Sarah Gibbons grades a new batch of Maple Syrup at Gibbons Family Farm in Frankville, Ontario, Canada, 31 March 2014. The annual maple syrup season marks the end of the often brutal central Canadian winters and heralds the beginning of spring. The maple tree, whose leaf dominates the Canada's flag, plays both a symbolic and practical role in the identity of Canadians who produce around 95 percent of the world's supply of maple syrup. (Photo by Stephen Morrison/EPA)

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)

Pakistan girls make selfies holding a Pakistan-made weapon displayed at the four-day International Defence Exhibition and Seminar (IDEAS) 2016 in Karachi, Pakistan, Wednesday, November 23, 2016. (Photo by Shakil Adil/AP Photo)

A woman wearing a scarf to cover her face looks on as she waits for a passenger bus on a smoggy morning in New Delhi, India, November 8, 2017. The Great Smog of Delhi is an ongoing severe air-pollution event in New Delhi and adjoining areas in the National Capital Territory of India, in November 2017. Air pollution at this time peaked on both PM 2.5 and PM 10 levels. It has been reported as one of the worst levels of air quality in Delhi since 1999. (Photo by Saumya Khandelwal/Reuters)

A horse buggy is headed for the stables on a foggy night in New Orleans, Monday, December 18, 2017. (Photo by David Grunfeld/NOLA.com The Times-Picayune via AP Photo)

Beyonce and Jay-Z leave Rihanna's 3rd Annual Diamond Ball at Cipriani Wall Street on September 14, 2017 in New York City. (Photo by James Devaney/GC Images)

Boys play with a drainage culvert used for flood control in Las Pinas, Metro Manila February 28, 2016. (Photo by Erik De Castro/Reuters)

An armoured vehicle surrounded by Chicago cops at the time of the American depression, 1933. (Photo by Rolls Press/Popperfoto/Getty Images)