English: This Landsat 7 image of clouds off the Chilean coast near the Juan Fernández Islands (also known as the Robinson Crusoe Islands) on September 15, 1999, shows a unique pattern called a " von Kármán vortex street ." This pattern has long been studied in the laboratory, where the vortices are created by oil flowing past a cylindrical obstacle, making a string of vortices only several tens of centimeters long. Study of this classic "flow past a circular cylinder" has been very important in the understanding of laminar and turbulent fluid flow that controls a wide variety of phenomena, from the lift under an aircraft wing to Earth's weather. Here, the cylinder is replaced by Alejandro Selkirk Island .