This combination of April 15, 2013 and April 2, 2014 photos show a police officer clearing Boylston Street following a bomb blast near the finish line of the 2013 Boston Marathon, and pedestrians crossing at the same corner nearly a year later in Boston. (Photo by Charles Krupa/AP Photo)

A humanoid robot named “Yangyang” shows a facial expression during its demonstration at the Global Mobile Internet Conference (GMIC) 2015 in Beijing, China, April 29, 20155. The android was produced jointly by China's Shanghai Yangyang Intellegent Robot Science Service center and Japanese professor Hiroshi Ishiguro, with the aim of popularising robotics among the young. (Photo by Kim Kyung-Hoon/Reuters)

This Thursday, April 30, 2015 photo shows Lebanese citizens walking on the Corniche, or waterfront promenade in Beirut, Lebanon. This photo was shot through the lowered veil of a niqab, which is worn by some conservative Muslim women. The cloth allows women to follow a strict interpretation of their religious beliefs by preventing others from seeing their faces. (Photo by Hassan Ammar/AP Photo)

A picture made available on 17 July 2015 shows the bright line of the Milky Way above the old oaks at the Rogalin landscape Park in Rogalin village, near Poznan, on the night of 16 July 2015. (Photo by Lukasz Ogrodowczyk/EPA)

A man shows medicine to an Indian policeman after he was stopped by the police during a curfew in Srinagar July 15, 2016. Curfew imposed in the disputed Himalayan region continued for the seventh straight day to check anti-India violence following the recent killing of a charismatic Kashmiri insurgent Burhan Wani. (Photo by Danish Ismail/Reuters)

This picture taken on August 4, 2016 shows three orphaned orangutan babies hanging in a tree whilst attending “jungle school” at the International Animal Rescue centre outside the city of Ketapang in West Kalimantan. (Photo by Bay Ismoyo/AFP Photo)

Miss Hawaii Allison Chu waves to the crowd as she holds one of her shoes during the 2017 Miss America pageant “Show Us Your Shoes” parade Saturday, September 10, 2016, in Atlantic City. (Photo by Chris Szagola/AP Photo)

A photograph made available on 30 September 2016 showing wind turbines at the site of the highest wind park in Europe at the Griessee, near the Nufenenpass in the Swiss south Alpes, Valais, Switzerland, on 23 September 2016. The four wind turbines of this wind park were developed by the company SwissWinds GmbH and are inaugurated on, 30 September 2016. (Photo by Olivier Maire/EPA)