How could an inter-temporal banking system work?

Question

(This question is meant to be an improvement and/or replacement for How would you bring wealth back to the past?, which some users have argued is off-topic for this group.)

Imagine a future world in which time travel is not uncommon. (Think of it as being like intercontinental travel today -- something that lots of people do, but it's pretty expensive, so most people can't afford to do it more than a few times in their lives, if ever.) In such a world, an entire infrastructure would eventually grow up around time travel: for example there might be temporal travel agents who would book your entire trip, complete with false identification papers and lodgings at your destination time. There would also presumably be some kind of inter-temporal law enforcement.

And, of course, there would probably need to be some kind of banking system. After all, the main users of time travel are the wealthy, and the wealthy are not going to want to travel back in time without access to their funds. An inter-temporal banking system would have to function as a bureau de change, exchanging currency from one point in time for currency from another. Such a system would have to cope with the "exchange rate" produced by the effects of inflation over many years, and would have to grapple with the fundamental problem of transferring wealth across time without it losing value. How could such a system function?

In posing this question I am specifically not looking for "get rich by betting on sports or buying stocks" answers -- that kind of personal enrichment would, I assume, be prohibited by the inter-temporal law enforcement as a form of fraud. The question here is not "How could you make a lot of money in the past?", but rather "How could a banking system move money from future to past?"

Moving money from past to future is of course simple: you just deposit it in an account in the past and retrieve it when you return to your point of origin. Presumably the legal system would have to figure out some way of preventing everyone from enriching themselves via a long-term interest scheme -- it would be pretty disruptive to the economy if everyone who could afford a ticket to the past just invested their money in a savings account and came back to their point of departure a billionaire! -- but the basic problem of moving money forward in time seems easy to solve. How would a banking system handle the problem of moving money backward in time without disrupting the economy at either the point of origin or their destination, and without screwing up the timeline along the way?

Answer 1

I’m about to hand wave a whole bunch of time travel paradoxes, tropes, and mechanics away.

This question is thinking about temporal monetary transfer the wrong way. Why would a bank want to move present day funds into the past in the first place? There seems to be one obvious reason: people want to access their money during their time traveling adventures. But why would a bank try to actively manage currency across geography and time? That seems tedious — depending on time and location the items and currencies that hold value could fluctuate wildly, not to mention that you’d need to reliably hide it from citizens of the time. And in the question you linked, we’ve found that knowledge is truly the best way to gain wealth in the past. So how do we combine these two?

The “bank” functions as a guardian of historical knowledge surrounding past funding events.

Using knowledge to gain wealth in the past sounds great until you want to visit some small town in Africa in the year 854. Knowing the Super Bowl winners or lottery numbers isn’t going to help you there. And Google (or your futuristic search engine of choice, probably Google) is unlikely to help you get much further. Sure, you could go back and try to sell some modern technological knowledge or invention, but who wants to go through all that work just to be able to eat and sleep at your destination?

This is where your “temporal bank” steps in. You see, they have employees and contractors who scour geographical locations throughout history for accessible events that, with the right knowledge, you could utilize to acquire money in that time and place. Events like that local horse race outside a small Asian village in the early 300s BC for which no written record still exists. Over time they build a vast archive of these events — most of which would only have value to such a “bank” and its customers. When the excited time traveler comes knocking with hopes to transfer some money to the past, the bank looks up suitable events at times and locations near your destination that most closely match the money you want to acquire in that time period. And then they sell you the knowledge you need to access it. The bank takes possession of your modern currency and you can now easily acquire your currency in the past at a time, place, and type that is of use to you.

Answer 2

Moonlight as... a bank

There are a million ways to make this work if you own a bank. Banks don't typically have all of their money tied up in actual physical cash, so value can and has been assigned and moved around in many other ways. Use any of these 'back channels' to move money from the future version of the bank to the past. If you continue to move value from the future to the past, the future runs out of money, so you need to use a small portion of the money going into the past as investments, so that the future doesn't lose value.

Go back in time and acquire a bank somehow. As people use the bank (in the past), grab as much old cash as you can, and send it back in time to yourself. With regular shipments, you should have plenty of actual cash for use as spending money. If this isn't enough you can write a check you your past self, and make your past past self cook the books so its untraceable.

Answer 3

No different than a modern bank or currency exchange

There are going to be two groups of currency, the our-future/their-present currency (designated as F\$) and the our-present/their-past currency (\C$). C\$ currency can be any currency from any time/place but for simplicity sake, I'm just going to refer to it as US\$.

Functional Equivalents

• Time Travel = Jet Travel. You get in a box or a tube, wait a little while and arrive at your destination. There will be customs/border patrol when you go and come back. Probably medical quarantines too if the traveler is going someplace sufficiently interesting.
• Time Travel Agency = Travel Agency. You traveler will need someone to make arrangements when you arrive. Someone will need to map out the places that rich people would want to go.
• Currency Exchange = Currency Exchange. Whenever a traveler goes to a new country not denominated in the traveler's native currency, some funds will need to be traded into the local currency. That the traveler is going backwards or forwards in time is irrelevant to the transaction.

Bank Considerations

As the owner of the bank, you will keep a single ledger of your customer's transactions in F\$. You don't know, nor care if they are going to Earth:Europe:10,000BC or Magrathea:North:10,000,000 AD. The traveler's transactions with you must be strictly linear. If these interactions can't be made strictly linear then you need to invent new ways of doing accounting. Government regulation of the currency will help a lot with this.

Currency Exchange Operations

If you run a currency exchange for these time travelers, you'll need to keep on-hand sufficient quantities of currency to sell to time travelers. Just as on Earth in 2018, currency is a commodity that can be traded.

Buying from the Exchange The traveler will purchase the required amount of destination C\$ for some price denominated in F\$. Depending on the market, this will be either really cheap, or really expensive depending on supply and liquidity. The dynamics here will be very similar to modern currency exchanges on Earth.

Selling to the Exchange This is the really tricky part. If travelers can go back to arbitrary points in time, as many times as they like, then they have the chance to create arbitrary amounts of wealth. The schemes to make money using time travel are innumerable. ...Although, maybe that just means that the price of C\$ approaches zero when trading with the currency exchange in F\$ because the supply of C\$ is so great.

So, someone creates a ton of cash by investing in Nintendo in the 1990s then cashing out at the top of the Wii craze. First, they would need to get that currency in a form that will survive time travel, so physical bills. Hauling it back to the future will carry some cost thus preventing the sell price of C\$ from reaching zero.

My assumption is that wealthy people trying to make an extra buck from their travels will bring back unique artifacts that are not currency at all. These artifacts can be sold for F\$ to collectors.

Government Regulation

Enabling this kind of time travel would require a currency that knows where and when it is in time. There will also need to be strict laws and sufficient safeguards to prevent the F\$ from being doublespent and devalued. Some kind of forensics to detect if the F\$ has done any time travel will be essential.

Time travel with F\$ will be strictly prohibited; punishable by confiscation, fines and imprisonment.

Answer 4

Ok, we've established a pan-temporal agency to police time-travel to ensure no negative reprecussions on the future.

Given this, we can be sure that we have a presence at any arbitrary point in the past.

Sending wealth back 50 years is hard - But sending wealth back a year is pretty simple. So you just send wealth back 1 year, 50 times. Gradual drift in the concept of wealth and valid currencies is handled over the course of history, organically, just in reverse.

Answer 5

Bitcoin is the answer

Briefly, blockchain is a ledger shared by an entire network of computers, often to track transactions of things like currency.

If you built you built a network of computers to communicate with each other throughout time, you could create a non-physical currency that could be used in any time period(each transaction would be time-stamped, of course)

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One big assumption here: pocket dimensions outside of time exist, not unlike Issac Asimov's The End of Eternity, and Intertemporal communication is easy and used everywhere. https://en.m.wikipedia.org/wiki/The_End_of_Eternity

Answer 6

If you want to go back a few hundred years, your middle age peasant isn't going to understand whatever trans-temporal banking system gets dreamed up. It may be that you use bitcoin or something to trade with other time travelers, but to trade with the locals, you want historically relevant valuables. Like gold coins. Naturally you need a shop that will sell you gold coins as in use 300 years ago. Also available are spices, dyes and drugs that were valuable at the time.

For long time periods, the laws of increasing economic productivity cause things to get rather silly. If oodles of middle class people start going back 10 000 years, and bringing a load of mass produced iron tools, the amount of real ironware in that time period could be negligible compared to the amount brought by tourists to trade. For that matter the population of genuine cavemen could be far less than the tourists. If you take the techno-optimist position that earth has a long and happy future ahead of it, then the earth should be jam packed with time travelers (literately a K2 civ could easily have populations in billions of billions, if it lasts as long as history so far, and 1% of people go back for a week every few years, That still puts hundreds of trillions on earth. Packed crowds over the entire surface. A k3 civ lasting to the last stars burn out, and the weight of timetravelers creates a black hole.)

Another question is what laws are being enforced and why. Is, "Bob was hit by a bus las week, we're going back to save him" allowed? If so, what about "great uncle Bob was shot in WW2 ..."? Taken to its logical conclusion, everyone throughout history would be subject to advanced and prescient medical care. History gets replaced with techno-utopian future in its entirety. Even if everyone is entirely selfish, ancient kings will still have access to modern medicine. You need to have a good reason not to disturb history, especially when everyone else is trying to enrich their past selves. Once you have a coherent world that contains time travel and still has history looking like history, then try to fit trade into it.

Making time travel harder won't preserve history. (If it's easy enough that humanity ever gain the capability) If it takes vast amounts of tech and resources a K3 civ will work out where to make the biggest impact. Even if there are tight weight restrictions, a single stretch of DNA that encodes for a smarter, kinder and healthier human, sent back to an embryo 100 000 years ago could totally change history.

If it was impossible to go back to before the first time machine was made, expect normality till then, and as soon as the first machine is made, time travelers with super tech come bursting out, with everything planned and designed for maximum impact.

Answer 7

Banks using high interest bonds is one solution

Before we discuss bonds, lets discuss the limitation of using other methods.

Why it doesn't work with commodities and real items:

The reason why you cannot transfer things like gold or other tangibles into the past without disturbing history is as follows. Any attempt to take real wealth from the future back it into the past will result in there being much more of the item in the past than there originally was before the (mass) time travel.

At this point it is simple economics. There will be more supply of the item. The value of that item must then also change because it is in greater supply. You will then have a case of runaway inflation where anything you take back quickly becomes worthless, and changes history by making the formerly valuable item plentiful and valueless. This is obviously a deal breaker for a sustainable Time-Travel economy.

Why you have to use Banking & Bonds:

In banking all the value moved is just numbers in a system. You don't have to disrupt the world you are moving to. This is especially true if you are using the money of the time and it was voluntarily parted with. This, as opposed to printing new money by taking something of value back in time.

When you go back in time, someone goes with you and makes a deposit in the Time-Tavel-Bank for you. This is really just a receipt that shows how much of the Time-Travel-Bond's (explained below) funds you are entitled to based on your purchase in the future. The exchange rate will probably be brutal. Maybe 5 real dollars in the future equals 1 real dollar in the past.

The reason it has to be like this is because the only way you are going to be able to finance this is by offering Time-Travel-Bonds (https://en.wikipedia.org/wiki/Bond_(finance)). Aka, buy a time travel bond today at 100,000$ which goes to the Time-Travel-Bank and gives them funds to use. Then in 50 years you can cash in this bond for 500,000\$ or some other crazy profit, which you directly paid into with your wealth in the future before you left. This is how you motivate people of the time period to give money to the Time-Travel-Bank which then gives your time travelers money to use. This handles transferring money from the future to the past without disrupting the time-travel-ecosystem so to speak.

Why it has to be this way:

Remember that you can't bring anything tangible back into the past. This means that you can't pay people to coordinate or help in the past, which will no doubt be needed for a huge time travel industry (presumably with employees spanning several eras). The only thing you can pay them with is futures. So you gain the funds to finance this industry by trading the discussed high interest bonds. Rich people are always looking for ways to make more money from their vast wealth so I am sure that many would invest in this.

The industry then uses the redistributed money from the rich in the relevant era to pay employees and provide finances to time travelers. This system is also closed since you are not moving anything back in time except people. All their value remains in the future. This is how you could maintain a time travel industry where the act of time travel is almost common place.

Edit: From comments

There is no new money, only the redistribution of existing money. In the past the rich voluntarily give money to the time travelers, in the future the time travelers willingly forfeit their money to the rich. This isn't any different than buying stocks, handing out loans, buying real life bonds, etc. The people in the past are essentially loaning their money at an interest rate. The people in the future are paying with the money they have earned, in their own time when the past reaches the present.

If no one is willing to sell you the money/loan, for example there are too many travelers and they have bought up all the available money, then either the interest rates goes up (exchange rate is more expensive) or you can't travel to that time anymore by law. Presumably exchange rate costs will get so high that travelling to a particular time may become prohibitively expensive for our time travelers, preventing the need for legal action. Therefore we do not have to worry about regulating time traveler volume.

There will be a natural market limit on how many people you can send back. The only problem you have left at that point is the intrinsic difference of having more people in the past than there were before. And the legal dilemma of preventing time travelers from abusing time to change history, which is a different question.

Answer 8

You can't just park land, let alone cash

Moving money from past to future is of course simple: you just deposit it in an account in the past and retrieve it when you return to your point of origin.

It looks like you missed @VBartilucci's answer in the other thread. It is not that simple. Banks don't hold on to untouched accounts forever. They close them out after a certain fixed periods and pocket the funds. Even if you went to the trouble of hiring a lawyer and (e.g.) establishing a trust, there have been legal rules for nearly a millennium to limit the ability of a 'dead hand' to control property in common law countries. You'd need active trustees or escrow attorneys and, even if they didn't eventually just entirely pocket the cash (which they would certainly do in any premodern context and probably do the rest of the time), they'd still eventually be forced to find close-enough beneficiaries for the funds.

Banks as banks also (a) have not been around all that long, historically speaking, and (b) regularly fail, get robbed, or get raided or ruined by the powers-that-be. You'd generally be better off just leaving coin hoards in really inaccessible locations, like subterranean bunkers miles below seismically inactive mountains.

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Cash isn't wealth

Presumably the legal system would have to figure out some way of preventing everyone from enriching themselves via a long-term interest scheme...

Even if this were possible—and it really isn't, since the legal system already figured this out (supra)—everyone becoming a billionaire doesn't make everyone rich. It just returns everyone to their starting positions, with six to nine extra zeroes on every price in the economy. See also: every single coin debasement in history, along with almost any form of paper money. At the moment, $10 is equivalent to 227,000₫. That doesn't mean that vacationing in Vietnam makes you richer than Bill Gates; it's just a reminder that purchasing power is what's important, not numbers on the currency or account ledgers.

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You can't flood the past with wealth or cash

...the wealthy are not going to want to travel back in time without access to their funds.

Whether you're talking about wrecking the local currency with inflation or making the past legitimately wealthier by providing them with usable commodities and supplies, you're absolutely going to shift the past all over the place if you allow the present-day rich to carry over large chunks of their present-day wealth to the past. By most measures, minimum-wage laborers in the present-day United States have higher standards of living than medieval kings; the actual rich have ridiculously more stuff and, at least early on, knowledge allowing vast manipulation of the past's economy.

The two options are to (a) have a hard-sf Bill-&-Ted's style of time travel wherein nothing you do in the past will change the future because it's already baked in—the past and future are the way they are because all time travel has already happened and already created what we already see—or (b) to have the company protect the timeline as much as possible, including by limiting visitors' involvement in the local economy. Chinese tourists already mostly deal with traveling in Europe by cooking for themselves; there's no reason time travelers who enter the past with more clothes than a Terminator couldn't have some sandwiches or a box lunch in their backpack.

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Stable institutions are the key

"How could a banking system move money from future to past?"

Ok, if you can't accept that and just absolutely want to have a semiplausible hands-off tourism service? Well, the butterflies are going to start flapping so fiercely that everything will soon be unrecognizable and unexploitable (cf. my answer in the other thread) but you'd be looking for stable institutions that provide protection and access to period wealth in exchange for payment in the present-day.

What would make sense in a historical context is if all or several of the main religions turn out to have been money laundering operations for the time travelers. These things obviously have ups and downs (just ask the poor Templars) but the major financial institutions of the West since the dawn of civilization have been the Mesopotamian, Egyptian, and Roman churches. Tithes and income from their real-estate holdings could be easily redirected and, at a minor level, cause only minor deviation from what originally occurred. Obviously every adherent couldn't be in on it, but representatives of the firm could maintain a steady inner core within the organizations that facilitate all of the logistics for visitors. There's almost nothing similarly sacrosanct and long-lived in the Sinosphere but the the direct heirs of Confucius have always done pretty well for themselves, all things considered, and a Korean immigrant family ran Japan's Kongo Gumi temple construction company continuously from AD 578 to 2006.