similar reasons。 We seem to crave privilege； merited not by our work； but by our birth； by the mere fact that； say； we are humans and born on Earth。 We might call it the anthropocentric—the 〃human…centered〃—conceit。 This conceit is brought close to culmination in the notion that we are created in God's image： The Creator and Ruler of the entire Universe looks just like me。 My； what a coincidence How convenient and satisfying！ The sixth…century…B。C。 Green philosopher Xenophanes understood the arrogance of the perspective：
〃The Ethiopians make their gods black and snub…nosed； the Thracians say theirs have blue eyes and red hair 。 。 。 Yes； and if oxen and horses or lions had hands； and could paint with their hands； and produce works of art as men do； horses would paint the forms of the gods like horses； and oxen like oxen 。 。 。〃
Such attitudes were once described as 〃provincial〃—the naive expectation that the political hierarchies and social conventions of an obscure province extend to a vast empire posed of many different traditions and cultures； that the familiar boondocks； our boondocks； are the center of the world。 The country bumpkins know almost nothing about what else is possible。 They fail to grasp the insignificance of their province or the diversity of the Empire。 With ease； they apply their own standards and customs to the rest of the planet。 But plopped down in Vienna； say； or Hamburg； or New York； ruefully they recognize how limited their perspective has been。 They bee 〃deprovincialized。〃
Modern science has been a voyage into the unknown； with a lesson in humility waiting at every stop。 Many passengers would rather have stayed home。
CHAPTER 3 THE GREAT DEMOTIONS
＇One philosopher＇ asserted that he knew the whole secret 。 。 。 ＇H＇e surveyed the two celestial strangers from top to toe； and maintained to their faces that their persons； their worlds； their suns； and their stars； were created solely for the use of man。 At this assertion our two travelers let themselves fall against each other； seized with a fit of 。 。 。 inextinguishable laughter。
VOLTAIRE； MICROMEGAS。 A PHILOSOPHICAL HISTORY （1752）
In the seventeenth century there was still some hope that； even if the Earth was not the center of the Universe； it might be the only 〃world。〃 But Galileo's telescope revealed that 〃the Moon certainly does not possess a smooth and polished surface〃 and that other worlds might look 〃just like the face of the Earth itself。〃 The Moon and the planets showed unmistakably that they had as much claim to being worlds as the Earth does—with mountains； craters； atmospheres； polar ice caps； clouds； and； in the case of Saturn； a dazzling； unheard…of set of circumferential rings。 After millennia of philosophical debate； the issue was settled decisively in favor of 〃the plurality of worlds。〃 They might be profoundly different from our planet。 None of them might be as congenial for life。 But the Earth was hardly the only one。
This was the next in the series of Great Demotions； downlifting experiences； demonstrations of our apparent insignificance； wounds that science has； in its search for Galileo's facts； delivered to human pride。
WELL； SOME HOPED； even if the Earth isn't at the center of the Universe； the Sun is。 The Sun is our Sun。 So the Earth is approximately at the center of the Universe。 Perhaps some of our pride could in this way be salvaged。 But by the nineteenth century； observational astronomy had made it clear that the Sun is but one lonely star in a great self…gravitating assemblage of suns called the Milky Way Galaxy。 Far from being at the center of the Galaxy； our Sun with its entourage of dim and tiny planets lies in an undistinguished sector of an obscure spiral arm。 We are thirty thousand light years from the Center。
Well； our Milky Way is the only galaxy。 The Milky Way Galaxy is one of billions； perhaps hundreds of billions of galaxies notable neither in mass nor in brightness nor in how its stars are configured and arrayed。 Some modern deep sky photographs show more galaxies beyond the Milky Way than stars within the Milky Way。 Every one of them is an island universe containing perhaps a hundred billion suns。 Such an image is a profound sermon on humility。
Well； then； at least our Galaxy is at the center of the Universe。 No； this is wrong too。 When the expansion of the Universe was first discovered； many people naturally gravitated to the notion that the Milky Way was at the center of the expansion； and all the other galaxies running away from us。 We now recognize that astronomers on any galaxy would see all the others running away 。 from them； unless they were very careful； they would all conclude that they were at the center of the Universe。 There is； in fact； no center to the expansion； no point of origin of the Big Bang； at least not in ordinary three…dimensional space。
Well； even if there are hundreds of billions of galaxies； each with hundreds of billions of stars； no other star has planets。 If there are n other planets beyond our Solar System； perhaps there's no other life in the Universe。 Our uniqueness might then be saved。 Sing planets are small and feebly shine by reflected sunlight； they're hard to find。 Although applicable technology is improving wit breathtaking speed； even a giant world like Jupiter； orbiting the nearest star； Alpha Centauri； would still be difficult to detect。 Iii our ignorance； the geocentrists find hope。
There was once a scientific hypothesis—not just well received but prevailing—that supposed our solar system to have formed through the near collision of the ancient Sun with another star； the gravitational tidal interaction pulled out tendrils of sunstuff that quickly condensed into planets。 Since space is mainly empty and near stellar collisions most rare； it was concluded that few other planetary systems exist—perhaps only one； around that other star that long ago co…parented the worlds of our solar system。 Early in my studies； I was amazed and disappointed that such a view had ever been taken seriously； that for planets of other stars； absence of evidence had been considered evidence of absence。
Today we have firm evidence for at least three planets orbiting an extremely dense star； the pulsar designated B1257＋12； about which I'll say more later。 And we've found； for more than half the stars with masses like the Sun's； that early in their careers they're surrounded by great disks of gas aid dust out of which planets seem to form。 Other planetary systems now look to be a cosmic monplace； maybe even worlds something like the Earth。 We should be able； in the next few decades； to inventory at least the larger planets； if they exist； of hundreds of nearby stars。
Well； if our position in space doesn't reveal our special role； our position in time does： We've been in the Universe since The Beginning （give or take a few days）。 We've been given special responsibilities by the Creator。 It once seemed very reasonable to think of the Universe as beginning just a little before our collective memory is obscured by the passage of time and the illiteracy of our ancestors。 Generally speaking； that's hundreds or thousands of years ago。 Religions that purport to describe the origin of the Universe often specify—implicitly or explicitly—a date of origin of roughly such vintage； a birthday for the world。
If you add up all the 〃begats〃 in Genesis； for example； you get an age for the Earth： 6；000 years old； plus or minus a little。 The universe is said to be exactly as old as the Earth。 This is still the standard of Jewish； Christian； and Moslem fundamentalists and is clearly reflected in the Jewish calendar。
But so young a Universe raises an awkward question： How is it that there are astronomical objects more than 6；000 light…years away？ It takes light a year to travel a light…year； 10；000 years to travel 10；000 light…years； and so on。 When we look at the center of the Milky Way Galaxy； the light we see left its source 30；000 years ago。 The nearest spiral galaxy like our own； M31 in the constellation Andromeda； is 2 million light…years away； so we are seeing it as it was when the light from it set out on its long journey to Earth—2 m