News Stories

Like Water Going Down the Drain

We're not sure if water goes down the drain in ananticlockwise direction above the equator and in a clockwisedirection below it (or vice-versa), but scientists DO saythat dolphins in the northern hemisphere swim inanticlockwise circles, while dolphins in the southernhemisphere swim in clockwise circles.

Emma Marris writes in nature.com that dolphins swim in lazycircles as they nap, but they only sleep with one half oftheir brains at a time, so they can keep swimming as theysnooze.

When dolphin expert Paul Manger moved from Sweden to SouthAfrica, he noticed the difference in direction and wonderedwhat kind of global force could be causing this. Onepossibility is the Coriolis force?an effect of the Earth'srotation that produces large-scale currents in the ocean andthe atmosphere. This is the force that causes water to godown the drain in different directions in the northern andsouthern hemispheres, although scientists disagree aboutwhether this really happens.

Coriolis expert David McIntyre says, "If on a large scale,ocean currents are doing a certain thing, I imagine thedolphins may be able to pick up on that."

Another possibility is that dolphins all swim in the samedirection to stay together. Manger says, "When dolphins areawake they use their signature whistle to keep together.When they are sleeping, they don't want to be vocalizing,because they don't want to attract attention." But why wouldthey choice of direction vary according to the hemisphere?He says, "That's beyond me."

It's surprising how much wisdom can be gained in thetiniestplaces.

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