1\ A thought experiment: The year is 2277. You're the bartender at a spaceport in a faraway Earth colony on a planet orbiting α-Centauri: a distance of ~4 light years. Guy walks into your bar, slams down a credit chit, and asks for a drink.
How do you know his money is any good?
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2\ If the credit chit were guaranteed by a bank or a blockchain or something local to α-Centauri it'd be easy, just like it is here on Earth in 2018.
But say this guy is fresh-thawed after his long journey from Earth aboard a lighthugger. What kind of wealth could he even have?
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3\ He's unlikely to be carrying base metals. Like natural resources, they'd still be valuable, but too heavy to transport from Earth. Physical fiat (bank notes) wouldn't be accepted either: too easy to 3D-print forgeries.
So what form of wealth survives interstellar voyages?
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4\ Information! Wealth transfer between stars must be digital.
So the guy could present a statement from Bank of Orion or sign some blockchain transaction with his private keys to prove to you he is solvent.
"One Corellian Ale, coming right up sir..."
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5\ But what if, just before arriving, the guy beamed a transaction back at Earth spending all his funds? It would take 4 years to get to Earth and 4 years for Earth to relay acknowledgement back to α-Centauri.
During those 8 years, he could double-spend freely on α-Centauri!
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6\ Relativity can be confusing, so physicists use Minkowski diagrams to hone their intuitions in situations like these. Below is an idealized Minkowski diagram which depicts the scenario outlined above.
See en.wikipedia.org/wiki/Minkowski for more details on how to read these diagrams.
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7\ Another problem: say two ships leave Earth and α-Centauri at the same time, each bound for the other. Later, both Earth and α-Centauri broadcast spends. Due to the relativity of simultaneity, the two ships will receive the spends in *the opposite order*! What should they do?
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8\ These examples are not pathologies. They are fundamental problems of interstellar commerce.
I read a lot of sci-fi but I don't know of many authors who write about interstellar distributed consensus. Everyone writes about the engines, but the money is just as vital...
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Finally, Paul krugman’s 1978 thesis was on interstellar trade finance 🙂 princeton.edu/~pkrugman/inte
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Holy shit, I thought you were just joking.
How can you be appreciate the nuances of special relativity and local reference frames in commerce yet be so unconvinced of the value of a distributed cryptocurrency?
Dammit, Paul, younger-you would have loved Bitcoin!
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