Contributions
• Sokolov-Ternov effect • Hamilton's principal function • Hamilton's characteristic function • Experimental observation of Hawking radiation • Particle number operator* • Self-organization in biology* • Aleksandr Chudakov • Alexey Andreevich • A. P. Balachandran • Igor Ternov • Mark Trodden • Stanislav Mikheyev • Alexei Smirnov* • Shamil Asgarov • Seifallah Randjbar-Daemi • Habil Aliyev • Ahmad Bakikhanov • Aşık Khanlar • Suleyman Valiyev • Heino Finkelmann • Tom Lubensky • Lubna al-Hussein • Sheylanli tribe • Sheylanli • Boyat • Ashaghy Aylis • Agbash • International Liquid Crystal Society • British Liquid Crystal Society • International Centre for Theoretical Physics* • ANS Group of Companies • ANS TV • ANS ChM • Khudafarin Bridges • Azerbaijan Time • Yemen Türküsü • Jujalarim • Föppl–von Kármán equations

* Didn't create but significantly contributed

Picture of the day

• 
  Male
• 
  Female

The Alpine ibex (Capra ibex), also known as the steinbock, is a species of goat that lives in the Alps of Europe. Its closest living relative is the Iberian ibex. Alpine ibex have brownish-grey coats and sharp hooves adapted to steep, rough terrain. Found at elevations as high as 3,300 metres (10,800 feet), they are active throughout the year, primarily feeding on grass in open alpine meadows. Adult males, which are larger than females, segregate from them for most of the year, coming together only during the breeding season, when they fight for access to the females using their long horns. The Alpine ibex has been successfully reintroduced to parts of its historical range, but all individuals living today descend from a population bottleneck of fewer than 100 individuals from Gran Paradiso National Park in Italy. The species has few predators and is not threatened, but it has very low genetic diversity. These Alpine ibex, a male in winter and a female in summer, were photographed at Creux du Van in Switzerland.

Today's featured article

The siege of Baghdad took place in early 1258 when a large army under Hulegu, a prince of the Mongol Empire, attacked Baghdad, the capital of the Abbasid Caliphate. Hulegu had been sent by his brother, the Mongol khan Möngke, to conquer Persia. He expected Baghdad's ruler, Caliph al-Musta'sim, to reinforce his army, but this did not happen. Provoked by al-Musta'sim's arrogance, Hulegu decided to overthrow him. The Mongol army routed a sortie by flooding their camp, and besieged the city. After Mongol siege engines breached Baghdad's walls, al-Musta'sim surrendered on 10 February, and was later executed. The Mongol army pillaged the city for a week. The number of deaths was inflated by epidemics of disease, but Hulegu estimated his soldiers killed 200,000. The siege, often seen as the end of the Islamic Golden Age, was in reality not era-defining: Baghdad later prospered under Hulegu's Ilkhanate. (Full article...)