The overview effect is a cognitive shift in awareness experienced by astronauts when seeing firsthand the reality of the Earth in space, which is immediately understood to be a tiny, fragile ball of life, "hanging in the void", shielded and nourished by a paper-thin atmosphere.
“From space, I saw Earth—indescribably beautiful with the scars of national boundaries gone.” ~ Muhammad Ahmad Faris, Syrian Astronaut
From space, national boundaries vanish, the conflicts that divide people become less important, and the need to create a planetary society with the united will to protect this "pale blue dot" becomes both obvious and imperative.
Within this frame sits the planet which we call home. This one picture fits every person you have ever met, ever loved, and have ever even heard of, living or dead. All the nations, wars, politics, stories, history, empires, landmarks, songs, works of art, and every other thing you know started here. Lives here.
And in the background, that black backdrop of space is miles and mile of nothing. We are surrounded by nothingness, protected from solar winds, radiation, and the occasional wandering meteoroids by our atmosphere and magnetic fields. Upon this blue marble is a world abundant with life, millions of species, billions of humans, and even more animals, insects, and other forms of life. This is our planet, our Earth.