Safety when entering a spherical or one-way portal

Question

I'm imagining taking the "circle hovering in air" image of a portal into the third dimension; a portal shaped like sphere, about halfway sunk into the ground. When you step through the shell from the outside at location A, you set foot "inside" the portal at location B. When you step out from the portal, you step into location B. As an aside, if light obeys these rules, the portal may be invisible from the outside and it always looks like you are stepping into the "wrong" end of the portal.

The problem is that blood circulation will be forcing some of your blood back towards the "exit", and a similar issue would arise with flat one-way portals. Similarly, trying to pull one's leg back out of the portal would be ill-advised as it would end up on the wrong side.

Is there a way to enter the portal without a gortesque and fatal spray of blood from your veins, as well as lymph and other bodily secretions falling out?

Answer 1

There actually is no problem. Imagine having a 2D world, and the "portal" is a tube lifting out of the 2D world-sheet in one point, and landing in another. When seen from the 2D perspective, you see that the portal tube is always locally 2D - there are no discontinuities. You are distorted in the third dimension while you travel, but you are unaware of this because the light rays and everything else in your local space is distorted the same way:

If you are Mr. Green Circle, and look around you along the green lines, you see everything as usual. When you start looking towards your friend Mr. Pink Circle though, the light arriving at your 2D "eyes" is the light coming out of the portal from Mr. Orange Circle.

In 2D, you see the world in the direction of the portal becoming distorted hyperbolically, you can actually see infinite more and more distorted and thinned-out reflections of yourself, and then the distortion reverses and in the middle you can see, clearer and clearer, a different place.

Exactly the same thing happens in 3D. In this image you see a distorted Milky Way, and in the middle the opposite section of the same galaxy - the "inside" and "outside" of the distortion are 30,000 light-years apart.

The nearer you go to the portal, the more distortion you see far from you and the less distortion you see near you. Wherever you pass through, the local distortion is effectively nil (for a large enough portal of course - at least, say, one hundred times your own size).

All this assumes that there is a continuous isotropic distortion around the portal; otherwise, the behaviour of matter and light on the boundary is anyone's guess. The portal might even be impassable (or its borders could act like an atom-thin razor, in which case, in 3D, any object entering would effectively be instantly shredded at the atomic level - not even freezing would be enough to protect biological entities; some ultra-cooled crystals could make it through reasonably unscathed, with just their lattice defects rearranged).

If the distortion is anisotropic, then there is a "backwash" effect. Taken to the extremes, the distortion becomes one-way - particles can only move in one direction. In that case, traversing the portal would deliver a nasty hydrostatic shock when blood finds itself incapable of moving in those vessels that run in the wrong direction. For very small times - one hundredth of a second or less, the shorter the better - you would receive the equivalent of a coin sock to the head. Confusion, perhaps loss of consciousness. The longer the time (and passage repetitions), the more damage - up to brain haemorrhage and death. A short passage, or a very thin anisotropic portion of the interface, would reduce the damage down to nothing.

Incidentally, this implies that the danger of a portal (if more than one kind exist) may be visually estimated by measuring the distortion and comparing it against its aperture. A large portal with wide, continuous distortion would be innocuous except to very large objects; a narrow one with irregular distortions would be deadly).

Also, portals leading to areas with lower barometric pressure (higher up, or warmer air, or the eyes of hurricanes) would suck air, possibly at a considerable rate. If there is be nothing to "hold to" near a portal, you might have trouble avoiding going in, or in the other direction, attempting to go back.

Answer 2

Speed infrastructure

Making special infrastructure can make this doubly safe. First of all, you make sure that controlled infrastructure will prevent/seriously reduce the chance on any collisions or otherwise dangerous situations. Secondly you can add the speed required so little to no loss is happening. If you move with the highest speed of blood in any direction (or even faster), you can prevent such things from happening.

If you want to have some cool transition with stepping in and out of the bubble you can use techniques. Blood goes on average 4,8 to 6,3 km/h, or about walking speed. At max maybe 10km/h. Running (on average 10km/h) and jumping, or even just falling through the portal can already reduce the amount of loss to a minimum or fully eliminate it for most people. This is by simple virtue of not being long on the edge of the bubble and speed. Keep in mind that minor blood loss isn't a problem at all in most situations. With the speed of the body any other accidentally moving backwards parts will not exceed the threshold of the whole body. If you move 20km/h one way, you can't 'go back' if you move only 5km/h the other way.

Answer 3

One potential problem with a portal is the edge/surface. Imagine a circular portal perpendicular to the surface of the Earth. Push something halfway through and then drop it. What would happen? It’s an imaginary situation so this is not definitive, but one possibility is that the circle itself is a very sharp one dimensional edge between two different 3D spaces so the object might simply be cut in half on contact with the edge with one half falling into each side of the portal.

The same could also be true with spherical portals. You would want a fairly large portal and want to jump cleanly into it. What would not be good would be trying to use a small portal. Someone walking towards it might find only part of themselves transported through the portal. with the rest left behind. Could be a bit gruesome.

Answer 4

Situation A:

• Can you pause time inside a box?

Situation B:

• Can you completely freeze somebody at 0 Kelvin for 1 microsecond?
• Can you make someone's speed 0.9c just before entering the portal?

Those situations are some solutions to your answer.

Answer 5

Such a portal would be useful for communication.

Photons will not be put out by these rules. I could easily see you on the other side of the portal and you could see me. Radio communication would be equally easy because photons are not obliged to turn around. It is an ansible and you can use it to violate causality! Solid objects might be ok and we can play catch thru the portal. I do not see a way around the problem of a heterogenous object in motion like our bodies. If you want to get into the weeds, even the ball we are playing with is in heterogenous motion at a molecular level. You could make it so only photons can safely pass thru.

Unless you wave your hands, which you need to do anyway when it comes to portals generally. For example there will be pressure differences and so it would be windy next to the portal unless you decree it not be. A place close to the pole of the planet will be moving slower relative to one on the equator, and speed will need to be normalized to the new place via vigorous handwaving to avoid being hurled against the wall. Points on different planets pose an even greater problems. Places that are moving very fast relative to one another would red- or blueshift light traversing the portal which would be a nifty special effect.

You can assert these are nonproblems and broaden your fiat to let people poke appendages into the portal without coming to harm. Or you could keep the limitations you have invented which could be useful for a story.

Answer 6

The portal is one-way, but there is no fixed surface which particles can only travel one way through. It's more like an airlock: you go in, the portal closes behind you, the portal opens in front of you, and you go out the other side.

At no point is your blood ever restricted from flowing from the frontal direction toward the backward direction; while the entrance and/or exit surfaces are closed, particles cannot pass through them in either direction. As long as you are fully inside the portal while the entrance closes, you won't get cut in half by it. But it's a one-way portal because the exit can only open after the entrance is already closed.