notes-aliens

What should we say to aliens?

Mathematics seems like the sort of thing that, although it's true for everybody, different civilizations may discover different parts of it. And it tends to be pretty useful, and unpredictably so. So, if aliens contacted us, we should be pretty eager to learn their mathematics.

This suggests that really cool mathematical discoveries might be valuable.

Also, an advanced civilization may have the problem that the amount of information they can transmit is greatly eclipsed by the amount of information they possess. So, perhaps even if they beamed us their mathematical discoveries as fast as they could, they would be discovering new math even faster. This suggests that it might be okay to share one's mathematical discoveries without losing the entirety of one's 'edge'.

Futhermore, there is probably a way to create a zero-knowledge proof[1] of the fact that you know the proof of some true theorem. Apparently typical zero-knowledge proof systems are interactive but apparently there are some non-interactive ones (maybe; depending on the computational hardness of some cryptographic primitives?). This suggests that there is a way to credibly advertise one's possession of mathematical knowledge without giving it away (however in general, if you know for certain that some mathematical fact is true and provable, it becomes easier to prove, because you don't have to waste time trying to prove that it is false or undecidable).

Therefore, i suggest that aliens might trade using mathematical proofs in place of currency.

Proofs are not currencies, however, because they are not commodities; perhaps some sort of cryptocurrency would be used in addition. Because various alien civilizations would probably have computational resources to offer for sale, ethereum-style cryptocurrencies, where the currency has an intrinsic value because you can buy computation from the network servers with it, might be used. It would be even better if the currency also could be used to order the servers to provide communication services; these have been overlooked on Earth, where we have other efficient communications systems, but would be useful in alien communication, where various civilizations could usefuly provide mesh repeater services to each other for a fee.

The provision of computing services to aliens would be quite dangerous, however, because the program being run on the server could be an A.I. attempting to find exploits to break server security. A civilization providing such services would be advised to take extreme precautions, including possibly:

So, in summary:

Physical layer communications

Since the round-trip time between civilizations is very long and the S/N ratio very low, aliens would probably use lots of forward-error correction (channel coding). Although i suppose that it's most efficient to pick one FEC technique/stack of techniques, it's fun to imagine using a bunch at once. Here's some things they might do:

An interesting aspect is that you might choose a protocol that is easiest for others to recognize and understand (eg perhaps just repetition rather than some more efficient form of coding), rather than one that is most efficient. Otoh maybe not; maybe sufficiently advanced civilizations converge on a common set of efficient protocols, and these are what the aliens use to talk to each other.

Also, i get the impression that SETI etc are looking for strong signals, but it seems to me that aliens would actually broadcast extraordinarily weak signals (way below the noise floor) and then use lots of repetition to allow the recipient to detect the signal by averaging over a long period of time (you don't know ahead of time how long the signal is so you'd have to try a bunch of different periods but that's easy enough).