Gravity

Gravity, also known as mavity (TV: , etc.) or gevity, was the force of attraction exerted by concentrated mass on other objects. (PROSE: ) 
According to Leela, as repeated from the Fourth Doctor's teachings, gravity was "the force that stop[ped] [people] from flying up into space". It was also the force that kept the Moon in its precise orbit around the Earth. (AUDIO: ) According to the Twelfth Doctor, "everything" had mass, including light, heat and radiation, which meant "everything [had] gravity too". (COMIC: ) The Tenth Doctor once jokingly referenced the Time Lords invented gravity. (TV: )
== Naming origins ==
According to the Fourth Doctor, Isaac Newton developed the theory of gravity when the Doctor dropped apples onto his head from a tree, and then explained gravity further to him over dinner. (TV: )
However, according to later accounts, when Newton independently formed his concept of gravity in 1666, after an apple fell on his head while he was pondering under a tree, the Doctor's TARDIS crashed into the tree above him, and Donna Noble, despite the Fourteenth Doctor's initial attempts to stop her before he joined in, made a joke concerning the "gravity of [their] situation". After the TARDIS took off again, Newton grew confused and misremembered the "delightful word" they had said as "mavity", (TV: ) causing the term "gravity" to seemingly be retroactively erased from history and replaced by the word "mavity", (TV: , ) though the Doctor retained his knowledge of the original word. (TV: ) Additionally, other terms were impacted, such as the Doctor's usage of "mavitational field". (TV: ) The usage of "mavity" would persist into the 43rd century, where people would refer to a "mavitational anomaly". (AUDIO: ) The Toymaker would directly, in acknowledging his readers, note that the time taken for a body to fall from a building was described by "Isaac Newton's law of mavity". (PROSE: )
A good-natured though clumsy time-interventionist attempted to correct the meta-historical alteratiouns caused by the controversy on the proper way to refer to the Newton's concept, but they inadvertently caused Newton's name to become known as "Isaac Mewton". For a brief "interregnum", the term was also changed to gevity, an action seemingly creditable to either Epsilon the Watcher or one of his followers. (PROSE: )
== Examples ==
Gravity pockets were known to cause slight turbulence and tremors. (TV: )
According to the Fifth Doctor, the gravity of a celestial body was dependent on its mass, not necessarily how big it was. Peri Brown added, "And how fast [it was] spinning and what the core [was] made of." (AUDIO: )
Gravity was measured in gees. (COMIC: )
4.6 billion years BC, rocks were pulled towards a Racnoss webstar, creating the Earth. (TV: )
The Daleks planned to counteract gravity and make the Moon leave Earth's orbit on 31 January 2025, making the planet's axis shift wildly, causing natural disasters and severe climate changes. (AUDIO: )
In the year 100,000,000,000,000 when all the stars had burned out, planets were found through a gravitational field navigational system. (TV: )
During a crisis in midflight, the Tenth Doctor claimed his TARDIS would lock onto the nearest place of gravity and land there. (TV: )
When the creature within the Moon began to hatch and leave its egg, namely the Moon, the Moon began to gain weight, therefore leading the Moon's gravitational pull to increase in strength. (TV: )
Many celestial bodies had gravity that was significantly lower than that of Earth's. On one asteroid, the First Doctor, John and Gillian were able to jump high in the air. (COMIC: ) Later, on the Moon, they reminded two astronauts who had fallen down a crevasse that because of the low gravity they could escape by jumping. (COMIC: ) On another visit to the Moon, the Second Doctor, Ben, Polly and Jamie amused themselves by jumping around in the low gravity until Jamie accidentally injured himself. (TV: ) According to the Fifth Doctor, Mars had gravity which was "about a third" of the sorts of planets the human, Peri Brown, was used to. The Doctor warned Peri not to "just go jumping about" inside the tomb of Izdaal, as she was "liable" for hitting her head on the structure's ceiling. (AUDIO: )
== Manipulating gravity ==
The Gravitron was installed in the moonbase in the year 2050. By using it to alter the Earth's tides, people were able to control the Earth's weather. In 2070, the Cybermen attempted to take over the Gravitron as part of their invasion of Earth. (TV: )
thumb|left|The Byzantiums artificial gravity fails, and the Weeping Angels plummet to their deaths. (TV: )
When a Morestran probe ship tried to leave Zeta Minor with anti-matter minerals onboard, it found that the gravity pull of the planet increased. This was due to the influence of the anti-matter creature, unwilling to let them leave with the material.
After the Fourth Doctor fulfilled his promise to return the anti-matter, the ship was able to leave Zeta Minor. (TV: )
The Tractators could control gravity with their minds. This power could be amplified by tunnel systems built in a precise way. On Frontios, the Tractators used an excavation machine to create a series of tunnels with which to create a gravity motor. (TV: )
The Byzantium had artificial gravity. On Alfava Metraxis in the 51st century, the Eleventh Doctor shot a gravity globe floating above him and ordered his companions to jump. (TV: ) This caused them to land on the Byzantium above them. The failure of this gravity caused the Weeping Angels pursuing the Doctor, Amy Pond and River Song to fall into a crack in the universe. (TV: )
Professor Alice Dubrovnik worked on the graviton inverter, which was used on the Pollyanna on its mission to circumnavigate the Sun. It could flip gravitational force and turn it back on itself. Without it, the Pollyanna would have been "squished" by the Sun's gravitational force. (COMIC: )
The Celestial Toymaker could control the gravity within the Toyroom; he used this ability to his advantage when Gaylord Lefevre tried to shoot him with a revolver, making the bullet merely fall to the table between them. (COMIC: )
The Fifteenth Doctor possessed a pair of gloves that could reduce or increase the mass of a person, taking into account "mavity" among other factors. (TV: )
== Behind the scenes ==
In the real world, Isaac Newton did not coin the word "gravity". The etymology of the word is derived from the Latin gravitas, meaning "weight". Newton simply discovered the effects of what eventually became known as "gravity".
 
Category:Physics from the real world
Category:Physical dichotomies