Have you ever had this experience, or something like it?
It’s mid-October. You’re taking a leisurely stroll through the neighborhood park. The crisp autumn air fills your lungs. You take a crisp bite out of an especially crisp Honeycrisp apple. Your beloved corgi or dachshund stops to sniff a pile of crisp, freshly fallen leaves. You feel refreshed, invigorated, crisp. Everything feels, well, crisp.
“Hmm,” you say to yourself, “I sure am thinking about the word ‘crisp’ a lot. Fall and crisp just go together so well. Crisp, crisp, crisp. The more I say it, the stranger it sounds. Where does that word even come from? Why does it even mean what it means?”
More thoughts come to you—nagging thoughts. You look around and realize everything seems strange. You feel as though every last thing around you has become a mystery.
“I’ve always loved the colors of fall,” you think, “but why do the leaves turn orange and red instead of blue and black?”
“Honeycrisps are my favorite apples,” you think some more, “but how do they make so many different types of apples, and why do my taste buds prefer a Honeycrisp to a Cameo or a Golden Delicious?”
“This wool sweater I’m wearing is so cozy,” you continue to think, “but its pattern, its stitching—it’s too perfect! There must be a science to it!”
There is! In fact, there’s a ton of science behind every last thing we either take for granted or only kind of understand. The science of falling leaves has something to do with chemical compounds probably, but what exactly? The science of apple varieties has something to do with genetics probably, but what exactly? The science of knitting has something to do with mathematics, but what exactly?
Join us on this trip down a rabbit hole filled with fun facts about the science behind what makes fall fall.
Rabbit Hole Stop #1
The Science of Knitting
Destroying a sweater is easy. Just ask someone to hold a loose thread as you walk away.
Making a sweater is hard, and it’s something that belongs to more than just the fashion industry. In fact, you might need to consult a physicist before you break out your knitting needles!
Humans have been knitting for centuries and centuries. It’s one of those practical skills that you can learn how to do without necessarily understanding the scientific concepts behind what you’re doing. Only now, however, are researchers really beginning to really understand the underlying mathematics that determine how you can take a relatively inflexible material like yarn and turn it into a stretchy, comfy sweater.
Dr. Elisabetta Matsumoto runs a physics lab at Georgia Tech. She recently secured a grant from the National Science Foundation to spend five years unraveling the mathematics of knitting. The name of the project is punny and cute: “What a Tangled Web We Weave.” The science behind it, however, is complex. The project could have profound effects both on our basic understanding of certain areas of physics and our practical construction of everything from video game graphics to wearable electronics to “biocompatible weaves and networks used in tissue engineering.”
The work that Dr. Matsumoto and her graduate students do can be described by a branch of mathematics called topology, which is the study of mathematical spaces. Specifically, topology looks at what happens to a shape as it twists or stretches without being torn or cut. Sweaters, along with other knit objects, create some of the most complex examples of such shapes in the real world, as they can be made from a single strand of yarn. As the title of a 2009 article in the Journal of Mathematics and the Arts puts it, “Every topological surface can be knit.”
The science of knitting is a rabbit hole unto itself! We don’t have enough space here to even begin to do justice to the complexity of such thorny areas of study as knot theory, homeomorphism, and hyperbolic geometry—Oh my! Nor have we touched on how wool yarn gets made.
We do, however, have some recommended reading to offer:
- “The Science of Knitting”
- “The Science of Knitting, Unpicked”
- “Knit Theory”
- “‘Knitting Is Coding’ and Yarn Is Programmable in This Physics Lab”
- “Adventures in Mathematical Knitting”
And for a very interesting read on a knot that was “solved” just this year, “Graduate Student Solves Decades-Old Conway Knot Problem” is the way to go. It’s not exactly about knitting, but it’s a fascinating story.
Rabbit Hole Stop #2
The Science of Apples
Remember that delicious Honeycrisp apple you were eating at the beginning of this post? Would it surprise you to learn that it was developed in the 1970s and 1980s by researchers at the University of Minnesota and granted a United States patent in 1990?
That’s right: the Honeycrisp apple didn’t just magically appear in grocery stores and at farmer’s markets one day. Rather, it was engineered “from the cross number AE 603, Macoun x Honeygold,” reproduced by grafting, and then “further tested” under the name MN 1711. The developers used the British Colour Council’s Horticultural Colour Chart to describe the apple tree’s traits, including “prominent lenticels,” “ovate shape,” and “acuminate seeds.”
The Honeycrisp’s trademark crunch and sweet taste are no accident. Over the course of decades, the apple was bred to develop the fruit that is mass-produced today. The breeding process is complex, and this website from New Zealand does a great job of explaining it.
Just last year, the Cosmic Crisp became the newest darling of the apple world. After twenty years of development at Washington State University, it hit store shelves to great fanfare. It was produced by cross-pollinating a Honeycrisp with an Enterprise, which itself had been produced at Purdue University in the 1980s and 1990s.
Developing a new breed of apple is clearly a painstaking process that is part craft, part science, and part patience. Once the new variety, or cultivar, is perfected, it is cloned many, many times over so that everyone, even you in your own backyard, can take a shot at growing it.
If any of this piques your interest, the book Apples of Uncommon Character is worth a read.
Rabbit Hole Stop #3
The Science of Fall Colors
The Latin word decidere means “to fall down.” From that root—pun intended!—we get the English word deciduous, which describes any plant that loses its leaves every year.
We all know that deciduousness makes for beautiful fall colors, as well as healthy and predictable profits for rake manufacturers. What we might not know is why those fall colors happen and why all those rakes get such a workout every year.
Chemistry to the rescue!
Trees needs to consume glucose to survive, they need sunlight to produce that glucose, and they need leaves to take in that sunlight. A leaf’s chlorophyll molecules are responsible both for capturing sunlight and giving the leaf its green color. However, when the days get shorter and precipitation levels decrease in the fall, a leaf doesn’t have nearly as much work to do as it did in the spring and summer.
Rather than waste energy keeping those leaves alive with renewed supplies of nutrients, the tree opts to starve the leaf. It forms a layer of cells, called the abscission layer, that starves the chlorophyll of the nutrients it needs to avoid breaking down. Once the green of the chlorophyll begins to fade, the yellow of the leaf’s carotenoids take center stage, followed by the red of the leaf’s anthocyanins. Carotenoids are most prominent in such plants as corn and daffodils, while anthocyanins help give cranberries and red apples their color.
Long story story: nature is a mad scientist operating in a chemical laboratory filled with leaf-shaped beakers and vials.
You never know exactly how a leaf’s color change will progress as fall unfolds, as each leaf’s chlorophyll, carotenoids, and anthocyanins interact in unpredictable ways, depending on the weather. That means each year’s fall foliage is guaranteed to be unique.
The carotenoids and anthocyanins don’t stick around very long either, though. They eventually give way to the great survivor among a leaf’s chemical compounds: tannin. Tannins give the leaf its brown color, which it maintains as the carbon cycle ushers the leaf back into the soil as broken-down matter.
Looking for a good book about trees? Look no further than The Hidden Life of Trees.
Rabbit Hole Stop #4
One last thing, in case you’re actually curious:
The word “crisp” derives from the Old English word cyrps, which described “stiff, closely curling hair.” From there, the word went on to refer to surfaces “curled or fretted into minute waves,” to objects “which have little cohesion and are easily crushed by the teeth,” and “to frosty air, and thence to bracing air generally.”
Also, for what it’s worth, the Oxford English Dictionary notes that the Old French word crespe, meaning “curled,” and the modern French word crêpe, the thin pancake filled with your choice of sweet or savory treats and prepared with spectacular precision from Parisian street vendors, “do not appear to have influenced the English word in form.”