A giant Rubber Duck created by Dutch artist Florentijn Hofman is towed along Hong Kong's Victoria Habour Thursday, May 2, 2013. Since 2007 the 16.5-meter (54 feet)-tall Rubber Duck has traveled to various cites including Osaka, Sydney, Sao Paulo and Amsterdam. (Photo by Vincent Yu/AP Photo)

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)

"Steve McCurry: India", co-organized by the Rubin Museum and the International Center of Photography, brings together photographs of India-its people, monuments, landscapes, seasons, and cities. The exhibition at the Rubin Museum in New York runs from November 18, 2015 – April 4, 2016. Here: A boy in mid-flight in Jodhpur, Rajasthan, India, in 2007. (Photo by Steve McCurry)

An Airbus A380 aircraft prepares to land at Mumbai airport in this May 8, 2007 file photo. Sentiment at some of Asia's biggest firms deteriorated again in the fourth quarter, falling to a four-year low under the weight of concerns about slowing growth in China, the region's biggest economy, a Thomson Reuters/INSEAD survey showed. (Photo by Arko Datta/Reuters)

Workers demonstrate outside the factory of Hua Yang Printing Holdings Co Ltd on October 30, 2007 in Shenzhen of Guangdong Province, China. Over 1,000 workers of the company have blocked the 107 State Highway where the firm is located, to protest against their employer, who owed half a month's salary to the workers. (Photo by China Photos/Getty Images)

“Contrails (short for “condensation trails”) or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets or, if the air is cold enough, tiny ice crystals”. – Wikipedia

Photo: An airplane leaves a vapor trail as it flies in front of he moon on January 17, 2007 above Hanover, Germany. (Photo by Alexander Hassenstein/Getty Images)

Female Chimpanzee “Fifi” eats carrots as she sits in her enclosure at Taronga Zoo on her 60th birthday May 21, 2007 in Sydney, Australia. Fifi is the oldest of the Zoo's chimp population, which consists of 19 individuals. (Photo by Ian Waldie/Getty Images)