How do you prove you're from the future?

Question

Let's say a time traveler from the year 2100 comes back to the year 2015. He has a very important message: [horrible thing] is about to happen soon, and he wants to warn us so we can avoid/prevent it. (Yes, this assumes a model in which "paradoxical causality" is not an issue.) The problem is if he goes around saying, "I'm a time traveler from the future," no one's going to believe him. They'd dismiss him as a crackpot.

So, he brings along proof, in the form of...?

This is actually a pretty tricky question, if we place two restrictions on it:

1. He does not have a "time machine". His device sent him back without coming along with him, so he has no way to demonstrate that he's a time traveler by actually demonstrating time travel. (Just as an side note, this is very much on purpose; he doesn't want knowledge of the mechanics of time travel to fall into the hands of people who might use it for nefarious purposes, and part of his plan is to actively sabotage scientific research that led to the development of time travel.) The thing he used -- let's just call it a "time catapult" -- was able to send a small payload back in time, maybe comparable in volume to a phone booth, certainly quite a bit less than the interior of a car.

2. He wants to get the issue of establishing proof of identity over with and out of the way as quickly as possible and move on to more important things, like averting future disasters. This is a real issue; he can't go back arbitrarily far in time; the Temporal Frobulence Theorem shows that it becomes increasingly unsafe the further back you go; it's a bit of a stretch even to reach our time!

The two obvious candidates for proof are future technology and knowledge of future events. The first is tricky, because current technological advancement puts us perilously close to the boundaries of Clarke's 3rd Law: any sufficiently advanced technology is likely not to be easily recognizable as such, and anything insufficiently advanced would be likely to just look like someone working in his garage made a breakthrough in some field, and that's pretty cool and all, but it doesn't prove he's from the future.

The second is also tricky. There are two major classes of unpredictable future events: natural and manmade. Bringing official government records of earthquakes, hurricanes, etc. could certainly establish that he is who he says he is, but it would take a lot of valuable time for Mother Nature to furnish the proof. On the other hand, if he predicts unpredictable manmade events, there are all sorts of potential troubles there. Point out the time and place of a major crime? Obviously, he was in on it; let's arrest him! Produce a table of stock market closing values for the next month? Well, he might be right for a day or two (coincidentally, of course!), but as soon as someone starts using the data he provides and attempting to profit by making trades based on it, the Butterfly Effect flutters in and destroys the accuracy of the data.

So, what would be the quickest, most efficient way for our unfortunate herald to establish beyond a reasonable doubt that he is a time traveler with accurate knowledge of future events, and at the same time, get enough people to listen to him so he can spread his doomsday message?

Answer 1

I would say bring news videos from the future, near future, and of the events, needed, make sure that the news anchors shown are very prominent ones that would be hard to miss

Answer 2

I'd just write down the lottery winners for the near future before it's announced, hand them in to the people I want to convince, in an envelope, and ask them to verify after they're announced. After 2 or 3 times, they should believe.

Answer 3

Have someone ask this question, and then post this answer.

Hello all, I am from the future. I come from 2345 AD. We are looking for test subjects for our experiments, and we've been running short. All volunteers will be paid generously, using future cash, or, as we call it, "rubber". I can't say any more or this will cause a ripple effect. Thank you.

Answer 4

It can't be done. If you show me advanced technology, I will assume that you come from a society with advanced technology. If you make predictions of the future, I will assume you have advanced technology that can make those predictions. You might be able to convince specific individual people by targeting a message specifically to them, but any general future predicting or technology marvels are easier to explain without time travel.

Answer 5

I'll assume that the time machine can be used multiple times:

Step 1: Get some attention. Go to the pentagon, try to break the security and fail. This way some official people will hear what you have to say.

Step 2: Threaten them: "In 4 hours a bomb is gonna explode at some precise place." This place will be heavily watched after this.

Step 3: Send something from the future at this precise place and time. It can be anything, the important thing is that people see that an object has appeared out of thin air.

From here on out, people should listen to you a lot more.

Answer 6

The iPad one is interesting, but "theoretically" someone could have had a secret processing plant employing one million people, underground, working independently for 50 years, funded by an alien race if necessary. Anyway, the physics of an iPad was known in 1995, if not the mechanics.

So - what about simply predicting a solar flare? Or better still - bring a photo.

Answer 7

If this traveler were time travelling 'within one universe' instead of jumping to other 'local' universes in different states of relative co-existance, you immediate destroy the universe you 'jump from'.

If you are going for the more linear classic approach to time travel, the traveler could bring back something which co-exists in 2100 which is iconic and priceless to boot, but most of all unique - and dare the objector to prove falsehood.

Depending on how many universes you believe in (if any), you could tell them to damage it and then watch the corresponding damage occur. Go further and destroy the item and poof! It disappears. But if so, then so did the traveler's effort obtain it, because it never existed to bring back... but only because he went back with it was it destroyed in the first place. I know causality is not meant to be an issue, but it is! So I think you probably destroy the universe by going back in time at all - at the very least the chances of doing so rise geometrically (towards tangent 90, or something, per unit of observable time, probably). Regardless, he rips wide open the future, which has or has not happened. Perhaps he's beaten the odds? And of course he must, because he exists in the first place!

So I'd wonder whether this time traveler.... is there a future ahead of him with time travel?

My personal feelings are that future events are so intrinsically sensitive to present conditions that one irrevocably determine the outcome of the universe simply by doing nothing. Hell, I am just part of the universe playing itself out as intended, am I not? And if I never learned to tie my shoelaces until I was six, instead of five, for example - stuff like 9/11 wouldn't have happened.

Which is absurd surely? OR IS IT? Time travelling, and a pre-determined future (whilst the chances of one existing are non-zero, is definitely, definitely not our realm.

But yeah OK, causality is not an issue - if he were travelling linearly backwards and wanted proof, an object he could bring back might be something like a radioactive vial with a unique signature of something which has shown measurable decay. Perhaps also the traveler possesses a residual charge of something, or has a little extra amount of 'entangled' particles in all his orbits. A quantum signature.

/BLURT

Answer 8

Bring a future weapon. If I know humans, we continue to grow better at killing each other. Why a weapon? Well, if you are going to the past to change the course of history, that means you are interrupting the plans of powerful people, leaders (upsetting them at least). Once they are on to your motivation, they will try to silence/terminate you even if they are convinced you are from the future. I would even bring a doomsday device as an insurance policy. If the future is so bad that you were sent to the past to alter it, would it really be that bad to destroy the world in the past if your mission failed?

Answer 9

I don't think there is a way to prove that you're from the future without showing off your TARDIS. Yes, you can predict forty trillion data points accurately, but we as a species are far too skeptical. However, this is meant to be more constructive than a simple "No" so here we go.

Given the rate at which science is advancing, it's fairly safe to say that new fields of study will pop up in a hundred years time. Instead of showing off massive advances in robotics, or matter manipulation, show off a new kind of thing, as alien as my cell phone is to Socrates. Most people will still have a little bit of doubt in their heads, so reveal the quadrillion data points ya got. Give stellar maps that show galaxies and planets that are too far away for the light to have reached us yet. Do all the other things these answers say. Before you leave for the past, study all kinds of stuff; biology, robotics, computing, chemistry. Make sure you can answer any question a scientist can throw at you.

Answer 10

We're talking about around 100 years of history and rather than proof, I see credibility as a bigger problem, proof is worthless without it.

Assuming there is no language barrier, even if the protagonist were speaking the same language as the people around him it would be language separated by around 100 years or gradual change. Look at how laughable films from the 1950s look now then invert the context that 1950s language, attitudes and social mores are the norm and the observer is in a minority of 1.

Credibility issues are common to history documentaries. They use the viewer's "modern" perspective to frame events in a way that conforms to biases. A quick glance at 20th century newsreels containing "white man's burden" topics underlines what I'm driving at, all of them from less than 80 years ago. The concept of "modern" is very nebulous and changes from generation to generation.

History is not an absolute - it is simply an interpretation of events and the present is a huge jumble of events with future implications interpreted by the conventional wisdom of that time.

So even with future hindsight, the future time-traveller would have to choose several events that the people of that time and geographic location would care enough about to want to have their preconceptions challenged, and would likely fall foul of any powers that had vested interests in seeing an outcome to fruition. Lets say traveling back in time to stop the birth of Islamic State cells, a little shy of 20 years ago, would pit the protagonist against a hawkish American government policy intent on invading Iraq using a "for us or agin us" approach to anything seen as being critical, and using kidnapping and detainment in Guantanamo Bay against people they deemed to be "enemy combatants".

Answer 11

If your time traveller wants to prove they came from the future, you don't send a man you send a woman instead. Because she will be wearing clothes of her own future time. But just to be sure, she carries an extra set of her underwear. Why an extra set of her underwear? you chime. The answer's quite simple. No garments change as much as women's underwear.

Think how much difference there is in the styles, construction, and materials of underwear between now and, say, sixty years ago. Any woman in 1950 being shown a set of contemporary undergarments would immediately recognise how much better they were and wouldn't take much convincing they came from the future.

Using underwear as your future person litmus test doesn't lead to any problems with reverse engineering or likely causality violations. Also it's simple and readily portable.

Since a picture is worth a thousand words then picture this and for good measure this too.

Answer 12

Get the largest prime number found from the future.

Now 2^74,207,281 − 1 is the largest prime number. If he is from future it will be larger than this number.

So he can prove he is from future.