I can understand how the holodeck creates virtual environments. But I don't see any mechanism that prevents people from walking into walls. Are the floors moving? Are they in a different dimension that has more space? Do they simulate the feeling of movement while keeping you stationary?

Some simulations appear to take up far more physical space than the holodeck would allow (as in people are physically all over the virtually created world - like Voyager's 24/7 running Irish city).

  • possible duplicate of How does the holodeck create the illusion of distance?
    – Valorum
    Commented Feb 16, 2014 at 22:08
  • 1
    Rabid guard dogs near the edges?
    – MDMoore313
    Commented Feb 16, 2014 at 23:52
  • They show the relatively small size of the holo-deck in the first TNG episode Encounter at Farpoint - Data throws a rock and it either hits the wall of the deck and causes a distortion of the holo-illusion, or causes a glitch in the separate zones of force fields. Commented May 25, 2016 at 1:25
  • "Modern technology, William"
    – komodosp
    Commented Jul 4, 2017 at 15:40

2 Answers 2


From the TNG Technical Manual;

Matter conversion subsystem creates physical props using replicators. Replicated props are generally created when an object is likely to be touched by the participant. Some props are animated under computer control by precision-guided tractor beams.

Holographic imagery subsystem creates three-dimensional images of simulated environments. Shaped forcebeams give physical substance to foreground objects so they have the illusion of being solid.

Substrate forcefield creates "treadmill" effect, permitting participant to remain stationary while the simulated environment "scrolls" by within the limits of the simulation program.

TNG Technical Manual

  • 10
    What happens if two people in the holodeck try to walk away from each other? Will they eventually hit the walls?
    – Tim S.
    Commented Feb 16, 2014 at 23:42
  • 9
    @TimS. if I remember correctly, that's addressed elsewhere in the same section of the technical manual: the holodeck creates separate sections of the moving forcefield under each person, so that neither one of them truly moves very far, but it also manipulates the propagation of light and sound between them so that they appear to each other to be far away. Maybe someone who has the book handy can confirm.
    – David Z
    Commented Feb 17, 2014 at 0:55
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    @AaronKlap: I always assumed that the "treadmill" was more complex than just moving the floor from under you, as that would create noticeable inertial effects but also couldn't create certain other kinds of inertial effects (Like constant acceleration). Presumably the holodeck makes use of a lot of force fields for positioning, holographics to draw even other participants, and artificial gravity to make the movement unnoticable. This way each person only needs to be just out of arm's reach of every other person and their actual positions need not change at all during the entire simulation.
    – Phoshi
    Commented Feb 17, 2014 at 13:21
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    @AaronKlap - As much as I hate to give an "out of universe" answer but the reality is that certain aspects of the technology are genuinely nonsensical; sci-fantasy rather than sci-fi.
    – Valorum
    Commented Feb 18, 2014 at 17:16
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    There's a Voyager episode in which B'Elanna is skydiving in the holodeck. She kills the simulation upon being ordered to the bridge (if I remember correctly) and as the simulation ends, there's a scene where the holodeck visibly alters her perceived velocity along with the effects of gravity.
    – user14952
    Commented Aug 14, 2015 at 6:03

With an omni-directional treadmill! They can already do that today!

  • 7
    +1. Certainly not Trek canon, but it's a freakin cool technology, and certainly a low tech proxy of whatever a real holodeck would use.
    – Dacio
    Commented Feb 17, 2014 at 1:56

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