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X-Ray Astronomy
2004-10-19 04:45:44

X-Ray Astronomy -- Although the more energetic X-rays (E > 30 keV) can penetrate the air at least for distances of a few meters (they would never have been detected and medical X-ray machines would not work if this was not the case) the Earth's atmosphere is thick enough that virtually none are able to penetrate from outer space all the way to the Earth's surface. X-rays in the 0.5 - 5 keV...

Word of the Day
  • an ornament or knob in the shape of a flower
  • In architecture, a floral ornament; specifically, the large conventional flower usually placed in the center of the abacus of a Corinthian capital or classic ceiling-caisson; also, the floreated termination of a Gothic finial.
[ "The word 'fleuron' comes from French."]