UFOs (or Unidentified Aerial Phenomena - UAP) are flying objects of unknown origin, often seen as luminous, disc-shaped, or spherical. Many believe that these are spacecraft of extraterrestrials (intelligent aliens from other planets) visiting or monitoring Earth. Thousands of UFO sightings have been reported worldwide, including more than 2,000 in the first half of 2025 alone. Recent research suggests that some sightings are related to nuclear testing and that extraterrestrials may be interested in dangerous human activities. However, the Pentagon and scientists insist that most cases have a natural explanation (such as drones, balloons, or atmospheric phenomena) and that there is no definitive evidence of extraterrestrial visitation.