Martin Schmidt

Publication Date





One of the main strategies in Search for Extra Terrestrial Intelligence (SETI) is trying to overhear communications between advanced civilizations. However, there is a (seeming) problem with this approach: advanced civilizations, most probably, save communication expenses by maximally compressing their messages, and the notion of a maximally compressed message is naturally formalized as a message x for which Kolmogorov complexity C(x) is close to its length l(x), i.e., as a "random" message. In other words, a maximally compressed message is indistinguishable from the truly random noise, and thus, trying to detect such a message does not seem to be a working SETI strategy.

We show that this argument does not take into consideration the {\it time} necessary for compression and decompression of message. If we take this time into consideration, and therefore consider time-bounded versions of Kolmogorov complexity, then the above ``problem'' disappears. We also show which version of time-bounded Kolmogorov complexity is most appropriate for formalizing SETI strategies.