As of 2023, there is no conclusive evidence or proof of the existence of extraterrestrial life, also known as aliens. However, there have been several scientific findings and phenomena that have led some to believe in the possibility of extraterrestrial life.

One of the most compelling arguments for the existence of aliens is the vastness of the universe. There are billions of galaxies in the observable universe, each containing billions of stars and planets. Given the sheer number of planets in the universe, it's statistically likely that some of them have conditions suitable for life.

Moreover, scientists have discovered several exoplanets, or planets outside our solar system, that may be habitable. In 2015, NASA's Kepler spacecraft discovered Kepler-452b, an exoplanet that is located in the habitable zone of its star and has a similar size and orbit to Earth. While these findings do not provide conclusive evidence of the existence of aliens, they do suggest that there may be planets with conditions suitable for life beyond Earth.

Another phenomenon that has led some to believe in the existence of aliens is the Fermi Paradox. The Fermi Paradox is the contradiction between the high probability of the existence of extraterrestrial civilizations and the lack of evidence for or contact with such civilizations. Some have speculated that the lack of evidence for aliens may be due to the limitations of our technology or the fact that aliens are simply too far away or too advanced to communicate with us.

Additionally, there have been several unexplained sightings and encounters that have been attributed to aliens, such as the Roswell incident in 1947 and the more recent sightings of unidentified flying objects (UFOs) by military personnel. While these sightings have not been conclusively proven to be the result of extraterrestrial life, they have sparked interest and speculation in the existence of aliens.