Chinese paramilitary guards monitoring passengers as they head to their train to travel to their hometowns for the “Spring Festival” or Lunar New Year at Nantong Railway Station in Jiangsu province, near Shanghai Travellers taking part in the world' s largest annual human migration must be home by January 27 to usher in the new year on January 28. (Photo by AFP Photo/Stringer)

A participant prepares for the Red Bull Air Race World Championships in Abu Dhabi, United Arab Emirates on February 6, 2017. (Photo by Red Bull Content Pool/SIPA Press/Rex Features/Shutterstock)

A member of the “Exit Point” amateur rope-jumping group jumps from a 44-metre high (144-feet high) waterpipe bridge in the Siberian Taiga area outside Krasnoyarsk, September 28, 2014. Fans of rope-jumping, a kind of extreme sport involving a jump from a high point using an advanced system of amortization including mountaineering and rope safety equipment, attended the Golden Autumn group's jumping season. (Photo by Ilya Naymushin/Reuters)

A hot air balloon flies close to the ground in the Jezreel Valley in northern Israel during an international hot air balloon festival October 14, 2014. (Photo by Nir Elias/Reuters)

A visitor walks on a giant chalk artwork called “Wasting Time” at the Chalk Urban Arts Festival in Sydney on October 25, 2014. The picture is the biggest 3-D artwork created in Australia by two artists, Leon Keer from Holland and Jenny McCracken from Australia. (Photo by Peter Parks/AFP Photo)

A truck is seen in a hole after part of the structure of a bridge collapsed into a river in Changchun, Jilin province May 29, 2011. Two truck passengers were injured, while the cause of the accident is still under investigation, local media reported. (Photo by Reuters/China Daily)

A boy holds his mother's leg as he cries in front of their damaged house after a strong 6.6 magnitude earthquake at Longmen village, Lushan county in Ya'an, Sichuan province. (Photo by Jason Lee/Reuters)

In this undated photo made available by journal Nature on January 15, 2014, a northern bald ibis (Geronticus eremita) flies in Tuscany, Italy. A new study released Wednesday, January 15, 2014 says the birds choreograph the flapping of their wings, getting a boost from an updraft of air in the wake of the flapping wings by flying behind the first bird and off to the side. When a flock of birds take advantage of these aerodynamics, they form a V. (Photo by Markus Unsöld/AP Photo)