In this image provided by the Ministry of Defence, Prince William takes the controls of a Sea King helicopter on April 14, 2011 in Holyhead, Wales. Search and rescue co-pilot Prince William, based at RAF Valley will marry his fiancee Catherine Middleton in Westminster Abbey in London on April 29, 2011. (Photo by MoD Crown Copyright via Getty Images)

Masaaki Nagumo controls the Land Walker robot at Sakakibara Kikai Co., Ltd Headquarters on May 12, 2005 in Maebashi, Japan. The two legged robot stands at 3.4 metres high and weighs 1000kg. The Land Walker is available to buy for 36,000,000 yen (approximately US $340,000). Masaaki Nagumo developed Land Walker on the basis of the dream he has had in his childhood that enables a person to go on. (Photo by Koichi Kamoshida/Getty Images)

Axel, a research prototype rover for exploring the Moon, Mars and other planets, is remotely driven over rocks as engineers from Jet Propulsion (JPL) and grad students from Caltech (California Institute of Technology) demonstrate its mobile over the steep and rocky grounds of the JPL Mars Yard on January 14, 2009 in Pasadena, California. The rover is capable of descending cliffs or into craters and returning by a cable tethered to its starting point. Development of the Axel rover is a point effort funded by NASA Exploration Systems Mission Directorate (ESMD) and lead by Principal Investigator Issa Newnas and Co-Investigator and Caltech professor of mechanical engineering bio engineering Joel Burdick. (Photo by David McNew/Getty Images)

Guadalajara-based artist Gonzalo Lebrija created a public art installation in the parking lot (1430 Delgany Street, Denver, CO 80202) across from the Museum of Contemporary Art Denver (MCA Denver) in the summer of 2010. The installation, entitled History of Suspended Time: Monument for the Impossible, was developed as a dual collaboration with MCA Denver's museum-wide exhibition, Energy Effects: Art & Artifacts from the Landscape of Glorious Excess, as well as Denver's inaugural 2010 Biennial of the Americas, an international event that celebrated the culture, ideas and people of the Western Hemisphere.

Riot Police form a cordon as a Police car burns on the opening day of the European Central Bank (ECB) in Frankfurt am Main, western Germany, on March 18, 2015. Supporters of the so-called Blockupy alliance consisting of social movements, activists, workers, trade unions and parties are expected to stage large protests against austerity and the authority of the European Central Bank when the bank's new headquarters officially will be on March 18, 2015. (Photo by Odd Andersen/AFP Photo)

Harry Potter collectible busts are displayed in the home of Menahem Asher Silva Vargas, after he was presented with a Guinness World Record title certificate for the largest collection of Harry Potter memorabilia, in Mexico City, Monday, September 29, 2014. Silva's collection consists of more than 3000 individual items, including trading cards, wands, and books in multiple languages. (Photo by Rebecca Blackwell/AP Photo)

Chief priest Gbenga Saala raises a cutlass to kill a dog during an annual prayer and sacrifice celebration of the iron god Ogun in Abuja, Nigeria, June 23, 2015. Every year worshippers offer a dog as sacrifice to Ogun, a traditional Nigerian deity, in hope of an auspicious year ahead. Taxi drivers, blacksmiths, panel beaters and mechanics – trades that depend on metal for their livelihood – pay homage to Ogun, led by high priest Gbenga Saala. As part of the ceremony, the priest pours the dog’s blood on symbols of these workers’ trade: keys, spanners and other tools piled up in a metal barrel. (Photo by Afolabi Sotunde/Reuters)

A Chinese exhibitor checks lighting products at a booth during the China Import and Export Fair, also known as Canton Fair, in the southern Chinese city of Guangzhou October 15, 2015. Around two thirds of exporters at China's largest trade fair expect the slowdown in their markets to persist for at least six months, a Reuters poll has found, with the country expected to announce its slowest economic growth in decades early next week. (Photo by Bobby Yip/Reuters)