If you were a time traveler what's a fast and easy way to prove that?

Inside this envelope are 6 different colored pens, a piece of paper, envelope and stamps. Go down to the post office, (I’ll stay here with your trustworthy friend) pick one or more of the pens, write a letter and post it to the below address. Once you have done that, text me.

When they’re done and text me, I text back with a photograph of their friend holding the envelope and letter that I will receive a few days from now.

But aren’t there stage magicians who’ve done similar things as a magic act? Of course, nobody believes that they were actually predicting anything; we know that there is some sort of sleight of hand involved, probably in swapping the sealed envelope just before the reveal, even if we don’t know how exactly it was done. People would have a similar suspicion about our time traveller.

I would say anthing like weather or the stockmarket that relies on an extremely accurate number has noise that has a good chance of changing just through chain reaction effects of you and your friends actions or inactions, even after only an hour.

Sure, by any measure it would be impressive. But would it be sufficiently impressive for a 1950s person to conclude that the item must be from the future, rather than, for instance, some top secret research project that’s far ahead of anything commercially available but still within the realm of what’s imaginable with existing technology, if only as a fake? The calculator, for instance, could be explained away by postulating someone in the background controlling the device remotely so as to output the result of calculations.

You can set it up so sleight of hand isn’t possible. Having many recipients is one way to do this. You can also have the envelopes get handed off 24 hours ahead of market close, and having the recipients be nowhere near the traveler at any time after the hand off.

Other than that, it comes down to revealing, shortly before they happen, the who/what/when/where/why/how of major events that will occur over the course of the next day. Plane crash, house explosion, death of someone famous, and so on.

Common scam. Send out 256 letters predicting the winner of an upcoming baseball game. 128 will have the right winner. Send letters predicting the outcome of the next game to those recipients and for 64 of them you’ve got 2 games in row correct. Send out 64 letters to … do I have to explain this further? Hopefully someone will fall for the scam before you run out of games to predict. Predicting other events with more complex outcomes just requires more letters. Maybe hundreds of thousands of letters but it’s the year 2050 now… oops… forgot… you think it’s only 2024 right now, but email will still work so no need to lick all those stamps and envelopes. Oh wait, forgot again, you guys have peel and stick stamps and envelopes in 2024, right?

That’s what you would have to do. The problem is that this is exactly what stage magicians have been doing for a long time: Find a clever way of applying sleight of hand where it seems to the audience that none is possible. I think the only way to eliminate any doubts in this regard is to actually publish the predictions prior to the event happening. But then you end up risking influencing the outcome rather than merely predicting it.

Well, hopefully they wouldn’t think I was a witch and burn me at the stake. I guess that would be 1750, not 1950. LOL

If it’s the same few dozen people getting the predictions every time, and everybody on the list knows everybody else on the list and can confirm that they’re all getting consistently accurate results over several days of trials, that would rule out a scam.

Things like the Powerball and Mega Millions drawings are pretty closely guarded, and are done on live TV with physical balls in a tumbler; it’s hard to imagine how someone could fix a draw like that. If the traveler wins all of the big lotteries repeatedly over the course of a week or two, and lottery officials can’t find any evidence of fraud (other than your surmounting of astronomical odds against you), that would be extraordinary evidence in favor of the traveler’s claim.

Assuming a time-travel scenario that allows going back in time and meeting myself, that’s what I would do. I could easily convince my younger self that I was looking at an older me by telling him secrets and memories that only we knew, and by showing him our striking physical similarity.

After persuading him that I was him, I would ask him to help me prove to the world that we were the same person (I know younger me would be onboard with that). There would be no records of me having a twin, and genetic tests would confirm our identity.

That sounds like the sort of thing that people could handwave away as a failure of record keeping. More compelling than genetics would be your completely identical fingerprints, scars, dentistry, etc

I don’t think you could get people to believe you. That might be subtly different than being able to prove it.

Lots of these responses could prove it, but I won’t believe you because they all seem like clever magic tricks. If I’m opening an envelope, that’s a magic trick to me - presenting the information that way will never work for me. The explanation is meaningless because I’ll never get past that it seems like a magic trick and I’ve seen many magic tricks that are incredible/impossible. Then, when you say how you did this was that you’re actually a time traveler…sure, Jan. I would just think you don’t want to tell me how it’s actually done, I’ll never believe you’re from the future because, from my perspective, it’s not possible.

For me, it would take several other smarter people I respect believing it and saying yes this actually means they could only know this by time traveling and that it’s possible. Which is not where I was expecting to end this reply.

The sheer computing power of the cheapest current day cell phone would be utterly unimaginable in the 50’s, it’s either from the future or alien tech.

Yeah, I know what you mean - a lot of these things are like “I have in my hand a perfectly ordinary coin - look, see? A perfectly normal and unmodified coin!”

Perhaps I’m not cynical and skeptical enough, but you could have shown a 2024 iPhone to me in the 80s and probably even 90s, and I’d be convinced you’re either a time traveler or necromancer or some mix of both.

It would be hard to explain an identical twin that was 20 years older.

The thing that stands out to me is a particular conversation from the mid-nineties. I was in the car with a friend of mine–a genius friend, who was working toward his Ph.D. in chaos math–and we were shooting the breeze about computers. I idly speculated about how one day in the future, we might be able to replace the paper road atlas we were using with a dashboard computer that contained all the maps of all the roads in the nation. My friend scoffed. “There is no way computers will ever be able to do that,” he said. “That’s way, way too much data to hold on a computer.”

That’s thirty years ago, and it was inconceivable to him that maps could be stored. If I could show him a tiny computer in my pocket that I could pull out and say, “Hey Siri, give me directions to 333 Dorkness Avenue in Sacramento, California,” and it’d plot the best route?

Time traveler, baby.

But you could not do that carrying your phone into the past, which was the point of my previous post about moving images. Siri doesn’t run locally on your computer; it takes sound bites and sends them to a server for processing. If you take your phone into the past, the server (and the network to connect your phone to it) wouldn’t be there. You’d be strictly limited to things that run locally on your phone.

I couldn’t do exactly that. But I believe that with Google Maps, I can download maps to my phone, and I could then type in any two addresses on one of those downloaded maps and get directions from one to the other, even while in airplane mode.

It wouldn’t be evidence of time travel to me, it’d be evidence that someone had found a way to defraud the lottery that officials haven’t been able to figure out. As others have said, if it looks like a magic trick, that’s what I’m going to assume is what it is. I’m going to conclude that they good at doing something seemingly extraordinary and concealing the mundane explanation of how they did it. I’m not going to jump to the conclusion that they are time travelers or performing literal magic. I’m sure it would be frustrating if they were actually a time traveler or performing literal magic, but I’m going to go with the mundane explanation 10 times out of 10 before concluding something as extraordinary as time travel or magic being real.