THE 1960S:
 In 1963 A.D., the First Doctor and his grand-daughter, Susan, met Ian Chesterton and Barbara Wright in the junkyard at 76, Totters' Lane.   The two school teachers discovered the TARDIS and inadvertently precipitated its departure for 100,000 B.C. (A).
 That sudden departure prevented the Doctor from recovering the Hand of Omega, which he had left behind.  Eventually, he returned for it, now in his Seventh Incarnation, with Ace, but had to fight both Daleks and Imperial Daleks from the future in order to secure it (7H).
 That same year, possibly precipitating the above events, as well as the assassination of President Kennedy, the Silver Nemesis circled near Earth (7K).
 In 1964 A.D., the First Doctor and his Companions, Susan, Ian and Barbara, found themselves miniaturized to insect-size, but still defeated an evil industrialist named Forester, whose lethal pesticide, DN6, threatened all life on Earth (J).
 In 1965 A.D., eing Daleks from the future, the First Doctor, Ian, Barbara and Vicki, made a quick landing at the top of the Empire State Building in New York.  Soon afterwards, Ian and Barbara returned to London in the Dalek time machine (R).
 On Christmas Day of that same year, the First Doctor and his Companions, again trying to escape the Daleks, made a brief stop at a Liverpool police station.  A week later, the time travellers made a short appearance in Trafalgar Square during the New Year's festivities (V).
 In 1966 A.D., the First Doctor and Steven Taylor paused briefly in London to pick up a new companion, Dodo Chaplet, on Wimbledon Common (W).
 Later that year, the First Doctor, Ben Jackson, Polly and Dodo defeated the evil computer WOTAN and its War Machines, which threatened to take over London.  At the end of this adventure, Dodo decided to stay in London, while Ben and Polly left with the Doctor (BB).
 The Second Doctor, now accompanied by Jamie, brought Ben and Polly back to England (Gatwick Airport) the very same day they had left, but much later in the time travellers' own timeline.  There, they fought the alien Chameleons.  Afterwards, Ben and Polly chose to remain behind (KK).
 Immediately following the previous adventure, the Second Doctor and Jamie were lured back to 1866 A.D. by Prof. Waterfield's time machine.  There, they met Victoria Waterfield and thwarted an attempt by Daleks from the future to infect Mankind with the Dalek Factor (LL).
 In 1969 A.D., the Second Doctor, Jamie and Victoria renewed their acquaintance with a much older Prof. Travers, and fought the Great Intelligence and its robot Yeti in the London Underground.  There, the Doctor met the then-Colonel Lethbridge-Stewart for the first time (QQ).
 [ Note:  The Yeti invasion was, with the possible exceptions of the Daleks' brief attack of 1963 and the Chameleons' secret assault of 1966, the first credible instance of an alien enemy attempting to invade or destroy Earth.  This convinced the powers-that-be of the necessity for an international, United Nations-backed entity to deal with such global threats.  This led to the formation of several multinational organizations such as UNIT and the World Ecology Bureau.  Thus began a process of international cooperation, which resulted in the unification of Earth by the beginning of the 21st century.]
 Soon afterwards, the Second Doctor, Jamie, Ben Jackson and Polly helped stop a mad scientist, Prof. Zaroff, from using the unwitting help of Atlantean survivors to destroy the Earth (GG).
 Then, the Second Doctor, Jamie and Victoria defeated a sentient weed which threatened a North Sea gas refinery.  Victoria chose to remain with the Harris family (RR).
 [ Note:  It was probably after Victoria's departure, and before the Second Doctor's initial meeting with Zoe, that the Doctor and Jamie went on two unrecorded adventures, the memory of which were erased from their minds by the Time Lords:
 * In the first adventure, the two time travellers fought the Cybermen on Planet 14.  The Cybermen were, at the time, preparing to invade Earth, a fact that the Doctor and Jamie did not discover until the following year (VV).
 * In the second adventure, the Time Lords' Celestial Intervention Agency, which had secretly been monitoring, and possibly even influencing, the Doctor's travels for many years, asked the two time travellers to investigate unauthorized time travel experiments on Space Station J7.  This brought the Second Doctor and Jamie in contact with the Doctor's Sixth Incarnation and his Companion, Peri.  Together, they fought the Androgum Chessene and the Sontarans in Spain during 1985 A.D. (6W).]

 THE 1970S:
 In 1970 A.D., the Second Doctor, Jamie and Zoe, assisted by the newly-formed UNIT, defeated the Cybermen's plan to invade the Earth, using the resources of Tobias Vaughn's multinational corporation, Intl. Electromatics.  Thanks to the Cerebration Mentor of Prof. Watkins (a friend of Prof. Travers), the Cybermen succeeded in paralyzing Earth's population.  However, the Doctor foiled their schemes and the Cybermen's first invasion et was destroyed (VV).
 [ Note:  The Cybermen's second invasion et was destroyed by the Silver Nemesis in 1988 A.D.  The Cybermen mentioned above were "space" Cybermen, an offshoot branch of the original Mondasians, who only returned in 1986 A.D.
 Presumably, the first Moon Landing occurred on the "Earth-Who" at the same time as it did on our world, 1969 A.D., but it probably happened under more international auspices.  In any event, the failed Cybermen invasion accelerated the process of international cooperation in space exploration.  By 1971 A.D., manned space probes were dispatched to Mars (CCC).  By 1977 A.D., Mankind had sent a manned spaceship to Jupiter (4J).  All this eventually led to the formation of the International Space Control organization by the late 1970s or early 1980s A.D. (DD).]
 In 1971 A.D., after being tried by the Time Lords, and summarily forced to regenerate, the Third Doctor was exiled to Earth, his knowledge of time travel erased from his memory.  He became UNIT's scientific advisor, and with Liz Shaw's help, defeated the first invasion of the Nestenes, and their deadly plastic creatures, the Autons (AAA).
 Soon afterwards, the Third Doctor and Liz helped UNIT deal with the Silurians, who left their caves following accidental electrical discharges caused by an atomic reactor.  The Doctor was saddened to see the noble creatures re-entombed by Brigadier Lethbridge-Stewart (BBB).
 Next, the Third Doctor and Liz prevented General Carrington from destroying the so-called "Ambassadors of Death", in reality a trio of peaceful aliens (CCC).
 [ Note:  This adventure occurred at the time of the launch of Earth's first manned space probes to Mars which, by then, had long been evacuated by the Ice Warriors.]
 Later, the Third Doctor and Liz stopped Dr. Stahlman from completing his insane "Inferno" project, which would have doomed the Earth (DDD).
 [ Note:  During the course of this adventure, the Doctor traveled to another alternate Earth where England was ruled by a fascist dictatorship.  That Earth was destroyed by the forces unleashed by "Inferno".]
 Soon afterwards, Liz Shaw left UNIT to return to Cambridge and pursue her scientific studies.
 In 1972 A.D., the Third Doctor, now assisted by Jo Grant, helped UNIT thwart a second Nestene/Auton invasion, this time triggered by his old enemy, the renegade Time Lord known as the Master, who had just arrived on Earth (EEE).
 Then, the Third Doctor, Jo and UNIT defeated the Master's attempts to use an evil Mind Parasite to sabotage the first World Peace Conference (FFF).
 [ Note:  The Conference r cted the growing process of international cooperation mentioned above.  However, the Chinese did not fully participate until the next decade.]
 Soon afterwards, the alien parasite Axos was brought to Earth by the Master.  Promising to usher in a new Golden Age, Axos, in fact, planned to absorb all living energy on Earth.  Ultimately, the Third Doctor was forced to team up with the Master to imprison the evil entity in a time loop (GGG).
 [ Note:  The threat of Axos undoubtedly reinforced international cooperation, especially with the Soviet Bloc.  One can hypothesize that the series of events known as "Perestroika" took place in the 1970s and not the 1990s on "Earth-Who".]
 After a brief interlude with the Brigadier before being dispatched to 2472 A.D. by the Time Lords' Celestial Intervention Agency (HHH), the Third Doctor and Jo were confronted with the awesome threat of Azal.  The last Daemon had been summoned by the Master, who wished to inherit his vast powers.  However, Azal was unable to comprehend Jo's attempt to sacrifice her life in order to save the Doctor's, and the Daemon perished in the ensuing co gration.  The Master was captured by UNIT (JJJ).
 1973 A.D. opened with the Third Doctor, Jo and UNIT defeating an attempt to assassinate a famous diplomat, Sir Reginald Styles.  It turned out that guerillas from an alternate future where the Daleks had conquered Earth after World War III blamed him for their enslavement.  They thought that, by travelling back to the past and killing him, they would prevent that future from happening.  In fact, they achieved the exact opposite, Styles' murder being the actual starting point of the war.  The Doctor's intervention saved Styles' life and Earth's future (KKK).
 [ Note:  By 1973 A.D., peace efforts were concentrated on getting the Chinese to join the now-growing world community.]
 Next, the Third Doctor and Jo fought the Sea Devils, aquatic "cousins" of the Silurians, whom the Master planned to use first to help him break out of prison, and then to conquer the world.  The Master failed in his world domination scheme, but managed to escape (LLL).
 Soon afterwards, the Third Doctor, Jo and UNIT thwarted another of the Master's nefarious plots.  This time, posing as Prof. Thascales, the renegade Time Lord planned to release the powerful chronavore known as Kronos from the Atlantean Crystal which held it prisoner.  Eventually, the Doctor and Jo followed the Master back to the time of Atlantis.  However, they could not prevent Kronos's release -- and the ensuing destruction of the fabled island kingdom (OOO).
 In 1974 A.D., the Time Lords gathered the Three Incarnations of the Doctor to defeat the mind-boggling menace of Omega who, from within a black hole, threatened the entire Universe.  After Omega's defeat, the Doctor was pardoned by the Time Lords, who restored his knowledge of time travel (RRR).
 Then, in an unrecorded adventure, the Third Doctor and Jo, who were probably looking for Metebelis 3, arrived on the planet Karfel.  What they did there remains unknown (6Y).
 Next, the Third Doctor and UNIT fought the evil computer BOSS, who had taken over the multinational Global Chemicals Corporation, and its pollution-created "green death".  During this adventure, Jo fell in love with ecologist Prof. Clifford Jones and quit UNIT to marry him (TTT).
 In 1975 A.D., the Third Doctor met journalist Sarah Jane Smith.  Together, they investigated the disappearances of several scientists, who had been kidnapped and taken back to 1190 A.D. by a stranded Sontaran Commander, Linx (UUU).
 Upon returning to 1975 A.D., the Third Doctor, Sarah and UNIT fought a Dinosaur Invasion engineered by Sir Charles Grover as a decoy for his "Operation Golden Age", with which he hoped to reverse time and wipe out all of Earth's history (WWW).
 Later, the Third Doctor, Sarah and UNIT defeated an invasion of giant, mutated spiders from the failed Earth space colony of Metebelis 3 in the future.  At the end of this adventure, his body ravaged by a deadly dose of radiation, the Doctor regenerated with the help of fellow Time Lord K'Anpo (ZZZ).
 Almost immediately, in an unrecorded adventure, the newly-regenerated Fourth Doctor traveled to a nameless planet in the future.  There, he met a group of humans whose ship had crashed.  The Doctor tried to fix their experimental artificial intelligence, a system called Xoanon, but because of his own mental condition at the time, instead, he unfortunately made it schizophrenic.  The Doctor then returned to Earth at the very same time he had left it, having forgotten most of what had happened (4Q).
 Next, the Fourth Doctor, along with Sarah, UNIT Doctor, Harry Sullivan, and the Brigadier, defeated a plot by an organization called Think Tank to take over the world, using Prof. Kettlewell's giant, experimental robot (4A).
 In 1976 A.D., the Fourth Doctor, Sarah and Harry returned from their journeys through time and space to help UNIT fight the shape-changing Zygons who had emerged from Loch Ness and were using their Skarasen monster to try to conquer the Earth (4F).
 [ Note:  During the course of this story, we learn that Britain's Prime Minister was a woman, which leads us to assume that on "Earth-Who", Mrs. Margaret Thatcher became Prime Minister of England eleven years before she did in our world.]
 After the Zygons' defeat, Harry chose to stay behind with UNIT, but Sarah pursued her travels with the Fourth Doctor, who bri  took her back to an alternate present (or a potential timeline) where Earth had been destroyed by Sutekh (4G).
 In 1977 A.D., the Fourth Doctor and Sarah again teamed up with Harry and UNIT, this time to thwart the alien Kraals' Android Invasion (4J).
 [ Note:  This was soon after Mankind launched its first manned rocket to Jupiter.]
 Soon afterwards, the Fourth Doctor and Sarah helped the World Ecology Bureau and UNIT destroy a Krynoid, a hostile, alien, vegetable lifeform, whose pods had been recovered in the Antarctic, and which had been allowed to grow to full-size by the insane millionaire Harrison Chase (4L).
 Next, the Fourth Doctor fought Eldrad the Kastrian, whose fossilized hand had been buried during the Jurassic and which was accidentally found by Sarah.  To protect Earth from Eldrad's powers, the Doctor took the alien back to his home world, which by then had become a barren, lifeless world.  Then, after receiving a summons to Gallifrey, the Fourth Doctor had no choice but take Sarah back to her own time (4N).
 It was at approximately the same time that Brigadier Lethbridge-Stewart retired from UNIT and took a job as a teacher at the Brendan School, leaving the British branch of UNIT in the capable hands of Colonel Crichton.  RSM Benton also left, eventually to take over a car dealership (6F).
 Later that year, Tegan Jovanka and Nyssa of Traken, two of the Fifth Doctor's Companions, met the retired Brigadier at Brendan School and, together, they fought Mawdryn in 1983 A.D.  However, the Brigadier emerged from the encounter with his future self with selective amnesia (6F).
 In 1978 A.D., the Fourth Doctor, Leela and K9 defeated the Fendahl, which had been brought back to unholy life by Dr. Fendelman's experiments.  The Doctor eventually jettisoned the Fendahl Skull near a supernova (4X).
 In 1979 A.D., during their search for the components of the Key to Time, the Fourth Doctor, Romana and a second version of K9 prevented the pirate planet Zanak from rematerializing around Earth and totally crushing the planet (5B).
 Next, they rematerialized near an English Stone Circle, where they met Prof. Rumford and the mysterious Vivien Fay, who turned out to be the alien criminal Cessair of Diplos.  The Fourth Doctor, Romana and K9 defeated Cessair and her "Stones of Blood" (in reality, the alien Ogri) and outsmarted the Megara justice machines (5C).

 THE 1980S:
 In 1980 A.D., in Paris, the Fourth Doctor and a regenerated Romana met Scaroth's twelvth splinter, Count Scarlioni, who had been selling Mona Lisas to finance Prof. Kerensky's time travel experiments.  The two Time Lords stopped the Jagaroth from going back in time and preventing the creation of life on Earth (5H).
 Later that year, in an adventure of which there are only partial records, the Fourth Doctor and Romana fought Skagra in Cambridge (5M).
 In 1981 A.D., an Earthman was kidnapped by the alien Gaztaks mercenaries, who served the shape-changing Meglos of Zolfa-Thura.  Meglos impersonated the Fourth Doctor in an attempt to steal the Tigellan Dodecahedron, but was eventually defeated by the two Time Lords and K9 (5Q).
 In 1982 A.D., the Master returned, having stolen the body of Tremas of Traken.  He then engaged the Fourth Doctor in a battle of TARDISes near Heathrow, during which the evil Time Lord murdered Tegan Jovanka's Aunt Vanessa.  Before taking off for Logopolis, the Fourth Doctor was mysteriously warned of his impending regeneration (5V).
 Next, after unwittingly causing the destruction of Logopolis, the Master attempted to use the Pharos Project radiotelescope to blackmail the entire universe.  With the help of Adric, Tegan and Nyssa of Traken (Tremas's daughter), the Fourth Doctor was able to stop the Master.  During the battle, the Doctor fell from the radio-telescope's tower and regenerated once again (5V).
 The newly-regenerated Fifth Doctor was then taken by Nyssa and Tegan (Adric had been kidnapped by the Master) to Castrovalva, where he eventually confronted and defeated the evil Time Lord (5Z).
 Meanwhile, Sarah Jane Smith, and a third version of K9 sent to her by the Doctor, fought a coven of Witches in Moreton Harwood (K9).
 In 1983 A.D., the Fifth Doctor, Nyssa and Tegan solved the mystery of the disappearance of a Concorde airplane.  The craft had been hijacked back to the Jurassic by the Master who, disguised as Kalid, was trying to gain control of the alien Xeraphin.  At the end of this adventure, Tegan chose to leave the TARDIS crew (6C).
 Soon afterwards, Omega tried to take over the Fifth Doctor's body.  Tegan returned and rejoined the TARDIS crew in Amsterdam, where the Doctor finally confronted and defeated Omega (6E).
 Next, after a landing on a mysterious spaceship in orbit around the Earth, the Fifth Doctor became separated from Tegan and Nyssa.  The Time Lord beamed down to the Brendan School where he met the mysterious Turlough and the retired Brigadier Lethbridge-Stewart, who had forgotten their adventures.  There, they confronted the alien Mawdryn, who had stolen the Time Lords' Metamorphic Symbiosis Regenerator, and was cursed to live in a state of perpetual regeneration (6F).
 Meanwhile, Nyssa and Tegan had been transported to the Brendan School of 1977 A.D. where they too met the Brigadier.  Eventually, the explosion generated by the encounter between the two Brigadiers (from 1977 and 1983 A.D.) proved sufficient to end Mawdryn's suffering and restore the modern-day Brigadier's memory (6F).
 Later that year, Sarah Jane Smith was kidnapped by Borusa to take part in the Game of Rassilon.  She teamed up with the Third Doctor and, together with the Doctor's other four Incarnations and various Companions, helped thwart the megalomaniacal Time Lord's plans for immortality (6K).
 Meanwhile, having recovered his full memory, the Brigadier renewed his contacts with UNIT.  Borusa snatched him and the Second Doctor (who had transgressed the Laws of Time to visit his old friend) the day before a UNIT reunion.  Together with the Doctor's other four Incarnations and various Companions, the Brigadier helped defeat Borusa (6K).  Soon after that, he married Doris.
 In 1984 A.D., the Fifth Doctor, Tegan and Turlough defeated the Malus in the village of Little Hodcombe (6M).
 Then, the Fifth Doctor and his companions were caught in a Time Corridor set up by Daleks from the future.  The corridor took the time travellers to the London docks, where they fought a bloody battle against the Daleks.  Sick of the violence, Tegan decided to leave the TARDIS crew for good.  One of the Daleks' mercenaries, Lytton, was stranded on Earth (6P).
 Soon afterwards, the Fifth Doctor and Turlough met Peri Brown.  They then travelled to the planet Sarn, where they fought the Master.  At the end of this adventure, Turlough met his brother, Malkon, and chose to return to his homeworld of Trion (6Q).
 In 1985 A.D., following the Cryons' secret plan, Lytton made contact with Cybermen from the future who were trying to save Mondas (from the fate in store for it the following year) by crashing Halley's comet into Earth.  Their plans were eventually thwarted by the Sixth Doctor and Peri (6T).
 Next, in Spain, the Sixth Doctor and Peri teamed up with the Second Doctor and Jamie McCrimmon to stop the Sontarans and the Androgum Chessene from acquiring the secret of the Rassilon Imprimature (6W).
 In 1986 A.D., the First Doctor, Ben Jackson and Polly rematerialized near an International Space Control Antarctic tracking station.  Soon, space scanners showed that Earth's twin planet, Mondas, had returned.  The Doctor and his Companions thwarted a second Cybermen invasion, this time by the Mondasian Cybermen.  In the resulting co ct, Mondas was destroyed (DD).
 In 1987 A.D., due to the machinations of Fenric, a teenage British girl nicknamed Ace was taken away from her home in Perivale and transported through time and space to Ice World, a galactic trading post on Svartos (7G, 7M).
 On 23 November 1988 A.D., the Silver Nemesis returned to Earth and landed near Windsor Castle.  The Seventh Doctor and Ace fought a number of enemies who each tried to claim the deadly artifact for their own: Lady Peinforte, who had travelled forward in time from 1638 A.D. with the statue's arrow, a group of Neo-Nazis led by De res, who had obtained the statue's bow, and finally the Cybermen's second invasion et (from their 1970 A.D. invasion).  The Doctor eventually won, and the Silver Nemesis destroyed the Cybermen (7K).
 In 1989 A.D., the Seventh Doctor took Ace back to Perivale and, together, they solved the mysterious disappearances of several local youths who had been captured by the Cheetah People.  The Doctor also defeated the Master, who had fallen victim to the curse of the Cheetah People (7P).

 In 1992 A.D., the Seventh Doctor and Ace teamed up with retired Brigadier Lethbridge-Stewart and met Brigadier Bambera of UNIT.  Together, they fought the sorcery of a Morgaine from an alternate Earth.  The prize was Excalibur, which had been buried beneath a lake at Cadbury by a future incarnation of the Doctor (7N).
 [ Note:  This story is another proof that the Doctor's adventures take place on an Earth very similar but not quite indentical to our world, since there is no lake at Cadbury on our planet.]
 In 1996 A.D., eing the Daleks, the First Doctor, Ian Chesterton, Barbara Wright and Vicki paid a brief visit to a Horror Pavilion featuring robotic versions of Dracula and the Frankenstein Monster, at the Ghana World's Fair (R).
 Sometime during the late 1990s, the Urbankans returned to Earth for a fifth time.  The Fifth Doctor, Tegan, Nyssa and Adric prevented their leader, Monarch, from poisoning all humans (5W).
 As the 21st Century began, countries increasingly grouped themselves into blocs which became known as Zones (PP), while the management of the planet was entrusted more and more to international organizations and councils.
 This was not achieved without a number of local conflicts, during which tactical nuclear devices were used.  The young and brilliant Mexican scientist Salamander conceived a plan to sequester some "survivors" in a vast underground shelter in Australia, making them believe that the Earth's surface had turned into a radioactive wasteland (PP).
 Meanwhile, on the surface, global international cooperation had been achieved.  Priority was given to solving a number of ecological problems, such as the availability of adequate food supplies, an issue made more acute by population growth.  The development of planetary weather control was one of the tools being researched to that end.
 In the early days of the new century (2010-2020 A.D.), a Moon Base, managed by international personnel, was finally built, along with a number of orbiting space stations, known as "Wheels in Space".  This was done primarily with an eye towards helping the above-mentioned ecological effort on Earth, but it also fostered further exploration of the rest of the Solar System -- and beyond.
 In addition to the use of robot probes, several interstellar ships were launched.  Traveling at sub-light speed, they were crewed by volunteers placed in hibernation.  At least one of these ships made it to its final destination, forming the colony later known as Vulcan (EE).
 [ Note:  The Vulcan colonists kept their original dating system, hence for them it was still 2020 A.D., even though the Earth calendar indicated it was much later.]
 C. 2020 A.D., the Cybermen returned.  With the help of their Cybermats, they attacked Space Station W3, plotting to use it to conquer Earth (SS).  By then, Mankind had explored the asteroid belt, after dismissing Mars as a world incapable of sustaining life.  The various aborted alien invasions of the late 20th Century were no more than historical events.  Humanity was relatively unprepared to face a new series of hostile alien attacks.
 Fortunately, the Cybermen's plans were defeated by the intervention of the Second Doctor and Jamie, and that of the young and brilliant scientist Zoe Heriot, who joined the TARDIS crew (SS).
 In 2030 A.D., food sufficiency was achieved on Earth, thanks to Salamander's "Suncatcher" satellite.  But the megalomaniacal villain tried to use it to create violent earthquakes that would have killed off Earth's population.  He then would have repopulated the planet with his own "survivors".  His efforts were thwarted by the Second Doctor, Jamie and Victoria Waterfield (PP).
 By 2050 A.D., weather control was perfected with the use of the Gravitron device, housed on the Moon Base.  Mankind's space exploration had now spread out to encompass the entire solar system.
 In 2070 A.D., the Cybermen again returned, invading the Moon Base and plotting to use the Gravitron to destroy Earth.  They were defeated by the Second Doctor, Ben Jackson, Polly and Jamie (HH).
 Next, several events caused Mankind to turn its back on space travel: first, there was the Cybermen's attack, and the disasters it had created on Earth.  Second, there were a series of serious setbacks in space exploration, accidents with high death tolls, possibly connected with the research and development of faster-than-light engines.  Third, and possibly of greater relevance, was the fact that Mankind was about to go through a phase when great enthusiasm for exploration and expansion was followed by a desire for retrenching and coccooning.  Although the Solar System was virtually in their grasp, many on Earth began to wonder if it had been worth it, and campaigned to stop further "wasteful" exploration.  (Such attitude swings would reoccur several times in the future.)
 The nail in the coffin of space travel, however, was the development of T-Mat (XX) -- instantenous travel between two relay stations.
 Coordinated from the Moonbase, T-Mat not only took care of the majority of Earth-based travel, but also of journeys between Earth and its network of space stations.
 With the advent of T-Mat, Mankind stopped using manned spaceships.  All travel within the Solar System was entrusted to T-Mat.  Space exploration was all but abandoned.  Meanwhile, on Earth, relations between the Zones had deteriorated, perhaps as a result of this claustrophobic retrenchment.
 In 2084 A.D., the Fifth Doctor, Tegan and Turlough prevented the Silurians and the Sea Devils from starting a war between the blocs (6L).
 Opposition to T-Mat had already begun to appear, but the final straw was when, c. 2090 A.D., the Martians returned to the Solar System.  They invaded the Moon Base and tried to use the so-called "Seeds of Death" in an attempt to alter Earth's atmosphere and take over our planet.  Their plans were foiled by the Second Doctor, Jamie and Zoe (XX).
 [ Note:  The Martians had by then resettled on another planet -- "New Mars" -- but had become politically divided into two clans: one favoring a return to the Solar System and a conquest of Earth, the other continued, peaceful existence.  The "conquest party" won, which led to the attempted invasion described above.  After their defeat, the "peace party" took over, and the Martians did not attack Earth again.]
 The Martians' aborted invasion provided Mankind the boost it needed to "rediscover" manned space travel and enter a new phase of expansion.  On Earth, a true World Government was established, in the form of a Presidency.  A new push outward was initiated.

 As the 21st Century ended, and the 22nd Century began, Mankind discovered the first, still rudimentary faster-than-light (warp) propulsion.
 A second wave of colonization ships, this time, using warp drives, was launched. As a result, Earth started to colonize its neighboring solar systems and to have its first encounters with alien races on other worlds.
 However, some of these early ships never reached their intended destinations.  Or if they did, they were never heard from again.  These became known as the "Lost Ships."  One such ship was the exploration vessel "Hydrax", whose captain was Miles Sharkey. En route to Beta Two, the "Hydrax" found itself diverted into E-Space, possibly drawn there by the Great Vampire.  Its three officers built a decaying civilization of servants, preparing for the Great one's eventual rising.  A thousand years later, their plans were shattered by the Fourth Doctor, Romana and Adric (5P).
 Another ship which was lost during the early days of the 22nd Century crashlanded on the blue planet, Metebelis 3.  The Earth spiders it unwittingly carried mutated under the i ence of native crystals, and ended up ruling the human colonists for 430 years, until they were destroyed through the intervention of the Third Doctor and Sarah Jane Smith (ZZZ).
 Between 2100 and 2150 A.D., Mankind spread through its local galactic arm, settling new worlds, establishing new colonies, and meeting its first alien threats.
 Contact was re-established with the Vulcan colony, which had awakened from suspended animation and thrived.  Their calendar was off by a Century (EE).
 Another Earth colony was secretly taken over by the crab-like Macra, which forced the humans to toil to extract a gas the aliens needed for their survival.  They were exposed and defeated by the Second Doctor, Jamie, Ben Jackson and Polly (JJ).
 It was also during this time that the Fourth Doctor, Romana and K9 accidentally found themselves aboard the ships "Empress" and "Hecate", which had both rematerialized in orbit around the planet Azure at the same time.  They were able to unmask the villainous Tryst, who used the alien Mandrels and a primitive version of the Scope, to traffic in the deadly drug, vraxoin (5K).

 Mankind's slow but steady space expansion inevitably attracted the hostile attentions of other galactic powers.  One such power was the Daleks.
 [ Note:  By then, the Daleks had already conquered their space sector and driven their ancient foes, the Thals, off their homeworld of Skaro.  The Daleks were generally feared throughout known space for their aggressivity and ruthlessness.]
 By 2160 A.D., the Daleks had launched a secret plan to invade Earth.  First, they spread virulent plagues through a swarm of metorites.  As a result of the ensuing diseases, the Solar System was put under quarantine by the other human-colonized worlds, leaving the Daleks the free hand they sought (K).
 In 2164 A.D., the Daleks struck, invading an almost depopulated Earth.  Any attempt at space intervention by the other human worlds was firmly dealt with by the Daleks' space et, which blockaded the planet.  Obviously, other friendly races proved unwilling or unable to help.  This became known as the First Dalek War (K).
 Among the Colonists who participated in the First Dalek War -- and, sadly, never returned -- were the adult inhabitants of "Paradise Towers", an award-winning residential complex which, once abandoned, reverted to savagery.  Threatened by the return of its insane architect, "Paradise Towers" was saved by the opportune visit of the Seventh Doctor and Mel (7E).
 Meanwhile, the Daleks believed that, once Earth was gone, the other human-dominated worlds would be easily picked off, one by one.  This would have been so, if it had not been for the Doctor.
 In 2167 A.D., the First Doctor, Susan, Ian Chesterton and Barbara Wright helped Earth-based rebels to defeat the Daleks, who had ultimately planned to turn Earth into a mobile planet by draining its core and replacing it with giant star drives.  Susan chose to remain on Earth with freedom fighter David Campbell (K).
 [ Note:  The Third Doctor once visited an alternate future where Mankind suffered a Nuclear War in the late 20th Century, and where the Dalek invasion was totally successful (KKK).]
 C. 2187 A.D., Susan was kidnapped by Borusa to take part in the Game of Rassilon.  She teamed up with the First Doctor and, together with the Doctor's other four incarnations and various Companions, helped thwart the megalomaniacal Time Lord's plan for immortality (6K).
 The Dalek invasion had shown Earth and its colonies that there was force only in strength and unity.  Mankind could only count on its own ressources.  That lesson was not forgotten, and Earth took its first steps towards developing into a major galactic power.

 As the 23rd Century began, Earth (the term now included its colonies and allied worlds) came into direct co ct with another deadly galactic foe, one which had already attacked at least four times in the past: the Cybermen.
 During the First Cyber Wars, Man and its allies ultimately defeated the Cybermen by discovering that gold, which existed in abundance on the planet Voga, was fatal to their enemies.  Driven from their world(s), the Cybermen had no choice but to e.  Before they did so, they made an attempt to destroy Voga, but were only partially successful.  A fragment survived and began to drift towards the Solar System (4D).
 Soon afterwards, the Cybermen conquered the planet Telos and its native Cryons, and built "Tombs" in an attempt to heal and preserve their species for future assaults (MM, 6T).
 Meanwhile, c. 2220 A.D. (c. 2020 A.D. by Vulcan calendar), a few Daleks who had crashed on Vulcan after the First Dalek War were brought back to life and attempted to take over the Colony.  They were defeated by the Second Doctor, Ben Jackson and Polly (EE).
 After the Cyber Wars, Earth pursued its expansionist policies in its local Galactic quadrant, meeting other alien races, establishing new colonies and developing business opportunities.  Slowly but surely, Earth became a space power to be reckoned with.
 It was during the later part of 23rd Century that the Fourth Doctor and Romana visited the Leisure Hive on Argolis, and resolved a conflict between the Argolins and the reptilian Foamasi (5N).
 It was also during that time that Earth's Multiplanetary Corporations began to thrive, and often displayed a ruthlessness in the pursuit of their business objectives that made them formidable foes.
 But Earth's corporations also had adversaries to equal them, such as the cunning and rapacious Mentors of Thoros Beta.  It was during the later part of the 23rd Century that the Sixth Doctor and Peri defeated the Mentor Sil's attempts to corner the market of Zyton-7 on behalf of the Galatron Corporation by exploiting the inhabitants of the planet Varos, the unfortunate descendants of a colony for the criminally insane (6V).
 Soon afterwards, the Sixth Doctor and Peri confronted Sil on his homeworld.  Peri almost died through a series of events created by the Time Lords to prevent the Thoros Betans from acquiring the secret of Dr. Crozier's mind transfer technique.  Peri lived, and eventually married King Yrcanos of Thoros Alpha.  The Sixth Doctor was taken to a huge space station to face a tribunal of Time Lords (7B).
 During the 24th Century, possibly as a reaction to Earth's growing authoritarianism, or that of its Corporations, several colonies grew increasingly independent, isolated, and some might say, idiosyncratic.
 One such example was the colony of Terra Alpha, where residents were literally forced to be happy under pain of death.  The Seventh Doctor and Ace put a stop to ruler Helen A's misguided regime (7L)
 Earth's strong arm of the law was the Intergalactic Taskforce, which c. 2310 A.D. helped the newly-regenerated Sixth Doctor and Peri avert the threat of Mestor, tyrant of Jocunda (6S)
 The rest of the 24th century, as had happened before during Mankind's cyclical history, was spent in retrenchment and regrouping.

 Then, as the 25th Century began, Earth started a new period of expansion.  Deciding to open a new galactic arm, the robotic Mechanoids (R) were launched in order to prepare new planets for colonization.
 It was probably during this time that the budding Earth Empire -- although it was not as yet known by that term -- came into contact with the Draconians, rulers of another, powerful, but peaceful, galactic empire (QQQ).
 The Daleks, who had watched Mankind from afar since their initial defeat, decided the time was right to launch a second offensive.  Again, they may have decided to use a familiar weapon: a virus, which became a space plague.  An antidote was found -- Parrinium -- and ultimately located on the planet Exxilon.  But it was only thanks to the intervention of the Third Doctor and Sarah Jane Smith that Earth's Marine Space Corps was able to defeat the Daleks and secure a supply of Parrinium (XXX).
 Once the Daleks' role in the Space Plague became known, several galactic races -- possibly stirred up by the exiled Thals -- united to attack and punish the Daleks.  Thus was born the Alliance, which included Earth and the Draconian Empire.  The war that ensued became known as the Second Dalek War.
 During it, the Daleks were driven away from Skaro, which was reconquered by the Thals.  The Daleks were forced to relocate to another world which, out of pride, they christened Skaro (although we will refer to it as "New Skaro").
 One of the Second Dalek War's side effect was that a number of planets, stricken by the Dalek Plagues, became vehemently xenophobic.  One such world was Inter Minor (PPP).
 Towards the later part of the 25th Century, it was business as usual for Earth.  Several times, the Doctor found himself in conflict with the various corporations.
 In 2471 A.D., the Third Doctor and Jo Grant helped colonists fight the devious plans of the Interplanetary Mining Corporation -- in addition to preventing the Master from using the Doomsday Machine (HHH).
 Around the same time, the Fifth Doctor, Turlough, Tegan Jovanka and Nyssa of Traken fought the inhumane policies of Terminus, Inc. and helped prevent a second "Big Bang".  Nyssa chose to stay and help the victims of Lazar disease, possibly an offshoot of the Dalek plagues (6G).
 Of little importance in galactic terms, was the First Doctor, Ian Chesterton and Barbara Wright's first encounter with Vicki on the planet Dido (which the Doctor had visited before) in 2493 A.D.  The time travellers rescued the young girl from the villainous Bennett.
 Towards the tail end of the 25th Century, the Fourth Doctor, Sarah Jane Smith and Harry Sullivan thwarted the efforts of a small band of isolated Cybermen, remnants of the First Cyber Wars, who were trying to destroy the remains of Voga, which had drifted near Space Beacon Nerva in Earth's Solar System (4D).

 The 26th Century began with the insane Logician Klieg's attempt to resurrect the dreaded Cybermen, whose "Tombs" had been located on Telos, although his plans were foiled by the Second Doctor, Jamie and Victoria Waterfield (MM).
 [ Note:  It is likely that either once the Tombs were opened, they continued to reactivate Cybermen, who then emerged in force, or other Cyber Forces drifting in space may have appeared to complete the job the humans had begun.  In any event, the Cybermen, which had had time to regroup and reform, reemerged as a serious galactic threat.]
 In 2526 A.D., made aware of this new Cyber menace, the same Alliance which had defeated the Daleks, agreed to meet on Earth in a Galactic Congress to decide what steps to take.
 The Cybermen then attempted to destroy the Congress by causing a space freighter to crash on the planet, but their scheme was thwarted by the Fifth Doctor and his Companions.  The young Alzarian Adric unfortunately sacrificed himself, dying on board the freighter, which he had sent back through time to 65 million years B.C. (6B).
 A second series of Cyber Wars ensued.  Having found Voga, Mankind was in possession of a vast supply of gold.  The result was yet another defeat for the Cybermen.
 Just before the Alliance's forces made a final attack on Telos, the Cybermen's stronghold, the Cybermen used a captured time-vessel to launch a final, desperate attack.  They tried to not only save themselves, but alter the course of history.  This time, they planned to cause Halley's Comet to crash into Earth in 1985 A.D.  However, they were defeated by the Sixth Doctor and the courageous Cryons, who had secretly survived and contacted Commander Lytton stranded in Earth's past (6T).
 Around the same time, c. 2530 A.D., the human colonists of Metebelis 3 were finally able to free themselves of the domination of the mutated giant spiders, thanks to the Third Doctor's self-sacrifice (ZZZ).

 C. 2540 A.D., soon after the end of the Second Cyber Wars, the Daleks, who had been driven from Skaro, but were still at large, returned.  They decided that their best tactic would be to create a split between the two most powerful members of the Alliance: Earth and the Draconian Empire.
 They engaged the services of the Master to foment a war between Earth and Draconia, even offering him the use of their Ogron slaves.  But the Master's schemes were ultimately exposed and defeated by the efforts of the Third Doctor and Jo Grant (QQQ).
 Next, the Third Doctor and Jo, with the help of a Thal commando which had been monitoring the Daleks' moves, successfully froze an entire Dalek army which had been stored on Spiridon, and was poised to attack the Alliance.  They also prevented the Daleks from gaining the secret of Spiridonian invisibility (SSS).
 Eventually, the Thals notified the Alliance of the Daleks' activities, and the Alliance struck back.  This became known as the Third Dalek War.
 Soon afterwards, Inter Minor cautiously reopened itself to galactic trade.  The Third Doctor and Jo stopped there briefly, and resolved a crisis caused by galactic showman Vorg's use of an illegal Scope (PPP).

 It was during the later part of the 26th century that the Galactic Alliance began to fall apart.
 Its resources depleted by the Dalek and Cyber Wars, the Draconian Empire had begun its long period of stagnation, which would eventually lead to its "long night", the Draconians no longer being powerful players in galactic affairs.
 The Morok and Manussan Empires disappeared around the same time.  The Morok Empire simply crumbled, as its components revolted or broke away.  The First Doctor, Ian, Barbara and Viki were the witnesses of such a revolution in the Space Museum on planet Xeros (Q).  The Manussan Empire was a victim of its own unleashed evil, as embodied in the Mara (6D).
 Meanwhile, Mankind had spread ever further through the galaxy, escaping the control of Earth.  However, the Motherworld itself, also known as Earth, or the "Solar System", had entered another period of retrenching.
 During that time, the Fourth Doctor and Romana stopped on the alien world of Ribos, which was under the protection of the Alliance, in their quest for the Key to Time, and helped thwart the Graff Vynda-K's bellicous plans (5A).
 The Daleks took advantage of the Alliance's slow disintegration to launch an attack on Skaro.  They succeeded in exterminating most of the Thals, but the planet itself was turned into a a bombed-out ruin of no further use to them (or so they thought).
 However, towards the end of the 26th Century, the Daleks encountered a new enemy, the robotic race of the Movellans, whom which they could not crush.  Caught between the still-powerful Alliance, and the undefeated Movellans, the Daleks felt truly trapped.  New ways were to be found if they were to save their species.
 So, as the 27th Century began, the Daleks, still deadlocked against the Movellans, returned to the original Skaro to recover their long-buried creator, Davros.  But their efforts were thwarted by the Fourth Doctor and a newly-regenerated Romana.  Davros was taken back to Earth, where he was tried and sentenced to life in suspended animation (5J).
 Early in the Century, Steven Taylor accidentally landed on a planet colonized by the Mechanoids, and became their prisoner.  Soon afterwards, he met the First Doctor, Ian Chesterton, Barbara Wright and Vicki, who were eing Daleks from the future.  The Daleks and the Mechanoids exterminated each other, and the travellers escaped.  Ian and Barbara returned to 1965 A.D. in the Dalek time machine.  When the Doctor and Vicki left, they had unknowingly taken Steven with them (R).
 Eventually, deprived of Davros's help, the Daleks lost their war against the Movellans, who turned the tables on them by using a virus to decimate their enemies.  While striving to defeat the Movellans, the Daleks had made the most important discovery of their history: the secret of time travel.  However, it was a rudimentary form of time travel involving the use of time corridors.
 [ Note:  Although the Time Lords did not openly move to prevent the Daleks from acquiring time travel capabilities, certain facts suggest that they did not remain idle.  It is possible that the seemingly never-ending war of the Doctor against the Daleks -- which would, one day, result in the annihilation of the Dalek race (LL) -- was due to the Celestial Intervention Agency's manipulations.  It is also possible that it was at this point that the C.I.A. sent the Fourth Doctor back to Skaro to prevent the genesis of the Daleks (4E).  Lastly, it is interesting to note that the Daleks themselves had identified the Time Lords as among their enemies, since they planned to use replicas to assassinate the High Council of Gallifrey (6P).]
 Ninety years after Davros's trial, towards the end of the 27th Century, the Daleks hired galactic mercenary Lytton to free Davros from the Space Penitentiary where he was kept.  They also used their time corridor to trap the Fifth Doctor and plotted to use him in a devious scheme to strike back at the Time Lords.  With the help of Tegan and Turlough, the Fifth Doctor outwitted both the Daleks and Davros.  The latter barely escaped the Penitentiary's destruction with his life (6P).
 Davros found refuge on the world of Nekros and infiltrated the mortuary known as "Tranquil Repose".  There, he used human bodies to build his own army of "Imperial Daleks", who would obey only him.  His efforts were thwarted by the Sixth Doctor and Peri.  Betrayed by an employee from "Tranquil Repose", Davros was taken back to "New Skaro" by the Daleks, who now considered him a traitor to their cause (6Z).
 [ Note:  Davros somehow managed to escape the fate the Daleks had in store for him, and continued the production of Imperial Daleks.  Later, he either returned to the original Skaro, or took over New Skaro -- the records are unclear.]

 Meanwhile, as the 28th Century began, Earth entered a new expansion phase.  Stepping into the void left by the disintegration of the Alliance, it christened itself the "Empire" and embarked upon a new, imperialistic course.
 The Empire ruled the galaxy until the end of the 30th Century, mercilessly crushing and exploiting alien races to serve its own needs.
 C. 2750 A.D., the First Doctor, Susan, Ian Chesterton and Barbara Wright helped protect the shy, telepathic race of the Sensorites from becoming one more victim of the Empire (G).
 Another alien race which was preserved from the Empire's encroachements were the Kinda (also plagued by the evil Manussan spirit entity, the Mara), saved by the Fifth Doctor's intervention (5Y).
 Other alien races were not so lucky.  Among the alien races exploited by the Empire were the insect-like Wirrn (4C), and the Mogarians (7C).  The Empire was possibly responsible for the annihilation of the Movellans, who had won a Pyrrhic victory against the Daleks.
 It was during the Empire that the Second Doctor, Jamie and Zoe fought the notorious space pirate, Caven (YY).
 C. 2960, a last battle took place between the Daleks and Davros's own Imperial Daleks.  The two camps used their time corridor technology to travel to 1963 A.D. Earth and tried to seize the Hand of Omega.  As a result of the Seventh Doctor's intervention, both Dalek races were utterly decimated and Skaro (unless it was "New Skaro") was destroyed.  Davros, who had already taken to calling himself the Emperor Dalek, escaped (7H).
 C. 2986, the Sixth Doctor and Mel fought the Vervoids on board the space liner "Hyperion" en route from Mogara to Earth.  This incident was used by the Valeyard during the Doctor's second trial (7C).
 The so-called "Solos Crisis", which occurred towards the end of the 30th Century, was one of the catalysts of the Fall of the Empire.  The Third Doctor and Jo Grant were dispatched by the Time Lords to help the Solonian Mutants to reach their true, super-human form (NNN).
 The Solonians then became the unacknowledged models in a series of revolutions and guerillas which severely damaged the Empire.  It is possible that the Time Lords were secretly afraid of Imperial Earth's growing power and ruthlessness, and used both the Doctor and the Solonians to trigger its downfall.
 Another factor behind the Fall of the Empire was trouble on Earth itself.  That trouble was caused by an unprecedented string of solar flares.  Some Imperial scientists theorized that the flares, which at the time were estimated to last 10,000 years, would cause permanent damage to the human genoplasm.
 In the greatest secrecy, Space Beacon Nerva was converted into a Space Ark where "pure" specimens of humanity were stored.  All records of the Nerva Ark were then carefully hidden, and its existence became almost a legend.  The Ark's passengers remained in suspended animation for the next 10,000 years (4C).
 However, the strain on the Empire's resources proved to be the breaking point, and the Emperor was finally deposed.  The Empire had fallen.

 As the 31st Century began, the Empire had dissolved.  On Earth, surprisingly, the solar flares had abated.  They had not damaged the human genoplasm, but had had one unexpected consequence: a new Ice Age now threatened the Earth.
 The advent of the ice was fought off with the help of ionisers.  It was during that time of transition that the Second Doctor, Jamie and Victoria helped defeat a squadron of Martian "Ice Warriors" who had been discovered frozen in a glacier (OOO).
 Meanwhile, in space, the once-mighty Empire evolved into a loose combine of human and alien races, which the new democratic Earth was invited to join, but where it was to be no more than a single member.
 Manussa was now part of a local Federation.  There, the Fifth Doctor, Nyssa and Tegan finally defeated the Mara sometime during the 31st Century (6D).
 By the 32nd Century, all these regional alliances had evolved into a new entity, which called itself the Federation.  The Federation included not only humans from Earth and other human civilizations which had developed elsewhere, but also aliens such as the Draconians, the Alpha Centauri, the Arcturians, the "new" Martians, etc.
 C. 3200 A.D., the Fourth Doctor and Romana found themselves in E-Space and, with Adric's help, discovered the transformed officers of the Lost Ship "Hydrax" and killed the Great Vampire (5P).
 It was sometime during the interval between the 32nd and 38th Centuries that the Daleks re-emerged.  By then, they had not only restored Skaro (or "New Skaro"?) to its former glory, but they had also refined their time travel technology.  Using the rare element taranium, they were now able to build a crude, prototype time machine.
 One of their first enterprises was to send an execution squad to pursue the First Doctor, Vicki, Ian Chesterton and Barbara Wright through time and space.  The Dalek squad was eventually destroyed by the Mechanoids, and their prototype time machine put to good use by Ian and Barbara (R).
 C. 3700, then 3750 A.D., the Third Doctor twice helped the planet Peladon.  The first time, he helped it gain admission to the Federation with the Martians' help, against the designs of Arcturus (MMM).  The second time, he helped protect Peladon's trisilicate mines from the machinations of the traitor Eckersley, an agent of the hostile Galaxy 5 (YYY).
 Towards the 40th Century, Earth (or the Solar System, as it was also known) had gained more influence within the Federation.  Also, other galaxies were increasingly resentful and envious of the Federation.  The time had come for the Daleks to make their move.

 C. 4000 A.D., at the onset of the 41st Century, the Daleks allied themselves with various other Galaxies (including Galaxy 5), and plotted to attack the Solar System, which they perceived -- possibly blinded by their centuries-old feud with Mankind -- as the Federation's lynchpin.  This became known as the Fourth Dalek War.
 The Dalek invasion plans were first discovered on planet Kembel by Space Security Agent Marc Cory, who was murdered by the Daleks (T/A).
 Soon afterwards, the First Doctor, Steven Taylor and Katarina arrived on Kembel, and discovered a tape left by Cory.  With the help of another space Security Agent, Bret Vyon, they decided to warn Earth of the impending Dalek attack, and of the treachery of Mavic Chen, the Guardian of the Solar System.  Chen had given the Dalek the replacement taranium they needed to activate their supreme weapon: the Time Destructor.
 The time travelers stole the Daleks' taranium core, and fled Kembel.  In the course of their escape, Katarina sacrificed herself to save her companions.  Bret Vyon was killed by his sister, Sara Kingdom, who later found out the truth and helped the Doctor.  When the Time Destructor was finally activated, it was on Kembel, which put a stop to the Dalek invasion.  Unfortunately, its deadly effects also killed Sara Kingdom (V).
 Presumably, the Federation then retaliated, and the Daleks were again driven back to Skaro, their power and influence severely curtailed.
 A Century or so later, however, the Daleks managed to obtain some more taranium, and decided again to use their time travel capabilities to attack Earth.  By then, they were ruled by an Emperor Dalek, who could very well have been Davros, after possibly subjecting himself to further mutations.
 Resorting again to their favorite weapon, the biological one, the Daleks planned to infect humanity with the Dalek factor.  Having detected Prof. Waterfield's early time travel experiments, the Daleks travelled to 1866 A.D. Earth.  The Emperor's efforts were thwarted by the Second Doctor, Jamie and Victoria Waterfield.  Instead of infecting Mankind, it was the Daleks themselves who became contaminated with the Human Factor.  A "civil war " in which the Dalek race perished erupted on Skaro (LL).

 The period from the 41st to 50th Centuries was marked by several notable developments:
 First, on Earth, following the upheaval caused by Mavic Chen's betrayal, several important political changes occurred, each causing severe rifts with the Federation, and within the Solar System Administration itself.
 Earth eventually turned its back on the Federation, which it blamed for its problems, and entered into a new period of isolationism.
 In the galaxy, the Federation continued to thrive, except that it had now acquired a harder, more authoritarian -- some might even say, militaristic -- style.  The discovery of spectrox, a life-extending drug, had a profound impact on all the components of the galactic society.
 On Androzani Minor, the Fifth Doctor and Peri became involved in a co ct between Sharaz Jek, Morgus, the corrupt chairman of the Sirius Corporation, and Federation troops led by General Chellak.  Poisoned by raw spectrox, the Fifth Doctor sacrificed himself to save Peri's life, then regenerated (6R).
 Over the course of the next five hundred years, with Terran influence diminished, and its growing reputation for military interventions of the type mentioned above, the Federation began to disintegrate into new Empires, new Federations, etc.

 Meanwhile, on Earth, as the 50th Century approached, scientists at New Heidelberg developed the first Artificial Intelligences (A.Is).
 [ Note:  By then, early attempts at creating sentient computers, such as WOTAN or BOSS, had been either dismissed or forgotten.]
 Prof. Marius created the K-series of A.Is, culminating with the K9 mobile A.I. (4T).  Other experimental A.Is included sentient computers, such as Xoanon (4Q), which were installed aboard survey ships.
 It was during this period that the Fourth Doctor and Leela helped Prof. Marius and K9 defeat a Space Swarm, which had taken over the Titan Base (4T).
 Within the next hundred years, A.Is were well on their way to becoming widely used in several parts of the Galaxy, in spite of the latent robophobia inherent in humans.  One famous case took place on a Sand Miner where the Fourth Doctor and Leela stopped the mad Taren Capel from turning A.I. Robots into instruments of death (4R).
 A.Is were later refined into Androids of great sophistication by the neo-medieval Tarans.  The planet Tara was visited by the Fourth Doctor and Romana during their quest for the Key to Time (5D).
 However, on Earth, robophobia was more intense, and the presence of A.Is was not welcome.  It arrived at the end of a long list of problems plaguing the planet, including increased xenophobia, depletion of natural resources, growing pollution, etc.
 As a result of the above, during the 51st Century, a neo-luddite revolution occurred and the Supreme Alliance, a league of ruthless dictators, took control of the Earth.
 The Supreme Alliance was finally overthrown almost a hundred years later, at the Battle of Reykjavik, in which the Doctor claimed to have taken part.  After the battle, the Supreme Alliance's Minister of Justice, the evil Magnus Greel, and his Peking Homunculus, d to the 19th Century in a newly-developed time cabinet, christened the Zigma Experiment (4S).

 By the 52nd Century, Earth was not only a war-torn, emptied husk, but it was also becoming increasingly polluted, to the point of being virtually uninhabitable.
 The alien Usurians offered to move the human population to Mars, as long as they would work for their Company.  Some humans chose to go along with the Usurians' offer.  Others decided to leave Earth en masse -- a movement which became known as the Second (or Great) Break Out (4T).
 One of the ships which left at that time crashed on a nameless planet.  In an unrecorded adventure, the Fourth Doctor, fresh from his regeneration, tried to fix their experimental A.I., Xoanon, but instead made it schizophrenic.  As a result, Xoanon caused the survey team and the ship's technicians to evolve into two different tribes, who went to war with each other (4Q).
 Elsewhere in the galaxy, Earth's lesson had not gone unnoticed.  The Sons of Earth  made their appearance, who did not want to see other worlds become as polluted as Earth.  On Delta Magna's third moon, the Fourth Doctor and Romana, during their quest for the Key to Time, were caught up in a co ct between the native Swampies and human colonists, themselves in conflict with the Sons of Earth (5E).
 Several centuries later, the Fourth Doctor returned to Leela's world, and helped repair the damage he had caused to Xoanon's personality (4Q).
 Meanwhile, Earth was placed in ecological quarantine.  Those who had elected to stay in the Solar System lived under Usurian control on Mars.  Several centuries later, they were moved to Pluto, around which six artificial suns had been built.  The Solarians lived a heavily taxed life, toiling ceaselessly for the Usurian-dominated Company.  This was finally ended through the intervention of the Fourth Doctor, Leela and K9, who helped the Plutonians to rebel.  By then, Earth had returned to normal and Mankind was able to return to its homeworld (4W).
 The duration of this period of Earth's history, known as that of the "Sunmakers", is hard to determine with accuracy, but it is likely that Mankind reclaimed Earth around 10,000 A.D., almost five thousand years after it had abandoned it.
 During those five thousand years, a strange, new lifeform arose on polluted Earth: that of the vampiric Haemovores.  One of them, the Ancient One, was brought by Fenric to 1943 A.D. to help him defeat the Seventh Doctor, but turned against the evil entity and helped destroy it (7M).
 Eventually, as the planet's ecological balance was restored, the Haemovores became extinct, and Earth was ready to be reclaimed by Humanity.

 By 10,000 A.D., the galactic civilization had become a cluster civilization encompassing several galaxies, including Earth's "Milky Way", Galaxy Four (T), Galaxy Five, Andromeda, etc.
 At that time, many species began to engage in cautious attempts to either obtain or duplicate the Time Lords' secrets of time travel and bodily regeneration.
 Prior to this era, the Time Lords had often taken drastic steps to prevent their secrets from falling into alien hands.  Back in the galactic equivalent of 20th Century Earth, they had sent the Second Doctor and Jamie to investigate unauthorized experiments on Space Station J7 of the Third Zone (6W) and had even fought the Sontarans to protect the secrets of time travel (6W, 4Z).  Later, the Time Lords had outlawed the Scopes, which involved rudimentary time travel (PPP), and probably made successful attempts to stop the Cybermen from acquiring such secrets (6T).
 However, the Time Lords had been unable to prevent the determined Daleks from developing time travel.  Nevertheless, to many galactic observers, the fact that the Daleks had eventually become extinct, thanks mostly to the intervention of a Time Lord -- the Doctor -- often manipulated by the Gallifreyan Celestial Intervention Agency, as incentive enough to not pry into the Time Lords' affairs.
 By 10,000 A.D., two factors prompted many races to cautiously change this policy: one, the mistaken belief that the Time Lords had not seemingly intervened in another race's affairs since the Daleks' extinction of almost five thousand years; and two, what became known as the Morbius Crisis.
 A member of the High Council of Gallifrey, Morbius had sought to lead the Time Lords on a path of conquest.  Rejected by his peers, he had then left Gallifrey and raised an army of followers, promising them time travel and immortality, using the Elixir of Life produced by the Sisterhood of Karn's Sacred me.  Eventually, Morbius and his army were defeated by the Time Lords on Karn.  The Renegade Time Lord was placed in a disposal chamber and his body was vaporized (4K).
 Several years later, the Celestial Intervention Agency found out that the Brain of Morbius had been secretly preserved by one of his followers, Dr. Solon.  They sent the Fourth Doctor and Sarah Jane Smith to Karn, where they not only destroyed Morbius, but also restored the Sisterhood's dying me (4K).
 Meanwhile, the Morbius Crisis had spurred other races into cautiously looking into the Time Lords' secrets.  Spies from Andromeda successfully infiltrated the Gallifreyan Matrix, choosing Earth as their base of operations.  When they discovered the Andromedans' plan, the Time Lords struck back.  The actions they took against Andromeda itself are unknown, but they moved Earth out of the Solar System and rechristened it Ravolox.  This action, which seems to have occurred c. 14,000 A.D., resulted in considerable death and destruction, but was blamed on a freak cosmic phenomenon (7A).
 The Ravolox stratagem was eventually uncovered by the Sixth Doctor during his Trial, soon after he and Peri visited Ravolox.  Indeed, it is permissible to think that the Doctor was put on trial because the corrupt High Council of Gallifrey was afraid that he would eventually uncover and expose the Ravolox deception (7A-7C).
 After their callous scheme had been revealed, it is unclear whether the Time Lords moved Earth back to its original location, or simply allowed it to be "rediscovered".  In any event, the destruction caused by the planetary move was still being explained away as a "fireball" or "solar flares".
 This was presumably the time when the Seventh Doctor met Ace and, together with Mel, fought Kane, the master of Ice World on planet Svartos.  Mel eventually left to travel with Sabalom Glitz, whom the Doctor had previously met on Ravolox (7G).
 Ultimately, it seems that the Time Lords were unsuccessful in their attempts to prevent other races from discovering time travel since by the time the Seventh Doctor and Mel met the young Chimeron Queen, Delta, and her enemies, the Bannermen, time travel appeared to have become widely accessible throughout the known universe.  By then, Earth and its past seemed a quaint, backwater curiosity, a Shangri-La for alien tourists (7F).

 The "rediscovery" of Earth probably took place between the years 15,000 and 20,000 A.D.
 This was when the passengers of the Space Ark Nerva, who had been placed in secret suspended animation by the Empire, c. 3000 A.D., awoke.  They had been meant to sleep for 10,000 years, but had overslept by several thousand years.
 When they awoke, they found that Nerva had been infiltrated by the vengeful Wirrn, a race once crushed by the Empire.  It was only the intervention of the Fourth Doctor, Sarah Jane Smith and Harry Sullivan, and the sacrifice of the Ark's leader, Noah, which enabled the Ark to survive (4C).
 Spacemen from Earth's colonies had begun to return to Earth.   Like the passengers of the Ark, they assumed it to be lifeless because of the solar flares or the fireball.   [ Note:  However, unlike the Nerva people, they believed these flares to have happened c. 14,000 A.D., i.e.: when the Time Lords had moved the planet, and not during the 30th-31st Centuries.]
 The Fourth Doctor, Sarah and Harry helped the colonists thwart an attempt by the Sontarans to take over this space sector (4B).  Earth was now safe again for resettlement by the human race.
 At some undetermined date after the Resettlement, the Seventh Doctor and Ace defeated the Gods of Ragnarok at the Psychic Circus on Segonax (7J).

 Only fragmentary records exist of the future Earth history posterior to 20,000 A.D.
 C. 37,166 A.D., the Fourth Doctor and Sarah Jane Smith rescued the crew of a Morestran spaceship from an anti-matter creature on Zeta Minor, a planet on the edge of the known universe (4H).
 Even further in the future, Earth's sun was the victim of a cosmic collision, which forced the Solarians to undertake another "Great Break Out".  The Fifth Doctor, Tegan and Turlough helped a group of indomitable survivors defeat the alien Tractators on the planet Frontios (6N).
 Finally, 10 million years in the future, in what was then known as the 57th "Segment of Time", Earth's sun finally went nova (X).
 By then, Mankind had spread throughout the Universe, and probably evolved into many different forms.  Its relationship with the planet of its birth was unknown.
 The Solarians and the alien Monoids, and all life on Earth (in a miniaturized form) embarked on a seven hundred-year journey to the planet Refusis.  Eventually, the First Doctor, Dodo and Steven Taylor helped Men and Monoids to peacefully resettle on Refusis (X).