A woman smokes marijuana during the annual 4/20 marijuana rally on Parliament Hill in Ottawa, Ontario, Canada, April 20, 2017. (Photo by Chris Wattie/Reuters)

The book “Elektroschutz in 132 Bildern” (Electrical Protection in 132 Pictures) was published in Vienna in the early 1900s by a Viennese physician named Stefan Jellinek (1878-1968, a founder of the Electro-Pathological Museum). The pictures are nice and direct and unambiguous; they teach, graphically, that the surest way to kill yourself with electricity is to form a complete path from source (usually the bright red arrow) to ground (the screened back, pink arrow). Arrowheads provide the path for current flow. (Photo by The Vienna Technical Museum)

Globe-trotting photographer couple Peter Sedlacik and Zuzu Galova have found a fun way to document their travels around the world. Wherever they are, they face each other, frame up a great composition, and take a picture of each other… taking a picture of each other. Thus was born the photo series/project “Lens Between Us”, which is quickly scooping up followers on Tumblr, Facebook and Instagram alike. The resulting diptychs are creative, well-composed, and whimsical in the best way. A tribute to how their focus is always on each other, the images are part travel photography, part portraiture, and challenging to boot since each shot requires that they figure out not one, but two compositions. (Photo by Peter Sedlacik/Zuzu Galova)

Konishiki “The Dumptruck” of Hawaii stares down at his opponent during the first Sumo Bashai held outside Japan, at the Albert Hall in London, England. (Photo by Chris Cole /Getty Images). 1991

A World War II era P-51 Mustang fighter plane stands in front of a modern 747-8 freighter and a 757 passenger jet at The Boeing Company's centennial celebration in Renton, Washington, U.S. July 15, 2016. (Photo by Alwyn Scott/Reuters)

A photographer tested the concentration of several pairs of dogs as he captured their reactions to treat time in a series of shots. Christian Vieler, 47, of Waltrop, Germany, has been a professional dog photographer since 2016. He came up with the idea of snapping two dogs catching treats simultaneously. Here: Basset Hounds. (Photo by Vieler Photography/Caters News Agency)

View of a Spitfire from the cockpit of an He111,somewhere over Southern England 1941 – 2014. (Photo by Adam Surrey)

A high temperature alerts were issued as a record-setting summer heat wave continued to bake most parts of south China. (Reuters)