In November of 1974,
A small group from SETI, S.E.T.I. (Search for Extraterrestrial Intelligence),
Used the radio dishes at Arecibo to send out a message to whoever might be listening.

They sent about a quarter of a kilobyte...including: Structure of human DNA,
map of our solar system, population of the earth. Helpful facts like that.

In January of 1993, Arecibo received a message back.
From an extraterrestrial...of unknown source."