Is the Holodeck actually so far advanced that it transforms actual matter? I always assumed that the holodeck was basically an advanced projector with a few other matterializations, but not going so far as to actually materialize a bullet, or de-materialize the crew members, but Wesley Crusher says that he fears the people inside might "vanish" if he makes a mistake and the program aborts.


3 Answers 3


The holograms on the holodeck aren't only projections. The holodeck also uses technology similar to the transporters and replicators in order to give its illusions substance. This is why people can physically interact with the holodeck programs rather than passing through holograms. The resulting substance is known as holodeck matter, which is different from conventional matter.

Therefore, I would guess that what Wes was afraid of is that a malfunction would make the holodeck dematerialize the people inside as well as the holodeck matter. However, I also got the impression that after the early episodes of Star Trek TNG, which were very much conscious of the idea of holodeck matter, in later Star Trek episodes the writers were thinking of the holodeck as simply making holograms, though I don't know that any episode outright contradicts the idea. But to that point, I don't think any other episode ever mentions the danger of the people using the holodeck dematerializing or vanishing.

  • This is almost correct but not quite, since holodecks can create real matter as well as holomatter. Holomatter wouldn't need to be dematerialised by the matter conversion subsystems, as "this substance lost cohesion and quickly dissipated into energy" when outside the range of holo-emitters (it follows that the same thing applies when holo-emitters are simply turned off or disabled; we've seen Voyager's EMH instantly vanish under such circumstances). It's only the real matter that needs to be dematerialised. Commented Nov 28, 2020 at 20:50
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    However, the fact that it is called holomatter and dissipates when outside fo the range of holo-emitters suggests that the matter is based on holographic technology. Voyager's EMH specifically says he's made of forcefields and light, which he can make solid or non-solid at will (a property he uses to create an artificial lung in one case, but the patient is rendered immobile.) Holomatter could just be this sort of "material" build of forcefields and light.
    – trlkly
    Commented Nov 28, 2020 at 23:08
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    Also, Wesley was a kid, and kids have irrational worries all the time. Commented Nov 29, 2020 at 17:05
  • @AsteroidsWithWings And even adults have those too, although often more disguised
    – Pedro A
    Commented Nov 29, 2020 at 18:55

In the pilot episode of TNG, "Encounter at Farpoint", Data indicated that the environments created within holodecks are a mixture of holographic simulations and real matter.

RIKER: I didn't believe these simulations could be this real.

DATA: Much of it is real, sir. If the transporters can convert our bodies to an energy beam, then back to the original pattern...

RIKER: Yes, of course. And these rocks and vegetations have much simpler patterns.

DATA: Correct, sir.

This was further expanded upon within the Star Trek: The Next Generation Technical Manual.

The Holodeck utilizes two main subsystems, the holographic imagery subsystem and the matter conversion subsystem. The holographic imagery subsection creates the realistic background environments. The matter conversion subsystem creates physical "props" from the starship's central raw matter supplies. Under normal conditions, a participant in a Holodeck simulation should not be able to detect differences between a real object and a simulated one.

The Holodeck also generates remarkably lifelike recreations of humanoids or other lifeforms. Such animated characters are composed of solid matter arranged by transporter-based replicators and manipulated by highly advanced computer-driven tractor beams. The results are exceptionally realistic "puppets", which exhibit behaviours almost exactly like those of living beings, depending on software limits. Transporter-based matter replication is, of course, incapable of duplicating an actual living being.

Objects created on the Holodeck that are pure holographic images cannot be removed from the Holodeck, even if they appear to possess physical reality because of the focused forcebeam imagery. Objects created by replicator matter conversion do have physical reality and can indeed be removed from the Holodeck, even though they will no longer be under computer control.

When a holodeck program is ended, any real matter created by that program, and still present within the holodeck, is presumably converted back into energy by the matter conversion subsystem. (The same apparently does not apply to matter which is no longer in the holodeck when the program is ended, as was the case when Picard left a holodeck with a lipstick mark on his face in "The Big Goodbye".)

This isn't presented as something that could endanger real people when a holodeck is functioning normally, as we've seen programs ended with people still inside holodecks on multiple occasions. However, if a holodeck is malfunctioning -- as was the case during "The Big Goodbye" -- perhaps there's a risk that real people within a holodeck could be dematerialised if a program is summarily aborted from the outside. This is apparently what Wesley was concerned about.

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    This is correct. The system that cleans up replicated matter could clean up natural objects and people too. One can assume as holodecks became more advanced there was less replicated matter. A similar concern would be what would happen to a mouse if it was on a plate returned to a replicators for recycling. Commented Nov 29, 2020 at 3:10
  • The holodeck must be able to clean up natural objects. Imagine that somebody uses the bathroom during a scenario - the, ah, material would be left on the floor when the program was terminated if the holodeck couldn't deal with it.
    – GordonD
    Commented Nov 29, 2020 at 12:08
  • @GordonD Lower Decks has canonically established that that is indeed largely what happens, though it's "tidied up" for you and left for later collection by a junior crewmember. Commented Nov 29, 2020 at 17:08
  • " Transporter-based matter replication is, of course, incapable of duplicating an actual living being." Pretty sure that there's at least one "transporter malfunction" episode that disagrees. Heck, depending on what you mean by "duplicating an actual living being", I'm pretty sure that the Tuvix "fix" that split him back into two different people would count.
    – nick012000
    Commented Nov 29, 2020 at 19:11
  • @nick012000 - Yup, two Kirks were created in "The Enemy Within". In "Second Chances", it was established that a second Riker (Thomas Riker) had been created a few years prior to TNG season 1. The Trek franchise hasn't been entirely consistent on this point. Commented Nov 29, 2020 at 20:33

Whilst the TV series of TNG is pretty inconsistent on what physical effects are possible, the film "Star Trek: First Contact" makes it explicit that the holodeck certainly can "interact" with matter.

Picard uses a holodeck gun to kill two Borg, and it works. In order to do it he has to disable some safety cutouts, but it's clearly possible and the holodeck bullets do normal damage.

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    A Starfleet officer named Whalen was also shot and injured by a holographic gun in the TNG episode, "The Big Goodbye", as a result of the holodeck safety protocols malfunctioning. However this doesn't explain why real people in a holodeck program might vanish as a result of the program being aborted from outside. Commented Nov 29, 2020 at 0:38

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