# Would time travel make infinite coins?

I have a crap load of coins, enough to make 20 dollars USD. They fill up a relatively big jar. There is not an infinite amount of money in there though. There is a finite amount of money in the world. But one of the reasons that there is not an infinite amount of money in the world is that the US government destroys old money. So if you could go back in time, and take the money before the government or people destroyed the money without creating a paradox (time travel cloning) then could you have infinite money at a single point in time? In theory you could just keep getting money from the past and adding it to your stash in the future. Or you could travel to the future where more money (coins) is minted and take it back to the present. The same thing could be said with gold coins, silver coins, platinum coins, etc. Would this create infinite money, or would the money still be finite, just in larger amounts and with each individual piece worth a lesser amount?

If time travel allowed you to speed up the production of coins and recover destroyed coins, could you have infinite USD? Or is there still a finite amount of coins/money?

The point here is to determine if the governments and people's effective inability to destroy coins (since you can just recover them from the past) would allow there to be infinite coinage.

• As a side note, I wonder if people could still get rid of money in their time period, by dumping it in the ocean. They can't destroy it permanently, but they can still get rid of it. Commented Dec 14, 2022 at 22:48
• I think this is too entwined with the exact mechanics of time travel in your world to be answerable. In particular, you mention "time travel cloning" but does that mean you can steal the same money twice? Commented Dec 14, 2022 at 23:13
• Hello @Impala57, welcome to Worldbuilding. Please take the time to take our tour and read the following two Help Center pages (help center and help center) to better understand how to ask questions here. (a) Infinite would only exist in the case of infinite time, but we get what you're asking. (b) Time travel isn't real and there are no mathematical models to suggest any time travel rules. That means the only practical answer to your question is "yes, if you want it to." (*Continued*)
– JBH
Commented Dec 14, 2022 at 23:18
• ... Finally, (c) Just for fun, note that governments pay a lot of attention to what they're destroying. A LOT of attention. They record serial numbers and the expected number of coins in circulation and my point is that using the money you're stashing might not be as straight forward as you think. Of course, there's always black-market collectors willing to (*ahem*) launder some of that antique cash for you... except that it doesn't feel antique... odd that....
– JBH
Commented Dec 14, 2022 at 23:23
• Do you really mean "infinite" or just "more"? If so, then getting infinite coins logically requires infinite time travel. It also means that there are infinite time travellers with infinite clothing etc, which means that the world (and subsequently the universe) willonto be (see Dr Dan Streetmentioner's Time Traveller's Handbook of 1001 Tense Formations) a black hole of infinite mass from all the time travellers, coins, clothing, time machines and books of time travel verb usage rules... Commented Dec 14, 2022 at 23:38

### NO.

Your best bet is to go back in time to when bank rules and security were laxer. Ironically enough, your primary limiting factor in this scenario is --- time. In that you don't have enough of it to amass an infinite number of anything. Your secondary limiting factor is number of coins minted vs the number of coins you can reasonably obtain and transport through ordinary means. You don't specify some kind of 'magic' for getting & transporting the coins, so this means you're stuck either going to a bank or the Mint itself and making a withdrawal.

TIME... Withdrawals take time. Everything was done by hand, had to be recorded by hand in legers, and had to be removed from vaults by hand and accounted for by hand. Even if you took a ten thousand dollar bill into a large bank in NYC or Philadelphia, you'd be unlikely to maximise the number of coins you get. 10000 dollars in pennies is only 1 million coins. Banks are unlikely to give you so many pennies. They'll be giving you \$20 coins. That's still 500 coins, which have to be counted out and bagged up. This would probably be a 15 to 30 minute transaction.

TIME... Travel takes time. Setting up your time machine takes time, travel from time machine parking place to downtown takes time, travel from one bank to another takes time, travel back to time machine takes time, getting back to this timeline takes time. Call it 15 mins per. If you hit ten large banks in a day, that's an hour and a quarter or so travel time plus perhaps two hours in the banks themselves in the morning. Same for the afternoon. Seven hours or so doing business.

TIME... You've a long work day! You need to eat, you need to rest from your heavy physical labour, you need pee breaks. An hour for meals and an hour for rest and pee breaks gives you a nine hour day.

DAILY PAYOUT... If you got lucky and got 10k in pennies from each of the ten banks, you'd have ten million coins.

TOTAL PAYOUT... If you did this every single day for 100 years, you'd have 365 billion pennies. In the early 21st century, the US Mint churns out about 13 billion pennies a year. Your haul is approximately the total production of pennies from 1990 to 2020. Not quite "infinite" I'd say!

Depends on your time travel rules.

I struggle to think of where I got this idea from, but instead of, well, Dr. Who time travel, imagine time is written behind us like a book. If you go to the Lord of the Rings and rip out the page where golem falls into the volcano, it doesn't change anything. The next page happens anyway. It was already written.

Under this arrangement, the past can't be changed in any lasting sense. If you reached back to Aug 1, 2021, 5:06:34am, and took all the money out of your wallet, and brought it into the future, you will not have altered the past in any meaningful way. Aug 1, 2021, 5:06:34am + 1 nanosecond would find the money in your wallet. Like tearing a page from a book, you only took out a slice of the past, which did nothing to alter any other slice.

So yes, you could take infinite money (or as infinitely fine as you can slice time, anyway).

In some other time travel stories, you could also do this, but you'd just be taking the money from some parallel dimension, throwing off their story, but not yours.

In Terry Pratchett's Discworld, anything you do in the past echoes into the future, but in fact, you are already in the timeline where that happened, so however much money you steal is the amount you had to steal in order to be in the timeline you are in.

By Back to the Future rules, you'd probably just cause some unknown impact to your current timeline, possibly including the eradication of self. It's unlikely that the theft would go unnoticed ("where's the slag and ashes?") and the impact on the timeline would be unpredictable, so money theft is likely finite and very risky.

Realistically, any of these things would require "money" to be completely re-invented somehow, to prevent stolen timeline money from wrecking the economy. Perhaps crypto would resolve it.

• Aiiieeegh! You just caused my head to explode when I tried to imagine what crimes Sam Bankman-Fried would be accused of in a world where most investment banking transactions involve time travel. Commented Dec 16, 2022 at 3:18

With some basic assumptions, it is possible to have infinite "coins" at some point in time without any funny paradox business. Assumptions are as follows:

• Your time machine is able to perform an infinite number of operations in finite time (in other words, your time machine is also a supertask machine)
• Your universe has infinite empty space in which to store the coins at your chosen time. Your universe doesn't need to be completely empty, it can even have infinite matter if you like, but some infinite subset of your universe must be empty
• Your coins are unusually durable: they're indestructible, and are not subject to "aging" processes like nuclear decay, or at least not to an extent that they can ever stop being a coin, even if you wait infinite time

The process to obtain infinite coins is as follows:

1. Choose the timespan during which you want to have infinite coins. Something like "between 22:30 and 22:35 today" (though it can be arbitrarily long, it just has to be finite). We'll call those times Xstart and Xend.
2. Take one coin and put it in your time machine, or set it as your time machine's target.
3. Program your time machine as follows: "When I press the 'run' button, transport the coin to the first empty space at time Xstart, and start a 10-second countdown. When half of the countdown has elapsed (at 5 seconds), bring the coin back from Xend into the current time, to the same place where it was taken from. When half of what's left of the countdown has passed, transport the coin from the current time into the second empty space at time Xstart. When half of what's left of the countdown has elapsed, bring the coin back from Xend as described above. Infinitely repeat the process of transporting into the next empty space at time Xstart, halving the countdown, transporting back from Xend, and halving the countdown again. When the countdown reaches 0, transport the coin to some random space far in the future."
4. Press the time machine's run button and wait 10 seconds. Observe the coin appearing to flicker in and out of existence.
5. Enjoy having infinite coins when your chosen timespan comes around.

If you partitioned your space cleverly, such as defining the first few trillion "empty spaces" as being in or near your home planet, you'll even be able to interact with a finite subset of your infinite coins (or, if you prefer, "infinite copies of the one coin"). The vast majority of the coins will, however, be unreachable and invisible in the depths of space, at which point they will have little if any value.

If it's not obvious: the reason the coin needs to be durable is because it will have aged infinitely by the time the countdown has ended, and if it weren't indestructible, it would be almost certain to be destroyed by interactions with other stuff in your universe. The reason the coin should be transported elsewhere at the end of the countdown is because it might get very hot if it's exposed to stellar radiation. Also because it can be annoying to have a supertask without a well-defined end state ("the coin is transported away and then back at every other step, so where is the coin after the end of the supertask?").

No you can't have infinite anything, there is finite space and similar restrictions that make infinite anything impossible. As a random example taking the idea to the absurd eventually you would collect enough coins that their combined gravitational pull is so large that you create a black whole, at which point anything you add to that point in space is unlikely to qualify as a 'coin.'

But I doubt that is what your really asking. So lets ask instead could you have an effectively infinite amount of money with this system?

First it depends on your time travel mechanism. For instance if an item in the past disappears when you bring it's future self back then no. Likewise if your time travel is the type where you can't actually change the past then probably not.

However lets say you are using something more like the idea of parallell worlds, where instead of jumping to your past you are creating a new dimension identical to your past save for your presence in it. In this case you could bring things back in time with you, and continue to collect more.

The process here would be simple. at time X you leave a large quantity of money (or other thing you wish to duplicate). At time X+3 you travel back to X+2 with all your cash and pick it up again in that time period, doubling what you have. Then travel back to X+1 and X and pick up the money there. You now have 4 times your starting amount. Leave that at time X, wait (or travel forward in time) until X+3 and repeat the process for exponential gains.

You may run into duplicates of yourself from previous time travel runs if you do this all in one place, so you may want to move your money making scheme to a new location each repeat of this loop to avoid run-ins with past(?) selves and arguments over who gets to keep the loot.

However, money would not be a good idea for this. Money is very tightly regulated in the modern era, the government will notice if you start spending allot of this money and will end up assuming your a counterfeiter and shutting you down. The further in the past you go the less regulated money is, but the less you can buy with your money that's likely to be tempting to a modern time traveler. You also risk inflation and hurting the countries economy if you take enough money back in time.

Instead your better off bringing precious items that can be sold back with you. For example you could start with precious metals like gold and silver which can easily be exchanged for cash at a later point. Eventually you would see deflationary effects, you sold so much gold in the time period that gold is no longer worth as much money since there is an excess of it available. However, if you did this process with a few different precious metals you likely will be able to exchange them for a sufficiently large enough amount of money to provide you with everything you would want to buy without deflation of the metals being too significant. If you devalue the metals too much use some of it to buy something with more inherent value, like say coal or oil, and start to duplicate that instead to sell. Though you still might draw some suspicion if you suddenly have a massive amount of precious metals or fossil fuel to sell and no obvious source for this wealth.

Alternatively, and possible easier, consider going far back in time, picking up a few coins and hiding them somewhere no one is ever likely to get to them, then travel to the future and dig them up. These coins will now have a very high resell value as collector items. It's easier to explain away finding a large cache of rare coins through dumb luck to avoid people asking questions and may be easier to sell them. To avoid devaluing the coins by selling too many at once hide coins from different time periods and geographical locations so you have many types of coins to sell, or hide other non-coin collector items that different types of collectors may be willing to pay for.

Note you can not bring the coins back to the future directly, if you did that they would look brand new and thus be suspected to be forgeries. You need to let them age the old fashion way while ensuring that no one finds them until you are ready to dig them up.

Still too much work? Come out publicly as a time traveler, duplicate your time machine using the same process described above, and hire someone to use the duplicate machine to help produce value for you. Or just sell the time machine. Create a (quasi...) post scarcity world for everyone.