... During millennium two, humanity continually redefined its concept of "Universe": first as spheres centered on the Earth, in mid-millennium as the Solar System, a few centuries ago as the Galaxy, and within the last century as the matter emanating from the Big Bang. ... The Dust and Ion Tails of Comet Hale Bopp . ... Since it peaked on the other side of the Earth's orbit, however, the comet appeared only brighter than any comet in two decades. ... NGC 1850: Gas Clouds and Star Clusters . ...