Editing Mir (section)

===Microgravity===
At ''Mir'''s orbital altitude, the force of Earth's gravity was 88% of sea level gravity. While the constant free fall of the station offered a perceived sensation of [[weightlessness]], the onboard environment was not one of weightlessness or zero gravity. The environment was often described as [[Micro-g environment|microgravity]]. This state of perceived weightlessness was not perfect, being disturbed by five separate effects:<ref name="gravity">{{cite web|url=http://www.spaceflight.esa.int/users/downloads/userguides/physenv.pdf|title=European Users Guide to Low Gravity Platforms|access-date=13 July 2011|date=6 December 2005|publisher=European Space Agency|pages=1–3|archive-url=https://web.archive.org/web/20090327101925/http://www.spaceflight.esa.int/users/downloads/userguides/physenv.pdf|archive-date=27 March 2009}}</ref>
* The drag resulting from the residual atmosphere;
* Vibratory acceleration caused by mechanical systems and the crew on the station;
* Orbital corrections by the on-board gyroscopes (which spun at 10,000&nbsp;rpm, producing vibrations of 166.67&nbsp;[[Hertz|Hz]]<ref name="MirGyros"/>) or thrusters;
* [[Tidal force]]s. Any parts of ''Mir'' not at exactly the same distance from Earth tended to [[Gravity-gradient stabilization|follow separate orbits]]. As each point was physically part of the station, this was impossible, and so each component was subject to small accelerations from tidal forces;
* The differences in orbital plane between different locations on the station.