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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
swell-mobsman
  • A member of the swell-mob; a genteelly clad pickpocket. Sometimes mobsman.
Use of the word 'swell-mobsman' dates at least to the early 1800s.