Related to Would Star Trek holodecks physically affect you once you exit the Holodeck?

I was watching Elementary, Dear Data last night and I noticed that when Data realizes that something has gone terribly wrong, he leaves the holodeck with the holodeck generated paper with a drawing of the Enterprise. The paper does not disintegrate as he leaves the holodeck. If this can leave the holodeck, why can't Professor Moriarity? Indeed, the original ending to this episode according to Memory Alpha:

The original ending filmed was cut from the episode. (Star Trek: The Next Generation Companion 2nd ed., pp. 68-69) Hurley recalled, "In that ending, Picard knew how to defeat Moriarty. He tricked him. He knew all along that Moriarty could leave the holodeck whenever he wanted to, and he knew because when Data came out and showed him a drawing of the Enterprise, if that piece of paper could leave the holodeck, that means that the fail-safe had broken down. In turn, this means that the matter-energy converter which creates the holodeck, now allowed the matter to leave the holodeck, which was, up to that point, impossible. When he knew that paper had left the holodeck, he knew that Moriarty could as well, so he lied to him."

This is interesting because the whole premise of this episode and Ship in a Bottle is that Moriarity can't leave the holodeck. Moreover, the Doctor from Voyager always needs some kind of portable emitter to go places.

Given this and the water/other matter that leaves the holodeck in the linked question, why can some matter exist outside the holodeck while other matter cannot?

Is it tied somehow to the replicator - i.e. replicating a piece of paper into real matter is trivial, but replicating a human being or anything more sophisticated would be non-trivial?

  • The answers don't really answer why the Voyager crew was able to use the holodeck when on severe power rationing (and emergency food rations / Neelix-food) while using the holodeck much too often. In-universe discontinuity perhaps.
    – RoboKaren
    Commented Oct 27, 2014 at 20:14
  • Note that you can see an example of why this is true in an earlier episode: The Big Goodbye. In it, Picard exits the holodeck with a lipstick print on his face, but in the very same episode the character Cyrus Redblock dematerializes shortly after he exits the holodeck.
    – Zibbobz
    Commented Oct 27, 2014 at 20:22
  • 2
    The thing is, Moriarty isn't some replicated piece of matter. He's an interactive computer simulation that needs controlling. You can't 3D print a person. Commented Oct 27, 2014 at 21:18
  • 3
    "You can't 3D print a person" - Well, not yet...
    – Joe L.
    Commented Oct 28, 2014 at 5:59

3 Answers 3


The was actually addressed in one of the comments to the linked question.

From http://en.memory-alpha.org/wiki/Holodeck#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.

There are different reasons proposed for having both, one of them is that anything ingestible MUST be real matter (otherwise the user would have negative health effects after ingesting and leaving the Holodeck); another is that it's cheaper/easier to replicate some matter (e.g. water, or any such dynamic matter) than to fully computer-simulate and then holographically generate it.

On the other hand, as you noted, replicating a human is a whole lot more of a big deal that holographically project one.

  • 3
    The corollary is, of course, that humans cannot be replicated; the technology is limited to inanimate objects. Living things can of course be projected, and made to look and act real, but they are true holograms.
    – KeithS
    Commented Jan 12, 2012 at 16:10
  • 2
    I don't know that I really buy the "processing power to generate a convincing hologram of water" argument. I mean, computers today can create insanely convincing water... there is no doubt in my mind that the computers of the 24th century would be able to make holographic water that was visually perfect. A more convincing argument, in my mind, would be that if someone falls in the water, they need to actually get wet... which holographic water would not do.
    – eidylon
    Commented Jan 12, 2012 at 16:19
  • Add they do get wet when they fall in water. It was mentioned in one of the episodes (Encounter at Farpoint perhaps?) that when Data fell in water on the holodeck it took a long time to get all the water out of him.
    – Xantec
    Commented Jan 12, 2012 at 16:29
  • 1
    @Xantec, IN E@F it was Wesley who fell into a pond. But yes, he stayed wet when he left the holodeck. en.memory-alpha.org/wiki/Holodeck
    – eidylon
    Commented Jan 12, 2012 at 16:32
  • The water stayed because it was simple/small enough that it could be replicated. Commented Jan 13, 2012 at 2:16

This issue was specifically addressed in the "Star Trek : Voyager Technical Manual" handed out to potential scriptwriters for the Voyager series.

Simply put;

  • Anything that people are likely to interact with (props, food, clothing, etc) is created by using a matter-replicator.
  • Anything that visitors are unlikely to interact with (or that doesn't require physical texture) is created using a coloured forcefield.

How it works:

The Holodeck uses two main subsystems. the holographic imagery subsystem and the matter conversion subsystem. The holographic imagery system creates images of incredibly realistic background environments. The computer-driven holographic projectors also control a series of shaped-field forcebeam projectors which are capable of giving physical substance to these images. The second major subsystem is the matter conversion system. Using transporter-based technology, this system creates physical "props" and "set dressing" from raw material. Under normal conditions, a participant in a holodeck simulation should be unable to tell the difference between the two types of props.

The Holodeck and the reality of objects:

Objects created on the holodeck which are pure holographic images cannot be removed from the holodeck, even if they have apparent physical reality because of focused force beam imagery.

Objects created by transporter matter conversion do indeed have physical reality and can indeed be removed from the holodeck, even though they may no longer be under computer control.

  • Yet the EMH fits neither mode by that description! Commented Oct 27, 2014 at 21:27
  • @LightnessRacesinOrbit - We know from canon descriptions that he's wholly force-field based. It's not that close-up objects can't be made out of forcefields, it's just that there's no point wasting the energy of replicating something real if you can trick people with an effect.
    – Valorum
    Commented Oct 27, 2014 at 21:40
  • Yet he has physical texture and can be interacted with. Commented Oct 28, 2014 at 8:14
  • @lightnessracesinorbit - I refer you to my previous answer. You can make complex stuff out of fields, it's just harder.
    – Valorum
    Commented Oct 28, 2014 at 8:16
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    @JonStory - I suspect that's more to do with familiarity with the instrument. Note that Picard has his own saddle that he takes to the holodeck.
    – Valorum
    Commented Dec 7, 2015 at 15:35

The very first time a holodeck appeared in live-action Trek -- way back in the pilot episode of TNG, Encounter at Farpoint -- Data clearly indicated that holodeck programs employ a combination of holograms 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; then these rocks and vegetations have much simpler patterns."

Data: "Correct, sir."

Naturally, actual holograms like Moriarty and the Doctor can't exist in environments where there are no holo-emitters, but real matter can, regardless of whether it's been transported, or replicated, or whatnot.

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