University of Heidelberg

Talk Details

Monday, May 19, 2014 - 11:00am

Christoph Pfrommer (HITS):

"The Flea Circus"

Abstract. This is a fun talk originally designed as a habilitation talk - and delivered here upon great demand. The central question I try to answer is: how high can a flea jump in comparison to a human being or other animals such as a locust? I will develop a simple model, which does an astonishing job in explaining the measured jump heights. However, this model suffers from a large power requirement for small animals. Click beetles overcome this problem by storing energy in their exoskeleton. To further improve upon the simple model, we need to consider the air resistance. I show that this is the limiting factor for the jump heights of small animals, which have a large surface area-to-volume ratio. Using dimensional analysis by means of Buckingham's Pi theorem enables us to obtain a general description of the air resistance. However, during the flea jump, the characteristics of the flow transits from a turbulent to a laminar flow pattern. This effect modifies the jump height in accordance with the data. To account for the audience, I spice this talk up with a fun astrophysical application and show which drag forces are relevant for a spiral galaxy orbiting in a galaxy cluster.

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