Browsing 190 - 200 results of 361 programs for subject - General Science
Why do the hands on clocks go "clockwise?" Seems like a circular definition, but if you looked closely at sundials in the northern hemisphere, you'd notice that the shadow of the sun moves around the sundial in a "clockwise" direction. This was adopted by clock-makers and became the standard we know today.
In the southern hemisphere, the sun's shadow moves around the dial in the opposite direction, so if clocks had been invented there, our watches would move the other way. Our intrepid Exploratorium team shares experiences from their visit to Shackleton's hut. This hut is at Cape Royds, where Shackleton mounted an expedition to the South Pole and made a first ascent of Mt. Erebus.
We talk to photographer John Weller, who spent the austral summer 2008 scuba diving under the ice in Antarctica. The air is so dry here at McMurdo that anything that gets charged, stays charged. Moist air quickly discharges objects because the water in the air picks up charge from an object and quickly flies away, taking charges with it. This does not happen here. We are constantly getting shocks from our clothing, our bedding and when we exit vehicles. Geneticist Mark Stoneking discusses a special type of genetic material called mitochondrial DNA gets passed directly from mother to child. Largely unchanged from generation to generation, this genetic material gives researchers a way to track populations back in time. Evolutionary geneticist Ed Green discusses the key questions researchers hope to answer by analyzing the Neanderthal genome. Anthropologist Tanya Smith explains that invisible microstructure inside teeth creates a durable record of life history, including events such as birth, illness, famine, stress, and death. Anthropologist Jean-Jacques Hublin explains that unlike teeth, bones undergo a lifelong process called remodeling, in which they are constantly being destroyed and recreated. Anthropologist Philipp Gunz explains the process of virtual fossil reconstruction, a technique that can reverse the damage done to fossils by time and the elements. Anthropologist Katerina Harvati explains the rare convergence of circumstances that are necessary for the discovery of a fossil specimen.