Figures, Formulas and Calculations

Writers: Aaron, Estelle
Date Posted: 14th July 2018

Characters: K'don, R'fal
Description: K'don helps R'fal with his threadchart
Location: Dolphin Cove Weyr
Date: month 5, day 11 of Turn 9

K'don

R'fal frowned at the chart that had been scribed on the hide before him,
and chewed the end of his pen. He'd thought classes were getting less
intimidating as the sevendays passed, but the Threadfall and weather
charts they'd been studying over the past few days had defeated him. He
knew he ought to have spoken up in class, but he hadn't wanted to always
be the one asking stupid questions. Now he had an assignment to
complete, and he was stuck.

He wasn't the only one using the evening to study. Now they had their
own weyrs, some of the other weyrlings worked there, but R'fal found the
warmth and bustle of the dining cavern more appealing, especially when
he was struggling with hidework. He looked around him and saw another
weyrling working at the end of his table. Asking a younger boy for help
wasn't easy, but it was better than having to see the Weyrlingmaster
again about his work.

"Hey - K'don? Are you working on your Threadfall chart?"

K'don stared intently at his chart, scribbling with his pen in one hand,
the other in his mouth as he gnawed on his poor, abused fingernails.

"Hm?" K'don spat a bit of nail aside before noticing who it was who had
spoken to him. Ah, R'fal. "Oh. Sorry, yeah. What's up?"

"Well..." R'fal fiddled with his pen, struggling with embarrassment. "Do
you have any idea how these charts work? At all? I can't make head nor
tail of them."

"It's not easy," K'don confirmed, still staring at the chart as though
expecting it to move if he took his eyes off of it. It was easy,
actually, to lose one's place on the chart by looking away for a moment.
He wiped his fingers on his pants and then used his index finger to mark
his place. He was somewhat familiar with the math, but having riders for
parents did not mean he had spent all of his time learning the academic
side of riding.

"Here, come sit down," he said, pulling out the chair next to him.

"Okay. Thanks!" R'fal picked up his chart and writing materials and came
over to join K'don. "I get that these strips are where Thread falls, I
think...but I don't see why it moves about like that. You'd think it
would just fall in a circle, under the Red Star."

Hm. K'don tilted his head and bit his lip, pondering. He had never even
thought about why the shape of the fall area was not a straight line,
either east to west or north to south. To him, it had all been a matter
of applying the formula that had been worked out to go from one fall to
the next. The math itself was easy enough to mess up that anything
conceptual behind it escaped him.

"I always just sort of... went with it. But there has to be some reason,
I guess." K'don made a fist and then moved his finger through the air
around it, trying to imagine how the Red Star must go about dropping the
Thread onto Pern.

To R'fal, it looked at first as though the other weyrling was making
strange hand signals which he couldn't follow. "Um, what are you - oh!"
He thought he remembered a similar demonstration from a long-ago harper
class, and pointed to K'don's fist. "Is that Pern?"

"It's supposed to be," said K'don. He kept moving his finger this way
and that, up and over, around. "So, I think it's like... Pern goes like
this." He switched his hands, making the fist with his left and making
his right a single pointing finger.

"So, this is the sun. And we go around. If the Red Star gets closer to
us, then it has to..." He furrowed his brow. "Wait..."

"I don't think I get it all the way," he finally admitted after moving
each hand this way and that for a while. "But it probably has something
to do with how, you know, we turn around to get day and night. And the
Thread drops this way," he drew his finger north to south on his
fist-globe while doing his best to rotate it.

"Right?"

"Um..." R'fal frowned, copying K'don's gestures. He wasn't sure he got
it either, but at least he wasn't the only one. "If we're both moving
then maybe that's why it falls like that, rather than all in one place.
We could ask, in the next class. But do you know how to work out where
the next Fall is supposed to be?" He pointed to his chart. "I think
that's the last one, and I wrote down the date and time, but when they
started explaining how you predict the next one, I got lost."

"For that one, I mostly just have to keep trying until I get it," said
K'don. "It's mostly a sort of rectangle. A slanted one, anyway. So. If
you get the coordinates of the four corners with the protractor... See,
here, you put the zero on the corner of the grid lines, and then you can
kinda get a number for the south and the west. And then you plug that
into the formula thing, and if you do all the numbers right, it should
give you the next number."

K'don used his pencil to draw faint lines from the corner of one of the
threadfall zones to the ticks on the protractor. Then he wrote down the
numbers and crunched through the math. He slid his protractor over to
the next grid square, where his math said the new zone should start, and
then made a mark on the map.

"So, I think if you do the four corners, you can just kinda draw in the
lines with your ruler, connect the dots. Right?"

"So those formulas are for the corners?" R'fal thought he saw light
beginning to dawn. It helped to watch someone else doing the
calculation, without the tension he always felt when he was in class.
"Okay...let me have a go." He turned back to his own chart and began the
slow process of working out the coordinates of the corners of the first
Threadfall zone, then following the rules to work out the second.

Once he'd plotted in the new corners, he frowned. "Hmm - that doesn't
look right." Three of the corners seemed to be in place, but the fourth
was way out, creating what looked like a pointed shard rather than a
slanted rectangle. "I must have made a mistake on that one."

"Usually when I get one like that," said K'don, "it's because I swapped
the west and south numbers on accident." He looked back and forth from
the old shape to the new one. "But sometimes, I just did the math wrong,
too," he added. "I'm not the best with a slide rule..."

"You're most likely better than me. I was never any good with numbers."
R'fal started to work on K'don's suggestion of checking the coordinates.
He hadn't really been very good at any part of his harper classes, apart
from learning songs about dragons. He drew a dot in the new position of
the coordinate which had been out of position, and was delighted to see
that his Threadfall zone now looked about the same size and shape as the
previous one. "Hey - that looks better. What do you think - do you have
the same answer?"

K'don slid his map around to sit beside R'fal's.

"Looks about the same to me!" he said cheerfully. "So either we're both
right, or we're both wrong, yeah?" K'don chuckled. It would not be the
end of the world if they were wrong, but it was comforting to see
someone else come to the same result, one way or another.

"Bright side is, we'll have lots of time to get good at this before
anyone is using our charts without checking them."

"I think the Pass will be over by the time I get any good at this,"
R'fal said with a rueful glance at his slightly smudged chart. "But I'll
have a go at working out the next one. Thank you for helping me, K'don."

"I'm happy it actually did help!" K'don answered. He had never felt like
much of a good teacher himself, and he might have had to resort to
asking another of the weyrlings more suited to it for help if it had not.

"Good luck," he said with a cheerful smile.

"Thanks. I'll need it!" R'fal returned the other weyrling's smile, then
bent his head over his chart and prepared to do battle with figures,
formulas and calculations once more.

Last updated on the August 26th 2018

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