How Spiders Use Silk to Fly

How Spiders Use Silk to Fly

Sometimes spiders ride the wind. They spin out lines of silk that are caught by the breeze and carry them aloft. They have been reported to rise a mile or two above the earth, and perhaps even to cross oceans.

It’s called ballooning.

Moonsung Cho, an aeronautical engineer, was in Australia the first time he saw the flight of a spider. It was autumn, when baby spiders often balloon en masse and spread to new areas.

He was completely taken by the phenomenon and made it the subject of his studies toward a doctorate at the Technical University of Berlin.

The flights of spiders are well known, but not their physics, so Mr. Cho tested crab spiders both in nature and in a wind tunnel, and discovered, among other things, what holds the spiders up in the air.

They don’t actually have balloons, but rather numerous strands of silk that they spin up to six feet long. And those threads of silk, from 100 to a few hundred nanometers wide (a human hair is 80,000 to 100,000 nanometers in diameter), are so thin and lightweight that they are suspended in the air like a thread, or a hair, in molasses.

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