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Solar power has great potential, but it is estimated that it only suplies less than 0.02% of the world's total energy used. There are many competing technologies, including 14 types of photovoltaic cells, such as thin film, monocrystalline silicon, polycrystalline silicon, and amorphous cells, as well as multiple types of concentrating solar power. It is too early to know which technology will become dominant.
The earliest significant application of solar cells was as a back-up power source to the Vanguard I satellite in 1958, which allowed it to continue transmitting for over a year after its chemical battery was exhausted. The successful operation of solar cells on this mission was duplicated in many other Soviet and American satellites, and by the late 1960s, PV had become the established source of power for them. Photovoltaics went on to play an essential part in the success of early commercial satellites such as Telstar, and they remain vital to the telecommunications infrastructure today.
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Your brain is wired to learn a language!
If you've ever watched TV or a movie and seen an American actor rapidly speak a foreign language like they've been doing it their whole lives, you've probably wished you could do it too. Whether you believe it or not, you can: Your brain is already wired to learn a language in 10 days. You just need to activate it.
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A panic attack is a sudden episode of intense fear that develops for no apparent reason and that triggers severe physical reactions. Panic attacks can be very frightening. When panic attacks occur, you might think you're losing control, having a heart attack or even dying.
You may have only one or two panic attacks in your lifetime. But if you have had several panic attacks and have spent long periods in constant fear of another attack, you may have a chronic condition called panic disorder. Panic attacks were once dismissed as nerves or stress, but they're now recognized as a real medical condition. Although panic attacks can significantly affect your quality of life, treatment is very effective.
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November 9, 1934 – December 20, 1996
"A Galaxy is Composed of Gas and Dust and Stars - Billions Upon Billions of Stars." From the "Cosmos" television series and his frequent appearances on "The Tonight Show Starring Johnny Carson," Sagan became associated with both, the catchphrase "billions and billions" and the question: "Who Speaks for the Earth?"
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A year ago, when chemotherapy stopped working against his leukemia, William Ludwig signed up to be the first patient treated in a bold experiment at the University of Pennsylvania's Abramson Cancer Center. Mr. Ludwig, then 65, a retired corrections officer from Bridgeton, N.J., felt his life draining away and thought he had nothing to lose. He entered into an experimental treatment. Tiny magnetic beads force the larger T-cells to divide before they are infused into the patient.
Doctors removed a billion of his T-cells — a type of white blood cell that fights viruses and tumors — and gave them new genes that would program the cells to attack his cancer. Then the altered cells were dripped back into Mr. Ludwig's veins.
