The Ancient astronaut hypothesis is one of the most widely known hypotheses about aliens.
Throughout the 20th and 21st century, the idea of aliens visiting Earth for thousands of years has become very popular. The hypothesis proposes that "visiting aliens" had been mistaken for "gods and angels" in the ancient world. They appeared as divine beings who came down from the sky, from what they believed was "heaven". Due to this strong possibility, some believe that alien encounters started off theories in the ancient times that there were divine beings who lived in the heavens above. Thus, the Holy Bible has been questioned as to this possible influence.