Did That Message Come From Earth or Space? Now SETI Researchers can be Sure

When SETI researchers discover an intriguing radio signal, their first instinct is to ask, "Is the signal coming from Earth?" So many alien messages turned out to be Earth signals reflecting off objects in space, like satellites. Scientists have developed a new technique to vet these signals and confirm whether they came from outer space, even with a single message. When a signal passes through the interstellar medium, it should be affected by free electrons from cold plasma, and it's possible t...