Boeing RB-47

Credit - U.S. Air Force Museum

Number of UFO sightings

Credit - U.S. Air Force photo

Arecibo Observatory in Puerto Rico with its 300-meter dish antenna

Credit - NASA

Artist's concept of an intermediate size (300-meter) space SETI system antenna

Credit - NASA

Parabolic reflector antennas, part of NASA's worldwide Deep Space Network

Credit - NASA

Image generated by SETI software

Credit - SETI@home project