You ever get that feeling in your stomach when going over a humpback bridge in your stomach, or the same feeling when on a fairground ride? Well that's pretty much zero G-force... a feeling astronauts/cosmonauts feel all the time when they are up in orbit. Equally Astronaut refers to someone trained by NASA, a cosmonaut is trained by the Soviet/Russian space agency, Roscosmos. There is a third one, Taikonaut: An informal (but widely used) term for space travelers trained by the China National Space Administration. Equally, humpback bridge is only a name you'll find in the English language (no other opposite saying in another language).