LONDON - JUNE 04: A piece entitled “Entrance into wood” by Elke Krystufek goes on show at The Royal Academy Summer Exhibition on June 4, 2008 in London. In it's 240th year, the exhibition displays a wide range of recent work by both established and emerging artists. 10,000 artists submitted work for selection this year. (Photo by Peter Macdiarmid/Getty Images)

“Contrails (short for “condensation trails”) or vapour trails are artificial clouds that are the visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets or, if the air is cold enough, tiny ice crystals”. – Wikipedia

Photo: An airplane leaves a vapor trail as it flies in front of he moon on January 17, 2007 above Hanover, Germany. (Photo by Alexander Hassenstein/Getty Images)

A man dressed in traditional clothes tries to pull his opponent over the table at the 40th Alpine Country Championships in Fingerhakeln_finger wrestling_ in Woernsmuehl, Germany, Thursday, May 25, 2017. Competitors battled for the title in this traditional rural sport where the winner has to pull his opponent over a marked line on the table. (Photo by Matthias Schrader/AP Photo)

Food affected villagers cross flood waters through a bamboo bridge in the flood affected Morigaon district of Assam state, India, 05 July 2016. Continuous rain since last couple of days inundated six districts of Assam effecting more than 100 thousand people in the second wave of floods in Assam state. (Photo by EPA/Stringer)

A migrant labourer brushes his teeth in front of a scrapped helicopter model in Mumbai, India, April 13, 2016. (Photo by Danish Siddiqui/Reuters)

Gunfire was brought to the steps of President Truman's Washington home, Blair House, as two assassins tried to kill the chief executive, November 1, 1950. One of the gunmen, Oscar Collazzo of New York, lay wounded at the bottom of Blair House's front steps after the president's police guard had finished their work, at the cost of one guards' life, Dec. 9, 1950. The second gunman was killed. (Photo by Harvey Georges/AP Photo)

Milena Jami whips her llama to win the first place in the a race for children of ages seven and eight at the Llanganates National Park, Ecuador, Saturday, February 8, 2020. Wooly llamas, an animal emblematic of the Andean mountains in South America, become the star for a day each year when Ecuadoreans dress up their prized animals for children to ride them in 500-meter races. (Photo by Dolores Ochoa/AP Photo)

A sadhu (Hindu holy man) smokes marijuana using a “chillum”, a traditional clay pipe, as a holy offering during the Hindu festival “Maha Shivaratri” in Kathmandu on February 21, 2020. (Photo by Prakash Mathema/AFP Photo)