Hello!

[Drashner1]

Thanks for the answer. Is time dilation also the reason wormholes can't exist except outside a gravitational field? Or is that just an example of a limitation that a sufficiently advanced Archailect might find a way around?

Not exactly. The reason for this is known as 'asymptotic flatness' and essentially boils down to a matter of having to accept tradeoffs when engineering space-time to create wormholes. This is explained in more detail in the papers listed as references on the Wormholes: A Layman's Guide page.

Basically, when considering a wormhole, there are three main factors you need to look at: Stability, Mass, and Internal Tidal Forces.

There are apparently many many many possible types of wormholes, combining these elements in different ways. So there can be wormholes that are really really stable, but which require a galaxy's worth of mass-energy and exotic matter to create. Or you might have a wormhole that doesn't need a lot of mass and is very stable - but the internal tidal forces will shred anything made of matter that tries to go through. Or maybe it has reasonable mass and tidal forces - but is so unstable that even a single atom trying to pass through it will cause it to implode. And so on.

When trying to come up with a wormhole 'design' that would allow for a reasonable amount of mass, stability, and low tidal forces, Adam found that there were some other effects that came along for the ride, that you pretty much just have to live with. He also found (or invented if you prefer) several different types of wormholes, each having different values of the factors listed above. So far, in the current era in the OA universe you have:

Traversable Wormholes (aka Stargates):

These have relatively low mass for their size, low internal tidal forces, and are metastable, meaning they require active stabilization to prevent them from imploding. But they also have a large feature called the Transition that extends out from them for several hundred AU (essentially this can be thought of as the start of the mouth of the WH). Within the transition, 'asymptotic flatness' comes into play, which is a fancy way of saying that if anything sufficiently massive enters the transition, it will destabilize the WH and cause it to implode. In practice, if anything massing as much as even 1% of the WH enters the transition it can overwhelm the active stabilization systems and cause implosion. However, this is offset by the huge mass of the WH. A 'standard' 1000m radius gate (the radius being that of the WH Throat, not the Transition) generally masses as much as a planet and may outmass Jupiter by quite a bit. So getting 1% of it's mass inside the transition undetected (or at all) is no easy or common thing.

Hayward type Wormholes (aka Comm-gates):

Comm-gate type wormholes have a MUCH smaller Transition zone than a stargate. Only about 10,000x their own radius. However, they are also MUCH less mass efficient (a 1000m radius comm-gate masses more than 33x the mass of the sun) and have internal tidal forces that will shred anything made of conventional matter. But make them in sizes ranging from micrometers to nanometers and fire a modulated gamma ray laser through them and you can send messages over virtually any distance more or less instantly. Hence the name. And gates that small mass about as much as a large asteroid and can be scattered around a solar system or even placed inside the brains of the larger archailects to speed up internal signalling and their thoughts to 'ftl' levels.

Comm-gates are also harder to make than stargates btw.

Grazers:

These are the asymmetric wormholes that Steve mentioned. For all wormholes, passing matter or energy through them will calls the 'entrance' mouth to gain mass and grow larger, while the 'exit' mouth loses mass and shrinks (this due to conservation laws). With proper scheduling of two-way traffic you can balance this process so both WH mouths stay approximately the same size and mass (you can also add/remove mass-energy to/from a WH directly using specialized machinery).

With a Grazer, this process still happens (as do the asymptotic flatness requirements of a transport gate and the tidal forces of a comm-gate), but the grazer has the ability to 'shift' it's mass from one mouth to the other, causing one mouth to grow/become more massive, while the other mouth shrinks/becomes less massive. Done properly, and with enough mass-energy to feed into it, you can transport the small mouth across space to the vicinity of a star, set it on course to pass close to the star while still far enough away for it to remain stable, and then start shifting mass so that the mouth gets larger and more massive to the point that the solar system, up to and including the star, is sucked into it, shredded down to component atoms by the tidal forces, and spit out the 'exit' gate light-years away. Have machinery around the exit gate to grab, process, and transport the exiting matter flow and you can take whole star systems apart and convert them into whatever you want with a minimum of fuss.

There are also inter-universal wormholes, connecting this one to artificial space-times created by the archai (although these largely work like transport gates), wormhole bombs (metric bombs) and it's been suggested that we should add in a type of WH that converts anything that passes through it into anti-matter (or back again if going the other way). Although we haven't written up that last one yet, it has a theoretical basis in the real world and we probably will eventually.

Hope this helps,

Todd