Blasting out Earth’s location with the hope of reaching aliens is a controversial idea – two teams of scientists are doing it anyway

If a person is lost in the wilderness, they have two options. They can search for civilization, or they could make themselves easy to spot by building a fire or writing HELP in big letters. For scientists interested in the question of whether intelligent aliens exist, the options are much the same.

Signboards in Space

The Search for Extraterrestrial Intelligence (SETI) is expanding. Dominated for decades by the search for radio transmissions from aliens, SETI has recently included optical searches for laser beams. A third SETI option, the search for extraterrestrial artefacts, is also gathering pace.