Week in Geek: Low pressure pull edition

A team of engineers and biologists recently revealed that jellyfish pull rather than push their way through the water.

It has long been believed that the pulsations jellyfish make as they swim were acting to push off the water behind them to move forward. But a collaboration between Stanford engineers and Woods Hole biologists has found otherwise. Instead, it seems that jellyfish create pockets of low pressure behind their “heads” and so higher pressure water in front of them rushes around them to equal things out and in the process, they are propelled forward. The scientists found the same thing to be true for lamprey eels.

Snapshot of a lamprey eel (black outline) swimming in a water tank. Colors indicate low-pressure suction forces (blue) and high-pressure pushing forces (red) generated by the animal as it swims.

The way they figured this out is pretty freaking cool. It’s almost impossible to accurately calculate the rate of flow and the pressure exerted by each individual water molecule around the jellyfish (or lamprey) because the number of molecules is astronomical. However, by adding “proxy molecules” to the water in the form of tiny glass beads, they could measure the flow rate and pressure of the beads and thereby infer the same for the water molecules. Add some lasers and some high-speed cameras and they could track the motion of every bead and its affect on the surrounding beads as the jellyfish and lamprey subjects swam through the tank.

You can read the full press release here and watch videos of their data here. And if you were only reading this in the hopes of starring at some stunning jellyfish photos, you can go here.

I love science.

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@Summer_Ash, In-house Astrophysicist

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Week in Geek: Low pressure pull edition