Sometimes we forget how recently we Earthlings thought our planet was the center of the universe, which up until the 17th century ended at Saturn and used the "fixed" stars as a mere decorative backdrop. It was only in 1610 -- barely 400 years ago -- that Galileo looked at the heavens through a telescope, glimpsed their teeming infinity and figured that Copernicus might be right about Earth's place in the scheme of things.
Since then, our knowledge of the universe has expanded exponentially. At first, the discovery of additional planets beyond the seven that had been known since antiquity caused terrific excitement. When Keats famously compared his feelings about Chapman's translation of Homer with the thrill felt by "some watcher of the skies/ When a new planet swims into his ken," he would have had in mind William Herschel's discovery of Uranus in 1781, 14 years before Keats was born. In those days, such a find evidently resonated for decades.
But the pace soon picked up. By the end of the 20th century, the number of known major bodies in the solar system alone had jumped to more than 70 -- and astronomers were at the same time peering far beyond their own backyard, to what they like to call the very edges of the universe. So big was the window opened by the Hubble Space Telescope, in particular, that the momentous quickly became the routine. When scientists announced last year that they could now see so far into space they were actually looking back in time, in fact almost as far back as the Big Bang, the public yawned.