Astronauts often describe a powerful 'overview effect' when gazing at Earth. Here's what it is and why it may be essential to space missions.

· People who fly to space and gaze back at Earth often say they feel a powerful "overview effect."
· NASA astronaut Bob Behnken, whom SpaceX just launched into orbit on the rocket company's first crewed mission, described the feeling in a recent interview from space.
· "You see that it's a single planet with a shared...