“NASA's Pathfinder, Pathfinder Plus, Centurion and Helios Prototype were an evolutionary series of solar- and fuel-cell-system-powered unmanned aerial vehicles. AeroVironment, Inc. developed the vehicles under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program. They were built to develop the technologies that would allow long-term, high-altitude aircraft to serve as “atmospheric satellites”, to perform atmospheric research tasks as well as serve as communications platforms”. – Wikipedia

Photo: The solar-electric Helios Prototype flying wing is flies over the Hawaiian islands of Niihau and Lehua during the first solar-powered test flight July 14, 2001 from the U.S. Navy's Pacific Missile Range Facility on Kauai, HI. The 18-hour flight was a functional checkout of the aircraft's systems and performance in preparation for an attempt to reach sustained flight at 100,000 feet altitude later in the summer. (Photo Courtesy of NASA/Getty Images)

Journalists (L) walk along the new Caminito del Rey (The King's Little Pathway) in El Chorro-Alora, near Malaga, southern Spain March 15, 2015. Dubbed by many media outlets as the world's scariest pathway, the three-kilometre long pathway, which was built at about 100 metres (330 ft) above the gorge of Los Gaitanes between the years of 1901 and 1905, was closed in 2001 after five people died. A new walkway has then been built over the old walkway and will open to the public on March 28, 2015. (Photo by Jon Nazca/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)

A girl types on a computer as she demonstrates the interior of the new Volvo S90 during the Auto China 2016 auto show in Beijing April 25, 2016. (Photo by Damir Sagolj/Reuters)

The head of a 276-kilogram bluefin tuna that was auctioned for 207 million Japanese yen (about 1.3 million U.S. dollars), which was bought jointly by sushi restaurant operator Onodera Group and wholesaler Yamayuki, is carried by a sushi chef at an Onodera sushi restaurant after the first tuna auction of the New Year in Tokyo, Japan on January 5, 2025. (Photo by Issei Kato/Reuters)

The National Geographic Photo Ark is a travelling exhibition of photographer Joel Sartore’s quest to create a photo archive of biodiversity around the world. So far, Sartore has captured studio portraits of more than 6,000 species – a number that he hopes to double. On 1 July, the ark will open at Melbourne zoo – the first time it has been exhibited in the southern hemisphere. More than 50 portraits will be on display, including many of Australian endangered animals being protected by programs at the zoo itself. These captions have been edited from text supplied by Melbourne zoo. Here: Barking owl. (Photo by Joel Sartore/National Geographic Photo Ark/The Guardian)

Toyoda Gosei Co Ltd's personal mobility concept airbag car "Flesby" is displayed at the 44th Tokyo Motor Show in Tokyo, Japan, October 28, 2015. (Photo by Yuya Shino/Reuters)

A woman poses for a photographer (not pictured) as a man sits next to her in downtown Catania, Italy April 20, 2016. (Photo by Tony Gentile/Reuters)