Imagine this situation:

One warm night of 1890, you go home from a pub. You pass a creepy house. In the half-open door, you see the outline of a machine. You go in, and open the lights. You see a big machine, exactly like those time machines you imagined of when you were small. You sit in it, pull the lever, and... you fall out. The worlds goes black.

Then, you wake up, and you see everything is different. It isn't nighttime anymore, the room you are in looks a bit different then you remembered, and... there are two city officers shouting on you what the hell are you doing here. You ask, "What year is it?". "1890" "What!? Are you kidding me?" Sounds like you just got drunk too much last night. But the problem: They think you came from the future! That this is some kind of modern 20th century time machine you are on. The guards insist you come with them to some place and say something about time travel. You exclaim: "But I'm not from the future!" "We're not going to let you run just like that! You just came from another time and we're gonna let you go? No way! Now come on!"

So you screwed up. Again. How on Earth can you prove you're not from the future to a 19th/20th century person? How could you prove this to a 21st century person?

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    $\begingroup$ Why would you need to prove this to a 21st century person if you’re in 1890? Are there reql time travellers present also? $\endgroup$ – JDługosz Sep 29 '16 at 21:08
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    $\begingroup$ @JDługosz Why did people need to prove that they weren't sorceresses of the dark arts, once upon a time? $\endgroup$ – Ranger Sep 29 '16 at 21:18
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    $\begingroup$ What does that have to do with my question to the OP? $\endgroup$ – JDługosz Sep 29 '16 at 21:19
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    $\begingroup$ @JDługosz I'm saying that if there are or are not real time travelers... it doesn't actually matter. Further the need to prove is actually outside the scope of the question. The question is about how to prove. $\endgroup$ – Ranger Sep 29 '16 at 21:21
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    $\begingroup$ He asks how a person in 1890 can prove he’s not a time traveller to another indiginous person and to a person from the 21st century. That seems odd and requires more explaination. If there are 21st century visitors to 1890 then he may be mistaken for one of them? We need better explaination to figure out what he’s asking and in what context. $\endgroup$ – JDługosz Sep 29 '16 at 21:26

How did people prove a lot of things during that time period (and to this very day)?

Find people who believe your story.

"Officer, my boss, Bill Waggoner, at the docks will vouch for me. As will my ma Donna Smith, and my pa, Jacob Smith. In fact the Browns--you know, the ones that run the shop just outside of town--will vouch for me. I grew up alongside Bill and Mary!"

Same works in the modern day; enough eyewitnesses. Modern day we get a few more methods in developed countries, as in the US (for example) you'll have public records aplenty.

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    $\begingroup$ This is the same solution governments use when issuing security clearances to make it harder to inject a spy into their midst. They ask for years worth of past residences and work locations, along with people that can vouch for your existence during that time. If they see enough paper trail, they can assume that you did indeed exist for at least 10-15 years. That means a spy needs to have a good backstory for 10-15 years (or a whole lot of people who will lie for them about what they've done) $\endgroup$ – Cort Ammon - Reinstate Monica Sep 29 '16 at 22:59
  • $\begingroup$ But someone from the future could have learned all that stuff, with leisure if it is written down anywhere or with relative ease if they have used the time machine for multiple visits. I don't think this works as a proof of identity in this case. $\endgroup$ – SRM - Reinstate Monica Sep 30 '16 at 1:14
  • $\begingroup$ And not just learned, but also forged a backstory. Once a time machine gets involved, conspiracy theories really start to pile up. This is a really tough question, IMO. $\endgroup$ – SRM - Reinstate Monica Sep 30 '16 at 1:47
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    $\begingroup$ @SRM Just learning won't cut it. The officers then go and verify what he claims. If others back his story, the officers either have to believe him, or go off on a grand conspiracy tangent. $\endgroup$ – Ranger Sep 30 '16 at 12:49
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    $\begingroup$ Yes, but police have limited resources (like time). So they will likely find locals vouching good enough. What is more plausible; one guy at the wrong place at the wrong time, or a guy coming to the past and planing a host of people to claim he was there all along? It's easier to believe nothing is actually out of the ordinary than your town is overrun by people from the future. And if the later, what can the police reasonable do about it? $\endgroup$ – Tezra Sep 30 '16 at 18:21

I've got one good idea: quiz them on local news.

If this time traveler really is from the future, he'd know about big historical events, like wars, country elections, mass-murderers, etc. What they DON'T record is small-time news, like celebrities, store/school closings, etc.
So kids, if you suspect that you're speaking to someone from the 24th Millenium, just quiz them on the latest celebrity break-ups! If they don't know who you're talking about, then they're obviously from the future!

Well...at least that's just one idea.

  • $\begingroup$ Not necessarily true. If you quiz anyone over (let's say) 50 years old who Justin Beber is, they wouldn't know. Bottom line small news is not worth knowing anyways. $\endgroup$ – NuWin Sep 29 '16 at 23:45
  • $\begingroup$ And they could be lying. Not much of a proof. The question asks us to prove a negative. That's tricky. $\endgroup$ – SRM - Reinstate Monica Sep 30 '16 at 1:11
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    $\begingroup$ During the Battle of the Bulge, a German special ops team pretending to be Americans raised a good deal of mischief behind the lines. A common question used when encountering a stranger was something like "Who won the World Series?". Of course, this made life pretty hard for people who didn't follow baseball. Same principle (and same limitations - not everybody follows local news). $\endgroup$ – WhatRoughBeast Sep 30 '16 at 2:00
  • $\begingroup$ @WhatRoughBeast Famously, a sentry asked a suspicious looking General to tell him the capital of Illinois. When the genuine general answered, correctly, that it was Springfield, the guard arrested him - because the sentry thought it was Chicago... $\endgroup$ – Oscar Bravo Jan 4 '17 at 15:55
  • $\begingroup$ @NuWin they're a time traveller ... from the past. Try asking them about jazz musicians. $\endgroup$ – Andrew Grimm Mar 24 '17 at 7:49

Use your body and the records of the current date as proof. This is assuming that they are not accusing you of being originally from this current time and far out in the future, for at least a few years.

Find your birth certificate or some other identifying documentation - the certificate will show your date of birth. Yes, these can be forged by you, so more identifying information or papertrails will help. This is easier in the 21st century where your data may be in databases that are harder to manipulate. From there they can examine your body to see if you are older than offically listed. If you are the same age as on the certificate, you are likely not from the future.

If you have recent photos where you're standing next to someone you can find or have a landmark or datestamp, those can be looked at to compare your age to see if you are from this time. Security cameras, dental records, drivers license, and other records that can tie you back to your current time will also help.

Piggybacking on the idea that people can vouch for you: with the officials monitoring, those people can ask you what you ate at the carnival with them last week and other detailed questions that would be forgotten in a few years, or they can even even say you look the same and have had been wearing the same shirt for months now.

If you aren't allowed to collect external evidence and is stuck where you are, you could argue that you haven't gotten any futuristic enhancements. Your accent and manner if speaking is the same as the area - if your were far out in the future your accent is likely to change. Even if you practiced it would be difficult to get accurately. If you have had some kind of procedure done or an ailment that you think would be cured in the future, you could pose that too -"why would I be stuck with poor eyesight when it might be an instant fix in the future?"


A) Couldn't you just say you have committed no crimes, or they need a warrant or whatever legal reasons to investigate you? Even if you time traveled, the legal system doesn't punish time travelers, nor is there any reason for interrogation to happen in the first place.

B) Even if the officers have reason / probable cause to investigate, which A) specifies they do not, people are innocent until proven guilty, not guilty until they prove self-innocence. So even if your rights are violated, and you are probed, the court system will refuse to believe time travel occurred because they can't prove it happened - not because you can't prove it didn't.

  • $\begingroup$ But the're trying to get the time machine technology from me, even if I don't have any! (+1 for the answer) $\endgroup$ – RudolfJelin Oct 22 '16 at 19:56

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