an suppose。”
the analogy that is usually given for explaining the curvature of space is to try to imaginesomeone from a universe of flat surfaces； who had never seen a sphere； being brought toearth。 no matter how far he roamed across the planet’s surface； he would never find an edge。
he might eventually return to the spot where he had started； and would of course be utterlyconfounded to explain how that had happened。 well； we are in the same position in space asour puzzled flatlander； only we are flummoxed by a higher dimension。
just as there is no place where you can find the edge of the universe； so there is no placewhere you can stand at the center and say： “this is where it all began。 this is the centermostpoint of it all。” we are all at the center of it all。 actually； we don’t know that for sure； wecan’t prove it mathematically。 scientists just assume that we can’t really be the center of theuniverse—think what that would imply—but that the phenomenon must be the same for allobservers in all places。 still； we don’t actually know。
for us； the universe goes only as far as light has traveled in the billions of years since theuniverse was formed。 this visible universe—the universe we know and can talk about—is amillion million million million （that’s 1；000；000；000；000；000；000；000；000） miles across。 butaccording to most theories the universe at large—the meta…universe； as it is sometimescalled—is vastly roomier still。 according to rees； the number of light…years to the edge ofthis larger； unseen universe would be written not “with ten zeroes； not even with a hundred；but with millions。” in short； there’s more space than you can imagine already without going tothe trouble of trying to envision some additional beyond。
for a long time the big bang theory had one gaping hole that troubled a lot of people—namely that it couldn’t begin to explain how we got here。 although 98 percent of all thematter that exists was created with the big bang； that matter consisted exclusively of lightgases： the helium； hydrogen； and lithium that we mentioned earlier。 not one particle of theheavy stuff so vital to our own being—carbon； nitrogen； oxygen； and all the rest—emergedfrom the gaseous brew of creation。 but—and here’s the troubling point—to forge these heavyelements； you need the kind of heat and energy of a big bang。 yet there has been only onebig bang and it didn’t produce them。 so where did they e from？
interestingly； the man who found the answer to that question was a cosmologist whoheartily despised the big bang as a theory and coined the term “big bang” sarcastically； as away of mocking it。 we’ll get to him shortly； but before we turn to the question of how we gothere； it might be worth taking a few minutes to consider just where exactly “here” is。
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2 WELE TO THE SOLAR SYSTEMAS
tronomers these days can do the most amazing things。 if someone struck a matchon the moon； they could spot the flare。 from the tiniest throbs and wobbles of distant starsthey can infer the size and character and even potential habitability of planets much tooremote to be seen—planets so distant that it would take us half a million years in a spaceshipto get there。 with their radio telescopes they can capture wisps of radiation so preposterouslyfaint that the total amount of energy collected from outside the solar system by all of themtogether since collecting began （in 1951） is “less than the energy of a single snowflakestriking the ground；” in the words of carl sagan。
in short； there isn’t a great deal that goes on in the universe that astronomers can’t findwhen they have a mind to。 which is why it is all the more remarkable to reflect that until 1978no one had ever noticed that pluto has a moon。 in the summer of that year； a youngastronomer named james christy at the u。s。 naval observatory in flagstaff； arizona； wasmaking a routine examination of photographic images of pluto when he saw that there wassomething there—something blurry and uncertain but definitely other than pluto。 consulting acolleague named robert harrington； he concluded that what he was looking at was a moon。
and it wasn’t just any moon。 relative to the planet； it was the biggest moon in the solarsystem。
this was actually something of a blow to pluto’s status as a planet； which had never beenterribly robust anyway。 since previously the space occupied by the moon and the spaceoccupied by pluto were thought to be one and the same； it meant that pluto was much smallerthan anyone had supposed—smaller even than mercury。 indeed； seven moons in the solarsystem； including our own； are larger。
now a natural question is why it took so long for anyone to find a moon in our own solarsystem。 the answer is that it is partly a matter of where astronomers point their instrumentsand partly a matter of what their instruments are designed to detect； and partly it’s just pluto。
mostly it’s where they point their instruments。 in the words of the astronomer clarkchapman： “most people think that astronomers get out at night in observatories and scan theskies。 that’s not true。 almost all the telescopes we have in the world are designed to peer atvery tiny little pieces of the sky way off in the distance to see a quasar or hunt for black holesor look at a distant galaxy。 the only real network of telescopes that scans the skies has beendesigned and built by the military。”
we have been spoiled by artists’ renderings into imagining a clarity of resolution thatdoesn’t exist in actual astronomy。 pluto in christy’s photograph is faint and fuzzy—a piece ofcosmic lint—and its moon is not the romantically backlit； crisply delineated panion orbyou would get in a national geographic painting； but rather just a tiny and extremelyindistinct hint of additional fuzziness。 such was the fuzziness； in fact； that it took seven yearsfor anyone to spot the moon again and thus independently confirm its existence。
one nice touch about christy’s discovery was that it happened in flagstaff； for it was therein 1930 that pluto had been found in the first place。 that seminal event in astronomy waslargely to the credit of the astronomer percival lowell。 lowell； who came from one of theoldest and wealthiest boston families （the one in the famous ditty about boston being thehome of the bean and the cod； where lowells spoke only to cabots； while cabots spoke onlyto god）； endowed the famous observatory that bears his name； but is most indeliblyremembered for his belief that mars was covered with canals built by industrious martians for purposes of conveying water from polar regions to the dry but productive lands nearer theequator。
lowell’s other abiding conviction was that there existed； somewhere out beyond neptune；an undiscovered ninth planet； dubbed planet x。 lowell based this belief on irregularities hedetected in the orbits of uranus and neptune； and devoted the last years of his life to trying tofind the gassy giant he was certain was out there。 unfortunately； he died suddenly in 1916； atleast partly exhausted by his quest； and the search fell into abeyance while lowell’s heirssquabbled over his estate。 however； in 1929； partly as a way of deflecting attention awayfrom the mars canal saga （which by now had bee a serious embarrassment）； the lowellobservatory directors decided to resume the search and to that end hired a young man fromkansas named clyde tombaugh。
tombaugh had no formal training as an astronomer； but he was diligent and he was astute；and after a year’s patient searching he somehow spotted pluto； a faint point of light in aglittery firmament。 it was a miraculous find； and what made it all the more striking was thatthe observations on which lowell had predicted the existence of a planet beyond neptuneproved to be prehensively erroneous。 tombaugh could see at once that the new planetwas nothing like the massive gasball lowell had postulated； but any reservations he or anyoneelse had about the character of the new planet were soon swept aside in the delirium thatattended almost any big news story in that easily excited age。 this was the first american…discovered planet； and no one was going to be distracted by the thought that it was really justa distant icy dot。 it was named pluto at least partly because the first two letters made amonogram from lowell’s initials。 lowell was posthumously hailed everywhere as a genius ofthe first order； and tombaugh was largely forgotten； except among planetary astronomers；who tend to revere him。
a few astronomers continue to think there may be a planet x out there—a real whopper；perhaps as much as ten times the size of jupiter； but so far out as to be invisible to us。 （itwould receive so little sunlight that it would have almost none to reflect。） the idea is that itwouldn’t be a conventional planet like jupiter or saturn—it’s much too far away for that；we’re talking perhaps 4。5 trillion miles—but more like a sun that never quite made it。 moststar systems in the cosmos are binary （double…starred）； which makes our solitary sun a slightoddity。
as for pluto itself； nobody is quite sure how big it is； or what it is made of； what kind ofatmosphere it has； or even what it really is。 a lot of