If you put a wool sweater through the laundry, it shrinks.
So why don’t sheep, which are, you know, basically made of wool, why don’t they shrink
in the rain?
The answer comes down to friction.
像所有的哺乳动物的毛发一样 羊毛纤维被大量的一个压一个的鳞状物覆盖着 它们从末梢到顶端
Like all mammal hair, wool fibers are covered in overlapping scales that run the length
of each fiber.
These scales make it easier for the fiber to slide in one direction than the other,
which is why, if you grab a strand of your hair and pull it through your fingers, you’ll
find it moves more smoothly going toward the tip than toward the root end.
When a wool – or human hair – sweater gets thrown into the washing machine and tossed
甩来甩去 单向阻力成了一个问题 因为当每根纤维
around, this one-way resistance becomes a problem, because, as each fiber rubs against
与它的“邻居”们相互摩擦时 它的鳞状物就像小棘轮的作用一样 仅允许纤维
its neighbors, its scales act like little ratchets, only allowing it/the fiber to move
in one direction.
水使得情况更糟 它导致了纤维膨胀 这使得纤维联接
The water makes things worse, both by causing the fibers to swell, which brings them into
更紧密 使鳞状物变软 松软得足够让它们被
closer contact, and by softening the scales, which makes them floppy enough to get caught
on neighboring fibers more easily, but not so floppy that they can give way and allow
the fibers to move past each other.
Heat also exacerbates the ratchet effect, probably by making the hairs more bendy, which
使纤维连接更紧密 就像做熟的意大利面条 比还没有煮的硬硬的面条
brings them into greater contact, the same way cooked spaghetti noodles touch in more
places than hard, uncooked ones.
Throughout the course of the wash and dry cycle, the millions of tiny ratchets on the
thousands of individual fibers in the wool sweater draw the fabric into a tighter and
and tighter configuration, shrinking the overall size of the sweater.
当绵羊淋雨时 他们厚厚的毛皮上的纤维膨胀 而且纤维表面的鳞状物
When sheep get caught in the rain, the fibers in their thick coats swell and their scales
也变的松软了 但他们的羊毛不会被帅来甩去 也就无法形成刺轮效应
soften too, but their wool doesn’t get tossed around enough for the ratchet effect to cause
从而使它变紧 除非这些绵羊真的是疯了 到处乱撞
it to tighten…unless those sheep get really RAMbunctious.
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The idea for this video actually came from a viewer – thanks Rebecca!
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