The Overview Effect is the experience of seeing the Earth from space and realizing the inherent unity and oneness everything on the planet. I first named it and began attempting to understand it in my book by the same name, published in 1987 by Houghton-Mifflin.
At that time, I interviewed 16 people who had been in outer space to determine if the Overview Effect actually existed and could be documented. While everyone described their experience differently, there was a common theme of realizing that there really were no borders or boundaries on the planet, and a new ecological awareness of the need to protect and preserve the Earth. In 1998, the American Institute of Aeronautics and Astronautics published a revised version of the book, this time with 22 astronaut interviews.
While The Overview Effect certainly had an impact, especially in the space exploration community, the ideas in it were not, early on, disseminated to the larger society. However, as I have often said, the Overview Effect is a message to humanity from the universe, and it's important that this message be delivered. Over time, it has begun to happen.