A “creuseur”, or digger, a plastic lantern on his head, readies to enter a copper and cobalt mine in Kawama, Democratic Republic of Congo on June 8, 2016. Cobalt is used in the batteries for electric cars and mobile phones. Working conditions are dangerous, often with no safety equipment or structural support for the tunnels. The diggers say they are paid on average US$2-3/day. (Photo by Michael Robinson Chavez/The Washington Post)

Four pillars of light from the 4 Laser Guide Star Facility on ESO's Very Large Telescope (VLT) are shown reaching into the Chilean night sky in this image from ESO Photo Ambassador Fred Kamphues, on September 2, 2016. The lasers are a key part of the adaptive optics system on the VLT. Adaptive optics allows astronomers to drastically reduce the atmospheric distortion present at even the best sites in the world for astronomy, including Paranal in Chile, the home of the VLT. (Photo by F. Kamphues/ESO)

This photo taken on June 19, 2017 shows Indian yoga teacher Mahesh Yogiji attempting a world record for the longest yoga session in Ahmedabad, ahead of International Yoga Day on June 21. According to Guiness World Records, the longest yoga marathon undertaken by a man lasted 69 hours and was achieved by V Gunasekaran in Tamil Nadu in June 2016. (Photo by Sam Panthaky/AFP Photo)

An Israeli soldier takes part in during a rehearsal for a ceremony to mark Israel's Memorial Day for fallen soldiers at the Mount of Olives cemetery in east Jerusalem, Tuesday, May 10, 2016. Israel will mark the annual Memorial Day in remembrance of soldiers who died in the nation's conflicts, beginning at dusk Tuesday until Wednesday evening. (Photo by Oded Balilty/AP Photo)

Female Naval Academy plebes perform push ups with a twelve foot log on top of them during the annual Sea Trials May 17, 2016 at the Naval Academy in Annapolis, Maryland. The Naval Academy freshman class endures 14 hours of rigorous physical and mental challenges during the annual Sea Trials training exercise as part of the culmination of their freshman year at the academy. (Photo by Win McNamee/Getty Images)

Tourists dressed in yukatas, a light, unlined, summer kimono made of cotton instead of the traditional silk, climb steps to visit a temple on April 27, 2016 in Kyoto, Japan. Now the seventh largest city in Japan, Kyoto was once the Imperial capital for more than one thousand years, it is now the capital city of Kyoto Prefecture and a major part of the Kyoto-Osaka-Kobe metropolitan area. (Photo by Carl Court/Getty Images)

Iraqi pro-government forces fire an anti-tank cannon near al-Sejar village, north-east of Fallujah, on May 25, 2016, as they take part in a major assault to retake the city from the Islamic State (IS) group. Iraqi forces, consisting of special forces, soldiers, police, paramilitary-fighters and pro-government tribesmen, launched a major assault to retake Fallujah, the scene of deadly battles during the US occupation and one of the toughest targets yet in Baghdad's war on the Islamic State group. (Photo by Ahmad Al-Rubaye/AFP Photo)

A 10-year-old boy living on the streets of New Delhi lies down on cascading water of a fountain in the gardens of the India Gate monument on May 20, 2016. The Indian Meteorological Department issued warnings of “severe heat wave” conditions across large parts of India's north and west, including the capital Delhi, where temperatures hit 47 degrees Celsius. (Photo by Roberto Schmidt/AFP Photo)