Selfie picture shows Swiss pioneer Bertrand Piccard during the last leg of the round the world trip with Solar Impulse 2 over the Arab peninsula July 25, 2016. (Photo by Jean Revillard/Bertrand Piccard/Reuters/SI2)

Australian performers illuminated with real clocks titled “The Time Minder” attend a media preview of the Night Festival in Singapore on August 23, 2017. Singapore's arts and heritage district will be transformed into Singapore largest outdoor performing arts festival to celebrate its 10th year edition Night Festival from August 24 to 26. (Photo by Roslan Rahman/AFP Photo)

People take part in a snowball fight in front of the Colosseum covered by snow during a snowfall in Rome, Italy, 26 February 2018. Media reports on 26 February state that extreme cold weather is forecast to hit many parts of Europe with temperatures plummeting to a possible ten year low. (Photo by Angelo Carconi/EPA/EFE)

Meropidae are seen on a rock in Van in Turkey on March 03, 2018. (Photo by Ali Ihsan Ozturk/Anadolu Agency/Getty Images)

A colourful morning sunrise on Christmas Eve at Victoria Tower on Castle Hill, West Yorkshire, England on December 24, 2017. The history of human activity on the Castle Hill goes back over 4000 years. The site was developed as an iron age hill fort, surrounded by defensive ditches and ramparts. In the Middle Ages there was a castle on the hill, of which the well remains. The present tower was built to commemorate Queen Victoria's Diamond Jubilee of 1897. (Photo by Charlotte Graham/ZUMA Wire/Rex Features/Shutterstock)

The six-months-old female koala cub holds on to the back of zoo keeper Lena at the zoo in Duisburg, Germany, 23 October 2015. The yet unnamed baby weighs 580 grams. (Photo by Roland Weihrauch/EPA)

A couple watches the sunset over a sea of fog covering the Geneva Lake from Chardonne, Switzerland, 28 December 2015. (Photo by Jean-Christophe Bott/EPA)

A Russia-backed rebel looks at the flag covered body of an Ukrainian serviceman in Debaltseve, Ukraine, February 20, 2015. The struggle for the strategic rail hub, Debaltseve, a sleepy town with a pre-war population of 25,000 people, left the town in ruins and became one of the darkest pages in the ongoing conflict in eastern Ukraine, which has already killed more than 6,000 people. (Photo by Vadim Ghirda/AP Photo/File)