Clearly, if we can only leave a message on the planet we have little choice but to build megalithic stone structures, and we would inscribe into this stone a symbolic language that can hopefully be translated into understanding in that future epoch.
Clearly, if we can only leave a message on the planet we have little choice but to build megalithic stone structures, and we would inscribe into this stone a symbolic language that can hopefully be translated into understanding in that future epoch.