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Tick-Tock Atomic Clock

Modern navigators rely on atomic clocks. Instead of old-style springs or pendulums, the natural resonances of atoms -- usually cesium or rubidium -- provide the steady 'tick' of an atomic clock. The best ones on Earth lose no more than one second in millions of years. Sailers, truck drivers, soldiers, hikers, and pilots ... they all rely on atomic ...

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AtomicClock
Geology

Antarctica and Climate Change

Because of its influence on world weather and climate patterns, Antarctica lies at the heart of the debate on climate change and has become the premier location in which to study the effects of global ... Continue reading

AntarcticaandClimateChange
Geology

A Great Sunset Takes A Few Clouds

Although the twilight sky can certainly inspire awe even when it is devoid of clouds, the most memorable sunsets tend to be those with at least a few clouds. Clouds catch the last red-orange rays of ... Continue reading

AGreatSunsetTakesAFewClouds
Biology

The Blood-brain Barrier

In the human brain, there are approximately 400-425 miles of capillaries. Because the brain is basically a small neurochemistry factory, which makes our behavior a function of its interior chemical ... Continue reading

BloodBrain
Biology

Grizzly Bear, (Ursus arctos horribilis)

A symbol of America's wildlands, the grizzly or brown bear is one of the largest North American land mammals. The grizzly bear's historic range covered much of North America from the mid-plains ... Continue reading

GrizzlyBear

Subrahmanyan Chandrasekhar

SubrahmanyanChandrasekharNASA's premier X-ray observatory was named the Chandra X-ray Observatory in honor of the late Indian-American Nobel laureate, Subrahmanyan Chandrasekhar (pronounced: su/bra/mon'/yon chandra/say/kar). Known to the world as Chandra (which means 'moon' or 'luminous' in Sanskrit), he was widely regarded as one of the foremost astrophysicists of the twentieth century. Chandra immigrated in 1937 from India to the United States, where he joined the faculty of the University of Chicago, a position he remained at until his death. He and his wife became American citizens in 1953.

Trained as a physicist at Presidency College, in Madras, India and at the University of Cambridge, in England, he was one of the first scientists to combine the disciplines of physics and astronomy. Early in his career he demonstrated that there is an upper limit - now called the Chandrasekhar limit - to the mass of a white dwarf star. A white dwarf is the last stage in the evolution of a star such as the Sun. When the nuclear energy source in the center of a star such as the Sun is exhausted, it collapses to form a white dwarf. This discovery is basic to much of modern astrophysics, since it shows that stars much more massive than the Sun must either explode or form black holes.

Chandra was a popular teacher who guided over fifty students to their Ph.D.s. His research explored nearly all branches of theoretical astrophysics and he published ten books, each covering a different topic, including one on the relationship between art and science. For 19 years, he served as editor of the Astrophysical Journal and turned it into a world-class publication. In 1983, Chandra was awarded the Nobel prize for his theoretical studies of the physical processes important to the structure and evolution of stars. According to Nobel laureate Hans Bethe, 'Chandra was a first-rate astrophysicist and a beautiful and warm human being. I am happy to have known him.' 'Chandra probably thought longer and deeper about our universe than anyone since Einstein,' said Martin Rees, Great Britain's Astronomer Royal.