sábado, 29 de diciembre de 2012
lunes, 24 de diciembre de 2012
True stories about Santa Claus
Left: Santa Claus depicted as guarding the skulls of children taken as hunting trophies. According to some sources the pile grew so large it became Korvatunturi, Santa's mountain home.
Right: The archaic Santa Claus didn't spare the rod.
Publicado por Terra en 19:28
jueves, 20 de diciembre de 2012
lunes, 17 de diciembre de 2012
viernes, 14 de diciembre de 2012
sábado, 1 de diciembre de 2012
Argentavis magnificens: Magnificent Argentine Bird
With a wingspan of nearly 7 metres, Argentavis magnificens is the largest known bird to ever fly. It lived 6 million years ago in the open plains of Argentina and the Andes mountains, and it is related to modern-day vultures and storks—but with feathers the size of Samurai swords. It rivals some light aeroplanes in size, but it is believed to have flown on the wind more like a glider, soaring to speeds of 240 km/h. But with its massive flight muscles and enormous wings, the behemoth bird weighed 70 kilograms, so flapping its wings was not enough to achieve lift-off. “Birds are commonly compared with aircraft, but in reality helicopters are a better analogy,” says Sankar Chatterjee of Texas Tech University. Chatterjee and his team came to understand the bird’s flight by collaborating with a retired aeronautical engineer, inputting measurements from fossils into a computer program designed to study flight performance in helicopters. They determined that Argentavis must have run downhill into a headwind in order to become airborne, just like hang gliders, then gained elevation by circling inside columns of air known as “thermal elevators.” It would have easily hitched a ride a few kilometres up without even flapping its wings—then by just gliding to adjoining thermals, it would have been able to travel hundreds of kilometres per day
Publicado por Terra en 3:18