Text II

In 1960, astronomer Frank Drake began the first scientific search for extraterrestrial life at the National Radio Astronomy Observatory in West Virginia, US.

Drake aimed a giant antenna at two stars and detected no signals. He wondered how many alien civilizations we could detect, and he estimated 10,000 civilizations had technology or made enough ruckus for us to detect them.

Radio telescopes usually measure objects like stars or quasars; however, they occasionally search frequencies for alien life. In 1995, scientists detected the first planets outside our solar system, and they called them exoplanets. So far, scientists have discovered more than 5,000 exoplanets, and exoplanet Kepler-186f is in the so-called habitable zone where liquid water may support life.

People reported many unexplained UFO sightings, and some people believe alien explorers stop at Earth on a galactic road trip.