“A fter the former Soviet Union conducted its first nuclear test in August 1949, the US reevaluated its postwar defense policies. With the US monopoly on atomic weapons broken, military and political leaders chose to diversify the American stockpile by developing thermonuclear and tactical nuclear weapons. One of the more interesting concepts to come out of this period was atomic artillery, which was successfully tested at the Nevada Proving Grounds (now the Nevada Test Site) in May 1953”. – Alan Carr. Photo: Atomic Annie at work during the Upshot-Knothole test series, 1953. (Photo by Los Alamos National Laboratory/US Army)

Handout picture released by Telam showing the tarmac of the Pedro Palacios Avenue in Ramos Mejia, province of Buenos Aires, Argentina, under which the channeled waters of the Maldonado stream flow, after it collapsed on April 8, 2014 leaving a 40-metre-long, 1.4-metre-deep hole. About 3000 people had to be evacuated in the Argentine provinces of Neuquen (soutwest), Catamarca (northwest), Santiago del estero (center) and Cordoba (center)due to the foods caused by heavy rain, official sources said. (Photo by Daniel Dabove/AFP Photo)

Two drunk race-goers make their way home after the last race of the third day of the Royal Ascot horse racing week June 19, 2003 in Ascot, England. (Photo by Scott Barbour/Getty Images)

A woman rows her boat as she harvests tomatoes on Inle lake, in Myanmar's Shan State September 4, 2015. Inle is one of the country's most popular tourist sites. (Photo by Soe Zeya Tun/Reuters)

A P-51 Mustang named “Charlotte's Chariot” from the Southern Heritage Air Foundation flies past a cloud of smoke and fire from a nearby battle reenactment during the Wings Over Houston Airshow in Houston, on Saturday, November 1, 2014. Battle reenactments are part of the yearly show held at Ellington Airport. (Photo by Kar Hlava/AP Photo/Bay Area Citizen)

Hamar women dance before a bull jumping ceremony in Ethiopia's southern Omo Valley region near Turmi on September 19, 2016. The Hamar are a Nilotic ethnic group in Ethiopia. The construction of the Gibe III dam, the third largest hydroelectric plant in Africa, and large areas of very “thirsty” cotton and sugar plantations and factories along the Omo river are impacting heavily on the lives of tribes living in the Omo Valley who depend on the river for their survival and way of life. (Photo by Carl De Souza/AFP Photo)

Tribal artists and supporters from the southern Indian state of Karnataka dance outside the residence of Congress Party President Sonia Gandhi during her birthday celebrations in New Delhi, India, Wednesday, December 9, 2015. The Italian-born Gandhi is the widow of former Prime Minister Rajiv Gandhi and has led the Congress party since 1998. (Photo by Altaf Qadri/AP Photo)