Faster than the blink of an eye, or a speeding bullet... it's the sting of a jellyfish. NPR science correspondent Joe Palca reports on new research that reveals how fast jellyfish stingers move on their targets.
How fast? Less than a microsecond -- and more easily measured in nanoseconds, which is one-billionth of a second. The secret lies inside the nematocyst, a microscopic sac of poison with a razor-sharp dart inside.
The dart "fires" when an object touches the surface of the nematocyst. Because the object is touching the nematocyst, the dart doesn't have to go very far. But covering 10 to 20 micrometers in less than one-millionth of a second means the dart accelerates at an astonishing rate.
Astronauts can experience forces four to five times the normal pull of gravity, or g's. But when a nematocyst spits out its dart, the dart's acceleration generates a force equal to one million g's, creating as much pressure as a bullet hitting a target, and enough energy to allow the delicate jellyfish to stun even heavily armed crustaceans.
The source of that remarkable force is a special protein inside the nematocyst that stretches. It's similar to a rubber balloon filled to bursting, and when something brushes against the jellyfish -- hopefully not you -- the bubble bursts.
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