New York Police Department tactical police officers stand guard near the New York Stock Exchange on September 9, 2011 in New York City. Officials are stepping up security in New York and Washington D.C. a day after U.S. officials received a credible but unconfirmed terror threat to utilize car bombs on bridges or tunnels in New York or Washington. (Photo by Justin Sullivan/Getty Images)

Michael Bath, from McLeans Ridges in New South Wales, Australia, estimates that in his lifetime he has taken more than 3,500 images of lightning bolts illuminating the sky. Photo: Alstonville, New South Wales, Australia – January 8, 2003. (Photo by Michael Bath/Caters News)

An Indian toddler plays amid marigold flowers at a wasted flowers dumping site, besides a flower market in Mumbai, India, 28 September 2016. Marigold flowers are used in many religious ceremonies in the temples in India. Strung together they make colourful garlands and are used as an offering in temples and to decorate them. (Photo by Divyakant Solanki/EPA)

The town hall with the Mangia tower is seen in Siena, central Italy, January 29, 2016. (Photo by Max Rossi/Reuters)

Charli XCX performs at Hype Hotel on March 17, 2016 in Austin, Texas. (Photo by Lorne Thomson/Redferns)

Participants take part in an extreme run “Bison race” near the town of Logoisk, Belarus September 17, 2016. (Photo by Vasily Fedosenko/Reuters)

A girl sits on a pile of rubbish at landfill site on the outskirts of Sanaa, Yemen November 16, 2016. (Photo by Mohamed al-Sayaghi/Reuters)

The bride in her room, prepared for a traditional Chechen wedding ceremony in Grozny, Chechnya, Russia on November 24, 2016. (Photo by Valery Sharifulin/TASS)