The Night Sky

Awake! for Morning in the Bowl of Night
Has flung the Stone that puts the Stars to Flight.
Omar Khayyam's Rubaiyat (12th century Persian Astronomer)

The night sky is our window on the Universe. It stretches above our heads like a giant bowl. Accordingly, it is called the celestial sphere. The motions proceed in cycles ranging from the daily to tens of thousands of years. A cycle familiar to all is that of the annual calendar.

Planets dance among the stars and the atmosphere itself provides a wonderful array of colors and phenomena. Some of these phenomena, such as sunsets, are quite common; while others, such as the green flash or glories are much rarer.

For astronomers, the earth's atmosphere can be quite a nuisance; it distorts the light of celestial objects and absorbs many parts of their spectra. For wavelengths outside the atmospheric wavelength "windows", astronomers use spacecraft, such as the Hubble Space Telescope or the International Ultraviolet Explorer, to extend the spectral regions that can be examined.

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