Namely, I noticed that in Star Trek: The Next Generation, holographic characters and objects can actually travel a little distance/last for a few moments outside of the holodeck. (e.g. A couple of Dixon Hill villains manage to walk outside of the holodeck in one episode, and they actually remain there for a minute before disappearing. And a snowball that Wesley throws in the holodeck during another episode travels through the holodeck door and hits Captain Picard, who's standing outside.)

But in Voyager, the moment that a holographic character/object attempts to leave the holodeck (or any other room equipped with holo-emitters), he/she/it disappears immediately. (The EMH, for example, can't step outside Sick Bay without a mobile emitter because the moment he tries to so much as stick one of his limbs through the door, the limb disappears.)

Is this discrepancy/difference ever explained in-universe? Or is it just one of those things that was changed for technical and/or aesthetic production reasons, but never really given an in-universe explanation? (Like the way that - for many years, at least - the shows' creative teams avoided giving an in-universe explanation for the physical changes made to the Klingons starting in The Next Generation.)

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    I think you've explained it correctly as "just one of those things...". BTW the physical changes made to the Klingons were introduced in The Motion Picture, so they actually went over two decades before providing that in-universe explanation! Commented Feb 23, 2017 at 3:25
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    Also, I believe somewhere along they way it's explained in TNG that some things in the holodeck are real, such as food, drink, water, snow, certain objects, which are created by whatever process their food and matter replicators use. This explains the snowball, a dripping wet Wesley in the pilot episode, what they eating and drink in the setting, blunt and sharp weapons used when the safety protocols are disabled, etc. Commented Feb 23, 2017 at 3:30
  • The klingon were a horrible retcon. The better and original answer was... they always looked like that, just cause the budget didn't allow for it. Just like the updated planets and ships in the remastered episodes. You just lacked imagination....
    – cde
    Commented Feb 23, 2017 at 4:37

1 Answer 1


In both TNG and Voyager (and I guess DS9), they explain the holodeck is also an offshoot of transporter and replicator technology. It doesn't just use force fields and projections. It is not just hard light. Instead, the holodeck produces a variety of substances depending on what is required. Clothes may be projections but could also be replicated. Food is replicated when it is about to be eaten. Water when the subject gets wet. Or snow when thrown. It is smart enough to know when something should be replicated and when not. It won't replicate poison for example, or harm someone without the safety protocols disabled. It's a 50 year old technology that constantly evolves and was designed for complete sensory immersion, predictive replication is a prerequisite.

It is said explicitly in the Voyager episode involving the Doctor and Grendel. I believe it is also said in the TNG episode with Moriarty.

As to the border of the holodeck or emitters, they are not hard borders. The holodeck emitters are visual, line of sight, and the edge of the emitted hologram depends on the angle of the emitter. The Doctor's arm doesn't disappear at the doorway, but slightly outside of it. Just like the light of a light fixture doesn't end at a door unless it is blocked, casting shadows.

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