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This is discussion archived from a time before the current discussion method was installed.

Looney Toons: Is it possible to extract the examples from the descriptive text in this entry without causing the whole thing to disintegrate? I'd like to see it laid out in the format which is gradually taking over the rest of the wiki, but it's got description and examples fairly heavily intertwined.

BT The P: That's what I set out to do in my last round of edits, but I got distracted. It's a sticky wicket, to be sure.

Gus: It needs to be chopped up into separate entries: A thesis entry on the general topic, serving as the index page for the variations/instances, and the variation entries. The examples will sort into the variations quite nicely. ...

later: Scratch that. I took a stab.


Andyzero: This is just a curiosity question. One thing I've always wondered about was why location is fixed in Time Travel. The Earth moves; it spins on its axis, it goes around the Sun, the entire galaxy is headed slowly towards Alpha Centauri. Thus, the spot you are standing on right now is not where you were a second ago. Technically, unless physical transportation is involved, any major time travel should deposit you into empty space, since the Earth isn't there anymore. Yet Time Travel has no problem "connecting" locations. Has this ever been brought up in a series?

Robert: You're forgetting Special Relativity. To the right observer, you're now exactly where the centre of the sun was ten minutes ago — there's no such thing as a fixed point in space.

This replaces the problem you've described with a different one, not a great improvement. I suspect the whole topic is hand-waved away to keep things simple.

Ununnilium: If I wanted to justify it, I would talk about gravity wells "pulling" the traveler along.

Dark Sasami: Okay, yes, there's no such thing as a fixed point in space, but you're still dealing with a point that is accelerating due to gravity, and Special Relativity is specifically incapable of dealing with non-inertial frames of reference. That's why it's special and not general. You're still going to get dumped into empty space unless your time machine compensates for it.

Robert General Relativity makes my refutation stronger: in GR, the reference frame in which the Earth is absolutely stationary is as valid as any other. Talk about the earth accelerating, leaving the time machine behind, is meaningless.

What Ununnilium suggested does work, about from one small problem. The time machine should be intangible during travel, else people would be able to see it during intermediate times, but that means the solid earth won't be able to hold it up — the machine will do a ninety minute orbit inside the planet.

Of course, all this is implicitly assuming the machine is moving through space. If it uses a temporal hyperspace (like the Tardis) or wormholes (which GR seems to allow) all these problems go away.

Paul A: Answering the original question, Seven Days is one series where they explicitly have to take the motion of the Earth into account when time travelling.

(random passer-by): Not to be a wiseguy, but this whole discussion makes me think of another forum where I recently read some long arguments among people who wanted to rationalize faster-than-light travel, and someone said, approximately:

"all these arguments are equivalent to one person saying 'I will build a complex Rube Goldberg machine and it will make me rich by attracting fairies who will give me money' and another person saying 'aren't you worried that the fairies could take your money away instead?'"

At least according to our current understanding of the universe, which is subject to revision, "time travel," "alternate dimensions," and "faster-than-light travel" are, mathematically, meaningless noises.

This is not to say that no one's ever explored the concepts seriously. Do a Google search some time for "Kerr metric space warp," "Tipler machine," "closed timelike curve," or Kurt Gödel's 1949 paper on rotating universes. The reduction-to-practice aspects are daunting, and it remains to be seen whether any of these ideas is even experimentally testable. The logical contradictions that time travel would introduce seem to many physicists to be a strong indication of its impossibility. But note, also, that any of these "time machines" is far stranger and far more complex than Welles's Victorian concept. For example, Tipler's is a spinning black hole whose core is cylindrical in shape and lengthened the size of a solar system or even a galaxy, for example, and time travel requires making a very close approach to its event horizon at nearly the speed of light, at which point one's spaceship is abruptly elsewhere and elsewhen. Gödel's model requires the entire universe to spin.

And whether any of these ideas is any more practical than building a machine to attract fairies is something we may never know.

Ununnilium: No, The Time Machine didn't invent the concept of time travel, nor was it the first fictional work to use it. Among other stories, A Connecticuit Yankee In King Arthur's Court preceded it. It was the first one to have someone use a machine for the purpose, though.


Silent Hunter: I think we ought to add to the categories "pseudo-historicals" in which the characters go back in time and encounter aliens and high-tech stuff. Doctor Who being a major example of this.
Nobodymuch:Actually there is a reason why Hana doesn't do it. She hates the time travelling monsters so much she'd never let one of them possess her, but without one, she just isn't tough enough to do the job.


Etherjammer: Relocating the conversation from the Back to the Future entry to this page.

  • ..."jigawatts" (clearly a mispronunciation of "gigawatts" on the part of the actors)...
    • Giga can be pronounced as gigga or jigga. Oxford Dictionary
      • The "j" pronunciation is colloquial at best, and illustrates a lamentable ignorance of the origin of the prefix. "Giga-" is derived directly from Greek "gigas", where both "g"s are hard. Regardless, Christopher Lloyd was asked to pronounce the prefix that way by Bob Zemeckis, who'd heard "giga-" pronounced that way at a conference.


"In Jean Claude Van Dam's Timecop, there's a federal agency responsible for going after people who attempt to go back in time. He winds up having to go back in time himself to save his wife from dying, which is what he was hired to keep other people from doing."

It's been sometime since I saw this movie, but didn't his then pregnant wife survive because she was originally killed by a time traveller?
Idler: Regarding Star Trek; is the name "Donut of Forever" actually used in the series? Because it just amuses me; it sounds like the sort of thing you order along with the Milkshake of Eternity and the Burger of Infinity, or something.
Can someone find a way to add software into the list? Time Machine (Apple) would fit.