Scientists: Numerous theoretical alien civilizations could have already received Earth broadcasts

Radio waves from the last century could have reached 75 different star systems already.

Astronomers conducting surveys of relatively close star systems claim that numerous theoretical alien civilizations may have already received Earth broadcasts, with an even larger number of star systems also capable of detecting Earth’s presence in our Solar System.

In an article published this week in Nature, the researchers claim that over 1,700 star systems in Earth’s cosmic neighborhood are “in the right position to have spotted life on a transiting Earth since early human civilization,” about 5,000 years ago.

Scientists are currently working to fine-tune methods to detect signs of life in planets trillions and trillions of miles away. The paper in Nature asserts that alien civilizations that have already developed this technology could have observed Earth’s bio-indicators for many years. 

The astronomers also calculated how many nearby star systems may have been able to detect human-generated radio waves from Earth; those waves, they note, have only been broadcasting for a scant fraction of humanity’s presence on this planet, about the last hundred years. 

"We found that human-made radio waves have already swept over 75 of the closest stars on our list,” they said, estimating that, among the surveyed star systems, a full 29 planets in their stars' habitable zones may have been able to detect both radio waves from Earth and the presence of Earth itself.