Oct 1, 2014

On This Day - Oct. 1

331 BCE - Alexander the Great defeats Darius III of Persia at the Battle of Gaugamela. 




Photo of the Day
In the News



Quote of the Day
"Life is composed of exquisite moments, and the rest is shadows of them". --T.E. Hulme

Song of the Day




Film of the Day
Director - Lewis Milestone
Starring - Louis Wolheim, Lew Ayres




Wiki of the Day
An atomic clock is a clock device that uses an electronic transition frequency in the microwave, optical, or ultraviolet region[2] of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element. Atomic clocks are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, to control the wave frequency of television broadcasts, and in global navigation satellite systems such as GPS.
The principle of operation of an atomic clock is not based on nuclear physics, but rather on atomic physics and using the microwave signal that electrons in atoms emit when they change energy levels. Early atomic clocks were based on masers at room temperature. Currently, the most accurate atomic clocks first cool the atoms to near absolute zero temperature by slowing them with lasers and probing them in atomic fountains in a microwave-filled cavity. An example of this is the NIST-F1 atomic clock, one of the U.S.'s national primary time and frequency standards.
The accuracy of an atomic clock depends on two factors. The first factor is temperature of the sample atoms—colder atoms move much more slowly, allowing longer probe times. The second factor is the frequency and intrinsic width of the electronic transition. Higher frequencies and narrow lines increase the precision.


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