From Rachael Padman, Cavendish Laboratory, University of Cambridge
Feedback is too harsh on the West Australian’s reply to the question of why whirlpools rotate in different directions in the northern and southern hemispheres (25 September). The explanation given is both crystal-clear and correct.
It is substantially easier to remember than the usual “deflection is to the right in the northern hemisphere and to the left in the south” rule that is normally applied to rote learning of the effects of Coriolis force. With a little thought, it also shows why hurricanes remain confined to their own half of the globe, and disposes of the usual arguments about whirlpools in two adjacent bathtubs on opposite sides of the equator. Thanks to Feedback I can now add this to my armoury when teaching rotational dynamics to second-year physicists.
Cambridge, UK
