tRO amazing truck a matiest tant starster and even potential ability of plas muote to be seen—plas so distant t it ake us o get telescopes ture ion so preposterouslyfaint t total amount of energy collected from outside tem by all of togeting began (in 1951) is “less triking the words of Carl Sagan.

        In s, t a great deal t goes on in t astronomers ’t findo reflect t until 1978no one iced t Pluto    year, a youngastronomer named James Cy at tory in Flagstaff, Arizona, ine examination of pograpo ain but definitely oto. sulting acolleague named Robert on,    w    was a moon.

        And it    just any mooive to t, it    moon in tem.

        tually someto Pluto’s status as a pla,    anyo    to be one and t meant t Pluto was mucem, including our own, are larger.

        Noural question is ook so long for ao find a moon in our oem. t it is partly a matter of    trumentsand partly a matter of ruments are desigo detect, and partly it’s just Pluto.

        Mostly it’s ruments. In tronomer ClarkC people t astronet out at nigories and s t’s not true. Almost all telescopes very tiny little pieces of tao see a quasar or    for black    a distant galaxy. telescopes t ss t by tary.”

        e ists’ renderings into imagining a clarity of resolution tdoes in actual astronomy. Pluto in Cy’s pograp and fuzzy—a piece ofit—and its moon is not tically backlit, crisply delied panion orbyou    in a National Geograping, but rat a tiny aremelyindistinct    of additional fuzziness. Suc, t it took seven yearsfor ao spot tly firm its existence.

        One ouc Cy’s discovery    it aff, for it    Pluto    place. t semi in astronomy o t of tronomer Percival Lo Boston families (tty about Boston being to Cabots, o God), endoory t bears    is most indeliblyremembered for    Mars    by industrious Martians forpurposes of veying er from pions to t productive lands or.

        Loion    ted, someune,an undiscovered nint, dubbed Pla X. Loies ected in ts of Uranus aune, aed t years of    tofind t ain    tunately, least partly exed by , and to abeyance e. ly as a ing attention a), tory directors decided to resume to t end ombaugh.

        tombaugraining as an astronomer, but    and ute,and after a year’s patieed Pluto, a faint point of ligtery firmament. It    all triking tions on ence of a pla beyouneproved to be preombaug oulated, but any reservations    ter of t    aside in tattended almost any big neory in t easily excited age. t Ameri-discovered pla, and no one o be distracted by t t it a distant icy dot. It o at least partly because t tters made amonogram from Loials. Lo order, and tombaugten, except among plaary astronomers,o revere him.

        A feronomers tio t X out ten times ter, but so far out as to be invisible to us. (Ittle sunlig it o reflect.) t it be a ventional pla like Jupiter or Saturn—it’s mucoo far a;alking perrillion miles—but more like a sun t never quite made it. Moststar systems in tarred), wary sun a sligy.

        As for Pluto itself, nobody is quite sure    is, or    is made of, mosp    it really is. A lot of astronomers believe it isn’t a pla all,but merely t object so far found in a zone of galactic debris kno. t ually tronomer named F. C. Leonard in 1930,but tcive    are knos—te past pretty regularly—of s (among t visitors ake) e fromtant Oort cloud, about wly.

        It is certainly true t Pluto doesn’t act muot only is it runty andobscure, but it is so variable in its motions t no one    tell you exactly ury s orbit on more or less to’sorbital patipped (as it    of alig at an angle of seventeen degrees, like t tilted rakiss orbit is sular t for substantialperiods on eacs lonely circuits around t is closer to us tune is. Formost of tuem’s most far-flung pla.

        Only on February 11, 1999, did Pluto return to tside lao remain for t228 years.

        So if Pluto really is a pla, it is certainly an odd o is very tiny: just one-quarter of 1pert as massive as Eart it doop of ted States, it quite y-eigates. t extremely anomalous; it means tour plaary system sists of four rocky inner plas, fassy iants, and a tiny,solitary iceball. Moreover, to suppose t o findotion of space. terCy spotted Pluto’s moon, astronomers began tard t se of ttentively and as of early December 2002 ional traunian Objects, or Plutinos as ternatively called. One, dubbed Varuna, is nearlyas big as Pluto’s moon. Astronomers nos. ty is t many of typically tiveness, of just 4 pert, about t four billion miles away.

        Aly? It’s almost beyond imagining. Space, you see, is justenormous—just enormous. Let’s imagine, for purposes of edification aertai, t to go on a journey by rockets go terribly far—just to tem—but o get a fix on    a smallpart of it we occupy.

        No    be    t, it ake seven o get to Pluto. But of course    travel at anyt speed. e’ll o go at ther more lumbering.

        t speeds yet ac are t, ty-five thousand miles an hour.

        t ember1977)    Jupiter, Saturn, Uranus, aune    o use a “gravity assist” tec    to t in a kind of icversion of “crack t took to reacocross t of Pluto. t if    until January 2006 (entatively sco depart for Pluto) akeadvantage of favorable Jovian positioning, plus some advances iing ake rat allevents, it’s going to be a long trip.

        No to realize is t space is extremely ful. Our solar system may be t trillions of miles, butall tuff in it—ts and tumblingrocks of teroid belt, ets, and otius—fills less trilliont none of tem ely drao scale. Most scs ss ing oer t neigervals—ter giants actually castsrations—but t to get tune iy isn’t just a little bit beyond Jupiter, it’s er—five times farter ter is from us, so far out t itreceives only 3 pert as muc as Jupiter.

        Suces, in fact, t it isn’t possible, in any practical terms, to draem to scale. Even if you added lots of fold-out pages to your textbooks or used a reallylong s of poster paper, you    e close. On a diagram of tem toscale, o about ter of a pea, Jupiter ao    (and about terium, so you be able to see it anyauri, our    star, ten t Jupiter tence, and Pluto o ill be over ty-five feet away.

        So tem is really quite enormous. By time anning, life-giving Sun—o t is little more t star. In suderstand signifit objects—Pluto’s moon, for example—tention.

        In t, Pluto il tions, uo    to tain ty moons. total    y,” about a t t ten years.

        t to remember, of course, is t actually knoem.

        Noice as    Pluto is t Pluto. If you erary, you    trip to tem, and I’m afraid    t. Pluto may be t object marked onscs, but tem does, it isn’t even close to endingt get to tem’s edge until    celestial realm of drifting ets, and    reac cloud for anot ten ter edge of tem, asto is barely one-fifty-the way.

        Of course o tillrepresents a very big uaking for us. A manned mission to Mars, called for by tPresident Bus of passing giddiness, ly dropped    it    $450 billion and probably result in torn to tatters by icles from w be shielded).

        Based on ely no prospectt any    tem—ever. It is just too far.

        As it is, even elescope,    see even into t cloud, so actually kno it is ts existence is probable but entirely ical.

        *About all t    be said    t cloud is t it starts someretco t ofmeasure in tem is tronomical Unit, or AU, representing tance from*Properly called t cloud, it is named for tonian astronomer Ernst Opik, en 1932, and for ter Jan Oort, wions eiger.

        to to is about forty AUs from us, t of t cloud about fiftyt is remote.

        But let’s pretend again t o t cloud. t tnotice is    is out    it’s not eve star in t is a remarkable t t tdistant tiny to s in orbit. It’s not a very strongbond, so ts drift in a stately manner, moving at only about 220 miles ao time some of ts are nudged out of t by some sligational perturbation—a passing star perimes ted into tiness of spaever to be seen again, but sometimes to a long orbit aroundt ts, pass tem. Just occasionally tray visitors smato somet’s oer of tem. It is    is going to take a long time to get tleast—so    for nourn to it mucer in tory.

        So t’s your solar system. And    tem? ell,not deal, depending on    it.

        In t term, it’s not perfect vacuum ever created by    asempty as tiness of iellar space. And t deal of tilyou get to t bit of somet neigauri,ar cluster knoerms, but t is still a imes fartrip to the Moon.

        to reac by spacesake at least ty-five trip you still    be any a lonely clutcars in t no-years of travel. And so it ried to star-he os.

        Just reacer of our oake far loed asbeings.

        Space, let me repeat, is enormous. taars out t speeds approac, tasticallyces for any traveling individual. Of course, it is possible t alien beingstravel billions of miles to amuse ting crop circles in iltsening ts out of some puy in a pickup tru a lonely road in Arizona(t eenagers, after all), but it does seem unlikely.

        Still, statistically ty t t there is good.

        Nobody knoimates range from 100 billionor so to per one of 140 billion or so ot ell namedFrank Drake, excited by suc a famous equation desigocalculate ties.

        Under Drake’s equation you divide tars in a selected portion of tars t are likely to ary systems; divide t by tary systems t could tically support life; divide t by to a state of intelligence; and so on. At eac even    servative inputs tions just in t to be somewhemillions.

        an iing aing t. e may be only one of millions of advancedcivilizations. Unfortunately, space being spacious, taions is reed to be at least t makes it sound. It means for a start t even if to see us in telescopes, tc t leftEart and togs and poom is, ene, and y by rubbing a rodof amber ’s quite a trick. Any message o begin “Dear Sire,” and gratulate us on tery of ance so far beyond us as to be,    beyond us.

        So even if    really alone, in all practical terms ed ts in t large at 10 billion trillion—a number vastlybeyond imagining. But    of space tly scattered. “If ed into te, “t you    rillion trillion.” (t’s 1033, or a one folloy-three zeroes.) “orlds are precious.”

        is good ne in February 1999 ternational Astronomiion ruled officially t Pluto is a pla.
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