Serena Williams of the U.S. serves during her first round match against Italy's Camila Giorgi at the Australian Open tennis tournament at Melbourne Park, Australia, January 18, 2016. (Photo by Jason O'Brien/Reuters)

Rick Sorenson, owner of the Rio Ramaza Marina, wades in the Sacramento River after securing an old paddlewheel boat on his property as the river makes its way up the levee on Garden Highway in Sacramento, Calif., Monday, January 9, 2017. (Photo by Hector Amezcua/The Sacramento Bee via AP Photo)

West German police arrest a young man, one of the angry crowd throwing stones at a bus full of Soviet guards making their way to the Soviet War Memorial, 20th August 1962. The crowd were incensed by the death of 18-year-old Peter Fechter, who was shot while trying to cross the Berlin Wall a few days earlier. (Photo by Central Press/Hulton Archive/Getty Images)

Londoners sleep on the platform and on the train tracks at Aldwych Underground station,London, during heavy all night Nazi bombing raids, October 8, 1940. (Photo by AP Photo)

The War in Abkhazia from 1992 to 1993 was fought between Georgian government forces for the most part, and Abkhaz separatist forces, Russian armed forces and North Caucasian militants. Ethnic Georgians who lived in Abkhazia fought largely on the side of Georgian government forces. Ethnic Armenians and Russians within Abkhazia's population largely supported the Abkhazians, and many fought on their side. The separatists received support from thousands of North Caucasus and Cossack militants and from the Russian Federation forces stationed in and near Abkhazia. Here: Abkhazia. Sukhumi, 1993. A house-to-house combat. (Photo by Andrei Solovyov/ITAR-TASS)

Movement is the essence and meaning of our life. We feel so much more alive when we are in motion, while people who spend hours motionless tend to have trouble connecting with the outside world. Whether you dive from a high cliff, play your favorite sport, dance at a rave party, or simply walk down a path with autumn leaves rustling under your feet with the love of your life by your side, all those things make your life richer, more beautiful, and more fulfilling. This set of pictures beautifully captures the joy of never-ending motion that enriches our life. (Photo by Brian Snyder/Reuters)

Aerial Emery trains on the cyr wheel at the Aloft Loft circus training and teaching school which was converted from a church, in Chicago, Illinois, U.S., September 20, 2016. (Photo by Jim Young/Reuters)