Psi 2000 was an uninhabited planet in the Alpha Quadrant. This ancient world disintegrated in 2266. Before the sun of this planet went dark, this planet was remarkably similar to Earth. Science officer Spock of the USS Enterprise believed that what happened to Psi 2000 might happen to Earth in the distant future. (TOS: "The Naked Time")
In 2266, before the planet's end, a science team had been stationed on Psi 2000 on behalf of the Federation. The gravitational shifts associated with the disintegration of the planet resulted in the creation of large strings of water molecules known as polywater which resulted in the Psi 2000 intoxication.
Shortly thereafter, a landing party from the USS Enterprise beamed down to the planet and discovered the science team dead, while the crew aboard the ship continued its mission of close scientific measurement of the break-up of the planet.
During the landing party's investigation, Lieutenant junior grade Joe Tormolen unwittingly contracted the Psi 2000 intoxication and brought it back aboard the starship. Suffering from the effects of the Psi 2000 intoxication, Lieutenant Kevin Riley powered down the ship's warp engines, causing the ship to begin spiraling towards Psi 2000. Chief Engineer Montgomery Scott was able to push the ship out of harm's way by initiating a cold start of the engines. (TOS: "The Naked Time")
In 2293, the location of Psi 2000 in the Milky Way Galaxy was labeled in a star chart in Captain James T. Kirk's quarters aboard the USS Enterprise-A. (Star Trek VI: The Undiscovered Country, okudagram)
In the final draft script of "The Naked Time", the surface of Psi 2000 was initially described thus; "The strange twilight of a dead world, a frozen wilderness... a deep purple sky... stark silent beyond belief... windless... desolate... not a gnarled root or fragment of vegetation... a textured cold that can almost be felt pressing against our eyes... ominous." From orbit, the planet was characterized as "a blue-white swirling mass of ice surrounded by a grey-green aura... silent... forbidding... ominous... a physical example of solid in vacuum... meant to be...." Also, Psi 2000 was scripted to be established in the episode's teaser with merely a view of the planet's surface, though the first shot of the planet in the final version of the episode is from an orbital perspective, before the planet's surface then appears.
For the pre-remastered version of "The Naked Time", the blue planet model for Psi 2000 was first used for Rigel XII in "Mudd's Women". This planet model would be used for Exo III ("What Are Little Girls Made Of?"), M-11 ("Court Martial" and "The Menagerie, Part I"), and Eminiar VII ("A Taste of Armageddon"). For the remastered version of "The Naked Time", a new planet model was created by CGI artist Max Gabl.