Currency for a spacefaring society other than credits/bitcoins

The idea is that at some point in the future people abandoned 'cryptographical' (to use a term someone else stated in a similar question) currency in favor of something tangible (def- something one can see and/or hold) rather than blips in a data file (perhaps because of an incident where peoples' savings were accidentally or deliberately erased, if that's possible).

What would work in this capacity? I've considered coinage made from alloys of precious metals that, while much less scarce than for a planetbound culture (found on asteroids or unihabited planets), are rarely, if ever found combined in nature- are there other possible alternatives?

• The typical rules for currency are: valuable (high value density), fungable (easily split into smaller pieces), and hard to counterfit. In your future civilization, what things meet those three basic requirements? – Cort Ammon Jan 7 '16 at 2:41
• Just think of something everyone would consider as having value. Like maybe some rare space-metal only found in the cores of large planets. – Xandar The Zenon Jan 7 '16 at 3:20
• @CortAmmon - You are confusing currency and the basis for currency. Currency does not need to be fungible. Pieces of eight were a classic example of fungible currency, but this usage stopped with the introduction of milled edges (or earlier). – WhatRoughBeast Jan 7 '16 at 5:26
• Curious as to why people would have abandoned cryptocurrency? – Thucydides Jan 7 '16 at 11:45
• fungible doesn't mean being divisible, it means having equivalent value. An old crumpled dollar bill has the same value as a brand new dollar bill. – Dave Halsall Jan 7 '16 at 11:50

(Or, "outer rim planets probably aren't going to take a check.")

Yep, that's right, "money". Even though you've moved away from a pure digital currency, you can make some technological improvements (some of which current world governments already use):

• Serial numbers, naturally. Not verified at the time of the transaction, but checked later, similar to how most real Earth money works. That way, if someone does manage to counterfeit bills, your banks can at least track the source, plus they have other benefits, in thefts, statistics, etc.
• The important bit: Include a small quantity of a radio-isotope such as Thorium from a single planet owned by the central bank (so no one else can gain access). The slow, predictable alpha decay signature of natural thorium (or any other stable radioactive solid) from a particular source into radium-228 can be easily verified, but it would be far harder to replicate. Even if a would-be counterfeiter could build the metallic strip on a twenty-token bill atom-by-atom, it will likely cost them far more than twenty bucks. The bank, on the other hand, has bins full of the stuff they just dig out of the ground, so it costs them comparatively very little.
• For very large amounts—where even today we wouldn't accept cash—might still have to be issued some other means, like specially-issued bank money orders with additional security and verification.
• Quantum money would be impossible to counterfeit, but also extremely impractical, so I won't be discussing it here, but it's worth a mention.

Backed by: Energy or virtual computing resources

Your currency ought to be fungible; that is, backed by something of value.

The key here is to imagine something unique to your universe that has value, and is interchangeable. (I.e., one type of frobnicator isn't superior to another.) The idea of "standardized" (and hence, fungible) computing opens up some interesting possibilities to back this currency:

• A unit of information transfer, like a terabyte
• A unit of information served storage, like a terabyte year or petaqubit-year
• Plain storage would not be as good for this purpose, as you'd essentially be backing your currency with hard disks or USB drives (or their future equivalent). I think the other options in this list are superior.
• A unit of computing effort, like a yottaflop

Non-computing-related:

• A unit of energy, like a megawatt-hour or terajoule. Presumably backed by a partnership with planetary/regional energy providers, and the physical delivery system doesn't matter, as a joule is a joule, as long as you take transfer efficiency into account of course.

But how are computing resources fungible?

(Extended discussion here, in case of nay-sayers. Feel free to skip over the next paragraph if you're already convinced.)

It's my position that all of the above items meet the fungibility requirement even if multiple organizations actually provide the services, and even if there are slight variations in quality of service. Why? First, for example, a FLOP is a FLOP—i.e., either the operation was performed or not, and any FLOP is thus "substantially equivalent" to any other FLOP, regardless of how fast any given computer is. To wit: "a good is fungible if one unit of the good is substantially equivalent to another unit of the same good of the same quality at the same time and place." A futuristic society is likely to have better reliability than we do today, and in our world we're already pretty much at the point of "commodity" computing with reliability exceeding the 99.999% range. I would call any 0.0001% variation well within "substantially equivalent", and probably better than the purity of most fungible gold reserves! Issues of downtime, availability, speed, etc., are irrelevant to the issue of fungibility, although, like any currency, you want to make sure you have enough of the backed good to cover it! Finally, fungibility doesn't imply that your $1000 bill has a 1:1 mapping with a specific lump of gold, or terajoule, or whatever, just that the equivalence exists and can be backed up. As I said above, this paragraph was really for the doubters, so I've probably gotten rather nitpicky here as it is, so please keep the big picture in mind. But what about Moore's law? This is the widely-known "law" that states that transistor density doubles every couple of years. People have misused it to draw similar conclusions about information storage or processor speed, but none of these figures are expected to continue to double indefinitely, as there are fundamental physical limits we are rapidly approaching, even now. Quantum computing (if it ever happens), would cause a big, albeit finite, jump. At any rate, if your future society hasn't already hit the fundamental limits of physics, there could be a little inflation, but it would be quite predictable, which makes it stable. Why not a precious metal? Or diamonds? While things like gold will still be relatively rare in other star systems compared to say, iron, the differences would still be significant enough to give certain planets an unfair advantage. Larger, younger planets could have far more easily accessible gold, or platinum, or uranium, or whatever another planet might consider "rare", and hence, valuable. Note that this differs from the alpha decay signature idea I mentioned above, as the metal used there is used to provide authenticity, not as an intrinsically valuable material like gold is to us now. Aside: Why abandon electronic currency? Although you've already stated the assumption to abandon digital currency, and offered a speculative reason, let me offer another one: Propagation speed. I don't know if your universe has faster-than-light (FTL) travel or FTL communication, but either way, over interstellar distances, it could take a very long time (several minutes to many years) to query, hold, and withdraw funds to complete a typical transaction. • However, the Bank will require multiple isotopes if it is to issue notes in different denominations. Otherwise, there will be a brisk cottage industry engaged in removing the isotope from 1-credit notes and attaching it to counterfeit 1000-credit notes. – WhatRoughBeast Jan 7 '16 at 13:27 • @WhatRoughBeast Good point. Fortunately there are ample stable radioactive minerals to choose from, and the quantities required would be quite small indeed. Also, like many Earth currencies, it's likely that they'd reserve the really good ones for the higher denominations. – type_outcast Jan 7 '16 at 18:33 • @type_outcast- I was orginally thinking of using a platinum-iridium alloy, if that helps any. Just out of curiosity, what did you use to make that 'note' in your answer? – king of panes Jan 8 '16 at 2:00 • OK, sure, Iridium could work. Its radioisotopes and isomers have short half-lifes (days), which could cause problems, so I'd suggest a combined approach: use plain, stable Platinum and Iridium in your base alloy, and then simply mix in a small, precise amount of the natural radioactive tracer sample from a bank-controlled planet or meteorite, and that sample should remain somewhat impure, so that it retains its unique and hard-to-counterfeit decay signature, but is cheap for the bank to dig up (maybe it's even an existing impurity in your alloy). Oh, and I used Adobe Illustrator. :-) – type_outcast Jan 8 '16 at 5:03 In the era of "Free Banking", individual banks could and often did issue their own currency. These were actual dollars, but instead of being issued by the Mint, they were issued by the bank. (This situation wasn't unique to the United States, Canadian banks also issued currency into the 1940's). A "Wells-Fargo" issued banknote was backed by the assets of the Wells-Fargo bank. Since most banks have (or at least had) very similar assets, such as outstanding loans, mortgages and credit instruments, the issue of fungibility was reduced, a$1000 mortgage might buy a different size of house deeding on where you were, but it was still a mortgage backed by a real asset.

Free banking had many downsides, particularly in the issue of making sure the currency being issued actually matched the assets it represented. A run on the bank, and economic downturn which caused defaults on loans and mortgages or other variables could cause issues (to say the least). Economic activity and actions happen faster than the physical printing and issue or destruction of bank notes as well, so there would always be a mismatch between the paper ands the assets. On the other hand, free banking systems rarely had inflation, and recessions and even depressions were less frequent and were shorter since the nature of free banking meant that the market cleared very quickly (and banks failing was a big part of that. Contrast it to the heroic efforts to prevent bank failures both ion the case of the Japanese "lost decade" of the 1990's or the 2008 economic crisis).

Perhaps the biggest problem in extending this model into a space based economy is distance makes auditing mores difficult. How do you know the Bank of Ceres really does have 2 trillion in assets backed by water when you are on Titan? Fungability could also be an issue, especially since some of the resources are not equally distributed across the system

Surprising as is, I think a spacefaring civilization knows no realistic need in materials and energy, so basing currency on one of those doesn't seem like a fair idea. You see, if space travel is affordable, you can mine billions of asteroids for resources, utilize energy of a thousand suns, build or create practically anything you like.

The keyword here is not "anything" but "practically". There are some astronomical-scale tasks hardly possible even with interstellar travel, von Neumann machines and practically free energy, and those things can be the base of the new currency. My favorite idea for the interstellar currency would be real estate. Building a habitable planet is extremely costy (in terms of energy and resources) and there is a limited number of those. (Yet we don't exactly know the limit.) So real estate is something you can base your currency on.

• It sounds like you're saying, currency is kinda meaningless, because there are practically "as many resources (specifically, asteroids and stars) as you like", yet "there are a limited number of [habitable planets]", so base your currency on that. I realize I paraphrased, and maybe I did miss your meaning, but that's my point, I suppose. Real estate might well be a reasonable currency after all, but perhaps you could strengthen your argument by elaborating on how there would be sufficient demand and how it would meet the fungibility requirement we've discussed in comments on other answers? – type_outcast Jan 8 '16 at 15:07
• @type_outcast Could you reflect what you are talking about here? Sorry, but I'm not native in English and your choice of phrasing is a bit too complex. – mg30rg Jan 8 '16 at 15:34

In the past money has either been gold or backed by gold.

This is less useful in space, but the idea is interesting.
Something that is valuable in itself, and that can be given so I don't have it anymore.

One idea is energy, or the means to make energy.
Dilithium, or batteries, or fuel of some kind. The means to travel. Basicly something that is valuable in itself, and not just because we decided to agree it's valuable.

Couple of options here:

"Paper" Currency

In the far future, printing has got to the point where governments and similarly large organisations can print uncopyable bills - ones immune to counterfeiting thanks to complex printing methods.

Each political grouping (be it local, national, continental, planetary, system wide or interstellar) has its own currency. This could lead to some fun heist situations as all that cash has to be carted about!

Heavy Metal

Another option is to go gold (or silver, dilithium, unobtainium, gold pressed latinum, unicorn farts etc.) Pressed into set shapes and sizes based on worth (bonus - combine with the above for extra fun and extra security) Cons include easier to counterfeit, particularly if you come across an asteroid or planet heavy with the stuff.

Barter

Finally, why not go with a barter system. "That's a mighty nice ray gun you've got ther Smeerg, can I trade you two months worth of Stimstix?" Its an old system, but has the advantage of traders from different areas being able to trade effectively with each other, no matter what they carry. Unfortunately, there is no guarantee what anything is worth, so you'll need to carry lots of different "barter" goods.

• In barter, there is no guarantee that you'd be able to trade effectively. Suppose Smeerg has a really nice ray gun, and wants rice. However, I only have a first generation frobnicator that I'm willing to part with. I'd have to find someone who wants a first generation frobnicator, and has something reasonably valuable to give me in return. This might not be the rice that Smeerg wants, so I'd have to find someone else for another trade, then another and another... By the time I finally have some rice, Smeerg might have given up waiting. I know you mention this, but it's a big problem in barter. – user Jan 8 '16 at 14:09

This may be a little "out there" but what if you had a society with some kind of marx-inspired conception of work-as-value? This isn't tangible, though – it only works if at an individual level it was accepted that a 'coin' could be earned via and exchanged for useful labour.

'Work' is a fuzzy concept. People would probably agree that an hour of designing a fusion reactor was more difficult (and useful to society) than an hour spent serving up fast food, so you don't map the currency to units of time or anything. But in a sufficiently organised society (it would have to be fairly authoritarian, most probably) it might be possible to systematise the pay of each person - a little like how workers unions sometimes decide on set rates for various roles, you might say that unskilled work is valued at 10 units per hour, while highly skilled or dangerous work was worth 100 units.

I figure the economics of this would be that I take my pay (whatever it is) into a restaurant, and I pay a price based on how much work goes into preparing my food - say 10 mins of the short order cook's time, 5 mins of the server's time, plus some inevitable mystery amount representing the minute fractional effort put into the transaction by the manager, the franchisee, the parent company, etc etc etc. My pay itself comes out of the account of my employer, who accrues the 'credits' of customers or whatever, takes a cut for the time taken to manage affairs, and then passes on the share afforded to me based on my pay-rate.

I get the feeling there's probably a lot wrong with this concept on some level, but at the very least it's divisible enough, and its value is easily understood and concrete if enforced within society - maybe if I can't quite make the bill at that restaurant, I can wash their dishes; and the economy is structured so that we all know exactly how much dishwashing I owe.

• Indeed, labour would be extremely difficult to quantize. Of course you've hit on the important point that not all labor is equal. The next logical thing is to say, "well, a fusion reactor designer is worth 100 bucks per hour, but a dishwasher is only worth 5, or maybe 6 if they're fast", which is still fuzzy, not to mention circular. You could trade slaves, I suppose, but even then, those tau Cet e folks sure are slow... :-) However I feel you have the makings of a good idea, here, so keep thinking! And, welcome to Worldbuilding. – type_outcast Jan 7 '16 at 9:25
• I think the only way to end the cyclic debate over what time was worth would be to declare the pay-rates more or less arbitrarily from on high - which would require a horrific bureaucracy, and in turn probably lead to corruption and widespread dissatisfaction. But it would allow a society to function to a point, where "a point" is probably the inevitable overthrow of this petty, soul-crushing system once everyone realises a promotion from sanitation (garbage disposal) [level 3] to [level 4] will not substantially improve their life. – Toadfish Jan 7 '16 at 9:35
• On the other hand, if one wanted to handwave it, just say the benevolent AI overlord whose intellect is beyond human comprehension figured it all out, everyone's pay is both fair and sufficient for their happiness, and so on - but if that's the story you wanted to tell, maybe better to do away with currency and work altogether, and have a post-scarcity scenario in the mould of Iain Banks' Culture series. – Toadfish Jan 7 '16 at 9:39

Information

Assuming the information cannot be conveyed by easier means (like electronic transmission), then information is the ultimate high density easily transported and exchanged currency.

Unlike material wealth information exchange is non-zero sum game. If I have an idea and you have an idea and we trade - instead of each of us only having 1 idea, we both end with 2 ideas (information increases quantity and is therefore devalued at the rate of exchange).

This might cause information inflation.

You need to spend your information currency quickly before someone else trades that information. If you ever played games like Master's of Orion or Civilization, you can witness information inflation. It makes the most sense to accept every offer of technology trading in games with multiplayers (even if they are computer players), because once someone has a technology, they won't trade with you for yours.

• The problem with this is that information is not fungible. How do you judge the worth of knowing that a shipload of unobtanium is going to arrive a week ahead of schedule, versus the worth of knowing the President's private phone number? One ounce of gold bullion can be substituted for any other ounce, but with information, it's hard to quantify how much you have, much less how much it's worth, and without that, you can't perform the substitutions that are the basis of fungibility. – Mark Jan 7 '16 at 5:17
• @Mark - "How do you judge the worth...?" has nothing to do with the basis of the currency. You know how much something is worth by what somebody will give you for it. – WhatRoughBeast Jan 7 '16 at 5:21
• @WhatRoughBeast, so you're advocating a return to a barter economy? – Mark Jan 7 '16 at 5:24
• @WhatRoughBeast, it doesn't need to be. It does, however, need to be easy to judge the value of the currency. If I've got a \$1000 gold certificate, I know I can redeem it for 48.38 troy ounces of gold, and I know I can use that certificate interchangeably with any other \$1000 certificate. If I've got a \$1000 "information" certificate, I can redeem it for...what? How can I know it's interchangeable with other \$1000 "information" certificates? – Mark Jan 7 '16 at 5:39
• @WhatRoughBeast, fungibility doesn't mean "can be cut up into little pieces", it means "one unit of the thing is substantially equivalent to another unit". – Mark Jan 7 '16 at 19:06