Animal locomotion, which is the act of self-propulsion by an animal, has many manifestations, including running, swimming, jumping and flying. Animals move for a variety of reasons, such as to find food, a mate, or a suitable microhabitat, and to escape predators. For many animals the ability to move is essential to survival and, as a result, selective pressures have shaped the locomotion methods and mechanisms employed by moving organisms. For example, migratory animals that travel vast distances (such as the Arctic Tern) typically have a locomotion mechanism that costs very little energy per unit distance, whereas non-migratory animals that must frequently move quickly to escape predators (such as frogs) are likely to have costly but very fast locomotion. The study of animal locomotion is typically considered to be a sub-field of biomechanics.

Locomotion requires energy to overcome friction, drag, inertia, and gravity, though in many circumstances some of these factors are negligible. In terrestrial environments gravity must be overcome, though the drag of air is much less of an issue. In aqueous environments however, friction (or drag) becomes the major challenge, with gravity being less of a concern. Although animals with natural buoyancy need not expend much energy maintaining vertical position, some will naturally sink and must expend energy to remain afloat. Drag may also present a problem in flight, and the aerodynamically efficient body shapes of birds highlight this point. Flight presents a different problem from movement in water however, as there is no way for a living organism to have lower density than air. Limbless organisms moving on land must often contend with surface friction, but do not usually need to expend significant energy to counteract gravity.

William Sanford "Bill" Nye (born November 27, 1955), popularly known as Bill Nye the Science Guy, is an American science educator, comedian, television host, actor, mechanical engineer, and scientist. He is best known as the host of the Disney/PBS children's science show Bill Nye the Science Guy (1993–1998) and for his many subsequent appearances in popular media as a science educator.

William Sanford Nye was born in Washington, D.C., the son of Jacqueline (née Jenkins; c. 1920–2000), a codebreaker during World War II, and Edwin Darby "Ned" Nye (died 1997), also a World War II veteran whose experience in a Japanese prisoner of war camp led him to become a sundial enthusiast. Nye is a fourth-generation Washington, D.C. resident on his father's side of the family. After attending Lafayette Elementary and Alice Deal Junior High in the city, he was accepted to the private Sidwell Friends School on a partial scholarship, graduating in 1973. He studied mechanical engineering at Cornell University, where one of his professors was Carl Sagan, and graduated with a Bachelor of Science in 1977. He was awarded an honorary doctorate by The Johns Hopkins University in May 2008. In May 2011, Nye was awarded an Honorary Doctor of Science degree from Willamette University where he was the keynote speaker for that year's commencement exercises.

Eadweard James Muybridge ( /ˌɛdwərd ˈmaɪbrɪdʒ/; 9 April 1830 – 8 May 1904) was a British photographer who spent much of his working life in California, and traveling in other parts of the United States. He is known for his pioneering work on animal locomotion in 1877 and 1878, which used multiple cameras to capture motion in stop-action photographs, and his zoopraxiscope, a device for projecting motion pictures that pre-dated the flexible perforated film strip used in cinematography.

In his earlier years in San Francisco, Muybridge had become known for his landscape photography, particularly of the Yosemite Valley. He also photographed the Tlingit people in Alaska, and was commissioned by the United States Army to photograph the Modoc War in 1873. In 1874 he shot and killed Major Harry Larkyns, his wife's lover, and was acquitted in a jury trial on the grounds of justifiable homicide. He traveled for more than a year in Central America on a photographic expedition in 1875.

In the 1880s, Muybridge entered a very productive period at the University of Pennsylvania in Philadelphia, producing over 100,000 images of animals and humans in motion, capturing what the human eye could not distinguish as separate movements. He spent much of his later years giving public lectures and demonstrations of his photography and early motion picture sequences. He also edited and published compilations of his work, which greatly influenced visual artists and the developing fields of scientific and industrial photography.