Senator Barack Obama (D-IL) (R) stands in front of Senator Hillary Clinton (D-NY) as they arrive for U.S. President George W. Bush's annual State of the Union speech to a joint session of Congress at the U.S. Capitol in Washington in this January 23, 2007 file photo. Hillary Clinton announced her second run for the presidency on April 12, 2015 starting her campaign as the Democrats' best hope of fending off a crowded field of lesser-known Republican rivals and retaining the White House. (Photo by Larry Downing/Reuters)

A humanoid robot named Kansei, meaning “sensibility” in Japanese, makes a facial expression depicting “happiness”, next to the word “Love” during a demonstration at a laboratory of Meiji University's Robot and Science Institute in Kawasaki, south of Tokyo in this June 4, 2007 file photo. Three-fourths of robot installations over the next decade are expected to be concentrated in four areas: transportation equipment, including the automotive sector; computer and electronic products; electrical equipment and machinery. Labor costs have climbed in countries such as China that have been popular for outsourcing production, while technological advances for robots allow them to be more flexible and perform more tasks. (Photo by Yuriko Nakao/Reuters)

A farmer is seen hanging from a tree during a rally organized by Aam Aadmi (Common Man) Party (AAP) in New Delhi April 22, 2015. The farmer hanged himself from a tree during a political rally in New Delhi on Wednesday, in what appeared to be a desperate protest against the hardship felt by many people scratching a living in rural India. Four people climbed the tree to try to save the man after he was seen hanging. (Photo by Adnan Abidi/Reuters)

A confiscated female orangutan smuggled from Indonesia looks out from a cage before being sent back home to Indonesia, at Khao Pratupchang Wildlife Breeding Center in Ratchaburi province, Thailand, 11 November 2015. According to media reports, Thailand will return fourteen smuggled orangutans to Indonesia on 12 November, after Thai authorities found them in 2010 by a roadside in Phuket province, apparently on their way to a private zoo. (Photo by Narong Sangnak/EPA)

A mother prays for success for her child in the college entrance examinations at a Buddhist temple in Seoul, South Korea, November 12, 2015. About 630,000 students on Thursday sat for the annual exams that could lead them to one of the country's top universities. In South Korea, there is no higher achievement than to be accepted by a prestigious university. As a result, many students prepare for these entrance exams from an early age, often studying up to 16 hours a day for years to take this test. (Photo by Kim Hong-Ji/Reuters)

Polish photographer David Kaszlikowski took a series of stunning photographs of a glacier in the Karakoram region of Pakistan while on a film expedition. At the Baltoro and Godwin-Austen glaciers near K2, the second highest mountain in the world, he sent his drone on flights to scout the surrounding landscape. Here: at the heart of Karakoram, a glacier formation found at Concordia at the very beginning of one of the longest glaciers on the planet, Baltoro. (Photo by David Kaszlikowski/Rex Features)

This picture taken on November 18, 2015 shows young participants preparing to release a hot-air balloon during the Tazaungdaing Lighting Festival at Taunggyi in Myanmar's northeastern Shan State. Every year in November as the full moon approaches, tens of thousands of people from all over the country gather in Taunggyi for the colourful hot-air balloons festival during which balloons lift fireworks or lanterns which illuminate the sky at night while balloons of all shapes are flown during the day. (Photo by Ye Aung Thu/AFP Photo)

A F-16 fighter jet from The Thai Royal Air Force performs during a media demonstration at the Korat Royal Thai Air Force Base, Nakhon Ratchasima province, Thailand, November 24, 2015. Thailand's military held an air show with China on Tuesday ahead of joint manoeuvres in a sign of warming ties, but Thailand said it was not distancing itself from the United States which downgraded the military relationship following a 2014 coup. (Photo by Athit Perawongmetha/Reuters)