I think holodecks would totally transform education. Imagine a history class where students could interact with characters? Or a chemistry class where molecules are expanded to a metre across? A great tool for staff training too, as sometimes used in Star Trek.
– An h2g2 Researcher

In the science fiction world of Star Trek, the holodeck is an advanced form of simulator on board Starfleet's biggest ships, providing a totally realistic virtual world.

As anyone who has spent time in an isolating environment such as a deep-sea rig drilling for oil and gas, a submarine or an Antarctic exploration mission will tell you, sooner or later you just want to get the hell out of there. Right from the earliest days of space exploration, psychologists have recognised this fact. Selection and training programmes probe potential candidates for signs of weakness in being able to handle the enforced close-community of life aboard spaceships, space-stations and the like. Those that show any such weakness are not accepted for these programmes.

In the Star Trek world, those who are selected to serve Starfleet need time off and the means to escape mentally from their environments, even if only temporarily. It is for these reasons that holodecks are a popular form of recreation and relaxation on board Starfleet ships. They are particularly effective in combating homesickness.

The holodeck can also be used to test the ability of officers seeking promotion to respond appropriately to real-life scenarios, and to practise difficult or dangerous procedures in a low-risk environment.

The Holodeck

What happens on the holodeck stays on the holodeck.
– Anon

Holodecks have been standard equipment on United Federation of Planets vessels from the Galaxy-class ships like the Enterprise-D onwards; Enterprise-D has four holodecks, together with 20 of the smaller holosuites. On a holodeck, 3-D simulations of many environments and scenarios are created, based on data held in the ship's computer databanks. These are known as holodeck programs or holoprograms. Such is the power of these simulations that it is almost impossible to distinguish what is virtual from what is real. If you want to go horse-riding in luxuriant grasslands, with the sun shining down and the wind in your hair, you can. If you want to go to sea in a three-masted sailing frigate, you can. If you want to play the role of a famous character from history or fiction, you can. You choose exactly which holodeck program you want to run. All you have to do is dress for the part (or undress, as the case may be) and take your own specialist equipment along, if required.

Although the interior of the holodeck occupies a finite space, the space in which the holodeck scenario is played out is not so constrained. The virtual reality experienced by the users is created by arrays of hexagonal Omnidirectional Holo Diodes (OHDs) built in to the tiled walls of the holodeck. These create the sights, sounds and smells of the chosen scenario and project 3-D images into the holodeck space. Objects that the user is likely to touch can be made to appear solid by forcebeams also emitted by the OHDs. If necessary, the computer can create solid objects using the facilities of the transporter and the replicator. These objects are entirely real and can be kept afterwards, whereas virtual objects created by the OHDs disintegrate spontaneously if any attempt is made to remove them from the holodeck. Although essential, holodecks do consume a significant amount of both the ship's power and the processing capability of its computers.

Entry to a holodeck is via an 'arch' at the side of which are controls to initiate the program before entering. Once inside, voice commands can be given to freeze, replay or modify the scenario. It is considered a serious breach of holodeck etiquette to enter a holodeck that is already in use by someone else, but a group may, by agreement, enter a holodeck at the same time to experience a particular program or one-off event together, such as Lt Tasha Yar's funeral.

Although the ship's computers will usually stop users becoming seriously injured, accidents can and do occur. Senior officers may override the safety systems that prevent serious injury, but any unauthorised attempt to interfere with holodeck safety is a serious breach of Starfleet regulations.

Holo-diction

Obviously with no imposed limit to the imagination and a discreet computer it is possible to get carried away. This is easy to understand; when confronted with an array of characters to skinny-dip with, would you choose Marilyn Monroe (or Clark Gable), indeed, why choose just one when you can go back again and again? As with many other forms of entertainment, people can become addicted to it and holodeck addiction ('holo-diction') is a recognised medical condition.

One socially inept TNG character, Lt Reginald 'Broccoli' Barclay, became so wrapped up in his personal holosuite program that his work began to suffer. He spent more and more time on the holodeck, turning up for work late and eventually began missing shifts altogether. Commander Riker investigated what was going on and overrode the security lock to find his holographic self being bossed around by Barclay. Outraged, he ordered the program to be shut down and reported Barclay to the Captain for disciplining. Ship's Counsellor Deanna Troi was the only one who defended Barclay's behaviour, and her offer of help for his holo-diction was eagerly accepted. Unfortunately for him, when Barclay was late for a counselling session, Deanna went looking for him on the holodeck. Her reaction upon finding her holographic self – 'the goddess of Empathy' – in a romantic set-up with Barclay, was not pleasant. Oops!

Holodeck Scenes

The holodeck provided Trek writers with an amazing array of scenarios to give us an insight into the personalities of the characters. Some were dreamed up for comedic effect or just a 'way-out' intro. Others provided more substance to a story, with a few taking up the whole episode. One unforgettable opener involved the android Commander Data enjoying a game of poker with Sir Isaac Newton, Albert Einstein and Professor Stephen Hawking, the latter playing the part himself.

Programs

I think 95% would use it for sex. The other 5% would march up and down outside with banners saying 'Down with this sort of thing'.
– An h2g2 Researcher

Primarily meant for relaxation during off-duty time, holodeck time is a privilege rather than a right. A ship with holodeck facilities keeps a library of basic programs stored in the computer's memory bank. Holoprograms can be created to suit individual taste and kept by members of the ship's crew for personal use only, or stored in the ship's computer, activated by voice recognition.

Use of the holodeck is not limited to individuals; couples can use it to relax on a white sandy beach, investigate a leafy copse, or to wander in the high mountains. Captain Benjamin Sisko says that parts of the eastern province of Bajor are like Eden itself; if you can't get to Bajor then the holodeck is the next-best-thing. Well-known beauty spots around the galaxy, such as Paris (the capital of France) on Earth, the stunning Chula Valley on Romulus, and the famed Emerald Wading Pool of Sumiko III are popular requests from couples wishing to indulge in a little romance. It could be a less well-known spot, such as Cleethorpes Boating Lake, as long as the computer has it in its databanks. Jadzia Dax and Worf's first 'date' was spent on the holodeck; when she discovered him making use of her Klingon exercise program, she ended up joining him for a workout session (with bat'leths).

Popular choices include the Alture VII relaxation program, where, following a protein bath, the patron is then levitated on vapours for the remaining time. Ship's Counsellor Deanna Troi says it's like floating on a cloud. A more physically stimulating program is personally recommended by Commander Riker: the Lauriento massage holoprogram (#101A for future reference) provides the services of a webbed-fingered masseuse to melt away all the tensions of a stressful shift.

Some crew members choose to partake in their favourite sport or enact the part of a historical character like fictional detective Sherlock Holmes favoured by Commander Data. Captain Jean-Luc Picard is particularly fond of the 'Dixon Hill' holoprograms, in which he plays the role of a 1930s San Francisco private detective. The ancient 'Wild West' features in a recreation of a town from 19th Century USA, Earth, complete with sawdust, spittoons, sheriff and a fistful of Datas. The holodeck also allows the user to experience things that are otherwise physically impossible, like sitting on one of the rings of Saturn to gaze at the awesome view.

Quark the Ferengi bar owner on space station DS9 kept a sharp eye on the holosuite programs which he rented out to punters. Special tastes would be catered for, but at a price, usually gold-pressed latinum. Happily-married Chief Miles O'Brien liked to spend his leisure time on DS9 white-water kayaking, but when he found a new friend in Dr Bashir, together they created a brand new WWI air battle re-enactment program. Quark was particularly perplexed by the human ability to attain a state of happiness where no illegal or dangerous substances were involved; but while his bar didn't serve healthy concoctions such as carrot juice, concentrating on more intoxicating beverages, he did once serve up a cola-based soda as an example of everything that is awful about the Federation.

Be Careful What You Wish For

A lecherous alien once asked Quark to create a holo-date with the Bajoran Major Kira Nerys. She became suspicious when Quark tried to take a holo-pic of her, and after 'persuading' Quark to tell her the truth, arranged a scenario of her own. When the alien went into the holodeck he found what looked like her body waiting seductively on a bed, but it turned out to have Quark's head on it.

Commander Geordi La Forge once made an almost fatal error. In order to provide a challenge for Mr Data, who liked to re-enact Sherlock Holmes adventures on the holodeck, Geordi La Forge asked the computer to make a Holodeck adversary who could defeat Data. The computer responded by creating a Professor Moriarty character who was a match not just for Sherlock Holmes but for Data himself. To do so, Moriarty was created as a sentient program within the computer, effectively a living, thinking being. Moriarty was able to assume control of the Enterprise-D via the computer, and only agreed to release her when Captain Picard offered to store the holoprogram until the technology became available to bring Moriarty back permanently.

Problems

Seven of Nine on Voyager hadn't a clue about human relationships and her verbal instruction from the holographic doctor wasn't assisting her romantic experience. After a disastrous first date with a fellow crew member (which ended up with him seeking treatment in Sick Bay), Seven set up a holosuite program featuring the true object of her passion, Commander Chakotay. They had several 'dates' and eventually became intimate, all without the knowledge of the real Chakotay, which caused difficulties in their working relationship when they interacted off the holodeck.

Chief Engineer Commander Geordi La Forge needed help to solve a problem and he used the holodeck to create a hologram of Dr Leah Brahms, the warp engine designer of the Enterprise-D, so he could discuss the problem with her. They got on so well that when he met the real Dr Brahms he acted like they already had a relationship, whereas she didn't know him at all. He assumed the pair would get along as well as they had on the holodeck, as he had asked the computer to implant every facet of her personality. Unfortunately the computer only extrapolated what was on Dr Brahms' personnel file; and there was no record that she was in a relationship. After she berated him for the invasion of her privacy and criticised his modifications of her engines, they became friends!

Researcher Contributions

h2g2 Researchers were asked to provide an idea of what they would go for if and when holodeck technology becomes available. You could do something like Groundhog Day, with the piano teacher, always just go back for the same lesson. Or you could let your imagination run riot. Here is a sample of their ideas:

I think a superhero sim would be great fun, where I got the choice whether to be good or evil. Or a fully immersive version of Grand Theft Auto/Saints Row.

Possibly echoing Captain Jean-Luc Picard's choice (he kept a highly-polished saddle in his Ready Room), horses and horseriding were a popular choice:

I'd have a dressage lesson programmed and eventually I'd be riding a grand prix freestyle test to music. Canter Pirouettes, piaffe and all.

Yet another equestrian dream:

Riding out through autumnal woods on a bright, cool day, coming out onto some dunes and then a good gallop down the beach... Followed by a gentle trot back across with the odd canter spot with a small log or two to hop over... And maybe an idyllic picnic while I'm there. And the odd camping trip...

Not heeding the warning of being wary of enacting one's fantasies, one Researcher insisted she'd die a happy woman after:

A date in a nightclub with someone I can't be with in real life. Dinner prepared by a five star chef and being waited on by Prince Charles. Serenaded by a middle-aged Frank Sinatra and a young Elvis Presley. Being asked to dance a slow dance with Patrick Swayze, with Maksim Mrvica on the piano playing the soundtrack from Somewhere in Time. Sigh!

One contributor, who insisted she's not on drugs, said:

Sitting on Arbor Low on an idyllic summer day. Waiting for the Guardians to come after dark and when they do, talking to them.

Some Researchers were not content with one idea, preferring a choice to suit their mood:

Prog 1 – Playing in the World Cup-winning Scotland team of 2010 and scoring the final penalty in the extra time decider against Brazil. Prog 2 – Playing in the Grand Slam Scotland Rugby team of 1990 and giving Will Carling the bird. Prog 3 – Hang gliding over Glencoe.

Another Scottish fan declared:

An Ardnamurchan simulator. The peace, the beauty, the relaxed pace of life, and the stunning night sky. Not too realistic, though – no midges, and no rain. And the sea could do with being several degrees warmer. Just don't try to mess with the scenery though, you simply cannot improve on perfection. Plus having my own dirt track for thrashing some old rally cars about.

There's always one who wants to act out a Trek scene:

My holodeck program would be indistinguishable from the environment on the outside of the holodeck. It would even contain another holodeck, running the same program.

Finally, there's the one who opted not to sample unlimited delights for himself:

Put all world leaders and others in positions of power into a re-enactment of the D-Day landings, Paschendale, an Afghanstani wedding about to be bombed and various other battles in the hope they think twice about invading other countries.