Editing Third Doctor (section)

=="Reverse the polarity of the neutron flow"==
A [[catchphrase]] devised during the Third Doctor's era was "reverse the polarity of the [[neutron]] flow". [[Terrance Dicks]] recalls that he had used the line in a script, and Pertwee approached him about the line. Knowing that Pertwee struggled with [[technobabble]] in the role, Dicks had feared that he would have to remove the line, but Pertwee stated that he found it manageable and wanted to see it more often.<ref name=FactFiction>"Terrance Dicks: Fact & Fiction" (''Horror of Fang Rock'',  BBCDVD1356)</ref>

The Third Doctor only said the full phrase "reverse the polarity of the neutron flow" twice on screen – in ''[[The Sea Devils]]'' (1972) and the 20th Anniversary special "[[The Five Doctors]]" (1983), with numerous other examples of "reverse the polarity" and earlier instances of "fusing the control of the neutron flow" and "change the polarity".<ref name=FactFiction /> Pertwee used the phrase when he acted in the stage play ''[[Doctor Who – The Ultimate Adventure]]'' in 1989. When [[Colin Baker]] took over the role in the play he amended the line to "Reverse the linearity of the proton flow." In the radio play ''[[The Paradise of Death]]'', the Brigadier asks "Reverse the polarity of the neutron flow?" and the Doctor proceeds to explain that the phrase is meaningless (though in reality neutrons can be polarized by a magnetic field, such that reversing the magnetic field's direction reverses the polarity of the neutrons<ref>{{cite journal |last1=Day|first1=Charles |title=Reverse the polarity of the neutron flow! |journal=Physics Today |year=2015 |issue=7 |page=19145 |doi=10.1063/PT.5.010323 |bibcode=2015PhT..2015g9145D |url=https://physicstoday.scitation.org/do/10.1063/PT.5.010323/full/|url-access=subscription }}</ref>).

The full phrase was used in several [[Target Books|Target]] novelisations. It was subsequently used by the [[Fourth Doctor]] (in ''[[City of Death]]'') and the [[Fifth Doctor]] (in ''[[Castrovalva (Doctor Who)|Castrovalva]]'' and ''[[Mawdryn Undead]]''). Together with "The Five Doctors", this resulted in the phrase being used as a nostalgic reference. In the [[Tenth Doctor]] episode "[[The Lazarus Experiment]]", the Doctor, while hiding in Lazarus' machine, comments that it had taken him too long to reverse the polarity due to being out of practice. The Tenth Doctor uses the full phrase in "[[Music of the Spheres (Doctor Who)|Music of the Spheres]]".

During the episode "[[The Almost People]]", a clone of the [[Eleventh Doctor]] speaks the phrase while reliving the memories of all his predecessors. He goes on to conflate it with his regeneration-spanning love of [[jelly baby|jelly babies]], remarking that they need to "reverse the jelly baby of the neutron flow".<ref>''Doctor Who'' (2005), S6E06, "The Almost People"</ref> In "[[The Day of the Doctor]]", the Eleventh Doctor invokes the phrase when confronting a time portal with the Tenth Doctor, suggesting that they both "reverse the polarity" with their [[sonic screwdriver]]s (which merely neutralizes each other's efforts). In "[[The Girl Who Died]]", the [[Twelfth Doctor]] tells [[Clara Oswald]] he is "Reversing the polarity of the neutron flow", followed by "I bet that means something. It sounds great." Clara herself uses the phrase, saying she "reversed the polarity" of a mind-wiping device to prevent the Doctor from erasing her memories of him from her mind ("[[Hell Bent (Doctor Who)|Hell Bent]]"). In "[[It Takes You Away]]", [[Yaz Khan (Doctor Who)|Yaz Khan]] suggests that the [[Thirteenth Doctor]] reverse the polarity on the sonic screwdriver in order to (successfully) open a locked inter-universe portal.