In most cases the recipient of an apocalygraphic message will be unknown to the sender, which means that even the existance of a recipient is unknown. Such a message is distributed in space to advertise the presence of the sender. An exception might be the dissemination of a message in deep time, in which expected descendants have lost knowledge of the sender's language.
It is probably true to say that no lost terrestrial language has ever been deciphered without links to existing language knowledge. In the case of Egyptian hieroglyphics, the Rosetta stone provided a translation table to the Greek language. Various Minoan scripts turned out to also be related to Greek. It is thus fair to say that we would have no hope of decoding an extraterrestrial language that eventuated with no points of correspondence to our terrestrial language and psychological environment.
The problem of apocalygraphy, although it has been dealt with at great length, is a difficult one, and one in which we have no current indication of success. All current tests of apocalygraphy have been carried out between persons with very similar background environments and who mostly even speak the same language and undoubtedly have very similar thought patterns. And the rate of success in these tests has been very low.
Any attempt at apocalygraphy invariably involves assumptions about the ability of the recipient to decode. The most common assumptions are:
The two most widely known examples of apocalygraphic messages sent into space and intended to inform any extraterrestrial recipients of our existence and facts related thereto are the plaques on the Pioneer spacecraft (mass transfer) and the Arecibo message (energy transfer).
|This plaque was carried by both the Pioneer 10 and Pioneer 11 spacecraft.|
|This is one possible decoded image of a message transmitted by the large Arecibo radiotelescope on 16 November 1974. The message was transmitted on a frequency of 2380 MHz with an effective power of 3x1012 watts, and used a binary phase shift modulation at a rate of 10 bits per second. The total message comprised 1679 bits. This number has only the factors 23 and 73 (both prime numbers) which allows it to be decoded as a two dimensional image. The message was sent in the direction of the globular star cluster M13 in the constellation of Hercules.|