So what is this Cosmic Tombstone any way? The basic concept is a message which is sent from humanity into space which is created to be comprehensible to a variety of possible intelligences.
On Nov. 16, 1974, astronomer Frank Drake dedicated a new observatory in Arecibo, Puerto Rico, by sending humankind's first deliberate communication to extraterrestrials.
We can speculate what the message should and should not say. We can ponder what method is the best to send a message.