The extremely rare Kelvin-Helmholtz cloud formation lurking in the skies over Northumberland in North East England on December 5, 2023. The distinctive formation gets its name from scientists Lord Kelvin and Hermann von Helmholtz who studied the physics behind the rare cloud. (Photo by Ian Davison/South West News Service)

A Gnawa traditional group performs in the city of Essaouira on December 14, 2019, to celebrate the decision of adding the Gnawa culture to UNESCO's list of Intangible Cultural Heritage of Humanity. Gnawa culture, a centuries-old Moroccan practice rooted in music, African rituals and Sufi traditions, was added to UNESCO's list of Intangible Cultural Heritage of Humanity earlier in the week. Gnawa refers to a “set of musical productions, fraternal practices and therapeutic rituals where the secular mixes with the sacred”, according to the nomination submitted by Morocco. Often dressed in colourful outfits, Gnawa musicians play the guenbri, a type of lute with three strings, accompanied by steel castanets called krakebs. (Photo by Fadel Senna/AFP Photo)

The lightest material ever made has been produced by a team of scientists in China, a Chinese university announced.

The sun bear (Ursus malayanus), also known as the honey bear, is a bear found primarily in the tropical rainforest (the dense lowland forests) in Southeast Asia; North-East India, Bangladesh, Myanmar, Thailand, Laos, Cambodia, Vietnam, Southern China, Peninsular Malaysia, and the islands of Sumatra and Borneo.

Elena Chernyshova's vision of Norilsk, Russia, the northernmost city in the world, is a series of surprises by which she extracts otherworldly beauty from ugly realities. Here: 2013. A woman is visible through a narrow passageway between two buildings. Norilsk's urban spaces were designed to shorten distances around large developments and give residents maximum protection from arctic winds. (Photo by Elena Chernyshova)

Roped up climbers leave the summit of Breithorn at 4,164 metres (13,661 feet) on the ridge marking the border with Switzerland (left) and Italy in the Alpine resort of Zermatt August 4, 2014. Switzerland will vote on November 30 on an initiative from the group Ecopop which proposes a cap on the number of immigrants. The group says it is motivated by concerns about a lack of living space exerting too much pressure on the land and natural resources, rather than by opposition to foreigners. (Photo by Denis Balibouse/Reuters)

A member of the Air Force's Wings of Blue Parachute Demonstration Team salutes as he jumps out of an aircraft, during the opening ceremony of Aviation Nation 2017 Nellis Air and Space Expo at Nellis Air Force Base, Nev., November 10, 2017. (Photo by Senior Airman Kevin Tanenbaum/Reuters/U.S. Air Force)