwölf gebildet haben.

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Ruby Red, with G-major, the magic of the raven, brings the Circle of Twelve home into safe haven.

He looked at the sole red logo and decided it was the on button. He thought about where he’d like to be, and pushed.

You get attacked, you have no backup, so you become your own.

I was tracing a design that was etched into the wall, and it started glowing and humming. And then my whole body was being stretched and pulled, like I was a giant rubber band. And there was a sound that vibrated through my skin and into my stomach, which is probably what made me want to puke—er, vomit.

Think of History as a living organism, with its own defence mechanisms. History will not permit anything to change events that have already taken place. If History thinks, even for one moment, that that is about to occur, then it will, without hesitation, eliminate the threatening virus. Or historian, as we like to call them.

Mr. B. invented a camera that takes pictures of the future.

It’s 1814: They’ve never seen fashion styles like ours before.

Wells: Yes, it’s possible, but problematic. Assuming you could create the conditions necessary to take that journey, that journey would then be fraught with potential pitfalls: the Novikov Principle of Self-Consistency, for example.

Joe: Wait—the what, now?

Barry: If you travel back in time to change something, then you end up being the causal factor of that event.

Cisco: Like . . . Terminator.

Joe: Ah!

Wells: Or is time plastic? Is it mutable, whereby any changes in the continuum could create an alternate timeline?

Cisco: Back to the Future.

Joe: Ah, saw that one, too.

About four years from now, most of the human race will be wiped out by a plague, a virus. We know it’s because of a man named Leland Frost. I have to find him.

—from “Splinter” [s01e01]

No, that’s not how it works. In our timeline, Barry’s mother’s already dead, and her death is a fixed point. And nothing can change that.

All of them except Luke Denton and around a thousand other souls who’d been left behind whilst the rest of the human race were evolved against their will, by a force conspiracy theorists around the world had put down to anything from governmental to extra terrestrial tinkering.

Each of the foregoing cases involves a self-defeating act—an act such that, if it were performed, it wold not be. Self-defeating acts are obviously impossible, since the performance of such an act would imply a contradiction. Yet time travel seems to make such acts possible. This suggests the following line of argument against backward time travel:

(P1) If backward time travel were possible, it would be possible to perform a self-defeating act.

(P2) It is impossible to perform a self-defeating act.

(C) Backward time travel is impossible.

You got me. I’m an android sent back from the future.

“What’s happening?” Benjamin cried. The dreidel spun faster and faster until the whole room whirled with it. He grabbed onto Devorah and shut his eyes.

You were right—the photograph, it was me, it . . . It will be. I don’t know how, but it will.

The notepaper was faded with age, and although I’d never seen it before, I knew he’d hidden it there the night I met him again, so many, many years before.

You want to shoot me into oblivion with no way to get home.

The Downloader is a real piece of work. There’s only a ten percent chance of success, eh? And even if they make it, half of them get caught by the Control Bureau.