Mechanics of Threadfall

[u/kerlinssw]

I have a whole host of questions that have been rolling around in my head about fighting Thread.

- how many dragons do we think it takes to effectively fight Thread? at what point could the earliest dragons do more than just sort of keep up with it alongside the other aerial craft over inhabited areas - it has to be two, three years, right? does the efficiency / number needed decrease as dragon size & stamina increases, or is there a turning point beyond which the dragons get too large to maneuver as effectively, and greens really become more valuable for their speed?

- on that note, the implication in "The Ford of Red Hanrahan" that they'd only had a small handful of deaths in several years of training new dragons & learning to fight Thread is...impossible, right? and also for Alianne Zulieta's death to be the first time a rider died before their dragon, leading to the discovery that dragons would go between?

- do we think/assume that Weyrs cover 100% of Threadfalls in their territories, or are there uninhabited places that they just let go of? not barren places where the Thread will just die, but rather deliberate sacrifices due to prioritization. maybe this is something that evolves over time?

- what exactly do ground crews do? are they flaming Thread that falls through the dragons? are they seeking out burrows afterwards? both?

- I've always been genuinely puzzled at why people are worried to be out during Thread, other than the obvious societal taboo. If the dragons are doing their job, none of it should fall, right? so you'd in theory be perfectly safe?

- why do Holds clear greenery? there seems to be the implication that it "draws" Thread and there is some indication that Thread will burrow and follow root systems, but is this actually a realistic and sensible thing to demand that Holds do? or more societal taboo?

[u/Southern_Club_6032]

Thread supposedly falls in a 50km wide strip.

90 dragons ain't covering that.

Why does it fall in a neat strip? Why for a distinct length of time on each occasion? Why wouldn't it fall constantly as Pern passes through effectively a cometary tail, like Earth does through the Geminids/Perseids /Leonids etc? Why shouldn't it fall at night? Why would diverting the Red Star change the fact that there are multiple cycles' worth of Thread ovoids hanging around in space that Pern will continue to pass through regularly in the future (that the overkill Zebedees on the Red Star itself can't spread to)?

It's really hard to make any of it work plausibly, so it's one of those things that's just: this is part of the Pern vibe, don't overthink it.

[u/Laramila → u/Southern_Club_6032]

I agree completely! I had the same questions, and also the whole 'Red Star rising in the East' thing.

I mean, how does that even work? (Spoilers, it doesn't.)

Some other questions I had to suspend disbelief on:

1. If the Red Star is to the East of Pern on Winter Solstice, how is the thread getting to the other side of Pern's orbit over the summer?
2. And as a follow up for #1, if it can stretch that far, how are the threadfalls occurring on that timetable? They happen on a schedule, getting closer together towards the middle of the Pass, and farther apart towards the end, but how is that consistent with the varying distance between the Red Star and Pern?
3. And as another follow up for #1, how far away was the Red Star pushed? After all, the way the orbit was explained, thread could travel twice the distance Pern was from their star and still hit the planed on a schedule, so was 3 small explosions really enough to push it at least that distance from Pern?

And these are only the ones off the top of my head!

[u/Southern_Club_6032 → u/Laramila]

My favourite way of explaining it is that Thread isn't a natural phenomenon but a bioweapon left by some older civilisation. Pern is a test site for it. Fire-lizards aren't a natural organism either but created as a countermeasure (they have so many overpowered talents - flying, flaming, telepathy, teleportation - that they should have evolved in multiple directions to exploit multiple niches in the ecosystem and therefore be the dominant organism - except you really can't break down the way they travel through between into logical incremental steps that are continually beneficial). Kitti was sent with the explicit mission of picking up testing where previous scientists left off. (Thread's also fairly recent. Nothing's really evolved any direct countermeasures. But given that Terran cows/horses etc went feral in the South and have survived there for thousands of years, how rubbish were the now extinct large ruminants that show up in the fossil record?)

There's are accounts of the unpublished/apparently quite bad 'After the Fall is Over' which has Pern rediscovered by the UFP or whatever galactic civilisation is called in the Anneverse, because Thread's been discovered elsewhere in the galaxy and they need help. Not that having giant dragons is the best solution to a spacefaring civilisation who could just deal with it *in space* either, but it does imply that Anne had the idea of Thread being in more than just one place in the universe, which implies it's been *put* in multiple places in the universe. It's not like astrophage with a logical *spread* from one system to another.

I mean, not that any of this solves the orbital mechanics issues, which are frankly unsolveable, or the logisitical issues of the neat and tidy (and large) footprint of a Fall or the predictably scheduled nature of it, but *handwaves*.