“I have seen batches of banknotes worth more than $2.6 million, but beyond all doubt, gold bars look much more attractive!”. – Shamil Zhumatov. Photo: Cooling-down gold ingot. March 14, 2013; Tien Shan mountains, Kyrgyzstan. (Photo by Shamil Zhumatov/Reuters)

Dan McManus and his service dog Shadow hang glide together outside Salt Lake City, Utah, July 22, 2013. McManus suffers from anxiety and Shadow's presence and companionship help him to manage the symptoms. The two have been flying together for about nine years with a specially made harness for Shadow. (Photo by Jim Urquhart/Reuters)

A hot air ball balloon floats past while people stand in line to climb the Pyramid of the Sun and welcome the spring equinox in the pre-hispanic city of Teotihuacan, on the outskirts of Mexico City, Mexico, March 20, 2016. Spring equinox in Teotihuacán is an annual event which takes place around the 20th and 21st of March at the pre-Hispanic site of Teotihuacán, Mexico. This event is mirrored by other similar events in other pre-Hispanic sites such as Chichén Itzá and Malinalco, Mexico State. (Photo by Edgard Garrido/Reuters)

Girls ride on a donkey cart with grass for animals on the outside of Nangarhar province, Afghanistan May 19, 2015. (Photo by Reuters/Parwiz)

A model walks off stage in the backstage area during Frankie's Bikinis show at Mercedes Benz Swim Fashion Week in Miami, July 18, 2014. (Photo by Carlo Allegri/Reuters)

An adorable baby owl has proved to be a real heart-breaker thanks to its heart-shaped head. Although Griffin the Lesser Sooty Owl might look like a feather duster, the tiny eight-week old chick will soon be ready to fly. And the heart outline that surrounds his giant eyes and beak means he is set to be the star of the bird show at Taronga Zoo, Sydney. (Photo by Caters News Agency)

A subway worker walks away after a train departed the station in central Pyongyang, North Korea May 7, 2016. (Photo by Damir Sagolj/Reuters)

The Hubble Space Telescope is shown following its release from the space shuttle Discovery Wednesday, February 19, 1997. The Hubble Space Telescope, one of NASA'S crowning glories, marks its 25th anniversary on Friday, April 24, 2015. With more than 1 million observations, including those of the farthest and oldest galaxies ever beholden by humanity, no man-made satellite has touched as many minds or hearts as Hubble. (Photo by AP Photo/NASA)