The human civilization began listening to the outer space only some 60-70 years ago. Consequently, no concrete results regarding the possible existence of extraterrestrial intelligent life are available yet. The Universe has over 100 billion galaxies each containing hundreds of millions of stars. This is why the probability of Earth being the only intelligent planet is very small.
The idea of space communication existed even before the radio was invented and some communication suggestions involved digging gigantic ditches in the Sahara Desert, filled with a mix of water and kerosene and set on fire each night. A less polluting alternative came from statisticians and meteorologists: mathematics.
Scientists are convinced that of all the possible types of communication, electromagnetic waves represent the most probable method a galactic civilization would use. Electromagnetic waves are the easiest to detect and the most commonly found in the outer space. The method would consist in using electromagnetic pulses, for example 2 pulses, then 3, 5, 7, 11…, just like prime numbers, suggesting intelligent action.
Another space communication method would be music because it involves the use of mental mathematical structures. Music is already known to exert a type of emotional influence on the human brain similar to that exerted by language.
In the 1960s, space pioneers built an anodized aluminum plate and attached it to an antenna to send basic information about the human species, our planet’s basic chemical elements, its position in the solar system, but also some audio recordings of human cultural products of those years.
Despite all these major efforts, extraterrestrial civilizations have not produced any signs of existence so far. Or maybe there were galactic civilizations thousands of years ago who, in turn, listened to the sounds of the outer space in the hope of establishing a minimum intelligent contact with our planet which, at that time, had not sufficiently evolved to be considered intelligent.