Balal, who killed Iranian youth Abdolah Hosseinzadeh in a street fight with a knife in 2007, is brought to the gallows during his execution ceremony in the northern city of Nowshahr on April 15, 2014. The mother of Abdolah Hosseinzadeh spared the life of the her son's convicted murderer, with an emotional slap in the face as he awaited execution prior to removing the noose around his neck. (Photo by Araash Khamooshi/AFP Photo/ISNA)

Senator Barack Obama (D-IL) (R) stands in front of Senator Hillary Clinton (D-NY) as they arrive for U.S. President George W. Bush's annual State of the Union speech to a joint session of Congress at the U.S. Capitol in Washington in this January 23, 2007 file photo. Hillary Clinton announced her second run for the presidency on April 12, 2015 starting her campaign as the Democrats' best hope of fending off a crowded field of lesser-known Republican rivals and retaining the White House. (Photo by Larry Downing/Reuters)

A humanoid robot named Kansei, meaning “sensibility” in Japanese, makes a facial expression depicting “happiness”, next to the word “Love” during a demonstration at a laboratory of Meiji University's Robot and Science Institute in Kawasaki, south of Tokyo in this June 4, 2007 file photo. Three-fourths of robot installations over the next decade are expected to be concentrated in four areas: transportation equipment, including the automotive sector; computer and electronic products; electrical equipment and machinery. Labor costs have climbed in countries such as China that have been popular for outsourcing production, while technological advances for robots allow them to be more flexible and perform more tasks. (Photo by Yuriko Nakao/Reuters)

An Zi, is squashed amongst other commuters in a subway train on his way to work in Beijing, China, November 12, 2015. An, a movie producer, moved to Dongsanqi village in Changping this year. His commute to work can take about 2 hours, with transportation costs topping 200 yuan a month, or about a fifth of his monthly rent. (Photo by Jason Lee/Reuters)

Marion (L) and Nikola (R), members of the Sport Saber League, pose with their light sabers in front of the Eiffel tower in Paris, France, November 26, 2015. Three "Star Wars" fans opened the French Academy of the Sport Saber League in September 2015 due to the increase interest for light saber fighting and the upcoming movie "The Force Awakens" which will premier in Paris, December 16th, two days before its worldwide official release. (Photo by Charles Platiau/Reuters)

“Kumbh Mela is a mass Hindu pilgrimage in which Hindus gather at the Ganges river. The normal Kumbh Mela is celebrated every 3 years, the Ardh (half) Kumbh Mela is celebrated every six years at Haridwar and Prayag, the Purna (complete) Kumbh takes place every twelve years, at four places (Prayag (Allahabad), Haridwar, Ujjain, and Nashik). The Maha (great) Kumbh Mela which comes after 12 “Purna Kumbh Melas”, or 144 years, is held at Allahabad.

The last Ardh Kumbh Mela was held over a period of 45 days beginning in January 2007, more than 70 million Hindu pilgrims took part in the Ardh Kumbh Mela at Prayag, and on January 15, the most auspicious day of the festival of Makar Sankranti, more than 5 million participated. The previous Maha Kumbh Mela, held in 2001, was attended by around 60 million people, making it at the time the largest gathering anywhere in the world in recorded history”. – Wikipedia

Photo: Sadhus (holy men) smoke at their camp near the ritual site at Sangam, the confluence of the Ganges, Yamuna and mythical Saraswati rivers during the Ardh Kumbh Mela festival (Half Pitcher festival) January 18, 2007 in Allahabad, India. Millions of Hindu pilgrims have flocked to the largest religious gathering in the world which lasts for 45 days in northern India. The festival commemorates the mythical conflict between gods and demons over a pitcher filled with the “nectar of immortality”. Devotees believe that taking a holy dip in the Ganges at this time washes away their sins and paves the path to salvation. (Photo by Mario Tama/Getty Images)

Workers demonstrate outside the factory of Hua Yang Printing Holdings Co Ltd on October 30, 2007 in Shenzhen of Guangdong Province, China. Over 1,000 workers of the company have blocked the 107 State Highway where the firm is located, to protest against their employer, who owed half a month's salary to the workers. (Photo by China Photos/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)