Time travel vs. seeing the future

Factual Questions
1

In short, how would you know the difference?

For the sake of argument, we’ll assume time travel is possible and any nasty paradoxes created by doing so are of no consequence. Also, we’ll have to assume that psychic prediction of future events is accepted.

If you traveled back in time (assuming you kept your memory, unlike Quantum Leap) it would appear to the people of the “past” that you had the ability to predict the future. You ought to have beforehand knowledge of any event that happns up until the time you traveled back.

Looking at it from the other direction, the ability of someone to predict the future could be explained equally well by psychic abilities or by the possibility that they are a visitor from the future.

Either phenomenon results in the ability to prognosticate. It seems to me that it would be impossible to distinguish one from the other.

So, if someone else can predict future events, how could you tell if it were a feat of prophecy or a result of time travel? If it were you who had this ability—and for some reason, you couldn’t remember travling back through time—how would you know which explanation was correct?

2

Who’s to say one would be able to predict the future if said one traveled to the past? Odds are they’re affecting and altering the very future their knowledge base stems from.

3

Forgetting the whole chaos-theory, cap yo’ granpa type situations… you’re right, it would be hard to tell.

I imagine showing up at a press conference with your past self, and providing DNA/fingerprints would be a good start. I suppose bringing some unique object back with you would be another way.

OTOH, if people can tell the future, they could reliably inform everyone the previous week that you had in fact made this stunning breakthrough. :wink:

4

They are the same class of event; physical time travel involves actual objects travelling backwards in time,
while ‘seeing the future’ would involve transfer of information backwards in time.

Both would produce identical paradoxes and both are actual infringements of causality.

If you are a clairvoyant of some sort and recieve reliable information from the future, it is not the act of foresight on your part which is the important part, but the backwards flow of information;

this backwards flow of information would break just as many rules of the universe as the movement of actual physical objects back in time.

5

Obviously if you can find physical evidence, you could show you’ve travelled back in time. But if you can’t find any, can you know?

I think you have to state in what way time-travel and seeing the future work. For instance, if the universe is ‘fixed’ so any information travelling back fits into the already-established timeline, then I don’t know if you could tell.

But if it’s possible to change things based on the future knowledge (eg. splitting off a parellel universe) you might have a clue - it seems likely that knowledge from a time traveller would go out of date as the future changed, but that of a clairvoyant would represent the future of the world as it is now.

Of course, there are other theories that I don’t know if are consistent but are represented in fiction, eg. a time-travellers memories changing as he alters events.

6

I like eburacum45’s idea. The backwards flow of information was something I hadn’t considered.

But everyone else is right…we’ve got causality issues to work out. I guess I could qualify the OP and say that you coudl restrict those future observations to things that aren’t easily affected, like SUper Bowl champions, or the weather. This would also require a high level of secrecy, to keep the information shared by the “prophet” from getting out and changing things.

Not saying that’s practical, but those are the sort of exceptions you have to make to get to the point of the question.

7

There is ONE case of clairvoyance that I take seriously…that is the case of the 19th century Italian priest (and labor activists) Father Don Bosco. Father Bosco was a prolific dreamer, and recorded his dreams in his diary (which was published after his death).
The one dream that fascinated me was this: sometime around 1870, Father Bosco had a long dream in which he saw a new city, in a region of Bazil which was uninhabited-the location he recorded exactly. This was the city of Brasilai, which was not built till 1956! His dream accurately described the layout of the city (like an airplane), and other details.
He also had dreamsin which he saw schools(run by the order he founded),in the cities of Boston and Los Angeles.
Quite amazing for a priest who never travelled outside of his native Italy!

8

Look for other evidence–birth records, employment history, tax and criminal records, friends and family, etc. If you can find no evidence that the person ever existed in the current world (i.e., they just “appeared” a few days/weeks/years ago), then it’s likely to be someone from the future.

Same as above, for starters.

After that, you have an added resource, namely you know the whole of your own info. resources (whereas the other person may be picking and choosing what to tell you). So it depends on the nature of information you have from the future. Do you only know major world events, etc.? Or do you have personal memories (i.e., you, yourself, actually walking down future streets and having conversations with future strangers, etc.). Though it would not be conclusive, it seems to me that if you had personal memories of doing things in the future ("…I remember eating a plutonium doughnut with nano-sprinkles…") that would strongly imply that you were from the future–esp. if the events occur far beyond the end of what would be your reasonable lifespan (i.e., the year 2300), so that it’s not just you seeing into your own life in say, 20 years.

9

Heinlein’s “All you Zombies…” describes a time-traveller’s consternation at discovering that he is his own grandmother and grandfather. The 1959 story predates choas theory by decades. Perhaps the author was prescient ? :wink:

10

The difference would seem to be that information that travels backward in time is massless, while a time traveler would involve the movement of mass.

From a practical point of view, the difference between psychically predicting the future and traveling back in time and reciting the future is that the time traveler is more likely to provide faulty information.

The time traveler probably experienced the event, but may not remember the details clearly. Was the score of the Superbowl 26-10 or 27-10? The psychic, however, is actively looking for that information and should be able to remember and proclaim that information more accurately. In other words, it is fresher in his mind.

11

Successful prognostications, it seems, tend to be pretty general and undetailed. A prophet might predict the teams which will play in the Super Bowl, and the final score, but an intense football fan who travelled through time might be able to give details about specific plays, describe the weather that day, comment on the quality of the play-by-play coverage, and describe a number of the TV commercials which accompanied the broadcast. The level of detail a person provided might not demonstrate for a certainty whether or not he was a time traveller, but it could might make it easier to make a guess.

If a person wanted to offer substantial proof that he was a time traveller, he might take one of two approaches. First, and most obvious, he could bring with him artifacts of the future; it strikes me that a person who wanted to go to the past and advise people of what was going to happen might bring with him newspapers, magazines, etc. which report on the future event.

Secondly, a person might leave his own artifact in the present to demonstrate that he had, in fact, lived at or after the time of the event he described.

Thus: In 2004 time travel is perfected. Traveller, who is in poor health and only expects to live for a few more years, goes back to the 1940s and contrives to become friends with his all-time favorite movie star, Leslie Howard. One day he reveals to Howard, who has come to trust him, that he is a time traveller and knows that if Howard gets on a plane that day he will die in the first-ever Nazi attack on a British commercial airliner. Howard isn’t sure what to make of this, but seeing that his friend is terribly distraught, he agrees to postpone his trip. The plane is shot down, and the story is passed down as a family tradition of how and why Leslie cheated death.

People who hear the story wonder, naturally, if there could possibly be any truth to the story about how Howard’s friend had come from the future. Traveller, knowing full well that he will die long before 2004 rolls around, established a trust. Included in this trust is the property in a safe deposit box. In accordance with the instructions he leaves, the box and contents are opened in 2004, and a sealed envelope is removed which is sent to Howard’s descendants. In it is a photocopy of a newspaper article from the day after Howard died in the plane crash, and a note from Traveller.

12

toadspittle, that scenario only really works for time travel or predictions across large gaps in time.

But whe if it’s only a short time comapred to a human lifetime? Like weeks or just several months. The shorter theinterval, the harder it would get to distinguish the two phenomena. But the ability to recite or predict future events is no less remarkable just because they’re in the near-term.

13

Nitpick: If I recall correctly, he finds out he is his own father and mother, not grandfather and grandmother.

[spoiler]”She” is born a girl, grows up and seduced at a fairly young age by a stranger who then disappears…

Left pregnant, she bears a child. But in the course of the birth, doctors find she is actually a kind of hidden hermaphrodite, and the trauma of childbirth has forever screwed up her girl parts. So they put her back together as a man, and he goes on living life now as a male. The child is given up for adoption.

“He” is later recruited as a kind of time cop by an older stranger, and his job is to keep the timeline intact. As part of the process of recruiting him, he is allowed to visit the past. He can’t resist the temptation to look up his younger female self, and eventually seduces her, getting her pregnant just before being spirited away by the older stranger to begin his new job. The child is an outwardly normal female, but is in fact a kind of hidden hermaphrodite, who grows up as girl, gets seduced by a stranger, has a baby, becomes a man, etc.

The older stranger who recruited him into the Time Corps and took him back in time to seduce himself reflects on his own past, having been born a girl, gotten pregnant, became a man, was recruited into the Time Corps by an older stranger, etc.

In other words, she/he is every major player in his own life. She is born, seduced by himself, bares herself as an outwardly normal baby girl, is recruited by himself, given the opportunity to father herself with herself by himself, etc. He is a continuous loop, complete in herself.

He wears a ring that is a representation of Ouroboros, the snake that eats it’s own tail forever. As the story ends, he reflects to himself that he knows who he is and where he came from, but what about all you zombies out there? [/spoiler]

A great story, one of my favorites.

14

I see what you’re trying to say, but all the ways of transfering information involve the transmission of an object, or at least a force, either of which would end up transfering energy of some sort. Did you have something else in mind?

15

> it strikes me that a person who wanted to go to the past
> and advise people of what was going to happen might
> bring with him newspapers, magazines, etc. which report
> on the future event.

Not true. Give me an hour and I can mock up almost any kind of “future” newspaper or magazine.

And, unfortunately, if the things in my magazine started coming true, it would be far too easy to accidently change the future I was describing.

Let’s say, for example, that I brought back a book of sports scores over the last 20 years (recall the plot of a famous movie) and I started using that book to correctly predict outcome of the games. Just the fact that I am using the inofrmation can easily change the chances that subsequent information will be correct.

Someone will notice that I am always getting the games correct and invesigate. Or, maybe my bookie is tired of losing. Someday, when I predict the Lakers will win 94 - 87, that might get back to one of the players who might want to actively make sure that my prediction is not correct. If he does manage to change the score, my book is now incorrect and suspect for all future games.

Whereas, I might not have the same problems if I were a psychic. I’d always be getting “fresh” information from the future.

> In 2004 time travel is perfected. … movie star, Leslie Howard.
> … agrees to postpone his trip. The plane is shot down
> … in 2004, and a sealed envelope … a photocopy of a
> newspaper article from the day after Howard died

Again, this could be dismissed as a fake. And, indeed, it will be determined to be a fake, since the newspaper that it was alleged to have been cut from will be able to prove that it never ran such a headline.

And, of course, there are the obvious time paradoxes.

Maybe that’s the big difference between between time travel and precognition; predicting the future won’t cause paradoxes, whereas time travel will.

By the way, in 1959, I will be talking the Big Bopper into giving up his seat on the plane. The details are all in my safe-deposit box.