How Do Spaceships Communicate on First Contact?

Question

While this is mainly from a Star Trek perspective, it could apply to other universes in SF as well (and even to our reality, really).

In this question the focus is on ships from 150 years apart communicating. But one comment there raises a bigger question.

If two ships are approaching each other in space, and they have never contacted each other before and have no knowledge of each other, how would they communicate with each other? I know if they know some of the same other races, they might have common protocols, but if there was no prior contact at all and no connections at all, how would they communicate with each other?

Answer 1

Encountering species with incompatible communications protocols is an integral part of interstellar exploration, so every species engaging in it would have developed at least some form of self-describing protocols.

We on Earth haven't even achieve interplanetary travel, yet there is already a branch of SETI called CETI (Communication with Extra-Terrestrial Intelligence) that attempts this. The idea is to use universally understood notions (such as numbers, prime numbers, atomic weights, well known spectral wavelengths) to communicate or built a common vocabulary.

We can safely assume that a species advanced enough to build a warp capable starship will also be able to develop a self-describing (or bootstrapping) communications protocol.

On the flip side, they will also have developed automatic protocol analyzers that can take an unknown protocol (even one that is not self-describing) and perform a statistical analysis to derive the protocol being used. Believe it or not, this is pretty much what Google Translate does!

So in summary:

1. Self-describing (or bootstrapping) communications protocols on the sending side
2. Automatic protocol discovery and conversion on the receiving side