Lightning strikes the Willis Tower (formerly Sears Tower) in downtown on June 12, 2013 in Chicago, Illinois. (Photo by Scott Olson/Getty Images)

Emma White, of Team Cyclocrossworld, hits the dirt hard during the USA Cycling Cyclo-cross National Championship Elite Women's race at the Valmont Bike Park in Boulder, Colorado, on January 12, 2014. (Photo by Jeremy Papasso/The Daily Camera)

Smoke rises during an explosion from an Israeli forces strike in Gaza City, Saturday, November 17, 2012. Israel bombarded the Hamas-ruled Gaza Strip with nearly 200 airstrikes early Saturday, the military said, widening a blistering assault on Gaza rocket operations by militants to include the prime minister's headquarters, a police compound and a vast network of smuggling tunnels. (Photo Hatem Moussa/AP Photo)

The British Breitling Wingwalkers, Danielle Hughes and Emily Guilding, soar above the Palm Jumeirah in Dubai at 1,500 feet (460 meters) in excess of 100mp/h, ahead of their Dubai debut performance at the 2014 UIM Skydive Dubai XCAT World Powerboating Series, on Saturday, 13th December 2014. The British team is the only aerobatic formation display team who employ full time wingwalkers and fly their two Breitling-liveried 1930's Boeing Stearman bi-planes at Air Shows and major sporting events around the world. (Photo by Katsuhiko Tokunaga/Breitling via AP Images)

Al-Shamiyah Front fighters inspect a new locally-made cannon named “Borkan” (Volcano) as it was being launched towards forces loyal to Syria's president Bashar Al-Assad located in Aleppo artillery school, March 7, 2015. The “Borkan” is made out of four tubes attached to a loader, which can fire four shells at a time, and have a range of three kilometers (1.86 miles). (Photo by Abdalrhman Ismail/Reuters)

A devotee takes a holy bath at the Balaju Baise Dhara (22 water spouts) during the Baishak Asnan festival in Kathmandu April 4, 2015. Devotees believe that the water from these stone spouts, which is collected from the catchment area of the Nagarjun forest behind the spouts, will cure pains and skin diseases. (Photo by Navesh Chitrakar/Reuters)

Cheng Chen (R), a 27-year-old worker at a state-owned enterprise, poses for a photograph with his nephew who is wearing his home-made Iron Man armour, in Xuzhou, Jiangsu province April 13, 2015. It cost Cheng about 500 yuan ($81 USD) to make the armour, which weighs about 4 kilograms, with plastic boards and LED lights, local media reported. (Photo by Reuters/Stringer)

A prototype battery-powered plane, called Greased Lightning or GL-10 is pictured flying at NASA's Langley Research Center in this undated handout photo obtained by Reuters May 1, 2015. The plane, which has 10 engines and can take off like a helicopter and fly efficiently like an aircraft, is currently in the design and testing phase. (Photo by Reuters/NASA)