Why does a scarf fold up but a ruler doesn't?

Think of your cozy winter scarf. Feel how soft it is in your hands. Wrap it around your neck, and it hugs you warm. You can fold it up small and tuck it in a drawer.

Now picture a ruler on your table. It stays long and straight. You cannot fold it up at all. So why does a scarf fold up, but a ruler doesn't?

Let's start with the scarf. A scarf is made of yarn. Yarn is a long, soft string. A piece of yarn droops right over your finger.

The yarn in a scarf is knitted, which means it makes loop after loop through itself. Each loop hooks into the next loop. Row after row, the loops make the whole scarf.

Every knitted loop has a small space around it. When you bend the scarf, the loops slide and turn. They move to make room for the fold. The knitted loops never get stuck, so the fold looks smooth and soft.

Because the loops can move, the scarf bends anywhere you like. You can fold it once, twice, three times, and it never breaks. Then it lies in a small, cozy pile.

Now look at the ruler. A ruler is one hard piece of wood or plastic. It has no loops and no spaces inside. What do you think happens when you push on its ends?

The tiny bits inside the ruler hold on tight to each other. They cannot slide or turn like the loops. So the ruler bends only a little, then springs back straight. It cannot fold like a scarf.

Let's remember our word: knitted. Knitted loops slide and turn, so a scarf folds, but a ruler's tiny bits hold tight.

Sleep tight, and give your cozy scarf a gentle fold tomorrow.