Let's assume that there is easy and very cheap method for someone to enter 'separate dimension' in one place, walk and exit in another. For an external observer it would look like instant teleportation. The person using would literary have to walk given distance and in their frame it would take time.


  • It's widely known technology
  • Users doesn't need any special equipment to enter/exit or to survive that place
  • It takes no time for external observer, but the same time as walking give distance for user (User would exit older by time that he spend inside)
  • Momentum is preserved therefore moving to/from moving vehicles would be a rather bad idea

  • It ignores any physical barriers that would be in 'normal' world (e.g. walls or ravines).

    • It is impossible to exit in place that is occupied. (You are safe from appearing inside wall or someone), small objects (gases,dust, small insects etc.) are pushed away.
  • One can easily protect any place from being accessible to/from there (So no entering vaults or escaping prisons)
  • It's impossible/very impractical to bring any vehicle with you ('roads' inside dimension while nice to walk on would be uncrossable even by cycling or skating, cars and bigger objects would be too big to be transported (point below)).
  • User can take with himself anything he can carry. Anything that touches ground (boards of flying/floating vehicles also counts) (also via any other proxy (except air))) will stay at one side. (Boots are fine for some reason).
  • There is no way to meet anyone in that 'dimension' (Two users would have to enter exactly at the same time, we can assume it would be impossible), except for using previous method to carry a second person.
  • When there are more than one person inside each of them can separately decide to exit, they would exit together only if (see above).

  • Anything left inside while there is no one would decay to dust, same happens to anyone who dies inside.

  • transfer happens when one decides they want to enter and is instant, even two tp would be too big difference for multiple users to be there at the same time.

  • It can't be limited who is allowed to use it, except for placing that person inside protected zone.

  • You are unable to see how current situation outside is, (it would be wise checking live feed of place where you plan exit just before you enter) You can only check if place corresponding to your current is empty enough.
  • Light inside is comparable to one in very cloudy day.
  • Terrain is monotone and gray.

My first ideas

  • It would make escapes much easier, while it wouldn't help in actual escape from protected place it would help fugitive to hide immediately after they would be outside protected zone.

  • Smuggling, that one is obvious

  • Crossing difficult and/or dangerous terrain, although riding around or flying above would be probably often better choice. Still there would be place where direct (via this method) route would be much more accessible than normal, but probably wouldn't be common

Ideas mainly from comments

  • Using it for calculations, you can bring computer with yourself and use it as long as you have power.
  • Using it for learning/work: similar to above.

One of answers made me think about one thing. Store owners wouldn't want people disappearing from they shops, most people wouldn't want possibility for others to appear in their houses. It would probably soon end in situation where almost everywhere in cities is restricted area, except for places specially designated for this purpose. It could be necessary in busy places to avoid constant accidents, while you can't appear inside someone, you can appear just in front of them.

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    $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Mar 10 '19 at 3:04

I think, without knowing it, you have solved the 'time crunch' problem.

How many people have said "I wish the day had four more hours in it, so I could sleep"? Well, now they can.

They just slip out, snooze for a few hours, and come back at the same time they left.

There are, however, a few considerations.

If they leave and come back at the exact same moment, then the laws of conservation of energy and matter are satisfied. There is always the same matter and energy in our dimension, it has just moved to a different place. Even as the body grows older, and the cells change and die, the same amount of cellular material leaves as comes back. This, of course, solves the 'pee break in the middle of the night' issue, as there could be no peeing onto the ground. You would have to bring it all back with you. Same for any physical object you took in. It all comes back.

The problem is, there is something physicists have completely ignored in all of their equations and theories. Well, almost all of them. There are a few that are wrestling with this issue. That is, what about the 'conservation of life'? There is a dichotomy in the 'amount of life' on earth, as you have grown older there instead of here.

We really don't KNOW what 'life' is. Physicists have never even considered it. We have the philosophical and religious concept of 'the soul', but is this adequate?

Can 'life'. apart from the physical, be removed from our dimension, continue in another, and then be returned back?

Also, consider that our life in this world would be reduced by all the time we spent in the other dimension. We would sleep more, of course, and the sleep would do us good at the time, but at what cost to our total life span? In fact, would our total life span in this dimension be altered? Would it be that we get more accomplished today, but over our lifespan is there any gain?

I posit that the 'conservation of life' falls into that category of 'Law of Unintentional and Unknowable Consequences'. Physicists take life for granted, and see absolutely no need to add it to any of their theories or computations, but they have absolutely no evidential data to support it.


Strategic Urban Combat
This has a military (and therefore legal if used within the stated rules of engagement of your country) in that your soldiers could have access to this portal technology in the heat of combat.

The problem with urban combat, especially clearing out an area building by building is that by the time you start, your enemy is already on to you. They know what you're up to and if you start at the wrong end of the street, they have time to prepare. You either face an ambush or they hide their weapons and pretend to be part of the civilian population.

But, if your soldiers can generate portals in every room across a street simultaneously, they can do a strike on a single building, single street or even single town simultaneously if you have enough soldiers. It's the perfect surprise attack scenario; today it's impossible because we just simply can't get enough people in place without being noticed, but in this environment you could get an entire regiment together in a warehouse close to the site, get them to open portals and move through together. For some, only minutes would pass to get into position. For others, it might be hours or even days, but the key thing is that they all come out together.

The element of surprise is preserved for the entire operation, because every strike occurs simultaneously.

  • $\begingroup$ While this would be great idea how to use it by governments it also could be main reason why it could be banned for civilian use. Which they probably would do if there were way to filter who is allowed to use it. $\endgroup$ – Kalumniatoris Mar 11 '19 at 8:48

Cities would become increasingly compact over time.

Folks who live within walking-distance of their work/school would have somewhat more free time, making walking neighborhoods more attractive. Rush hour would have a far smaller impact on walking neighborhoods' infrastructure.

There would be much less need for sidewalks, and some neighborhood amenities would no longer need much parking. Initial (unequipped) emergency response would seem instant to folks in trouble in the neighborhood.

Much of this freed space would eventually be re-used to make the neighborhood more dense, attracting more jobs, more firms, and more population. Lower-density housing stock will gradually be replaced with higher-density.

Storefronts that depend upon walk-by traffic will suffer.


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