Tuesday, April 25, 2006

Red Shift: Miracle with quasars

Red Shift, antagonist with gearShifts, are wonder of the modern discovery. This is a shift observed towards longer wavelengths in spectral lines of some or many celestial objects. Lastime when I was revamping my knowledge of astro-physics, red shift got deep in, consequently this brief in here from Encarta-2006 goes like:

Red Shift, shift towards longer wavelengths observed in the lines of spectra of celestial objects. The American astronomer Edwin Powell Hubble, in 1929, linked the red shift observed in spectra of galaxies to the expansion of the universe. Hubble suggested that this red shift, called the cosmological red shift, is caused by the Doppler effect and hence indicates the speed of recession of the galaxies—and, by using Hubble's law, the distances of the galaxies.

A second mechanism for the red shift is the gravitational red shift, also called the Einstein shift. It was predicted by Albert Einstein's general relativity theory, according to which periodic processes are slowed down in a gravitational field. The Einstein shift is noticeable in the spectra of compact massive stars, such as white dwarfs.

The large red shifts observed in quasars are generally believed to be cosmological. Some scientists, however, believe that the red shifts in quasars are caused by the Einstein shift or by another unknown mechanism.

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