# If you were a time traveler what's a fast and easy way to prove that? **URL:** \ **Category:** Factual Questions\ **Created:** [January 26, 2024, 3:25am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650 "2024-01-26T03:25:14Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Asuka](https://avatars.discourse-cdn.com/v4/letter/a/dec6dc/32.png) [@Asuka](https://boards.straightdope.com/u/Asuka)\ **Post date:** [January 26, 2024, 3:25am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/1 "2024-01-26T03:25:14Z")
Obvious answers are “Predict an earthquake or other natural disaster” but what if you wanted to predict something immediately? Like you have access to the Internet from 24 hours in the future and there’s no sporting events going on, what’s the easiest way you could “prove” it that people can’t disregard as either insider knowledge or dumb luck? ---
**Author:** ![epbrown](https://avatars.discourse-cdn.com/v4/letter/e/e47774/32.png) [@epbrown](https://boards.straightdope.com/u/epbrown)\ **Post date:** [January 26, 2024, 3:32am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/2 "2024-01-26T03:32:31Z")
The fast and easy way is to **bring back proof.** It’s why almost every story has some reason you don’t have your cell-phone or some-such. There’s no information you’re going to provide that people won’t explain away beforehand or be highly suspicious of afterwords. ---
**Author:** ![griffin1977](https://avatars.discourse-cdn.com/v4/letter/g/977dab/32.png) [@griffin1977](https://boards.straightdope.com/u/griffin1977)\ **Post date:** [January 26, 2024, 3:35am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/3 "2024-01-26T03:35:22Z")
The closing numbers of a few stockmarkets or important stocks, to the last penny would seem pretty hard to fake. ---
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [January 26, 2024, 3:38am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/4 "2024-01-26T03:38:19Z")
Recite that day’s exact closing prices on as many different stocks as it takes to convince them. Have them write a letter and mail it to you at an address you’ll have access to in the future. Drop it in the mailbox together. Go to the future, retrieve it, and hand it back to them. (You could conceivably do this _before_ you mail it if it’s unlikely to cause a universe-destroying paradox; but I’m not an expert in temporal mechanics so I don’t know if that would be prudent.) ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [January 26, 2024, 3:38am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/5 "2024-01-26T03:38:20Z")
Bring back an unknown virus. ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [January 26, 2024, 3:39am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/6 "2024-01-26T03:39:57Z")
You’d change the timey wimey stuff. If you were just nominally believed and people invested in a winner. Then you’ve lost the proof. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [January 26, 2024, 4:02am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/7 "2024-01-26T04:02:23Z")
Why would I let anyone know? I’m going to win the lottery but I’m not telling people how I did it. ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [January 26, 2024, 4:23am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/8 "2024-01-26T04:23:51Z")
You gotta prove it. You’ll have say something to do that. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [January 26, 2024, 4:31am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/9 "2024-01-26T04:31:51Z")
The result of applying SHA-256 to a randomly-chosen number several trillion times. While some hardware can perform this operation faster than others, there’s an upper bound to doing it sequentially, and the iteration count can be set so that the answer can’t possibly arrive sooner than some time in the future. I don’t trust stock market figures, natural disasters, etc. Butterfly effect and all that. The hash function is totally deterministic. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [January 26, 2024, 4:47am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/10 "2024-01-26T04:47:10Z")
> [@TriPolar](#): > > Why would I let anyone know? Because the title of this thread _isn’t_ “If you were a time traveler what’s a fast and easy way not to prove that?” 😁 ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [January 26, 2024, 4:48am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/11 "2024-01-26T04:48:38Z")
Didn’t work out for Biff. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [January 26, 2024, 4:51am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/12 "2024-01-26T04:51:55Z")
However, it takes that long into the future to prove you had the right answer. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [January 26, 2024, 4:59am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/13 "2024-01-26T04:59:30Z")
True (though that’s pretty much true for all of these ideas). That gives me another idea, though. Let the other person generate an RSA key of modest length. I’ll set my computer to brute-forcing the factors, then check the future for the answer. The other person can easily prove that my factorization is correct without waiting the entire time. If I can look arbitrarily far into the future, then I can just give them the factors of [RSA-2048](https://en.wikipedia.org/wiki/RSA_numbers#RSA-2048). Either there’s a quantum computer no one else knows about, or there’s one that exists in the far future. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [January 26, 2024, 5:04am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/14 "2024-01-26T05:04:03Z")
The OP doesn’t seem to mention if you are traveling from the future, or from the past. How could you prove that you are traveling from the past? ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [January 26, 2024, 5:19am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/15 "2024-01-26T05:19:45Z")
I’m always traveling from the past. I can’t seem to stop myself. ---
**Author:** ![Banksiaman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/banksiaman/32/3334_2.png) [@Banksiaman](https://boards.straightdope.com/u/Banksiaman)\ **Post date:** [January 26, 2024, 7:35am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/16 "2024-01-26T07:35:32Z")
> [@Czarcasm](#): > > How could you prove that you are traveling from the past? Thanks to the good work of many people over a long period of time there are numerous now-extinct species. You could bring a living dodo, Stellers Sea cow, auroch or any number of marsupials, whose DNA can be compared to museum specimens. ---
**Author:** ![Banksiaman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/banksiaman/32/3334_2.png) [@Banksiaman](https://boards.straightdope.com/u/Banksiaman)\ **Post date:** [January 26, 2024, 7:38am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/17 "2024-01-26T07:38:08Z")
Or you could bring a dodecahedron and show everyone how it was an executive toy like the Roman equivalent of the useless Newton’s Cradle all along. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [January 26, 2024, 7:56am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/18 "2024-01-26T07:56:48Z")
> [@Dr.Strangelove](#): > > The result of applying SHA-256 to a randomly-chosen number several trillion times. While some hardware can perform this operation faster than others, there’s an upper bound to doing it sequentially, and the iteration count can be set so that the answer can’t possibly arrive sooner than some time in the future. > > I don’t trust stock market figures, natural disasters, etc. Butterfly effect and all that. The hash function is totally deterministic. Wut??? The non-deterministic nature of the future is precisely the point. If our claimed time traveler can consistently predict events in the future – all of which events are probably non-deterministic to some extent (even if due to quantum effects) – then that’s surely pretty strong evidence of something more than just information processing! ---
**Author:** ![Spoons](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spoons/32/3141_2.png) [@Spoons](https://boards.straightdope.com/u/Spoons)\ **Post date:** [January 26, 2024, 8:25am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/19 "2024-01-26T08:25:16Z")
If you’re going backwards, it would be easy: just look in your pockets. Coins minted in 2023, bills printed with the big portraits of Franklin, Lincoln, and similar. Pretty sure that none of these would go over in 1899. ---
**Author:** ![Q.Q.Switcheroo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/q.q.switcheroo/32/5713_2.png) [@Q.Q.Switcheroo](https://boards.straightdope.com/u/Q.Q.Switcheroo)\ **Post date:** [January 26, 2024, 8:34am UTC](https://boards.straightdope.com/t/if-you-were-a-time-traveler-whats-a-fast-and-easy-way-to-prove-that/996650/20 "2024-01-26T08:34:17Z")
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