How about if I took you back in time with me?
If we’re sitting in Yankee Stadium watching Babe Ruth and Lou Gehrig, you’re not going to be convinced? We then take a quick trip to watch the Gettysburg Address, and go buy a beer for Ben Franklin, not convinced?
If you can be convinced by this, the only question is what thing short of actually travelling through time yourself will be convincing.
No. Not at first. This all presumes I believe we are actually traveling through time and those people/events are the actual people/events - you know, time travel. I would never believe that is what we were doing. I would probably think, wow, I need to invest in Meta asap. This virtual reality stuff is cutting edge - I can smell the gunsmoke and taste the beer. It really feels like I’m there and I don’t even need the headset! How in the hell do they do it! Right? In my mind, I think that is possible to do today - not commercially or anything, but it’s in the realm of possibility. There’s good VR, there’s 4D movies, it’s all kind of close. I would of course be completely wrong and not believing my own reality because we are time traveling in this hypo. But I just don’t think I’m making that mental leap so quick to believe it versus some other more plausible explanation. I’m way too skeptical and in my mind time travel is not real so it must be something else.
I’m not sure how long we are in your hypo, or if we do it many times, but eventually I would believe it, or default to the assumption it’s true. It would take awhile and it would take other people explaining how time travel is possible, etc. For better or worse, I’m not sure I could ever get there by myself.
So, getting to OP, there appears to be three ways to prove you are a time traveler: (1) future information; (2) future tangible things; (3) performance. In your hypo we actually time traveled - pretty good evidence! Also, someone mentioned above just seeing the time traveler go in and out of existence - so something performative like that. Is there any other category of evidence?
Thinking about it…It could never just be (1) future information (eg, knowing the lottery, stock prices, etc.). That doesn’t require time travel, just access to future information which doesn’t require a human actually traveling through time. That actually seems like an extremely inefficient way to obtain future information. After discounting other ways, like some super quantum computer that can accurately predict 24 hours into the future, I’d eventually just believe you somehow tapped into a way to extract future information before I believed you transported human flesh through space and time - extremely amazing, but not a time traveler. I don’t think information alone proves you are a time traveler. I think a combination of all three would be needed and it would never be fast nor easy to prove it.
Damn. I should have done it without writing about it on an Internet message board.
I can’t give an example because if I could I would be the time traveller but could one not simply bring back a solution to a problem that is unknown today? Say for example a cure for cancer or a cure for anything that today’s science hasn’t yet discovered. Scotty’s formula for transparent aluminum type of thing.
The other thing that would not be proof per se would be societal attitudes from the future. Suppose in the future, criminal tendencies are cured harmlessly and automatically in the brain by some system we can’t even conceive at this moment in time. Our time traveller comes back and encounters police, criminals and jails and says something along the lines of “holy shit, this is barbaric!” Or suppose a time traveller comes back and hears people casually using the word “crazy” which in their time falls somewhere between the n-word and the r-word. They are absolutely shocked by how casually we compare mental health issues to things we do not understand and/or accept. It wouldn’t prove anything but it would show a different perspective.
Logically this would be impossible.
Every other explanation is always more likely than actual time travel: no matter how complex, how unlikely, how many co-conspirators I’d need.
The explanation without time travel is more likely.
You cannot convince a rational person with a basic understanding of physics that you are a time traveller.
Bribing a stock exchange or a major trader to end with the numbers I provide? More likely than time travel.
Bribing the players and the refs to end 10 matches with the results I give? More likely than time travel.
Getting Israel, Hamas, Ukraine and Russia to sign a world peace agreement? More likely than time travel
There is absolutely nothing you can predict that would convince me you are from the future.
Some trickery, no matter how complicated or far fetched will always be the more likely explanation.
How about I bring you something from the past?
I’ll open it up to anything (or things) I can carry on my person that cost $100 or less, that can be bought in NYC (let’s presume that is where we are for this experiment) between the years 1900-1980. Bottle of coke from 1905, NYT paper from Dec 17th 1950, Swanson TV dinner from 1963, and an Evel Knieval Stunt Cycle, whatever you want. Be bold, be random.
I’ll then walk out that door, and come back 1 minute later with all the things you wanted, in perfect brand new condition, because I will have just bought them at the store.
everything is more likely than time travel. This includes warehouses full of props.
Bring the Spanish Inquisition back from the past. Nobody will be expecting it.
I’m hiding a warehouse full of props outside your house and can whiz through the entire warehouse in less than a minute to pickup the 5 randomly selected things, from the endless variety of things from history you can dream up in your imagination. Seriously, you can walk through the door and see what’s out there, and it isn’t a warehouse.
Even just a randomly selected newspaper would be a virtually impossible task to select the desired newspaper from every single daily newspaper available in NYC from 1900 to 1980, to be returned to you within a minute of selection, in brand new condition. That’s like 150,000 different newspapers that I have to physically reprint and have on hand and keep that hidden from you when you look out your front window.
Or, your understanding of time isn’t as rock solid as you believe it is.
This assumes that the past can be changed, by a time traveller. If the Novikov conception of time travel is correct, then you can’t change history, and the loop itself is already part of the history. You can only change history in a universe where multiple timelines are possible, and this is certainly not guaranteed to be the case.
An example of Novikov consistency in fiction happens in Harry Potter and the Prisoner of Azkaban: Hermione and Harry perform exactly the same actions both times they can be seen in the loop, and history is not changed.
In a non-consistent model of time travel, all bets are off, and you can change history as much as you like, creating a new timeline each time. This sort of non-consistent time travel would be very difficult to prove, since every factoid you bring back from the future would be subject to change.
I would always assume some kind of force. (as in a magician’s trick)
It is infinitly more easy to fool me than to time travel.
I think future tech would be better. Something that cannot be currently known or recreated.
Otherwise I’d think you invented a really good 3D printer + computer that can make anything I can think up. I would think my imagination is likely more predictable than it seems. I would not think you time traveled into the past to grab a newspaper or bottle of Coke.
How fast is this happening? Maybe if you didn’t leave out a door and have to go buy these things in the past. If you just appeared and reappeared in front of my eyes somewhat instantaneously. Of course, then I’d just believe I’m going crazy and hope you left me alone.
Yeah, I suppose it all comes down to your personal philosophy. I think there are many things improbable-to-impossible enough that I’d consider them less likely than time travel. I don’t believe in time travel backwards through time, but I don’t have 100% certainty about it (nor do I really have 100% certainty about anything. Anything is possible, in my book. The fact that there is something instead of nothing I should consider impossible, yet we are here.) I mean if you brought me a selection of newspapers from a week from now, and a week passed and I saw each paper correctly matching the “time travel” paper, I’d conclude you’re a time traveler. I’d have to be sure to read the papers beforehand and to take some pictures and hide them so there wasn’t some sort of switcheroo, but, yeah, that would convince me.
If I wanted to convince someone from the past that I was from the future, I’d first travel far into the future, to a time when a super intelligent species evolved, after the extinction of humans, then bring a specimen of that species back in time to someone with an open mind—someone like Ben Franklin.
To Franklin: Ben, I’m from the near future, and my talking raccoon here is from the distant future.
To the super-raccoon: Rocky, explain to Ben, in easy to understand 18th century language, how time travel works, and convince him we’re from the future.
Sure, it’s a bit convoluted, but I bet it would work, providing the super-raccoon speaks English.
I figure, materializing out of thin air may be accompanied with an unknown amount of pyrotechnics from chronometric energy…and that may be considered a terroristic attack…and the authorities might respond accodringly.
Some things must be done subtly.
Establish Time Travel with the proper people first, then go public, if necessary.
Dr. Strangelove’s point is a good one that you rarely hear mentioned in these debates. We talk about the ‘butterfly effect’ and how it might change what happens, but the deeper point is that much of what happens in the world is driven by randomness. Why would you believe that the world will evolve in the same way a second time? Forget the time traveler. If we could just have a ‘do-over’ and reset everything to exactly the way it was in say, 1970, there is no reason to believe that we’d wind up with the same world today, even if no one messed with the past.
Many worlds allows for thhis. If you go into the past, you simply split off a new universem and it evolves anew. But the implication may be that if you travel to the past you won’t be able to predict much because each iteration of the past turns out wildly different.
As an analogy, if you take a double pendulum and try to start it swinging precisely the same way each time, you will still get radically different outputs. The future may be completely unpredictable, even if you travel into the past with your knowledge of ONE future that happened.
Right. I am surprised to learn from the wiki article that so far, a real paradox has not been found yet. Still, it has some unreasonable properties.
For instance, say I can only send a single bit into the past. I can then build a paradox machine (P) that sends a bit to itself if-and-only-if it does not receive one from itself in the future. Presumably, according to the Novikov conception, such a machine would self-destruct if I ever tried to turn it on.
But I can use that machine to do interesting other things. For example, say I set another machine to generate lottery numbers (which I then use to buy a ticket), waits for the lottery to happen, and then turns on P if I lose the lottery.
If everything goes right, then I win the lottery. Because aside from P failing or there being some other interference, the only consistent history here is that I win the lottery and P never gets turned on.
Though it does raise a question: how does the universe pick the method of resolving the paradox? Does it just pick the highest probability option? Or is there a kind of self-consistency wave that spreads out from the origin of the paradox?
Anyhow, you can use the same method to solve any problem that can be evaluated for success. For example, my example of factoring an RSA key. Just set another machine to generate random numbers and multiply them together, and if they don’t match the key I care about, turn on P. Self-consistency dictates that the random numbers I picked just happened to be the factors I want.
Being able to solve NP-complete problems, etc. seems like some evidence that this is an unreasonable conception, even by the standards of time travel.
Some things are predictable, though, like your earlier example of a meteor. Those are on fairly deterministic trajectories. They can be perturbed by random effects over long periods, but you could certainly predict a collision in the next month or so.
It’s hard to know what fits more in the deterministic category vs. not, though. The outcome of an ordinary election is probably largely determined a few days in advance. Aside from some improbable events, people have made their decisions already. But if the race is close enough, maybe not. Even purely random things like the weather might affect the turnout.
Things that are random from the beginning, like lottery results, I wouldn’t expect to play out the same way each time. It doesn’t necessarily require a full many worlds interpretation, though if that is the right interpretation, I think this version of time travel directly follows.
If any single event, even a quantum event, occurs that is different to the ‘original’ timeline, then you haven’t got Novikov consistency. In a self-consistent timeloop, you can only go back and do the things you have already done, and you have no freedom of action, because this time loop has always been there. If you go back and try to kill Hitler before 1945, you can’t, because he didn’t die at that time. The best you can do is stand at the back and become one of the onlookers who didn’t kill him; and you have always been there in the background, looking on and posing no risk at that time. A Novikov time loop is immutable; you can’t kill Hitler, but if you show up in a photograph from the time, you can’t decide not to go, either.
There are a number of ‘multiple timeline’ interpretations of time travel that might allow changes to historical details. If there are an infinite number of branching timelines splitting off all the time, then you can go back and change history - or you could go back and be consistent with known history instead, because there are an almost infinite number of possible worlds emerging at any point in time. The problem with an infinitely-foliating model of time-travel is that you can never guarantee that you can go back to your own time - things change on large and small scales, and even if you back to a timeline that looks the same, there might be tiny Mandela effect changes you don’t notice.
Another possibility is that the only way to create a new timeline is by actively changing history by a deliberate act; this would create exactly two timelines, the old one you came from, and the new one you created. This is much simpler than the infinitely branching many-worlds idea - with only two timelines to choose from, you have a non-zero chance of getting back to the first one, by some method or other.
Yet another possibility is that you can only make small, insignificant changes, and the universe resets itself by some kind of macroscale recoherence. Who cares if the lottery numbers change, if no-one wins.
I know; I think Novikov is implausible even by time travel standards for those reasons (and more). If you can coerce the universe into solving any NP-complete problem, then there’s probably something wrong with the idea.
There’s no might about it; things will play out differently in this conception. Quantum events are purely random. It’s not so much that you didn’t go back to your own timeline–it’s that once you play that forward again, anything sensitive to small changes will happen differently the next time around. The lottery will get different numbers each time because it’s a chaotic system where tiny quantum perturbations result in macroscopic differences.