Holodeck

"The holodeck has given us woodlands and ski slopes... figures that fight... and fictional characters with whom we can interact."
 * - Jean-Luc Picard, 2364

A Holographic Environment Simulator, or holodeck for short, is a form of holotechnology designed and used by Starfleet. They are installed aboard starships, space stations, and at Starfleet institutions for entertainment, training, and investigative purposes. A typical holodeck consists of a room equipped with a hologrid containing omnidirectional holographic diodes, enabling holographic projections through the manipulation of photons contained within force fields.

History
Prior to the late 24th century, Federation starships were not equipped with holodecks. 

However, in 2151, the Starfleet vessel encountered a vessel belonging to an alien race known as Xyrillians, who had advanced holographic technology in the form of a holographic chamber similar to the holodeck, which Federation Starfleet developed two centuries later. A holo-chamber was later installed aboard a Klingon battle cruiser, given to the Klingons by the Xyrillians in exchange for their lives. 

In the 23rd century, starships were equipped with a recreation room, which employed holographic technology. The USS Enterprise (NCC-1701) had a recreation room located in Area 39 of the ship. 

By 2364, the Federation Starfleet had begun installing holodecks aboard their vessels. 

During the 2360s and 2370s, a starship could have one or more holodecks depending on the vessel's size or purpose. For example,  starships did not have a holodeck, while  vessels had several. 

The two holodecks of starships were the only places other than sickbay where the EMH was able to exist (without a mobile emitter) after the crew modified his program so it wasn't as tightly integrated into the sickbay's systems. In starships, the EMH could move more around the ship freely because all decks were equipped with holoemitters. 

Purpose
The most obvious function of a holodeck is to provide entertainment and diversion for the crew. 

A holodeck can be used to create training simulations and exercise environments not otherwise available or safe. 

The holodeck can be used as a laboratory to aid in analysis, such as recreating the scene of a crime or accident to aid in forensic investigations. They can be used to visualize a 3D scene from alternate data sources for analysis or used as a brainstorming tool. 

Design
A holodeck combines transporter technology with that of replicators, by generating actual matter, as well as projecting force fields to give the objects the illusion of substance. It can be controlled from an exterior control or the interior arch control. This arch can be summoned at any time to change the parameters of a running holoprogram. Matter and energy are interchangeable as such objects created on the holodeck can be either matter or energy. 

In the early 24th century, matter replication was primarily used for objects and characters that would be in direct contact with the occupants which gave them an extreme sense of realism. Water, for example, would feel like actual water because on some level, it was, and it could create experiences like odors. This also enabled simple matter to exist outside of the holodeck for brief periods of time (such as snow) before they would lose cohesion without the support of the holodeck grid and revert back to energy. This, however, used an extreme amount of power, and caused repetitive problems to occur in its safe usage. Some time in the mid 24th century, this was slowly phased out in favor of simpler 'true' holographic technology by focusing on the photons contained within micro force fields. This was not only safer and used less power, but had more varied usage and could be easily controlled with quicker reaction times. Some would argue this made it lose its appeal, but advances in the technology has made it as real as the matter replication method, which is still used for more complex, tactile objects, as well as food, odors, etc.

Holodeck walls can generate holographic images that appear to extend for an unlimited distance, seemingly much larger than its own dimensions. In doing so, however, the holodeck is aware only of its users; it does not recognize its own created objects. For example, if a person were to throw a holographic rock at the holodeck's walls, the rock would not be allowed to pass beyond the wall (if it were of replicated matter). It does this by continuously adjusting the projections of the force fields and the use of a force field "treadmill". With this, an individual approaching a wall causes an instant shift away. It can also manipulate light photons, 'lensing' them to make individuals appear further away if two persons were separated in a scenario. The holodeck can change gravity in three dimensions, so occupants don't notice the change, (Star Trek: The Next Generation Interactive Technical Manual) as observed during the stop of B'Elanna Torres' holographic orbital skydiving session. 

Holodecks are equipped with safety protocols to prevent serious injury during their use, though these can be disengaged by the user when required. While active, a force field that is likely to cause a certain level of physical harm to a living humanoid collapses before making contact with them, allowing them to escape uninjured. When protocols have been deactivated holographic obstacles have the same effects on a person as the objects or instances they simulate; holographic bullets or a steep drop could be fatal in such a scenario. How the security protocols are circumvented differs; in one instance, it required the voice authorization of two senior officers, while in others the authorization of the individual such as the ship's captain, or the person who started the program was enough. Safety protocols can also be unintentionally disabled due to software errors or physical damage to the holodeck's hardware system. The status of safety protocols can be reviewed by the computer upon the request of an operator. The use of a tricorder within the holodeck can be also be done to query the current safety protocol status.

Holodecks employ spatial orientation systems to simulate parts of a holocharacter, such as left- or right-handedness. 

Holodeck characters have been known to include a program element designed to hide anachronisms to the program's time period, such as uniforms and communicators, and prevent them from raising the character's ire and curiosity.

Among the viewing modes on a holodeck is objective mode, in which the user doesn't interact with the characters, and subjective mode, in which the viewer can interact with the characters as well as alter his or her surroundings. 

Abilities and limitations
Holodeck matter can impersonate real matter at the molecular level. Molecule-sized magnetic bubbles replace molecules in full resolution holographic objects, which a computer can manipulate individually in three dimensions. However, the complexity of electron shell activity and atomic motions that determine biochemical activity in living creatures cannot be projected holographically. This prevents replicators from duplicating life and resurrecting the dead. Advances in computer technology may allow this, permitting a person to live forever in any chosen environment while interacting with real people and objects visiting the holodeck. The computer may use large magnetic bubbles to simulate surfaces and textures rather than create an object at the molecular level. However, objects created within the holodeck would not exist beyond the holodeck itself, as they only exist as energy. Since holodeck technology can be used with replicator technology, there are some instances where real objects are replicated within the holodeck and are used to interact with the holographic program and/or users; since these objects are real material composed of matter, they can leave the holodeck fully intact.

A holodeck can modify the appearance of persons within it.
 * The holoprogram depicting the final mission of the starship  can project uniforms suitable to the participants' role over them.
 * A holodeck is able to superimpose an entirely different appearance over a participant.
 * Tom Paris' holoprogram "Captain Proton" exists as a monochromatic environment.
 * As part of "The Big Good-Bye", appropriate attire can be projected over participants of the program.
 * Simulations can also be projected inside living organisms, including that of pregnancy.
 * B'Elanna Torres' leg appeared to dematerialize while she was participating in the holonovel "Photons Be Free" as the holographic main character.
 * Seven of Nine used the holodeck to hide her cybernetic implants.

Holograms can be augmented with force beams to simulate solid, tangible objects or with replicator technology to create actual solid matter such as foodstuffs. All food eaten on the holodeck are replications. No other type of simulation would survive outside of the holodeck.

A holodeck also has the ability to create holodecks within holodecks, and holodeck programs are able to be saved to a cube that can be inserted into special devices with information to "last a lifetime". 

The energy matrix of a holodeck is incompatible with other ship systems. 

Failure of a holodeck's matter conversion subsystem can cause the loss of solid objects within the holodeck environment. Materialization errors occurred in the USS Enterprise (NCC-1701-D) holodecks in 2370 following the ship's exposure to plasmonic energy in the atmosphere of the planet Boraal II. 

Even though holographically created characters, just like characters in a story book, are never self-aware and never know that they are not real, there have been a few rare instances in which that rule has not held true. During a Sherlock Holmes holodeck simulation in the late 2360s, Geordi La Forge and Doctor Katherine Pulaski argued that playing with Data was impossible and unfair to them as he had memorized all the Sherlock Holmes novels and could easily solve the cases. In order to level the playing field, La Forge requested that the holodeck create an opponent intelligent enough to defeat Data. Even though La Forge meant Holmes, his request had specifically noted Data. As a result, the holodeck created a self-aware holographic character of James Moriarty who was not only fully aware of his own consciousness, but who subsequently argued that he had a right to exist and leave the holodeck to pursue his life as he wished. Another holographic writer - known as "Felix" - created the fully self-aware program of Vic Fontaine for the crew of Deep Space 9, Vic being completely aware of his holographic nature despite being a 1950s lounge singer, often offering the crew personal advice on relationship issues. 

Holoprograms
Starships with a holodeck normally had a vast list of holoprograms in their computer. Several notable programs aboard the USS Enterprise (NCC-1701-D) included:


 * A woodland setting, resembling Earth, which featured a rock-jumping challenge, some of which were seemingly impossible to complete.
 * A New Orleans jazz nightclub.
 * A recreation of the voyage on the Orient Express.
 * Sherlock Holmes mysteries, where the user assumed the role of Sherlock Holmes and/or Dr. Watson
 * Prospero's island, decor for Shakespeare's The Tempest.
 * Café des Artistes – "Enjoy a meal at a French cafe."
 * Charnock's Comedy Cabaret – "Laugh in a 20th century comedy club."
 * The Big Good-Bye – "The 1940s world of gumshoe detective Dixon Hill."
 * Cliffs of Heaven – "From planet Sumiko IV, a safe experience."
 * Equestrian Adventure – "Horse riding in an open country..."
 * Karate Dojo - Shown by Tasha Yar to the Ligonians before she was kidnapped.
 * Calisthenics Program of Lieutenant Worf – a swamp-like setting where various alien enemies tested ones fighting skill.
 * The bridge of the USS Enterprise (NCC-1701) – the user could select any of the five (at the time) bridges of the various Federation starships named Enterprise to view. Captain Montgomery Scott only wanted to see the original Enterprise bridge, "no bloody A, B, C, or D."
 * The Final Mission of Enterprise – this program allowed a user to view or take part in the final mission of the NX-01 Enterprise, commanded by Captain Jonathan Archer, as well as showcasing the signing of the Federation Charter.
 * Natasha Yar's Living Will – designed by Lieutenant Natasha Yar to be played in the event she was killed, where she bid farewell to her comrades. The Enterprise bridge crew unfortunately had to watch the program when Yar was killed by Armus on Vagra II.
 * Celtris III Underground – a simulation where the users could prepare for missions on the Cardassian planet of Celtris III.
 * Lieutenant Barclay's various programs – these included a mock-up of Ten Forward, where the user could attack Commander Riker and Lt. Commander Geordi La Forge to "blow off some steam" as well as win the heart of Deanna Troi; a mock-up of Counselor Troi's office where the user could receive counseling from a hologram rather than the real Troi; a woodland setting where the user could duel with recreations of Captain Picard, Data, and La Forge in a sword-fight, complete with a recreation of Deanna Troi as "The Goddess of Empathy"; a mock-up of the Enterprise-D bridge, where the user could bid farewell to the bridge crew; the Einstein program where the user could debate mathematics and science with Albert Einstein; a synaptic interface where the user could control the main computer of the Enterprise with the power of their own thoughts (however, removal of the user by conventional means would result in death); and various other programs.
 * A game of poker with three famous scientific minds: Albert Einstein, Sir Isaac Newton, and Stephen Hawking.
 * USS Enterprise – an 18th century Earth brig.

Notable programs aboard the USS Enterprise (NCC-1701-E) included:


 * The Big Good-Bye – "The 1940s world of gumshoe detective Dixon Hill."
 * Café des Artistes – "Enjoy a meal at a French cafe."
 * Champs Elysees – "Famous section of Paris."
 * Charnock's Comedy Cabaret – "Laugh in a 20th century comedy club."
 * Emerald Wading Pool – From planet Sumiko III, a safe experience."
 * Equestrian Adventure – "Horse riding in an open country side with a choice of..."

Notable programs aboard the USS Voyager included:


 * Chez Sandrine
 * Janeway Lambda one
 * Paxau Resort
 * Insurrection Alpha
 * Leonardo da Vinci's Workshop
 * The Adventures of Flotter
 * Velocity
 * The Adventures of Captain Proton
 * Fair Haven
 * Photons Be Free
 * Holographic family

Notable programs aboard the USS Enterprise (NCC-1701)'s recreation room included:


 * A beach setting allowing for swimming.
 * A woodland environment allowing for a nature walk.
 * An arctic wasteland.
 * An 18th century style hedge-maze.

Background
The concept of the holodeck originated in, when Gene Roddenberry came up with the idea of a "simulated outdoor recreation area" on the Enterprise for the third season of Star Trek: The Original Series. This idea never came to fruition, probably because of budget constraints. (Inside Star Trek: The Real Story, p. 404) The idea was later used in the Star Trek: The Animated Series episode, which was basically the first appearance of the holodeck, then called a "recreation room". It never came to existence in live-action production until the pilot of Star Trek: The Next Generation. Its inclusion in that series was originally proposed by Robert Justman, who initially thought of and suggested it as a place where crew members could be "psychically connected" with their homeworld. (Starlog issue 115, p. 71)

In early episodes of TNG, the series' production staff had an unwritten rule that the floors in a holodeck simulation shouldn't go below the floor level of the holodeck's door. This made sense, as burrowing down to the deck below would probably be inadvisable on a starship. Subsequent story requirements and set designs eventually influenced producers to alter their "rule," deciding that at least one holodeck was a multi-story chamber. (text commentary, DVD)

The appearance of the holodeck on TNG was affected by having limited finances. Production Designer Herman Zimmerman commented, "We were in a budget constraint that made us do a set that is a wireframe look." Zimmerman and other members of the design team that worked on TNG had a long-standing interest in demonstrating the machinery of the holodeck from inside the room, though this was not made possible until the advent of the Cardassian holosuite in Star Trek: Deep Space Nine. (The Deep Space Log Book: A Second Season Companion)

Despite the fact that the Galaxy-class starship was meant to have numerous holodecks, a single set represented these environments on TNG. This was one of the last sets to be built for the show and was also used to represent the Galaxy-class cargo bays, shuttlebays and gymnasium. (Star Trek: The Next Generation Companion 3rd ed., p. 10)

The holodeck arch was a prop that was originally made for TNG:. Although some holodeck programs incorporated the arch to make the task of finding the way out easier, the arch originated as a way to let outsiders know when it was safe or appropriate to enter. (text commentary, DVD) The same arch set piece was featured in both TNG and the film. (Cinefex, No. 61, p. 69)

For its first appearance on Star Trek: Voyager in, the exterior of the holodeck was the same set piece as had previously been seen on TNG, right down to the octagonal door frame, although all had been repainted to match the color scheme for the new Voyager corridors. It did not receive a square door arch and updated door panels until its second appearance.

There are many discrepancies between episodes pertaining to the abilities and limits of holodeck technology. For example, in, the young Wesley Crusher remains wet with holodeck water, after exiting into a corridor. In, a piece of paper given to Data by James Moriarty is able to be carried outside of the holodeck and into a hall, but upon Moriarty's return in , a book thrown outside of the holodeck instantly disappears. Also, in, Cyrus Redblock and Felix Leech disappear slowly after a few moments outside of the holodeck, although a lipstick smudge from a holographic character stays with Picard all the way onto the bridge. Although these inconsistencies can be partially explained by the difference in the types of objects leaving the holodeck, it still leaves quite a few questions about what exactly constitutes the differences. The holodeck can use a degree of replication to make realistic objects for the holodeck occupant to use, so there is a possibility of the computer replicating a real piece of paper with the picture on, as it would be a relatively simple pattern.

Some may argue that another discrepancy is the need for holodeck users to change into the appropriate costumes before entering and leaving the holodeck, since the holodeck has the ability to change the appearance of its users (established in ). But this may just be an issue of taste, on the user's possible preference of replicated clothes versus holographic clothes.