When time travel is invented I will be able to view my future posts so that I can correct mistakes in advance.
Oh. You say I can already do that?
As Isaac Asimov pointed out, such a device would fundamentally change our notions of privacy, if made commonly available. Anything you ever did could be seen, possibly recorded, as long as somebody can get a futurescope to where it happened. 
prurient indiscretions at parties… finding out security codes and guard rotations while in the midst of a burglary… time-papparazzi trying to set up futurescopes in the places that famous movie stars lived, or stayed on vacation.
And then, there’s the question of how the futurescope knows ‘what happened there’ when locations remaining the same through time is largely a convention of our frame of reference moving through time… considering who quickly the earth is spinning, orbiting the sun, while our sun is moving through the galaxy and the galaxy is hurtling through intergalactic space. 
This idea was used in the minor movie Grand Tour: Disaster in Time, which was in turn based on some sci-fi story I forget the name of. (But if I invent time travel, i’ll come back and remind myself was it was.)
DarrenS
this is your future self communicating through this primitive message board.
Yes you were right - timetravel is possible.
BTW…anyone know where I can get a working flux capacitor? Mine seems to be flat
You missed the fact that your future self will have to pay a lot of taxes to use the Government-licensed Time Machine.
:eek: - I’ve said too much…
There is also the possibility that your Future Self is El Supremeo President For Life Darren, and simply too darn busy with job interviews for his female security staff to flit around time traveling.
How do you know that isn’t exactly what happened? Can you prove that our history is not the result of meddling time travelers? Perhaps chrononauts push Boothe, Oswald, JFK, etc back and forth until one time-meddler somehow prevails? Can you prove that the past is not constantly being changed by chrononauts? Maybe Lincoln originally survived. A chrononaut goes back and changes that. History changes. Everybody else is now from a timeline in which Lincoln died. The chrononaut has changed history, but nobody else realizes it.
My problem, as I’ve said before, is that my future self refuses to tell me anything or do anything. I eventually realized that the ghost in this apartment was me. The birthmark was the final clue. I knew all along that the ghost looked like me. But, apparently, I at least discover time travel around fifty years in the future. I travel back to at least 1998, rent this apartment for a brief time and die. After death, I continue to haunt my younger self who began to live in the apartment in 1999.
The problem is that my older is unwilling or unable to speak English. He occasionally communicates with me in what I think is Yiddish. He has an odd accent and does not annunciate clearly. I’ve tried using my knowledge of my self to explain the actions of a fifty year older me. This has, not surprisingly, failed. I am often at a loss to explain the actions of my present and past self.
At least one movie whose description I kept seeing in the tv guide but never actually watched is based on that premise. A man notices many strange tourists in his small town. He discovers that they are time travellers. He thinks they are here to watch some disaster happen.
Re Location
Some stories do deal with it. In one, an elderly tinkerer decides his time machine (designed to take him anytime in the past and anywhere on earth) is a failure because it only takes him to twenty years ago and the downtown shopping district. In the film Time After Time, the time machine cannot move through space. It takes the passengers to wherever the machine is located at the destination time. Wells uses it and finds himself decades into the future, sitting in the machine which is part of a museum exhibit on HG Wells. Piers Anthony’s Bearing An Hourglass has a brief section in which somebody explains to Time that his hourglass moves him through time and not space because he subconsciously wills it that way. He instructs Time in using the hourglass to move through space.
Didn’t I already move this thread?
samclem
Because many jackpots go unclaimed. Or at least not won every week.
If there were lots of time travellers, many of them in need of present-day funds, they’d be buying winning lottery tickets. If there are enough of them, then every jackpot would not only be won, but won by multiple people, each of whom bought a single ticket. The officials running the lotteries would suspect some kind of flaw or chicanery in the games and start hunting for it. Meanwhile, they’d probably shut down the games it’s found.
So the fact that we have seemingly honest games indicates that there are no time travellers. Or at least that they don’t need money.
No, it only indicates that there is not a large number of timetravellers interested in giving money to people in our present. Come to think of it, it does not even indicate that much. It indicates there is a large number of timetravellers interested in giving money to people in our present by telling them the winning lottery numbers. We can safely say that the lottery is not rigged by massive amounts of time travellers. We cannot say why.
My G-d, in the future, we take over! ;j
There’s a deeper flaw here. Think about some historical event occurring in the past. It is a fact, plain and solid, that Washington crossed the Delaware. You can’t change that, because it’s done. How would you change it? Well, suppose you did go back in time, and convinced ol’ Georgie boy to take a different tactic. But … if you or anyone else had done so, we would all know that Washington didn’t cross the Delaware. That we all know that he did means that any time travelers in the area didn’t change that fact.
Now, think about this - there is no priveliged “now.” The now of someone living in the year 4100 is just as valid as yours, and to her everything in her past is fixed and unchanged. The same goes for anyone living in any time period. According to general relativity, and all of the physics contained within it (particularly electromagnetism), there is no preferred direction to time. Time doesn’t “flow.” It just is. All of time, like all of space, exists simultaneously in the four dimensional spacetime manifold that is the Universe. If you travel back to the Mariana Trench for 20 minutes in 1960, then you have always been at the Mariana Trench, you are always at the Mariana Trench, and you always will be at the Mariana Trench, because that (arbitrarily defined) chunk of spacetime isn’t changing.
Relativity does seem to imply a fixed past and a fixed future. But quantum physics does not. Another reason why they’re incompatible.
Recently, I have started thinking about the design necessities implied in the construction of a Time Machine (as featured in general SF).
1.- You need to separate the “universal time flow” from the “personal time flow” of its occupants
2.- Afterwards you need to accelerate/reverse the “universal time flow”
3- You need to re-integrate the “personal time flow” to the “universal time flow”
Putting the technical difficulties aside (which are obviously not trivial to begin with, since you’d probably have to create some kind of dimensional separation/warp zone, or whatchamacallit), the mere energy necessities to achieve step 2 are staggering… we are talking about the WHOLE UNIVERSE, after all.
Recently I read an article rating civilizations energy-wise, level 1 being a civilization that uses the entire energy output of a planet, 2 the entire energy output of its home star, etc. etc. Since we are per that definition a level 0 culture, and a time machine would require at the very least the energy output of an entire star, my guess is any time traveler would have absolutely no interest in visiting us at all.
After all, with that energy at their disposition, they’d long have built holo-decks and would have covered all their entertainment needs without having to indulge in dangerous experiments with time…
Prove it.
Wrong. If a time traveller did go back and change that, history would be altered. The timeline in which Washington crossed would never have been. In the new timeline, everybody would know that Washington never crossed the Delaware. Folks in 2006, or 1790 would not be able to sit and watch the history books change. The history books in that timeline will have always said that Washington did not cross the Delaware.
Prove to me that Washington originally did not cross the Delaware and that history was altered by a time traveller. We would all know that Washington crossed the Delaware, the time traveller ensured that and it was recorded in all the history books.
If I go back to 1990 and burn down my old high school, folks in 2006 will not watch in awe as the school is replaced with charred ruins, or a new school. The fire happened in 1990. Every ones memories, all books, tapes etc will always have included the fire.
Define “originally”. Since we’re mucking around with time, you can’t use “originally” to mean “at an earlier time”. If you invoke some sort of meta-time, then we have the question, what happens when you invent meta-time travel?
Good point. How about “Prove to me that Washington was able to cross the Delaware only due to the aid of a time traveller, and would have failed on his own.”
I’m not sure exactly what you mean by meta-time.
I can’t believe this discussion – this is just the old Grandfather Paradox in modern garb. It’s been discussed to death. If you try to change the past, it changes the present, so it affects your desire or ability to go into the past, which keeps you from changing it.
The ways off the Gradfather Paradox treadmill are to either:
1.) declare that anything you did in the past is already in place in your present. If you go back in time to change something, it’s already happened and you aren’t really changing anything. This is the POV of Robert Forward’s Time Master and countless other works. As Larry Niven put it, if you go back in time to assassinate Jesus, your machine gun will definitely jam.
2.) Somehow or other your tampering with the past creates a new Time Line, a sort of Reimannian manifold that’s not the same as the time sttream you started out in, so you can’t go back to your “old” future – if you travel forwards in time, you’re stuck with the consequences of your actions. But somewhere (vaguely defined) the original unaltered time-stream keeps a-goin’, sdo you can be born and grow up and decide to use the Time Machine to go and change the past. This seems bound up with that “Many Worlds” interpretation of quantum, and it’s always bothered me – where are all these different worlds coming from and going to? How do you jump time streams in this way, if no one else can? Where exactly is that “old” future that you changed when you interfered in history? You have to come back in time from there, after all.
Neither option satisfies me completely, but the only other one I can see is No Time Travel Allowed. And, curiously, you can meaningfully argue that physics disagrees with that absolute.
As one of my first sigs read:
“Of course,” said my grandfather, pulling a gun from his belt as he stepped from the Time Machine," There’s no paradox if I shoot you!"
Well, he was standing up in the boat . Don’t see how that would have worked.
See the guy, second from the right with an Ipod? That’s our boy.