# Designing a time thief proof safe

I'm a time traveler. Yes I know it's amazing for you to grasp but once Jebsus invented time travel in the mid 54th century we all became time travelers (he open sourced it).

Now recently I came across a ring made of foreverium I would like to keep safe, said ring is one of a kind & can't be reproduced as it is made from the entire universe supply of foreverium atoms, a material which was only created in small quantities during the big bang. Aside from its rarity you can consider it being a normal ring in every way that matters.

Said material also makes this ring very expensive & I would like to keep it safe, the problem is how can I design a safe place to keep it when every thief on Earth can just time travel to a period where the safe\alarm\etc broke down due to rust\old age\etc?

You can assume the following:

• foreverium will always keep its state & shape.
• There is no more foreverium than what's in the ring.
• I can't move the ring or safe, I need to pick a spot where it will be safe,
• No living guards, the future is fully automated.
• Machines have a shelf life, no matter how long it is it will break at some point so the thief will be able to just time jump after that date to bypass a broken machinery.
• Money and resources are not a problem, if it can be done I can afford it.
• I can't hide it somewhere it will never be found, time travel leaves a very detectable signal which means every step I've taken in life since my first jump (which already happened) is tracked.
• Time travel is easy, it takes nothing more then a special wrist watch everyone has.
• In that case, store it in the lava of Mount Doom. Take a couple friends and walk there, make new friends along the way. When you want to retrieve it, drill it out of the granite. Set your ephemeral machines and lackeys merely to prevent anybody else mining upon your claim. Sauron might make a good lackey, he's long lived and comes with excellent references. – user535733 Sep 20 '19 at 12:23
• Uh, what's to stop someone travelling back in time before you acquired it, and taking it for themselves? Or killing you before you acquired it? Or marrying one of your parents before you were born so as to become your father or mother (or whatever), and then killing you and becoming the executor of your estate? Or... etc etc ad nauseam. Time travel wrecks everything. Don't be doing that. – Starfish Prime Sep 20 '19 at 12:45
• You're going to need to provide more constraints on your time travel, especially on how malleable the timestream is.. If the past can be changed freely, the item will be acquired at the first point possible during a fight between the most powerful and ruthless time travellers capable of going there, possibly killing you in the process, before you can secure it. If the timestream can't be changed, just ask your future self if and where he kept it. – notovny Sep 20 '19 at 12:47
• "There is no more foreverium than what's in the ring." y'know, that's a slippery concept, when you can time travel. You've got the ring, now you can travel forwards in time, collect it from yourself, then you'll have two rings... – Starfish Prime Sep 20 '19 at 14:14
• Also, a small problem: why would anyone want to steal it from you? I mean, you're not immortal, right? You're going to last 0.0000000......0000000003% of the time span of the universe. Couldn't they just snag it at some point where you're not alive? Even if you're jumping around, it's not like you're going to occupy a larger percentage of the timeline than before, so that ring's going to be awfully unused if it's just you with it. – Kevin Sep 20 '19 at 23:12

# Just track it

Since:

1. Nothing other than foreverium is forever
2. You're a time traveller

There's no real reason to worry about this ring, whoever has it right now is as ephemeral as any security system. All you need to do is know where and when the ring is at any given point and you can pick the thing up.

Wait until the end of time if you want to and just collect it when everyone else is done trying to keep it. Though finding out where and when it was made and collecting it direct from manufacturer would be more fun. Given the nature of the ring, the skills and knowledge of the manufacturer are far more valuable than the artifact itself anyway.

Let's consider a simple example.

## The bedside table:

You don't want to be wearing the ring today. Leave it on your bedside table here and now. Collect it from here and now when you next want it. Time travel is like that.

• Oh, I like the bedside table idea. It is always safe because it is either on your person (assuming that is a safe thing) or on the table where literally no time will pass in which bad things could happen before you collect it next. +1 for that. Hell, you could skip the table and just give it to yourself. – Starfish Prime Sep 20 '19 at 12:55
• How does this make it safe? It's vulnerable to a simple mugging. – Innovine Sep 20 '19 at 16:06
• @Innovine Or: Someone tries to mug you. Time-Police show up, stop the mugging, and arrest the criminal. You go down to the TiPo station, give your statement. They then send cops to stop the mugging, and arrest the criminal. Combined with regular "check-ins", and if you miss one then someone shadows you from the last check-in. If you die in the past, they can retrieve your body so as not to contaminate the timestream. If they save your life, you skip the next check-in, and go to the one after. (Check-ins are regular in real time, not your time) – Chronocidal Sep 20 '19 at 16:40
• [knocks on bedroom door] Hey, I need it today. - Dude, this is like the 12th time in half an hour. - I know. I'm sorry, me. – Mazura Sep 21 '19 at 2:15
• Bedside table: one of the characters in the Magic 2.0 books does this with his toilet. He travels back to his present any time he has to go, rather than dealing with period facilities in 1452. The other characters remark on how much water his landlord thinks he's using. – Draco18s no longer trusts SE Sep 22 '19 at 18:37

The correct answer is to just join the crowd of time travelers getting their own foreverium ring at Evaporation Point.

Think about how you've described your foreverium ring for a second. It's immutable, unalterable, and undecay-able. So, what happens when the universe goes old? It survives heat death, it survives particle decay, and it survives at the center of the black hole that our galaxy will eventually turn into. And at some point, ~$$10^{1000}$$ years from now, that black hole will finally evaporate... leaving behind a foreverium ring.

Hah, no, just kidding. It won't leave behind one ring. Because if Alice decides she wants to grab a ring after that evaporation point and go back in time with it it... well, then, there'd be two of those foreverium rings in the past, wouldn't there? Which would mean there would actually be two rings when the black hole evaporated - the original one, and the one that Alice took back and had actually gone through the process twice. Which means there's one for Bob as well... except, if there were two people picking up rings, then there'd actually be three rings available: the original, the one Alice had, and the one Bob had.

In fact, you could have ten million people time travelling to Evaporation Point (the coolest spacetime point in the cosmos! Join the crowd!) and there would, conveniently enough, be exactly enough rings for everyone that shows up... with one additional ring left over.

• That's one hell of a paradox... being one of a kind made it not be one of kind. – cypher Sep 20 '19 at 21:29
• The ring is given away as a door prize at the end of each meal at the Restaurant at the End of the Universe. – Avi Cherry Sep 20 '19 at 22:30
• I think it's safe to assume that you wouldn't be able to time travel past "evaporation point" (at least not and survive - unless you yourself and your time machine are all made of foverium). Hence there will only be one ring at the very moment of evaporation point. – David Ljung Madison Stellar Sep 21 '19 at 1:10
• @Michael - the true cause of the accelating expansion of the current universe is the gravitational side effects of exponentially large numbers of future time travelers visiting the past. However, eventually they will be surpassed by the number of past time travelers visiting the future, resulting in an opposite effect slowing and reversing the expansion of the universe, leading to the Big Crunch. – Paul Sinclair Sep 21 '19 at 2:24
• @DavidLjungMadison it depends on how time travel works in this question's reality... For example if the time machine 'teleports' you to the evaporation point you weren't there for the universe collapse so you skipped it. – beppe9000 Sep 21 '19 at 17:03

When you are done with the ring, give it to yourself the next time you need it and then when you need it again go back to when you were last finished with it to receive it from your past self.

The ring then only exists when you are using it and there's no need to store it at all.

If it's stolen while you have it, go back to before that and tell your past self, take the ring, and then return a point after the theft would have happened.

When you are done with it and you don't meet a future self coming to receive it, you no longer need it and can throw throw it away. If it still had any value for you after that, you would have come back to get it. It can not be stolen at that point because someone else having it does not deprive you of it.

The retropreemption of the ring being stolen directly from you does the problem of being a causality paradox. If you prevented the theft from being possible, why did you go back? The thief might also just kill you to prevent any future you from stopping the theft. You could try to find out whether your future self will be murdered and prevent that, which just causes more causality paradoxes.

Theft while you have the ring out of the storage (or in this case the absence of storage) isn't really a problem with the storage (or absence thereof) though so even if it doesn't work because the wibbly-wobbly timey-wimey won't allow the paradox, it's somewhat outside the scope of this question anyway.

It's somewhat irrational to worry about theft if time travel is ubiquitous. If the item mysteriously disappears, you can just travel back in time to when it still existed, and take steps to prevent it.

Moreover, thieves cannot hide. Every location is space is essentially under surveillance. At any point where some crime occurred, anyone can travel backwards, and by a binary search process, zero in on the time when that happened, catching the criminal in the act.

Under the parallel futures interpretation of time travel, there is no issue. Anyone can go back to a time and place just before something got stolen, and chase a parallel future in which that is prevented.

Install a time-machine alarm. The moment your safe fails or is on the verge of failing it sends a signal back to you. Now you can zip forward to that moment. Either replacing the safe with a new one or taking the ring back in time and placing in a brand new safe.

Repeat and rinse. You will remove the ring from the safe before any thief can strike. This will give a lifetime's hobby to keep you out of mischief.

This answer assumes you have placed the safe containing in a safe spot or several safe spots (depending on how many times you go forth and back to the future).

• You should get a signal the moment you install the device. If you don't it means that no theft will occur in this timeline. Or you may not get a signal at all depending if time traveling generates timelines (the alarm system travels back in time and then sends the signal to you). – beppe9000 Oct 16 '19 at 18:25

The safe is a self-replicating Von Neumann device. You put the ring in the safe and enter a secret timespace coordinate. The safe replicates 10 copies of itself and transfers the ring into one of the copies. Then all the safes teleport away to random spacetime coordinates in inhospitable locations. At those locations, they replicate again. And teleport. And so on. Until eventually, after many hops, the one with the ring teleports to the secret coordinates you entered originally. You go there to retrieve the ring. Anyone wanting to get the ring has to either know the secret coordinates or has to track the safes... all the safes... the exponentially increasing number of safes. And they have to do it from those inhospitable locations (lava, Jupiter core, black hole, etc.).

• You missed the part where it is not movable... – Dagelf Sep 22 '19 at 22:32
• @Dagelf the system was designed to go to a fixed location (your secret coordinates) — that’s what I took by the requirement that there be a fixed location. Time travel is cheap and easy... the fixed location has to be because they want to give address to someone else. – SRM Sep 23 '19 at 0:48

Charles Stross, in the Merchant Princes series, had his characters deal with similar security problems in an analogous situation (certain people, while not able to truly time travel, could travel back and forth between the same place in alternative histories in a many worlds hypothesis type scenario).

For example, often they would put valuables at high elevations in places, where for some reason alternative historical timelines would not have been able to do so.

In some ways, a time travel scenario is easier. You just need to find a place that will stay in its current land use for more or less eternity and lock it up.

How about having the safe itself (running off a permanent power supply of unobtanium or solar or something) autonomously jump around in time, analogous to spread-spectrum digital radar operation? You know the pattern and thus can get to it when you want to, but the chances of anyone else being able to track it are rather slim.

• "time travel leaves a very detectable signal which means every step I've taken in life since my first jump (which already happened) is tracked." Presumably, this means your safe will be trackable by the same method – Chronocidal Sep 20 '19 at 16:02
• @Chronocidal Well, seeing as an Ainsible can only transport non-living stuff, I'm willing to believe that only living things leave a time-travel signature :-) – Carl Witthoft Sep 20 '19 at 18:42
• Where are you getting that from? The standard definition of an ansible is an FTL communications device - capable of transporting Information, not Matter. The question makes no mention of ansibles at all. – Chronocidal Sep 23 '19 at 7:37
• @Chronocidal you are correct -- I should have said "runcible," or perhaps referred to LeGuin's "Another Story or A Fisherman of the Inland Sea" in which the narrator hopes to extend ansible to "churten technology" , thus transmitting matter instantaneously. – Carl Witthoft Sep 23 '19 at 13:44

Use cloning via time travel. Put the ring in a really good safe, close it and pick it up again in future. Come back to time few minutes later today, open the safe and put the ring next to the ring that is already in the safe.

Repeat, until you have enough rings that losing one will not be a problem. Scatter them everywhere. Observe the price and value of your ring to drop.

• You do get that a looped object is still a single instance, right? If you remove the original ring from the safe then all instances looped after that point no longer existed. Realignment of the timeline to prevent paradox would erase all interactions with the rings throughout time. – Corey Sep 22 '19 at 22:51
• I thought you can go back in time and meet yourself. Besides, how can event happening in future (removing the ring from safe 100 years later) affect something that is now (someone steps out from time machine with another ring). The time travel is itself a paradox, so we can hardly order a rulebook from Amazon to check this up – Congenital Optimist Sep 23 '19 at 8:55
• @Corey the looped item would be gone from the future timeline (until its new timeline catches up). But if the ring is on the table at 1:00 and you steal it at 1:05 and go back to 1:00 you can put it next to the ring that wont be stolen until 5 minutes later. Then you can watch yourself arrive to steal the ring... and suddenly have to make a choice which ring you take, left or right, or maybe you take both rings, then 4 rings, then 8 rings... – Demigan Sep 23 '19 at 16:55

It heavily depends on what kind of time travel you want and how easy it is. But considering that stealing it from a passed or future isnpossible it limits the options. if you truly want to build a safe then you could simply build an inconapicuous container and send it to a point and place in time where no one else is at that point in time. You send two things: the first arrives 1 minute before and is a bomb designed to kill anyone that arrives within a minute of the ring's location. The second is the ring itself in a safe, the first time travel track obfuscating then second. If you want it you go to that exact point in time and space to collect it while from the viewpoint of the safe it arrived seconds before. You can even leave defenses that last only a few days, as that is more than enough for you to come collect it. The safe can be build to take a day or two before it can be transported or broken open by people without the keycodes/keycards.

But time travel might not be that easy. It might be available but you cant just pop on over anywhere constantly, so you want it somewhere you can reach without time travel. The easiest solution to that would be to place it somewhere no one will look, like a high-energy reactor that is necessary to keep your environment running. It is foreverium and can withstand anything (which begs the question of how it was forged). So placing it in a dangerous environment that people think is necessary for their own survival seems a great place to (secretly!) hide something. If necessary have a fake hiding place and act like the ring was just moved somewhere else when someone comes looking. There are some hidden batteries allowing you to deactivate the reactor long enough to grab the foreverium when you want. Since foreverium is unmuteable it cant become toxic or radioactive itself as long as you wash the particles off.