Over a century ago, the astronomer Percival Lowell thought that he had glimpsed artificial canals on Mars and the radio pioneer Nikola Tesla believed that he had intercepted a Martian radio broadcast. Later attempts to signal Mars by means of huge bonfires and powerful radio broadcasts proved unsuccessful. Today people realize that although remnants of microbial life may exist within the solar system, the search for extraterrestrial intelligence (SETI) must extend to distant stars.

We do not know if and how we will first discover extraterrestrial intelligence, but most scientists do not expect it to happen quite like it does in the movie, E.T. The Extra-terrestrial (1982).

Search Strategies

Microwave SETI, which uses radio telescopes, was popularized in Carl Sagan's novel Contact (1985) and in the 1997 Jodie Foster movie of the same name. Dish antennas collect faint microwaves that are fed into receivers that scan billions of...