The shape of an ellipse is formed when a cone is cut at an angle. If you tilt a glass of water, the resulting shape of the surface of the water is also an ellipse. You can also see ellipses when a hula hoop or tire of a car looks askew. Though these are examples of optical ellipses, the ellipse also has practical uses in real life.
Foods are cut to form ellipses, offering a refined touch to simple foods. Cutting a carrot, cucumber or sausage at an angle to its main axis results in an elliptical slice. Wraps – tortillas wrapped around a filling such as chicken salad – are often cut into two elliptical wedges. The sharp focus of the ellipse gives everyday food a more elegant look.
A focus is one of two points that defines the shape and size of the ellipse; they're located on the long axis of the ellipse, at equidistant points from the center of that axis. If light or a sound wave emanates from one focus of a real-life ellipse, it will be reflected to the other focus. This property is used to create whispering galleries, which are structures that allow someone who is whispering in one area to be heard clearly by someone in another area but not by anyone else. Famous examples of whispering galleries include the United States Statuary Capitol Hall and London's St. Paul's Cathedral.
If you ever develop a kidney stone, you might discover the benefits of lithotripsy, a surgery-free method of destroying a kidney stone that uses the properties of the ellipse's two foci. For a lithotripsy treatment the patient lies in an elliptical tub, with the kidney stone aligned to one of the foci of the ellipse. Shockwaves emanating from the other focus concentrate on the kidney stone, reducing it to debris as small as sand that can pass through the body without discomfort. Because no incisions are made recovery from this treatment method is relatively quick and easy, and in some cases it can even be done as an outpatient procedure.
An elliptical training machine simulates the motion of running or walking, offering a low-impact cardio workout. When you walk or run in an elliptical trainer, your foot describes an elliptical path. An elliptical machine can be motor-driven or user-driven, and some elliptical trainers also feature handlebars that you can push or pull on to help move the foot pedals through their elliptical path.