Causal nexus A causal nexus , ( TV : " Logopolis " ) also called a time - space nexus , temporal nexus point , causal nexus point , nexus point , or just nexus , was a place in space and time that was malleable , ( PROSE : " Remembrance of the Daleks " ) points in the space - time continuum that were very rare and hard to access . ( PROSE : " Invasion of the Cat - People " ) Where time would normally be able to resist or absorb minor changes , the Third Doctor noted that some locations in space and time were temporal probability nexuses where multiple strands of causality were exposed and weak , and the smallest alteration could produce aberrant loops of existence or even new alternate timeline s . ( PROSE : " The Eye of the Giant " ) As related to cause and effect , i . e . causality , nexus points often served as areas for potential anomalies , since the Fourth Doctor stated that every point in time had its alternative . ( TV : " Pyramids of Mars " ) In time . Causal nexuses existed within time fissure s , which were created all the time . Though not visible , they could be sensed by time sensitives , and larger events could create fissures where time track s diverged from the nexus point , allowing for travel to parallel universe s . ( AUDIO : " The Wreck of the Titan " ) The Doctor ' s TARDIS became caught in a spatio - temporal causal nexus point when it hit a bump in the time track , generated by the Dalek s of an alternate timeline using a time corridor to pull the Fifth Doctor into their future . ( AUDIO : " The Mutant Phase " ) The causal nexus divided when Nyssa changed history , causing the universe to exist in two quantum states and releasing blinovitch energy . When the time paradox was corrected with another paradox , the Fifth Doctor became the causal nexus as the paradox resulted from knowledge he would claim not to know in his personal future . ( AUDIO : " Prisoners of Fate " ) In keeping with this , the " Wenley Moor Affair " was a crucial nexus - point in Earth ' s time stream because countless futures could diverge from that moment into alternate realities . ( COMIC : " Final Genesis " ) The Sixth Doctor detected a temporal nexus point which turned out to be Evelyn Smythe , whose ancestors were slowly disappearing from history . ( AUDIO : " The Marian Conspiracy " ) The planet Chronos in 3286 was a nexus point which could have led to the creation of the Cyberverse . ( WC : " Real Time " ) The temporal period surrounding 1941 Earth was a crucial nexus point in the planet ' s development , and any alternations , such as killing Hitler , would disrupt the Web of Time . ( COMIC : " Me and My Shadow " ) Rose Tyler , having travelled to Donna ' s World , refused to reveal her name . She stated that " one word in the wrong place can change an entire causal nexus " . ( TV : " Turn Left " ) When asked why he couldn ' t just take the TARDIS back to the previous day , the Tenth Doctor recited , as if by rote , " I can ' t go back within my own timeline . I have to stay relative to within the causal nexus . " He earlier called the same set of events a convergence . ( TV : " The End of Time " ) When the Kin ' s take - over of Earth led to human ity dying out by 2010 , the Eleventh Doctor explained to Amy Pond that she still existed because she was an independent temporal nexus , " chrono - synchronistically established as an inverse . . . , " but eventually agreed with Amy that the reason was " timey wimey . " He also referred to the divergence point in 1984 for the alternate timeline as the nexus . ( PROSE : " Nothing O ' Clock " ) While discussing changing her personal past , Older Amy Pond capped a list comprised of destiny and causality with the nexus of time itself , a structure of causal nexus points that described or defined time . However , at the time she was referencing changing her own recent personal history from within a stable temporal anomaly that was generated artificially . ( TV : " The Girl Who Waited " ) In space . Causal nexuses seemed to exist as actual structures of the universe , based on planet s . Earth was widely recognised as one of the causal nexus points of the Mutter ' s Spiral . ( PROSE : " " ) Logopolis and its inhabitants ran the Charged Vacuum Emboitment s that kept N - Space going past the point of collapse . When stopped Logopolis , he caused the unravelling of the whole causal nexus . This released a wave of entropy that engulfed parts of the universe , killing them . ( TV : " Logopolis " ) A nexus resided in the transjovian space near Jupiter , which the Hand of Omega reached using faster - than - light travel , after which traversing the nexus to reach Skaro in its own time zone by punching a hole in reality . ( PROSE : " Remembrance of the Daleks " ) In both . The particles of the Time Vortex could clump together at a nexus point . A TARDIS could hold onto a nexus point with mathematical anchors to resist the streaming delta flows . ( PROSE : " " ) The Seventh Doctor considered ( and blamed ) Earth as a " major time - space nexus " for the reason he was on Earth at certain times and the coincidences that came from that . These included him being in Mesopotamia in the time of Gilgamesh ( PROSE : " " ) and being in Ife during the 10th century . In the latter travel , there may have been static electricity involved which made the Yoruba believe he was Shango , the thunder god . ( PROSE : " Transit " ) The Edifice ' s interior dimension s were mapped onto its exterior , making it the same size inside as outside , cancelling its dimensional transcendence . This also caused it to become a " nexus point " , affecting past and future events along the " causal pathways " , generating temporal anomalies in the resulting temporal pulses . ( PROSE : " The Ancestor Cell " ) Outside time and space . A hyper reality nexus was created by Godwanna to access hyper reality and absorb all the energy she created from destroying Earth in 1994 . ( PROSE : " Invasion of the Cat - People " ) There were points in the universe where parallels collided , where the Parallel Sect created a reality web threaded through the whole infinity of the universe . ( AUDIO : " The End of the Line " ) Behind the scenes . The term " temporal nexus point " first appeared in FASA ' s " The Doctor Who Role Playing Game " , but was not used in a valid story until " The Marian Conspiracy " .