(covers information from several alternate timelines)
Earth, also known as Sol III or Terra, was the inhabited third planet of the Sol system. Earth was the homeworld of the Humans and the Voth, among others, and was the capital planet of the United Federation of Planets and the home of Starfleet Headquarters from 2161 to 3089.
In 2150, with the last countries joining, the planet was unified under the United Earth government. It was a founding member of the Coalition of Planets in 2155, and of the United Federation of Planets in 2161. (ENT: "Broken Bow", "Zero Hour", "Home") By the 24th century, hundreds of humanoid species lived there, including Bolians, Vulcans, and Ktarians. (VOY: "Hope and Fear") The President's office, the Federation Council, as well as Starfleet Headquarters and the main campus of Starfleet Academy were all located on Earth. (Star Trek: The Motion Picture; Star Trek IV: The Voyage Home; Star Trek VI: The Undiscovered Country; TNG: "Conspiracy"; DS9: "Homefront", "Paradise Lost"; VOY: "In the Flesh")
Located at the very core of the Federation, Earth's strategic importance was on par with worlds like Andor, Berengaria VII, and Vulcan during the Dominion War. It was also targeted by two Borg cubes. (DS9: "In the Cards"; TNG: "The Best of Both Worlds"; Star Trek: First Contact)
- 1 Planetary data
- 2 History
- 3 Climate and geography
- 4 Parallel universes and alternate timelines
- 4.1 Alternate timelines
- 4.1.1 Earth devastated
- 4.1.2 Humanity sentenced by Q
- 4.1.3 Nazi Earth
- 4.1.4 Borg-Earth
- 4.1.5 Earth destroyed
- 4.1.6 Alternate reality
- 4.2 Mirror universe
- 4.3 Reverse universe
- 4.1 Alternate timelines
- 5 Appendices
Earth was a spheroid-shaped terrestrial planet with a circumference of 24,874 miles (40,075 kilometers), a mass of 5.98 ×1024 kilograms and a mean density of 5.517. Its atmosphere had an average temperature of 75 °F (24 °C) and consisted of 78% nitrogen, 21% oxygen, and smaller percentages of krypton, neon, and argon. (TOS: "Miri", "Metamorphosis", "Bread and Circuses")
Earth's orbit around its sun, Sol, measured more than two hundred million kilometers in diameter. (TNG: "Relics") Earth was located in the Alpha Quadrant, less than ninety light years from the boundary to the Beta Quadrant. (ENT: "Broken Bow", "Two Days and Two Nights"; Star Trek Into Darkness production art) It was a little over sixteen light years away from the planet Vulcan, less than ninety light years away from the Klingon homeworld, and approximately ninety light years away from Risa. (ENT: "Two Days and Two Nights", "Home")
In 2254, the orbit of Earth was depicted on a map of the inner system, which was stored in the USS Enterprise library computer. This was one of multiple records that were scanned by the Talosians in 2254. (TOS: "The Cage" production art)
In 2267, the orbit of Earth was depicted on "Chart 14A: The Sol System", which was stored in the Enterprise library computer. This chart was scanned by the probe Nomad in auxiliary control. (TOS: "The Changeling" production art)
|The Sol System|
|Mercury • Venus • Earth (Luna) • Mars (Deimos) • Asteroid belt • Jupiter (Io; Ganymede) • Saturn (Mimas; Rhea; Titan) • Uranus • Neptune (Triton) • Pluto|
Around 4.5 billion years ago, ancient humanoids seeded many worlds in the Milky Way Galaxy, including Earth, with a DNA code to guide evolution to a form resembling their own. Approximately 3.5 billion years ago, the first life on Earth was formed from a group of amino acids that combined to form the first proteins. (TNG: "The Chase", "All Good Things...") Nonetheless, according to James T. Kirk, three hundred million years ago life had not yet emerged on Earth. (TAS: "Beyond the Farthest Star")
Approximately sixty-five million years ago, at the end of the Cretaceous period, a comet collided with the planet Earth. This mass extinction event resulted in the death of many reptilian lifeforms. One of the surviving lifeforms belonged to the genus Hadrosaur, which evolved into the Voth. The Voth eventually left Earth, leaving no apparent trace of their civilization, and colonized a world in the Delta Quadrant. Around the same time, mammals rose to prominence on the land and in the sea, eventually leading species like Humans and Humpback whales, respectively. Humans and their immediate ancestors shared the basic humanoid appearance, which may be the result of genetic seeding that occurred long ago, by the first sentient species to inhabit the galaxy. (Star Trek IV: The Voyage Home; TNG: "The Chase"; VOY: "Distant Origin"; ENT: "Azati Prime")
Earth produced several major religions, including Christianity, Judaism, Islam, Hinduism, Buddhism, Shinto, and Wicca. Some of these religions, in one form or the other, survived into the 23rd and 24th centuries. (TOS: "Balance of Terror"; DS9: "Penumbra"; VOY: "The Killing Game")
In the 17th century, scientist Galileo Galilei taught the masses that Earth moved around the sun and not the opposite way. For these teachings, he was tried and convicted of heresy by an inquisition of the Roman Catholic Church, and his books were burned. (DS9: "In the Hands of the Prophets")
Earth was also visited, observed, and occasionally manipulated during its history, prior to official First Contact by Vulcans. One of the earliest extraterrestrial visits was by a race known as the Sky Spirits, originally native to the Delta Quadrant. These visits also included those by an ancient humanoid species, the Preservers, descendants of Humans abducted around 4000 BC, and Vulcans themselves, although this was disputed, as there was no proof or evidence offered by the Vulcan High Command. The Humpback whales were being observed by an unknown entity who, upon loss of contact with the species, sent a probe to investigate the absence of whale song. In the 19th century, a race called the Skagarans abducted several thousand Humans from the American West and then used them as slave labor. The El-Aurian Guinan also stayed discreetly on Earth. In the 1930s, the Briori visited Earth and abducted several individuals, including famous pilot Amelia Earhart. In 1947, three Ferengi inadvertantly crash landed near Roswell, New Mexico. In the 1950s, a team of Vulcan explorers were temporarily stranded on Earth. (TOS: "Assignment: Earth", "The Paradise Syndrome"; Star Trek IV: The Voyage Home; TNG: "The Chase"; TNG: "Time's Arrow"; ENT: "Carbon Creek"; VOY: "The 37's"; VOY: "Tattoo")
From the mid-20th century onward, manned and unmanned spacecraft were launched from either the surface or the orbit of Earth. Several prominent craft that were launched from Earth include Apollo 11, Nomad, Phoenix, Friendship 1, Enterprise, and the USS Enterprise. (TOS: "The Cage", "Where No Man Has Gone Before", "The Changeling"; Star Trek: First Contact; VOY: "Friendship One") Starting in the 22nd century and continuing on into the 24th, there were major construction projects on the surface and in orbit of Earth that supported the burgeoning expansion of Humans into space. Some of these projects were the Warp Five Complex, the San Francisco Fleet Yards, Spacedock, and Earth Station McKinley. (ENT: "Broken Bow"; TOS: "Where No Man Has Gone Before"; Star Trek III: The Search for Spock; TNG: "Family")
Following the Burn in the 31st century, Starfleet became concerned about security on Earth and ultimately moved Starfleet Headquarters off the planet. Earth subsequently seceded from the Federation, and remained independent – even from other worlds in the Sol system such as Titan – as of 3189. (DIS: "People of Earth")
Attacks on Earth
During its long history, the existence of the planet has been threatened by both natural disasters and actions of alien intelligence.
- In 2153, Earth was preemptively attacked by the Xindi, who were unwittingly helping a faction fighting the Temporal Cold War. Using a smaller, prototype version of the planned Xindi weapon, the weapon destroyed a section of the planet stretching from Florida to Venezuela, killing seven million people. This event began what was later known as the Xindi crisis. (ENT: "The Expanse")
- On February 14th of 2154, a working version of the Xindi weapon entered Earth orbit to destroy the planet. The weapon was destroyed by Captain Jonathan Archer before it could complete its task. This marked the end of the Xindi crisis. (ENT: "Zero Hour")
- In 2155, Terra Prime – under the command of John Frederick Paxton – used the verteron array on Mars to attack Starfleet Headquarters. Thanks to the efforts of Commander Charles Tucker III, the array fired harmlessly into the San Francisco Bay. (ENT: "Terra Prime")
- In 2257, Earth was the intended target of a Klingon fleet during the Federation-Klingon War, shortly after the fall of Starbase 1. This attack was aborted shortly before it could begin after L'Rell, the new leader of the Klingon High Council, ordered a cease fire. (DIS: "Will You Take My Hand?")
- In the 2270s, a massive machine lifeform called V'ger threatened to destroy all biological life on Earth, if its demands were not met. The attack was narrowly averted by the crew of the USS Enterprise. (Star Trek: The Motion Picture)
- In 2286, an alien probe of unknown origin wreaked ecological havoc while trying to contact an extinct species of Humpback whale by transmitting massive amounts of energy into Earth's oceans and unintentionally caused them to begin evaporating. The threat was ended when the former crew of the USS Enterprise, having used a stolen Klingon Bird-of-Prey to travel back in time to before the species' extinction, returned to the present with two Humpbacks; after the two whales gave a response to the probe, it departed the Solar System with little, if any, real harm done to the planet. (Star Trek IV: The Voyage Home)
- In 2367, a Borg cube entered Earth orbit following the Battle of Wolf 359 with the intention of assimilating the planet and its population. It was destroyed by the USS Enterprise-D before it could attack the planet. (TNG: "The Best of Both Worlds, Part II")
- In 2373, a second Borg cube attacked Earth and, after a devastating battle, was destroyed in orbit by a Starfleet armada. As the cube exploded, a Borg sphere escaped from within the craft and subsequently traveled into the past, where its complement of Borg drones attempted to prevent Humanity's First Contact with Vulcans in 2063. (Star Trek: First Contact)
- In 2375, the Borg decided to create another strategy, since all direct assaults on Earth had failed, thus far. They planned to detonate a biogenic charge in Earth's atmosphere, infecting all lifeforms with nanoprobe viruses, triggering a gradual assimilation. According to the Borg Queen, half the population would be drones before the effects were discovered. (VOY: "Dark Frontier")
- Also in 2375, the Breen Confederacy attacked Earth in a surprise attack on Starfleet Headquarters in San Francisco during the Dominion War. (DS9: "The Changing Face of Evil")
- In 2379, Praetor Shinzon attempted to destroy all life on Earth using a thalaron weapon built into the Reman warbird Scimitar. The Scimitar was destroyed by the USS Enterprise-E, Valdore, and an unidentified Valdore-type warbird in the Battle of the Bassen Rift. (Star Trek Nemesis)
- By 3189, Earth had left the United Federation of Planets and was under the protection of the United Earth Defense Force. Raiders like Wrenn made several attacks on the planet for supplies like dilithium. The tensions were settled by Captain Saru and Commander Michael Burnham of the USS Discovery. (DIS: "People of Earth")
Climate and geography
Earth was a class M world by planetary classification standards. (TOS: "Return to Tomorrow"; TNG: "Justice") It had just about every ecosystem one could think of. (VOY: "Hope and Fear") These included ice caps and deserts. There were a number of continents.
|Continents of Earth|
|Africa • Antarctica • Asia • Australia • Europe • North America • South America|
Once Humans began leaving Earth in the 20th century, they photographed and drew pictures of the planet for various reasons. These pictures were then displayed in homes, offices, and recreation facilities. The earliest images of Earth were from the space agencies which sent Humans into space. These included official mission photos and insignia. Many of these images were preserved into the 22nd century and beyond. (TOS: "The Cage"; ENT: "First Flight")
Parallel universes and alternate timelines
Earth was devastated in several alternate timelines.
Red Angel's timeline
Accidental time travel from 2371 led to the premature death of Gabriel Bell in 2024. An altered future was created where the more inhumane wars of the 21st century left Earth a pre-warp civilization that never even expanded to the solar system. Consequently, the Romulan Star Empire had expanded to include Alpha Centauri. (DS9: "Past Tense, Part I", "Past Tense, Part II")
When the temporal agent Daniels was instructed to remove Jonathan Archer from the timeline in 2152 and bring him to the 31st century, an alternate future was created where the United Federation of Planets was never formed and a planet where Daniels had come from was almost completely destroyed. (ENT: "Shockwave", "Shockwave, Part II")
Humanity sentenced by Q
In 2370, an alternate past was created for Earth by the anti-time eruption, where 3.5 billion years ago, amino acids never combined with the first proteins, and life never formed on the planet. This was how the Q Continuum fulfilled its judgment to deny Humans existence. (TNG: "All Good Things...")
Edith Keeler's world
In two alternate timelines, the history of Earth was significantly altered when Nazi Germany was not defeated in World War II. In one, Doctor McCoy saved the life of Edith Keeler in 1930. Keeler went on to form a massive pacifist movement in America, delaying the country's entry into World War II, allowing Nazi Germany time to develop the A-bomb first and take over the world. (TOS: "The City on the Edge of Forever")
In another alternate timeline, Lenin was assassinated in 1916, preventing Russia from turning to communism. This allowed Adolf Hitler to concentrate his war effort on the West. With assistance from the Na'kuhl, France and England were conquered before the American East Coast by 1944. (ENT: "Storm Front", "Storm Front, Part II")
In an alternate timeline, the Borg were successful at preventing First Contact in 2063 and assimilated the Earth. In 2373, the assimilated Earth had an atmosphere containing high concentrations of methane, carbon monoxide, and fluorine. It had a population of approximately nine billion Borg drones. (Star Trek: First Contact)
The Earth was completely destroyed in two alternate timelines. In one of the timelines, Jonathan Archer's brain was infected by interspatial parasites and Earth was destroyed by the Xindi weapon in 2154. This timeline was erased in 2165 when the parasites were destroyed by a subspace implosion aboard Enterprise – because the organisms existed outside normal space-time, their elimination prevented Archer from ever being infected in the first place. (ENT: "Twilight")
Henry Starling's world
In another alternate timeline, Earth and the entire solar system was destroyed by a massive temporal explosion in the 29th century. The explosion was caused by Henry Starling, when he used the stolen timeship Aeon to travel from the 20th century into the 29th century through an unstable temporal rift. (VOY: "Future's End", "Future's End, Part II")
In the year 2258 of the alternate reality, the Romulan mining vessel Narada fired on Earth using a drill platform. Nero was attempting to dig a hole to Earth's core and create a black hole using red matter to destroy the planet. Luckily, Spock was able to destroy the drill well before it could reach the planet's core. (Star Trek)
A year later, Starfleet traitor John Harrison masterminded a bombing on the Kelvin Memorial Archive in London and then attacked Starfleet Headquarters. He later returned to Earth, having commandeered the USS Vengeance, crashing it into San Francisco. (Star Trek Into Darkness)
- Main article: Terran Empire
In the mirror universe, Earth's counterpart, locally named Terra by 2256, was the throne world of the Terran Empire. History followed a similar yet skewed course on this Earth, by comparison to the history of Earth in the United Federation of Planets, with a more violent, war-ridden past. According to Jonathan Archer, the Empire existed "for centuries" prior to 2155. A significant divergence in the timeline was the official First Contact with the Vulcans in 2063; Zefram Cochrane shot the Vulcan who greeted him, and, with the other Terrans present, stormed the Vulcan ship, taking its technology, which allowed the Empire to expand. (ENT: "In a Mirror, Darkly"; DIS: "Terra Firma, Part 1", "Terra Firma, Part 2"; DIS: "Die Trying")
In the reverse negative antimatter universe, where the flow of time was reversed, Arret was Earth's counterpart. In 2270, Karla Five and her son Karl Four helped the crew of the USS Enterprise to return to the prime universe. (TAS: "The Counter-Clock Incident")
A list of all actual appearances of planet Earth (excluding holodecks, simulations, visions, opening credits, etc.)
- "The Magicks of Megas-Tu" (Season 1)
- TOS films:
- TNG films:
- "Broken Bow" (Season 1)
- "Fortunate Son"
- "Shadows of P'Jem"
- "Shockwave, Part II" (Season 2)
- "Carbon Creek"
- "First Flight"
- "The Expanse"
- "Twilight" (Season 3)
- "Carpenter Street"
- "Zero Hour"
- "Storm Front" (Season 4)
- "Storm Front, Part II"
- "In a Mirror, Darkly, Part II"
- "Terra Prime"
- "These Are the Voyages..."
- AR films:
- Earth animals
- Earth cities and towns
- Earth insects
- Earth geography
- Earth plants
- Earth regions
- Duplicate Earth
- Objects in Earth orbit
In such episodes as TOS: "The Cage" and TAS: "How Sharper Than a Serpent's Tooth", the name "Earth" is used interchangeably with "Sol" when referring to the whole Sol system. Gene Roddenberry preferred that Star Trek writers used the name "Earth" for the planet instead of "Terra". (Star Trek: Communicator issue 113, p. 13)
That Star Trek was obviously to be filmed on Earth led Gene Roddenberry to suggest, in his original 1964 pitch Star Trek is..., the notion of making Star Trek affordable by setting episodes on planets similar to Earth (for instance, those with class M environments as well as those fitting Hodgkin's Law of Parallel Planetary Development). He wrote, "It means simply that our stories deal with plant and animal life, plus people, quite similar to that on earth [....] The 'Parallel Worlds' concept makes production practical by permitting action-adventure science fiction at a practical budget figure via the use of available 'earth' casting, sets, locations, costuming and so on." Among several story ideas Roddenberry proposed in Star Trek is… were "Mr. Socrates" (which hypothesized that Earth of Star Trek's era may have been secretly under telepathic observation by an alien society over centuries), "Reason" (which seemed to suggest that the decimation of intelligent life on Earth, leaving merely a robot society, had been a "long speculative" issue on Earth) and "Torx" (which pertained to "the first major menace to Earth," a non-corporeal alien being that "devours" intelligence such as that which "the Earth could supply in quantity").
In a fantasy scene included in the script for first Star Trek pilot episode "The Cage" (dated 20 November 1964) but not included in that installment, an Earth trader referred to Captain Pike as having sent Earth "blistering" reports about Orion traders.  Similarly, in an ultimately unused Kirk voice-over which originally introduced the second pilot "Where No Man Has Gone Before" (for example, in that episode's final revised draft script, dated 9 July 1965), Kirk was scripted to say, "Our Earth is but a pinpoint [in our galaxy], one speck of dust."  A filmed but deleted version of this voice-over featured Kirk instead citing the planet as one of multiple "specks of dust" while the Enterprise was on a heading out of the Milky Way Galaxy. ("Where No Man Has Gone Before" (Rare and Unaired Alternate Version), TOS Season 3 Blu-ray special features)
When it came to depicting a digital matte painting of Mojave in the remastered version of "The Cage" and "The Menagerie, Part II", the ethos behind Star Trek's presentations of the planet proved inspirational. Dave Rossi, VFX Line Producer for Remastered TOS, clarified, "The whole idea about Earth in the 23rd century is that it's a paradise and [....] that also the environment has changed. So, it was very important for us to make sure that everything looked beautiful and lush and green and living, because that's the planet of the future." ("The Menagerie, Part II" Starfleet Access, TOS Season 1 Blu-ray)
During the making of Star Trek: The Original Series, representing Earth of the 23rd century was virtually impossible. (text commentary, Star Trek: The Motion Picture (The Director's Edition) DVD) Ronald D. Moore noted, "Kirk and company never went to present day 23rd century Earth, their contemporaneous Earth, ever. Gene wouldn’t do it."  This was due to budgetary limitations. (text commentary, Star Trek: The Motion Picture (The Director's Edition) DVD) Specifically, portraying future Earth believably would necessitate elaborate sets and matte paintings, all of which would be extremely expensive. Visiting Earth might also involve the use of costly spacedocks and other ships, though these were all in very short supply on TOS. The financial impracticability of depicting Earth resulted in few visits to the planet, with one of the foundations of Gene Roddenberry's concept for Star Trek consequently being that the show almost never voyaged to Earth. Another motive for this was that Roddenberry believed portraying future Earth might also require showing how the planet's political and economic systems had developed. Politically liberal, Roddenberry was anxious that such revelations might bring about arguments with sponsors and others who might not share his views. ("The Menagerie, Part II" text commentary, TOS Season 1 DVD) Earth of the future was nonetheless imagined as a unified if not peaceful planet, as was implied by the fact that the Enterprise's "U.S.S." designation were initials that stood for "United Space Ship".  Roddenberry also intended for Earth to be metaphorically alluded to aboard the Enterprise, with the planet's many nationalities being represented by the ship's multinational crew. The idea of reflecting the unified diversity of Earth on board the starship was central to Roddenberry's vision of Star Trek. ("The Birth of a Timeless Legacy", TOS Season 1 DVD and TOS Season 1 Blu-ray special features)
In the document The Star Trek Guide, Gene Roddenberry wrote, "For one thing, we'll never take a story back [to Earth] […] and therefore don't expect to get into subjects which would create great problems, technical and otherwise [....] References by our characters to Earth will be simply a logical projection of current scientific and social advances in food production, transportation, communications, and so on. If you want to assume that Earth cities of that future are so splendidly planned with fifty-mile parkland strips around them, fine. But for obvious reasons, let's not get into any detail of Earth's politics of Star Trek's century; for example, which socioeconomic systems ultimately worked out best." Despite the instructions that writers not write specifically about the future political state of Earth, the same article did indicate the planet was now a unified if not peaceful place, politically. After making it clear that any stories representing "an autocratic, regimented, inhuman Earth of the future" would be rejected, the article continued by stating, "We must have an optimistic projection from Earth of today if we are to approve of and identify with Captain Kirk, the crew of the Enterprise, and their mission."  Roddenberry later often postulated that the Earth of both Kirk's and Picard's time periods was a paradise, with no poverty, crime or war. (Star Trek: Deep Space Nine Companion (p. 138))
First serialized depictions
In a story document dated 21 March 1966, an undeveloped TOS episode entitled "Kafka's Trial" was described as involving a potential threat to Earth; the Enterprise crew was told by a "universe alien patrol" which invaded the ship that a trial was being held, aboard the vessel, to decide whether Earth would be destroyed.
Amid the making of the first season (i.e., on 5 April 1966), writer Barry Trivers pitched a story concept (the genesis of the episode "The Conscience of the King") in which Earth was established as having been horrifically invaded by "an army of marauders," in James T. Kirk's childhood. Gene Roddenberry was completely opposed to portraying such a bleak future for Earth, so a similar incident was established as having instead occurred on Tarsus IV. (These Are the Voyages: TOS Season One)
On 12 April 1966, Robert Justman sent a memo to Gene Roddenberry which outlined a potential story for the series that centered on Earth as the main setting. The memo read, "The Enterprise is returning to Earth [....] The Enterprise does arrive back at Earth, but this is Earth of 1966 and not of their time [....] Kirk begins to see, by breaking through time, he is starting off a whole sequence of events which will affect the history and civilization of our planet in future years." The way Earth was featured in this story springboard pre-empted but didn't directly inspire the contemporary Earth setting of the episode "Tomorrow is Yesterday", which was written by D.C. Fontana and whose first story outline was submitted roughly half a year later (on 3 October 1966). (These Are the Voyages: TOS Season One)
In the final draft script of TOS: "The Naked Time", Kirk specified that he wanted the Enterprise to head "toward Earth", upon setting the ship on a reverse course during the episode's climax, though he also admitted that the heading was of no consequence. In the final version of the episode, the reference to Earth is omitted, though the rest of that line of dialogue remains exactly as it was in the final draft script.
When the first draft teleplay of "Tomorrow is Yesterday" was delivered on 1 November 1966 (though the script itself was dated 31 October 1966), Robert Justman issued some advice about the upper parts of Earth's atmosphere. Since Fontana and Gene Coon intended the outing to incorporate stock footage of airplanes, Justman suggested to the pair that a limit of up to about 60,000 or 70,000 feet would be possible for the planes and stated, "This is still within the atmosphere limits of the Earth, and there is still daylight up there – we are not in inky blackness at that altitude." Justman concluded that the sky would also have to serve as the background for several shots of the Enterprise, necessitating the creation of new effects footage. Because the script referred to the Enterprise as being detectable but not discernible from a ground installation using radar, Justman proposed "a large body of water, such as the Atlantic or Pacific" might be under the starship. (These Are the Voyages: TOS Season One)
Blue screen was used as a replaceable background for the filming of scenes showing the cockpit of Captain John Christopher's jet. Some footage involving Earth's atmosphere, with the Enterprise flying through it, was shot by the Howard A. Anderson Company (though the Westheimer Effects Company was also used for the episode). One such shot, of the ship climbing through the atmosphere, was filmed by the Howard Anderson Company but never used. Also, footage of Earth was reused from the earlier season 1 outing "Miri", in which the globe had been used to represent Earth Two. Despite the planet having been depicted without clouds in that installment, clouds were added for the shots of Earth in "Tomorrow is Yesterday". (These Are the Voyages: TOS Season One)
Even though Gene Roddenberry publicly blamed Harlan Ellison for apparently not being able to write "The City on the Edge of Forever" without making it go hugely over budget, Allan Brennert – a writer and former producer – subsequently assured Ellison that the episode's 1930s Earth scenes clearly necessitated over-expenditure. This was largely because, as Brennert informed Ellison, "The planet's surface […] [and] all the Old Earth interiors had to be constructed." Brennert went on to say, "Roddenberry had to've known this from the very first [story] treatment, as did the people responsible for budgeting the segment, it didn't take them by surprise, and both they and NBC gave you the green light to go to teleplay first draft." (The City on the Edge of Forever, 1996 ed., "Perils of the 'City'")
After receiving the story outline for "Space Seed" (written by Carey Wilber), NBC executive Stan Robertson enthusiastically wrote to Gene Coon, "There is an exciting blend of past Earth history – the similarity of the plot with the colonization of Australia; [plus] a current problem of our contemporary society – over-population." How "Space Seed" actually portrayed Earth at first, though, initially frustrated Gene Roddenberry. Following delivery of the episode's second-draft script, Roddenberry commented in a memo to Coon, "It is hard to believe the world of the 1990s sending men off to a penal colony in the stars. Romantic, but impractical. No 'advanced' world of the 1990s would do this; no barbaric or dark ages world of the 1990s would spend the hundreds of millions required to do it, when a simpler expedient for a barbaric world would be simply to put the men to death. So the entire concept is rather shaky to start with." Instead, a reference in the script to what Wilber termed "The Dark Ages of the 1990s" influenced Roddenberry to devise the era of Earth's Eugenics Wars and suggest that, in the 1990s, the planet had gradually come under the control of Augments. (These Are the Voyages: TOS Season One)
For stories set on Earth in contemporary times, maintaining the audience's suspension of disbelief could be quite challenging. "It's always a dangerous idea to take the Star Trek characters into the present," stated Director Marc Daniels, who helmed the TOS installment "Assignment: Earth". "Suddenly you're in a very tangible situation. The show's reality becomes that much harder to maintain." (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 63) Such episodes were often extremely successful, though. In a 1968 letter which Gene Roddenberry wrote in an unsuccessful attempt to pitch a new television series based on "Assignment: Earth", he commented, "It is a matter of record that Star Trek's most exciting and successful audience shows were those three in which Captain Kirk and Mr. Spock returned to 20th-century Earth and played out their story there." (Star Trek Creator: The Authorized Biography of Gene Roddenberry, p. 334)
First film appearance
Shortly before Star Trek: The Motion Picture was written, a story idea which Harlan Ellison verbally pitched to Paramount as one of many ultimately nixed stories, each of which were separately conceived as a potential narrative foundation for the first Star Trek film, was set primarily on Earth. "The story did not begin with any of the Enterprise crew, but started on Earth where strange phenomena were inexplicably occurring," recorded writer James Van Hise. Both a building in India, wherein a family had been having dinner, and one of the Great Lakes in the United States suddenly vanished. In a public square, a woman suddenly screamed and collapsed to the pavement, where she turned into a form of reptilian creature. Though the truth was suppressed, the Federation realized these sudden changes on Earth were due to alterations in the planet's distant past, caused by an alien race of intelligent humanoid reptiles from a planet in a far away galaxy where snakes had become the dominant lifeform. Earth had been likewise populated by the snake-aliens eons ago, in the Pleistocene period, but the snake-creatures there had been destroyed by early Humans. After submitting the story, Ellison explained, "A snake-creature who had come to Earth in the Star Trek feature, had seen its ancestors wiped out, and […] had gone back into the far past of Earth to set up distortions in the time-flow so the reptiles could beat the Humans." The mission of saving Earth, journeying into the planet's far past, was made the responsibility of the Enterprise and its crew. (The City on the Edge of Forever, 1996 ed., "Perils of the 'City'")
Earth was also a setting in another of the multiple stories that were suggested as the first Star Trek film, this one titled Star Trek: Planet of the Titans. In a story treatment which Philip Kaufman wrote for that movie, the planet was described thus; "We have never seen the Earth of the 23rd century before on Star Trek. Seeing it for the first time, we are struck by the progress mankind can make. It's a thoughtful, optimistic world. The industrial revolution has long ago given way to the organic revolution. Much of the surface of the Earth has been restored to nature; man has returned to living comfortably in the earth. The great cities of centuries past are now public parks, their ruins preserved for pleasure and for education."
Despite Gene Roddenberry's fears about the dangers of portraying future Earth's political and economic systems, later incarnations of Star Trek featured futuristic depictions of the planet more than TOS had. ("The Menagerie, Part II" text commentary, TOS Season 1 DVD) Though an illusory version of 23rd-century Earth appeared in "The Cage", the first real glimpse of the planet in that century was in Star Trek: The Motion Picture, which includes only a single scene set on Earth's surface. The concept that the first Star Trek film would feature Earth being jeopardized with destruction by a massive object (which eventually became V'ger) approaching the planet was conceived as early as the writing of the Gene Roddenberry script The God Thing. (The Longest Trek: Writing The Motion Picture, Star Trek: The Motion Picture (Blu-ray) special features) The opportunity to visit the planet was extremely attractive to Robert Goodwin. "I suggested to Gene that since it had never been done in the series before, that we should come up with a story in which Earth was threatened," he recalled. "In all the Star Trek episodes before, they never even came close to Earth." Subsequently, the agenda of depicting Earth fit well with the story for "In Thy Image", written by Alan Dean Foster. ("The Next Phase", The Fifty-Year Mission: The First 25 Years) Depicting the planet in Star Trek's future time period was ultimately made doable in The Motion Picture only because the makers of that film were able to take advantage of the higher budget associated with a feature film project. (text commentary, Star Trek: The Motion Picture (The Director's Edition) DVD)
At first, Director Robert Wise was attracted to the prospect of directing The Motion Picture specifically because it entailed him doing a science fiction movie imbued with a greater scope than if it had been set entirely on Earth, as The Day the Earth Stood Still had been. (Star Trek: The Magazine Volume 2, Issue 8, p. 14) On the other hand, Wise was insistent that part of The Motion Picture be set on Earth's surface, saying, "It is very important that we show the Earth in this film." (Star Trek Magazine issue 173, p. 63)
In the script for The Motion Picture, a view of Earth as the Enterprise leaves the planet was described as a "lovely bluish, cloud-laced image of Earth." 
Various techniques were used to represent Earth in The Motion Picture. (audio commentary, Star Trek: The Motion Picture (Blu-ray) special features) The planet was depicted from orbit in the film via matte paintings illustrated by Matthew Yuricich. (The Making of Star Trek: The Motion Picture, pp. 211 & 212) These illustrations were incorporated into shots via use of a matte. Daren Dochterman – who served as a visual effects supervisor for a director's edition DVD release of the movie – reckoned, "I don't think they built [a model of the planet]." However, Michael Okuda claimed that the different methods of depicting Earth in the movie included a dome onto which powder was sprinkled to create cloud shadows. (audio commentary, Star Trek: The Motion Picture (Blu-ray) special features)
Upon creating new views of the San Francisco Bay area for the Director's Edition of the film, the associated visual effects artists took inspiration from how Gene Roddenberry had imagined Earth. "Part of Star Trek's future is that it's not just more technologically advanced, it's more ecologically advanced," commented Adam Lebowitz, another visual effects supervisor on the project. "Humans have taken great pains to clean up the planet, to remove the pollution from the atmosphere, and to beautify the landscape." (Star Trek Monthly issue 86, pp. 52–53) Some new CGI shots featuring the planet as seen from orbit, being encountered by V'ger, were also created for the Director's Edition, generated by Foundation Imaging. (audio commentary, Star Trek: The Motion Picture (The Director's Edition) DVD)
The movie's only scene set on Earth's surface was met with varying reactions. Michael Okuda described it as "such a simple scene, but it says so much about Gene Roddenberry's vision of the future." (audio commentary, Star Trek: The Motion Picture (Blu-ray) special features) Roddenberry himself was unhappy with an establishing shot that, in the film's theatrical cut, begins the scene and is the only establishing shot used to represent the planet's surface. "It didn't really present the look of 23rd-century Earth that Gene was hoping to show," explained Robert Wise. (audio commentary, Star Trek: The Motion Picture (The Director's Edition) DVD)
Other films and spin-off series showed future Earth even more than it had been depicted in both TOS and The Motion Picture. The growth in visitations to the planet was made possible thanks to advances in visual effects technology and increases in Star Trek's budgets. ("The Menagerie, Part II" text commentary, TOS Season 1 DVD)
The script for Star Trek III: The Search for Spock poetically referred to "the grandeur of the horizon arc of the great blue marble."  In that film, Earth was portrayed using matte painting in some cases and a model in others. Painted by Frank Ordaz, the model had two halves. Clouds and part of the planet's surface were on one half, whereas the other side showed only clouds atop a dark under-layer. The clouds on the latter half were later to be double-exposed over the planet surface at a slightly different rotation speed. (Cinefex, No. 18, p. 47)
Like the script for Star Trek III, the revised shooting script for Star Trek IV: The Voyage Home and the revised final draft script for Star Trek V: The Final Frontier also referred to Earth as the "blue marble." Elsewhere in these descriptions, both scripts specified the planet's name and the screenplay for Star Trek V referred to the marble as "big."   Also, a visually spectacular journey through the cosmos which was originally to serve as the credits sequence for Star Trek V was intended to culminate in what was scripted as "a breathtaking shot of Earth." 
Earth appears as the first planet in the opening sequence of Star Trek: The Next Generation's first and second seasons. It is shown orbiting the sun and is followed by the moon, Jupiter, and Saturn before the USS Enterprise-D starts its exploration of unknown space.
The idea of featuring Earth as the central setting of TNG: "Family" was thought up by Michael Piller. Though many people were extremely hesitant about focusing on the planet in such a way, the concept was accepted by Rick Berman. Piller later recalled, "Rick said, 'I'll let you take Picard to Earth.'" (Cinefantastique, Vol. 22, No. 2, p. 36) To create views of Earth in "Family", satellite photos of the planet were used. (To Boldly Go) Piller ultimately suspected that using Earth as a central setting of the story resulted in the episode having some of the lowest viewing figures in Star Trek history. (Cinefantastique, Vol. 22, No. 2, p. 36)
When Michael Piller and other members of Star Trek: The Next Generation's resident writing staff pitched the story for TNG: "The First Duty" to Rick Berman, the fact that Earth was the most used setting in the episode almost led Berman to disallow any subsequent progress on the installment. He furthermore declared that Star Trek was "not about going back to Earth," in Piller's words. Berman was eventually persuaded by Piller into approving the episode, on condition that only three sets were to be used to represent interiors on the planet. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 242)
In a scene which was scripted for DS9: "Emissary" but not included in that episode's final edit, Commander Benjamin Sisko was to have received a recorded follow-up message from Earth, where a university chancellor told him that an old house he had inquired about, on Moravian Lane, was available if he wanted it. David Carson explained, "There were clear indications that he was being offered a job back at a university on earth." (Cinefantastique, Vol. 24, Nos. 3/4, p. 101)
Director Paul Lynch once commented that Earth could easily have been the main setting in DS9: "Battle Lines", instead of an unnamed moon. Lynch remarked, "It could have happened on Earth, and that's what made it compelling to me." 
In Star Trek: Deep Space Nine, Ira Steven Behr took care not to contradict Gene Roddenberry's view of Earth as a paradise but started having the main characters examine the subject further. Likewise, whereas Roddenberry had been fond of describing the future Earth as a paradise, the DS9 writing staffers were more interested in demonstrating exactly how difficult it was to maintain that paradise. (Star Trek: Deep Space Nine Companion (pp. 138 & 303)) "The whole Roddenberry thing was believable when you're living back on Earth," Behr observed. "We thought it was a fundamental thing to state." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 59) He further explained, "The one thing that ST:DS9 has done to its credit – it's probably backfired on us to an extent – is we keep questioning this whole thing that Gene Roddenberry came up with supposedly about the 24th century and Earth being a paradise and 'what is paradise?' We like to test it [....] We're not saying that it's not real or it's not a worthy goal, but paradise is a delicate commodity." (Star Trek: Deep Space Nine - The Official Poster Magazine, No. 10)
In DS9 Season 3 installment "Past Tense, Part II", Special Effects Supervisor David Takemura was tasked with rendering a shot of Earth, with the USS Defiant orbiting the planet. "I used an eight-by-ten NASA transparency of the real Earth to create the footage," he explained. To make it seem as if the shot wasn't still, Takemura devised a motion-control move in which the transparency panned in one direction while the motion control camera panned in the opposite direction. "I thought it was a nice shot," Takemura concluded. (Star Trek: Deep Space Nine Companion (p. 202))
Earth was originally set to feature at the end of DS9's third season. "We were planning a big two-part episode where we go back to Earth – maybe the Academy – and realize that there has been changeling infiltration," René Echevarria recalled. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 99) Explaining why Earth was chosen as the plot's setting, he admitted, "We'd decided that the scariest thing would be to set the story at home, with people we care about." The two-part narrative focusing on Earth and events there was at first intended to provide a cliffhanger ending to season three and be concluded at the start of the fourth season. The Earth-based two-parter was thereafter planned, by the DS9 producers, to launch the show's fourth season, but was then delayed again, finally airing as "Homefront" and "Paradise Lost", midway through season four. (Star Trek: Deep Space Nine Companion (pp. 250 & 253))
In "Little Green Men", Earth of the past was once again visited, specifically the Roswell Incident of 1947. "It's one of those things that Star Trek can do," commented Quark actor Armin Shimerman. "It can combine fantasy and history, and do a take on it. That started in the original series when the Enterprise would visit Earth back in the past." (Cinefantastique, Vol. 28, No. 4/5, p. 61) Shimerman particularly liked how the planet was used as a setting for "Little Green Men". "In my wildest dreams, I never saw Quark going to earth ever," he revealed. "So it was nice, not only to be on Earth, but to be on Earth in the Forties." ("Period Piece", Star Trek: Deep Space Nine - The Official Poster Magazine, No. 6) Shimerman also remarked that, for DS9 recurring character Nog, being on Earth full-time (in order to attend Starfleet Academy) implied that Nog actor Aron Eisenberg would have less to do on the series. (Cinefantastique, Vol. 28, No. 4/5, p. 47)
During the development of "Homefront" and "Paradise Lost", the DS9 writing staff chose to create a story "focusing on Earth and humanity, and being on Earth." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 112) Indeed, the two-parter gave the writers a welcome opportunity to test how paradisical the planet actually was, in the 24th century. "We've tested it on other occasions too in the series, so this was a test to see what it was like," said Ira Steven Behr. (Star Trek: Deep Space Nine - The Official Poster Magazine, No. 10) The notion of Earth being infiltrated by Changelings turned out to be popular, but viewers repeatedly pointed out to Behr that the setting wasn't really in the purview of the series. Even Behr himself conceded, "Earth isn't our franchise." (Star Trek: Deep Space Nine Companion (p. 422))
When it came time to shoot the Earth scenes of "Homefront" and "Paradise Lost", the planet had to be shown on a tight budget. "We had to paint that world a little better and we were really feeling the budget crunch," Ira Steven Behr related. (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p. 112) He elaborated, "I wish we could have had a little more location stuff, a little more outside stuff." (Star Trek: Deep Space Nine - The Official Poster Magazine, No. 10)
In the first draft script of DS9: "Body Parts", Earth was mentioned, Worf advising Miles O'Brien to send his wife and daughter, Keiko and Molly O'Brien, to the planet as that had worked, in Worf's opinion, between himself and Alexander Rozhenko and because Miles was stressed by his wife's activities, since she was pregnant. The planet is not referenced in the final version of that episode, though.
If the DS9 Season 6 episode "Waltz" had ended as it was originally scripted to – with Dukat threatening to kill Jake Sisko – sending Jake to Earth was one of two optional precautions which Ronald D. Moore suspected Jake's father, Benjamin Sisko, would have had to take, the other being the deployment of "a twenty-six-hour guard" to carefully watch Jake. (Star Trek: Deep Space Nine Companion (p. 522))
Earth was on Ira Steven Behr's mind as he invented Section 31, during DS9's sixth season. "Why is Earth a paradise in the twenty-fourth century?" he pondered. "Well, maybe it's because there's someone watching over it." (Star Trek: Deep Space Nine Companion (p. 551))
Sending Captain Sisko to Earth was part of the story for DS9 Season 6 finale "Tears of the Prophets" at least as far back as when Ira Steven Behr gathered the writing staff and announced, for the first time, details of the plot to them. A real Native American chant about the planet, entitled "Only the Earth Endures", provided the genesis for a Klingon death chant (referencing Qo'noS instead) in "Tears of the Prophets". (Star Trek: Deep Space Nine Companion (pp. 586 & 588))
Molly O'Brien actress Hana Hatae thought it made sense for the O'Brien family to relocate to Earth in DS9 series finalé "What You Leave Behind". "Earth seemed like a safe move for a Human family with two young kids," reckoned Hatae. 
Owing to the premise of Star Trek: Voyager, Earth could not be shown as a regular setting in that series. (Star Trek: Voyager - A Vision of the Future, p. 164) Earth nonetheless did appear on the show. Ronald D. Moore observed, "There have been more episodes [in VOY] that have taken place on Earth, or alternate Earth, or past Earth than I think the original series did in its whole run, and the original series was set over in the Alpha Quadrant." Brannon Braga even considered permanently returning the starship Voyager to the planet. Moore, who imagined an initial two-parter focusing on the vessel's arrival at Earth, argued against this option, believing it would waste Star Trek: Voyager's "golden opportunity" to be different from all the other Star Trek series. 
Earth was additionally to have been featured in an ultimately undeveloped episode of Voyager. One idea which Brannon Braga concocted for the story was starting it with Voyager apparently above Earth, returning home to the planet, though the craft was actually a biomimetic duplicate of the actual starship Voyager. For the same story, Braga also suggested the planet be a point of convergence for about a thousand similar duplicates of the ship. (Cinefantastique, Vol. 31, No. 11, p. 49) One reason this story concept was abandoned was that the writing staff thought it would undermine the moment when the real Voyager returned to Earth, which the creative team, even then, intended to eventually have happen. (Star Trek: Action!, p. 6)
Prior to learning the events of Star Trek: Voyager series finalé "Endgame", many of the main cast members from that series were hopeful, at the beginning of the show's seventh season, that the crew of the USS Voyager would have time back on Earth to explore the implications of their return home. Tuvok actor Tim Russ perceived both positives and negatives in featuring Earth so prominently towards the end of the series. He said, "It will be very dramatic and exciting to return to Earth, and it has been the focus of our journey. But by the same token, the show will no longer be the Voyager of the series, as we will no longer be on our own in the far side of the Galaxy, making new discoveries." (Cinefantastique, Vol. 33, No. 5, pp. 38 & 39)
Actor Ethan Phillips was glad Earth was not the final destination of his character of Neelix, Phillips not being able to imagine Neelix on the planet nor what he would have done there. Phillips also believed that, even if Neelix had ended up on Earth, the planet's population would have included no other Talaxians. 
Harry Kim actor Garrett Wang was highly frustrated by the fact Earth is shown from orbit in the last shot of "Endgame", with Voyager approaching the planet. "We don't even step foot on Earth," Wang pointed out. "Hello! After seven years, I think the fans wanted to see us actually step foot on terra firma."  B'Elanna Torres actress Roxann Dawson felt similarly about the depiction of Earth in Star Trek: Voyager, as one thing she thought would have been interesting for the series to have explored was what Torres and husband Tom Paris were like, once they were back on Earth. 
The series that became Star Trek: Enterprise was originally imagined as having an Earth-bound setting. In fact, when series co-creator Rick Berman first approached fellow series co-creator Brannon Braga about the initial concept of the show, Berman referred to it as a prequel series set "in the mud," featuring the construction of Earth's first warp 5 ship. ("To Boldly Go: Launching Enterprise, Part I: Countdown", ENT Season 1 Blu-ray special features) The pair wanted at least the series' first season to be set on Earth, proceeded by the launch of the craft. (Star Trek: The Official Starships Collection, issue 82, p. 12; "To Boldly Go: Launching Enterprise, Part I: Countdown", ENT Season 1 Blu-ray special features) Braga once explained that this was their first idea for the show. (Star Trek: The Official Starships Collection, issue 89, p. 12) The concept was vetoed, however, by executives at Paramount Pictures, who favored a more conventional Star Trek setting. ("To Boldly Go: Launching Enterprise, Part I: Countdown", ENT Season 1 Blu-ray special features) Nonetheless, much of the series' pilot episode, "Broken Bow", was ultimately set on Earth. Braga remarked, "It's really a fun place to be, strangely enough, because it's kind of a fresh setting for us." The series turned out to be conceived in such a way that more stories than usual were to have ramifications on Earth and references to the planet. "In terms of how close this Earth is to Roddenberry's vision, I think it falls somewhere between now and Kirk's time. Not everything is perfect," Braga pointed out. (Broken Bow, paperback ed., pp. 256 & 250) He and Berman even established that Earth had an antagonistic relationship with Vulcan. (Star Trek: The Official Starships Collection, issue 55, p. 15) Before it was decided whether the NX-class starship Enterprise would ever fly back to Earth, though, Braga announced that such visits to the planet would not be frequent. (Broken Bow, paperback ed., p. 256)
Enterprise's opening titles sequence begins with two shots of Earth. These were initially intended to be two particular IMAX shots taken from a space shuttle. However, Paramount failed to secure the rights to use them, so they asked Eden FX to intricately reproduce the shots exactly in CGI, allowing the visual effects house only two days in which to do so. Eden's Robert Bonchune recollected, "That was kind of tough, to put together Planet Earth and have it look like those IMAX shots [....] Fortunately, we have CG models of the Earth, fully mapped with clouds and everything. We had to up-res some detail on them [....] It had to look exactly like the IMAX shots in terms of cloud patterns and where the glint of the ocean is. That was pretty specific, so it took some work. But I don't think anyone would know, watching those opening shots, that they were pure CG shots of the Earth." (Star Trek Monthly issue 106, p. 46)
In the first draft script of ENT: "Fortunate Son", this planet was mentioned when Matthew Ryan asked Captain Archer whether, if Ryan handed over a Nausicaan prisoner he was secretly holding prisoner aboard his ship, Enterprise would "fly all the way back to Earth" to put the Nausicaan on trial.
In the final draft script of ENT: "Detained", Earth was referenced a few times in dialogue that didn't make it into the episode. For example, Travis Mayweather told a Suliban girl named Narra that he lived on Earth, whereas his backstory actually established him as meanwhile living aboard Enterprise. In a later scene, T'Pol imagined Earth someday establishing "formal relations" with Tandar Prime.
Earth was further discussed between Archer and Zobral in ultimately unused dialogue from the final draft script of ENT: "Desert Crossing". At one point in the conversation, Archer stated about the planet's ecology, "There's plenty of sea life, but most people live on land." Archer later referenced the planet again in the script, as part of another excised comment, this time to Charles "Trip" Tucker.
If things had gone according to what the ENT producers had planned, Earth in Star Trek: Enterprise would have been literally left behind. Although that essentially is what happens in the first two seasons of the series, the threat to the planet posed by the Xindi was written to be a significant feature in second season installment "The Expanse" as well as the show's third season. "The irony of season 3 was that even though there was a threat to Earth, we only really spend one episode on Earth [i.e., 'The Expanse'] and then we're out exploring the Xindi," observed writer/producer Mike Sussman. (Star Trek: The Official Starships Collection, issue 82, p. 13)
In a deleted scene from ENT: "E²", Earth was mentioned by Phlox; he pointed out to Archer that, following the Xindi incident, the crew of a particular version of Enterprise from a specific alternate timeline would probably be happy to return to Earth. (ENT Season 3 DVD and Blu-ray special features)
It wasn't until the Xindi arc came to an end that the choice to focus on Earth was made. Commented Mike Sussman, "It certainly seemed natural after spending an entire season in deep space saving the Earth from a threat, that we now had to deal with the repercussions of what had happened [....] How is the Earth recovering?" (Star Trek: The Official Starships Collection, issue 82, p. 14)
When Manny Coto took charge of the Star Trek: Enterprise writing staff for the series' fourth season, he decided to develop stories that showed the links between Earth of "Broken Bow" and the 23rd century of the first Star Trek series. The planet's antagonistic relationship with Vulcan was of great interest to married writing couple Garfield and Judith Reeves-Stevens when they joined the series in season four. (Star Trek: The Official Starships Collection, issue 55, p. 15) During the course of that season, Earth was impacted on by Coto intending to establish the specifics of how the Federation had come to be and how Humanity had evolved past xenophobia (resulting from the Xindi threat), both of which resulted in the planet becoming a major setting for stories about those issues. (Star Trek: The Official Starships Collection, issue 82, p. 17)
When Mike Sussman was given the task of writing ENT: "Home", setting the episode on Earth was pitched to him as the key component, as it was felt that an installment which took place on the planet needed to be done. This notion took its cue from TNG: "Family", which is likewise set primarily on Earth. While penning "Home", Sussman considered some aspects of the planet which had never really been answered before, ultimately deciding that Earth's government would be United Earth (which had been canonically referenced beforehand, though hadn't been set up as the planet's government). (Star Trek: The Official Starships Collection, issue 82, p. 14)
Earth was briefly mentioned in an extended scene from "Home" (included in the ENT Season 4 Blu-ray). In the deleted portion of the scene, Charles Tucker suggested to Koss, who had never before met a Human, that he visit the planet at some point, to "broaden [his] horizons."
As described in the final draft script of ENT: "Demons", Earth was to be shown in the episode's first establishing shot of the Orpheus Mining Complex on Luna. However, the planet doesn't appear in the final version of that shot.
If Star Trek: Enterprise had been renewed for a fifth season, how Earth was evolving would have been dealt with in many more stories. Because Manny Coto wanted to show the Earth-Romulan War in ENT, the planet's continual developments would have been portrayed, visibly leading to Earth becoming the center of the Federation and the utopia Gene Roddenberry had promised. (Star Trek: The Official Starships Collection, issue 82, p. 17)
In Star Trek Nemesis, views of Earth from orbit were derived from 20K NASA images. Though these high-resolution pictures were completely accurate illustrations of the planet surface and visually appealed to Digital Domain Supervisor Mark Forker, the producers and director of the film were initially not entirely happy with them. Recollected Forker, "They requested some changes – England was too small, Italy was too close to Africa, and the boot [shape of Italy] was too big." Manipulating the images, Digital Domain made the appropriate changes and added digital clouds. "Of course, by the time we added clouds and atmosphere," said Forker, "the changes weren't that noticeable." (Cinefex, No. 111, p. 93)
Earth of the alternate reality
While the J.J. Abrams movies Star Trek and Star Trek Into Darkness were being conceived, Earth was considered important to establish as a major setting in the alternate reality. "The Earth needed to play more of a role in these movies, especially in the sense of giving the audience a degree of relatability," commented writer/producer Damon Lindelof. "I think that in the same way that New York City becomes this anchor point for people in the Marvel movies; that’s Spidey’s stomping ground, that was the stomping ground for Tony Stark, that was the stomping ground for The Avengers, it’s New York. We wanted to do the same thing with Earth in the Star Trek movies." 
For visually depicting Earth in the movies Star Trek and Star Trek Into Darkness, it was felt important that futuristic cities be kept realistic as much as possible, incorporating practical elements. By way of an example, Visual Effects Supervisor Roger Guyett stated, "It's not a concept art version of […] a city, it's a working version."  To represent Earth in Star Trek Into Darkness, location filming was used, most of which was done in Los Angeles. The locations were picked by Production Designer Scott Chambliss. (Cinefex, No. 134, p. 72)
Star Trek Into Darkness' visual effects team created the look of multiple cities on Earth, including London and San Francisco. "Our philosophy about doing cities, and respecting the canon of how the [world] is described by Gene Roddenberry," explained Roger Guyett, "is that you're only a few [hundred] years into the future. You're not that far away [....] We go through this process of, 'What would have happened? What buildings would they have hung on to? How would it have changed the nature of some of the design choices they made?' We like to take things that are real and try to make the architecture scalable. In other words, a scale that is not just totally ridiculous and massive. At the same time, you want a few landmarks in those shots to get the sense of what city you are in [....] But, at the same time, we want to elaborate on that and use our imagination on how that might have changed." (Star Trek Magazine issue 172, pp. 48–49)
The futuristic cities in Star Trek Into Darkness took a design cue from the previous film. J.J. Abrams recalled, "We wanted terrestrial cities to be consistent with what we had established, but at a much higher resolution. We got to live, breathe and chase within the city streets this time, but we also wanted to maintain a level of potential truth and realism [....] We didn't want to get so fanciful that it felt unrelatable." Abrams selected recognizable urban landmarks for both San Francisco and London, before Industrial Light & Magic created a model showing each of the two cities, both of which were added to with high-resolution CGI buildings. Abrams also described the challenge of imagining how cities might be changed in the future, based on their present conditions, as "fun." (Cinefex, No. 134, pp. 72 & 74)
Responding to viewer criticism after the release of Star Trek Into Darkness, J.J. Abrams acknowledged, "I can understand that this movie might not have gone as far away from Earth for as long as some people would have liked." 
Regardless of this, Nyota Uhura actress Zoë Saldana hoped that, in Star Trek Beyond, the crew of the Enterprise would "go back to Earth" and, for the first seven or eight minutes of the film, be shown there in the middle of having a day off.  However, Star Trek Beyond actually became the second Star Trek film, the first having been Star Trek: Insurrection, not to feature any scenes on or near Earth. A substitute was invented instead. "One of the notes that J.J. always directed towards us was that the threat in the movie have a very far-reaching effect and that it always come back to Earth," explained Star Trek Beyond co-writer Simon Pegg. "So how can we make Earth a potential victim of whatever's going wrong here with it being so, so, so far away? Because what we're trying to get across in this movie is that they're not anywhere near Earth any more, and so we created a sort of proxy Earth, which is Yorktown." ("Beyond the Darkness", Star Trek Beyond (Blu-ray) special features)
According to Star Trek: Star Charts (pp. 32, 36-37, 56-57, & "United Federation of Planets I") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), fifty years after Earth became warp capable, the United Earth government was founded on Earth in 2113. The government of Earth was divided into six major regional powers that were governed from their respective capitals. These capitals were San Francisco (North America), Paris (Europe), Kyoto (Asia), Lima (South America), Cape Town (Africa), and Christchurch (Oceania). In 2161, Earth was a founding member of the United Federation of Planets. The dominant species were Humans and Cetaceans. In the census of 2370, there were counted 4.2 billion Humans and 8.1 million Cetaceans living on Earth.
According to Star Trek: Star Charts (pp. 36–37 & 56-57), Earth was a hub world on the mid-22nd century Earth trade routes. It traded with Alpha Centauri, Altair, Andoria, Denobula Triaxa, Draylax, Ophicus Colony, Tellar Prime, Trill, Vega Colony, and Vulcan. In 2378, Earth was a hub world on the major space lanes. Points of interest on Earth included the UFP Council Chambers, Starfleet Headquarters, Starfleet Academy, Cochrane Memorial, Yosemite Valley, and Angel Falls.
According to Stellar Cartography: The Starfleet Reference Library ("The Dominion War: Strategy and Battles, 2373-75"), Earth was raided by the Dominion in August 2375.
David Gerrold verbally drew a parallel between the typical circumstances found on Earth of one particular time period and those of the Federation in TOS. Regarding conditions on Earth of the 18th century, Gerrold explained, "Then too, communications over vast distances were slow and uncertain. The arrival of a courier was always an event. Even if the news he was carrying was several weeks, months, or years old, it was still the most recent news available. When one government had to deal with another, they used diplomatic notes and couriers – and in matters of highest policy, they depended upon their ambassadors." Also, while criticizing the scientific accuracy of Star Trek II: The Wrath of Khan (or lack thereof), Gerrold commented that "the flat-Earth theory" was slightly more advanced than the film's view of the workings of the universe. (The World of Star Trek)
At a very early stage of Star Trek: First Contact's development, the film's writers – including Brannon Braga and Ronald D. Moore (as well as possibly Rick Berman) – discussed the possibility of beginning the film in a Borg-assimilated city on Earth. (audio commentary, Star Trek: First Contact (Special Edition) DVD/Blu-ray)
In its assimilated state as shown in the movie, Earth was represented with CGI done by Alex Jaeger. (Star Trek: The Next Generation Sketchbook: The Movies, p. 335) He depicted the heavily polluted version of the planet by creating a series of digital matte paintings. (Cinefex, No. 69, pp. 113 & 117) As Jaeger had only ever worked in the model shop at Industrial Light & Magic before serving as the company's visual effects art director on First Contact, he found the challenge of creating the altered Earth slightly daunting. "They kind of tossed me into this and said, 'Oh, yeah, we're going to need a Borg Earth,' and I go, 'Oh, OK,' so I did a few early Photoshop pieces that just showed a section of the Earth. Then they said, 'Yeah, that's good, but can you just make a texture for the whole planet that we'll just use in the movie,' and I'm like, 'Uhhh, OK – I've never done that before, but sure!' So, basically what I did was, I took a texture map of the Earth – it was this gigantic Photoshop file – and started changing it around." (Star Trek: The Magazine Volume 1, Issue 23, p. 88)
Included in the assimilated Earth are details hardly visible in the actual film, such as industrial pipes spanning the oceans. (Cinefex, No. 69, p. 113) "I saturated all the ground so it was gray and I added all these sort of factory-looking sections so it looked like the ground was completely covered by cities," remembered Alex Jaeger. "Then, I painted little bridgeways across the oceans and turned the oceans brown. [First Contact Director] Jonathan Frakes kept saying, 'No, the oceans have got to be brown, like they're full of crap! Just, you know, nasty; you don't want to be there.'" (Star Trek: The Magazine Volume 1, Issue 23, p. 88) Jaeger also noted that, in addition to turning the oceans brown and making the land masses "desaturated and gray, as though they have become overrun with Borg power plants and machinery," he also turned the clouds and atmosphere yellowish-green. (Cinefex, No. 69, p. 113)
Alex Jaeger was ultimately pleased with how he created the assimilated Earth, essentially destroying the planet visibly by doing so. He remarked, "It turned out fairly well [....] And to have something that I actually painted end up on screen, was kind of cool." (Star Trek: The Magazine Volume 1, Issue 23, p. 88) Brannon Braga agreed that the optical of the assimilated Earth was "very cool." (audio commentary, Star Trek: First Contact (Special Edition) DVD/Blu-ray)
According to Gene Roddenberry's novelization of Star Trek: The Motion Picture, there is a dam across the Straits of Gibraltar. This allowed the level of the Mediterranean Sea to be lowered, creating new farm and park land along the coast, and the world's largest hydro-electric project.
In an alternate future in the Deep Space Nine book series Millennium, Earth was destroyed in 2388 by the violent Grigari. Among the casualties were William T. Riker, Deanna Troi, Geordi La Forge, Beverly Crusher, Tom Paris, B'Elanna Torres, and the USS Enterprise NCC-1701-F.
In the Star Trek: Deep Space Nine - Dominion Wars video game, if the player plays as the Dominion, the Founders destroy the Federation, bombard Earth, and then declare it to be a secondary homeworld from which to rule.