Low Earth orbit
Videos
A low Earth orbit is an orbit around Earth with a period of 128 minutes or less and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, peaking in number at an al
A view from the International Space Station, in a low Earth orbit (LEO) at about 400 km (250 mi), with yellow-green airglow visible at Earth's horizon, where roughly at an altitude of 100 km (62 mi) the boundary between Earth and outer space lies and flying speeds reach orbital velocities
Weightlessness
Videos
Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g or, misleadingly, zero gravity.
Astronauts on the International Space Station experience only microgravity and thus display an example of weightlessness. Michael Foale can be seen exercising in the foreground.
NASA's KC-135A plane ascending for a zero gravity maneuver
Inside a Russian Ilyushin 76MDK of the Gagarin Cosmonaut Training Center
Zero-gravity testing at the NASA Zero Gravity Research Facility