In the last years we have been alredy see it some activity , an example is the area 51 where there have always been rumors of sightings and experiments with unidentified species.

in 1954 on a UFO convention Dolores and and her companions had belivers who were convinced by their extraterrestrial origins from venus because of the way she talked about venus and mysteriously disappeard one day without a trace 

Sending out pulses of radiation at different wavelengths, recorded plates attached to satellites or musical threads in a spacecraft forming a series of the type 1 pulse, 2 pulses, 3 pulses, 5 pulses, 7 pulses, 11 pulses, 13 pulses, etc.

 The U.S government has begun acknowledging the presence of unidentified area phenomena due to increased public interest , credible reports from military personnel and technological advancement . 

ancient evidence often cited includes mysterious artifacts , carvings and structures such as the pyramids or Stonehenge, which  some argue demonstrate advanced knowledge beyond human capabilities at the time .   

the  intentions of visiting aliens , if they exist . possible motives include exploration, sharing knowledge or observing humanity's development