For a long time I have been giving scientific lectures in different countries and on diverse topics, generally related to astronomy and to my work at the Arecibo Observatory. No matter which parti- lar topic I am talking about, the same question always comes up: Have we had any contact at Arecibo with ?them?? My negative answer does not satisfy anyone. In fact, the answer either confirms their suspicions that there is a conspiracy afoot by higher autho- ties not to release information or their intentions to deceive the general public. The reasons for the deception have to do with the idea that, as in the movie Contact, the received messages contain important and useful information that will bring great advantage to whoever gets it. Many of us want to believe that extraterrestrial creatures can talk to us, that perhaps they are even living among us, as UFO fans believe. It would be fascinating if it were true, a more than extra- dinary discovery, the answer to an eternal question. There is p- sibly a deep psychological motive in this desire to know if we are alone in this huge universe, and the need to believe in something beyond our limited world, in space and time. There is no doubt, then, that this topic brings with it many scientific and philosophical discussions, as well as speculations that, on many occasions, fall into pure pseudoscience because of the lack of a reference framework.