Bitcoin, the original and most popular cryptocurrency, has had a ton of media coverage recently, and there has been a lot of press on some valid and invalid concerns with the underlying technology. While there is still considerable debate on the current challenges, some interesting challenges are presented by the idea of blockchain in space.

What changes between earth and space? At the heart of problems with interstellar blockchain is communication time. On earth, anyone with an internet connection can communicate with others in mere milliseconds, soon from anywhere in the world. However, when you scale distances to the astronomical, even the theoretical fastest communications take years to reach the closest star. Unless physics as it is currently is wrong, there is no way to quickly transport information from one galaxy to another.

This hurts bitcoin. With a block time of only 10 minutes, all mining is constrained to a single planet and its celestial satellites. Anything outside of 111,769,200 miles from a block with most likely not be able to mine, because the central mining planet wouldn’t be able to accept blocks before generating its own. This number seems large, but the average distance between Earth and Mars is 140,000,000 miles.

To compound this problem, transactions from non-bitcoin-centric planets would take years to confirm. A transaction would take years to reach the “cryptoplanet”, and then take years to be transmitted back to the source. even if the sending and receiving parties are located on the same planet.

All this is, of course, assuming that all computing power is concentrated on one planet. What happens if mining is separated equally between multiple galaxies, years apart? This scenario is even worse. Assuming that each galaxy has the power to create its own blockchain, and galaxies are separated by a minimum of ten light years, chains could grow and even adjust difficulty independently of one another, creating multiple “accepted” ledgers. However, this is not practical, as any increase in computing power on one planet would lead to its slow but eventual takeover, destroying any other ledgers on other planets and destroying years of economic records. If this is possible, then transactions would not be confirmed after three blocks, but rather after years and years, rendering the entire system unusable.

Does this mean the blockchain is not suitable for space? Maybe. In its current state, bitcoin would work better if each planet set up its own ledger, but that doesn’t mean that future cryptocurrencies couldn’t be designed to voyage across space. Maybe a new altcoin is created for this specific purpose, or maybe bitcoin is modified to work at a universal scale. There’s no way of telling what our extraterrestrial economic future holds.