"The Algebraist": How did the Dwellers move their portals?

Question

In The Algebraist, a key element of the plot revolves around portals, with the Algebraist itself being a list of co-ordinates to Dweller portals. Early in the story we hear about the destruction of a portal, during which we learn of the following limitation:

Portals were only ever positioned at Lagrange points or other orbits distant from large heavenly bodies because they needed a section of space-time that was relatively flat. Too great a gradient - too near the gravity well of a planet or other large object - and they stopped working. Increase the S-T curve only a little more and they imploded and disappeared altogether, usually violently.

Later in the book Fassin Taak discovers the transform required to determine the Dweller portal co-ordinates from the list and all seems to make sense, except perhaps for this:

The only way to get an arteria portal from one place to another was to put it in a spaceship and physically take it, slower than light, from one place to another, leaving the other end – usually – anchored where you'd started out.

How did the Dwellers actually move a portal from its initial point to its final destination, without destroying it at either end? Is this a significant plot hole?

Answer 1

It's not a plothole. One of the key plot points of the book is that the Engineership Est-taun Zhiffir (portal-carrying) is traveling from a nearby star system to Ulubis to reconnect the system with the wider portal network. There's no mention of the specific tech used to hump a portal around, but it would seem that it's possible for a non-emplaced wormhole-end to be within a gravity field without exploding. It's only once it's emplaced that it needs to be in zero-g.

The Engineership Est-taun Zhiffir, portal-carrying, set out from Zenerre for Ulubis less than a year after the disaster, with a travel time initially given as 307 years, later reduced by increments to level out at 269 as the Eship upped its velocity even closer to light speed, the Engineers aboard fine-tuning the systems which insulated the hauled portal from the effects of its own and the ship's relativistic mass. - _{^{The Algebraist}}

Since we know that...

• The dwellers are perfectly capable of non-FTL travel
• Non-emplaced portals can be moved around, even within gravity fields.

...that would strongly suggest that the Dwellers moved their portals in precisely the same way, by leaving them closed until they need to.

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Speaking of plotholes, it might interest you to notice that based on the fact that the Eship can be communicated with at distance, a portal can apparently be opened (presumably wide enough to pass a radio signal) without going all explodey, even if it's within a gravity field.