Atmospheric sprites have been known for nearly a century, but their origins were a mystery. Now, a team of researchers has evidence that sprites form at plasma irregularities and may be useful in remote sensing of the lower ionosphere.

A fleet of orbiting satellites monitors Earth constantly. The satellites from NASA and other space agencies give us a fresh, wide perspective on things that we can see from the ground – and things that we can’t.

Satellite -- A satellite is an object that orbits another object.
With sufficient tangential velocity, the object does not collide with the primary object it orbits, but maintains a distance from that object as the rate at which it falls towards that object is similar to the rate that it travels away, thus the object orbits the primary object and becomes a satellite.
In other words: gravitational force serves as the centripetal force needed to make the object circle the primary...

A pivoted catch designed to fall into a notch on a ratchet wheel so as to allow movement in only one direction (e.g. on a windlass or in a clock mechanism), or alternatively to move the wheel in one direction.