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I / A Journey to the Center of the Milky Way
                                                       . . . Thoughts,
              Which ten times faster glide than the sun's beams. . . .
                                                        -- Shakespeare

Our Sun and its planets lie in the environs of the Milky Way Galaxy.
    To go to the center of the galaxy would require navigating a 
distance of some thirty-thousand light-years.  Such a journey lies far 
beyond the technological capacity of our species in this century; 
interstellar distances are vast, the energy required to traverse them 
enormous.  Some say we shall never be able to do it.  Others say we 
might.  No one expects that we shall do it soon.
    Yet we can make the trip today, aboard the ship of the 
imagination.  This may seem like mere daydreaming, but dreams have 
preceded our earlier journeys, as when our forebearers contemplated 
oceanic horizons in the days before we mastered the seas.  And the 
sights to be seen during such a journey need not be _pure_ 
imagination; we have learned enough about the galaxies to predict in 
general terms what we might hope to see if we traveled through them.
    If we need further encouragement, let us consider the remarkable 
accommodation of science to fantasy represented by the time-dilation
effect in Einstein's special theory of relativity.  The theory, 
verified in many an experiment, tells us that the passage of time 
slows down dramatically aboard a spaceship that is accelerated to 
velocities approaching that of light.  (The speed of light itself can 
never be attained, it adds.)  We can spend energy to buy time. 
    Owing to this effect a starship able to maintain an acceleration 
equal to the force of gravity here on Earth could reach the center of 
our galaxy, thirty-thousand light-years distant, in under twenty-five 
years of on-board time.  Neighboring galaxies could be achieved in 
less than thirty years, and gulfs separating clusters of galaxies 
crossed in perhaps a decade longer.  So let us imagine ourselves 
aboard such a ship, and see where it might take us.
    The ship's appointments may be left to the preference of each 
passenger.  We might envision a giant vessel complete with baseball 
teams, string quartets, a hardwood copse and trout pound, and a crew 
of thousands selected from backgrounds sufficiently varied to ensure 
that things will never quite run smoothly.  Or a more modest cruise 
starship, with a tiny nightclub, an indefatigable recreation director, 
many outside cabins with portholes.  Or a military starships, all 
drums, boots, and salutes.  Each to his own.  There is ample room in 
the imagination for imaginary starships, as there is in the cosmos for
real ones.
    The day of our departure is sad, its farewells permanent.  We 
travelers will be able to take advantage of the time-dilation effect.  
Friends and families who stay at home will not.  They will have been 
dead for tens of thousands of years by the time we reach the center of 
our galaxy.  Together we sing the anthem of interstellar explorers 
everywhere, a song of final farewell.  Then we depart.
    The early years of the voyage pass uneventfully while our ship 
accumulates velocity.  Years pass before we can celebrate having 
attained the distance of the nearest extrasolar neighbor, Alpha 
Centauri, a little over four light-years out.  The Sun is now but a 
dot of light in the constellation Taurus.  Soon it will become 
difficult to identify the dim little Sun in the sky.
    In the years that follow, the stars crawl across the sky, slowly 
distorting the constellations we have known on Earth until most are 
unrecognizable.  Our course takes us along the plane of our galaxy 
directly toward its center.  Our view is composed of stars and of the 
clouds of dust and gas that lie in the spaces between the stars.  The 
interstellar clouds are mostly dark, but when we encounter one of the 
spiral arms of our galaxy, we find them lined with bright nebulae -- 
regions where newly-formed stars have lit up the surrounding clouds --
and the sight of these glowing shoals cheers us as we speed on.
    Many a flower of these starry pastures could hold our attention -- 
the high-density dwarf stars, neutron stars and black holes, the 
endlessly-varied matchups of multiple stars, the variable and flare 
stars, and the billions of ordinary stars like our Sun, not to mention 
their planets.  But we must hurry on.
    After decades of travel, the interstellar clouds at last fall 
away.  Ahead lies the central region of the galaxy, an elliptical 
cosmos of stars glowing through the relatively-unsullied spaces with 
fantastic clarity.  The color of this great egg is that of a bloodied 
yolk, the red and orange light of old stars that have been burning 
steadily for billions of years.  Behind us the inner portions of the 
dusty disk hang like the walls of a canyon; thousands of light-years 
down one wall we can discern the elbow joint where one spiral arm 
emerges from the central regions and begins a winding path that will 
eventually take it out past our sun.
    We plunge into the central regions.  Country dwellers on our first 
visit downtown, we are surprised at the congestion of the stars, their 
hustling pace.  Their light is as warm in hue as torch-light.  They 
pursue jitterbug orbits that seem hurried by the standards of the 
solar region, and the clearances among them are narrow.  Yet all
conduct their affairs without colliding.
    Our destination is the nucleus of the galaxy.  We can see its 
brilliant lamp ahead.  What will we find there?  An enormous star 
cluster, sitting like a clutch of diamonds at the center of the 
galactic diadem?  The ominous warren of a black hole, a creature out 
of the Inferno rather than the Paradiso?
    It is just at this point of the voyage of our imagination that we 
must turn away.  We know that our galaxy has a nucleus, but do not yet 
know enough about it to be able to describe it.  The captain orders 
our course altered, and our ship describes a sweeping arc that takes 
it up and out of the plane of the galaxy.  Ahead lies intergalactic 
space.


II / A Journey Out of Our Galaxy

We speed out of the Milky Way in our imaginary spaceship like divers 
ascending from the depth of the sea.  The myriad bright stars which 
had been our companions now diminish and number, then fall away behind 
us.  In their stead we are left with the scattered stars of the 
galactic halo.  Most are dim dwarves, remnants of stars that formed
more than ten billion years ago, when the infant galaxy was more 
nearly spherical and had not yet collapsed to its present, flattened 
shape.  A few "runaways," younger stars ejected out of the plane of 
the galaxy by quirk gravitational encounters, flit among these elders 
like bright tropical fish venturing from their accustomed shallows.
    To exit a galaxy is no handy matter, but eventually we attain a 
sufficient remove to be able to view the galaxy spread out below us.  
The central bulge of galaxy looms directly under us, its shape and 
color like that of a hill of sand.  The galactic disk surrounds it, a 
monumental tangle stretching to the celestial horizons.  The glowing 
clouds of the spiral arms wend their way out through the disk, often 
obscured by intervening dark clouds, like a river cutting through a 
jungle.  Here and there dark tattered towers are reared up out of the 
welter of the disk, masses of interstellar gas and dust that have been 
heaved out of the galactic plane in the course of the collisions of 
clouds and the explosions of stars.
    We climb further and our view of the galactic disk improves.  The 
time comes when we can discern the Sun, a little yellow star nestled 
in the embrace of the out reaches of one of the spiral arms, a dot of 
light barely visible through the ship's telescope.  Here long ago was 
our home.
    The globular star clusters make for spectacles close at hand.  
From time to time one of these chandeliers of stars passes abeam of 
our ship.  We are tempted to stop and explore its hundreds of 
thousands of stars, but we are bound for territories more remote.
    When the outermost of the globular clusters along our course has 
fallen away aft, we celebrate having left our home galaxy behind.  The 
choice of demarcation is rather arbitrary, for we still lie well 
within the gravitational domain of our galaxy.  But we feel the need 
of a cheering toast, for we are embarking upon the awful gulf of some 
of the emptiest space known in a universe that is mostly space.  Out 
galaxy hangs behind us like a gong, its slowly diminished starlight 
painting shadows across our ship from aft, while ahead yawns the void, 
its only light the pearlescent background haze of a universe of 
galaxies.
    Our eyes seek out landmarks lest we be seized by vertigo.  Well of 
to port hangs the most evident galaxy in sight after the Milky Way, 
the Large Magellanic Cloud.  Beyond it we can make out the less-
orderly patches of starlight that comprise the Small Magellanic Cloud 
and the Sculptor and Fornax dwarf galaxies.  To starboard lie two 
other dwarves, the little Leo I and Leo II galaxies.  We steer for 
them.
    Seven hundred fifty hundred-thousand light-years separate the 
Milky Way from the Leo pair.  Our activities during this phase of the 
voyage are those suitable to a long haul.  We carve crimshaw, repair 
our gear, read all the back issues of the _National Geographic._  Down 
below the stokers shovel whole planets' worth of fuel into the engines 
to maintain our acceleration.  Leo I and II slowly grow in the forward 
viewports.
    Now we can look back upon most of the Local Group in a single 
gaze.
    The Milky Way Galaxy, though still imposing, has shrunk until it 
covers less than ten-degrees of sky; we can eclipse it with an 
outstretched hand.  A little train of satellite galaxies stretches off 
to one side of the Milky Way.  In the same part of the sky but far 
deeper in space hangs the spiral galaxy M33, and near it the majestic 
M31, dominant galaxy of the Local Group.  Beyond them we can glimpse 
the elliptical galaxy Maffei I and its spiral companion Maffei II.
    Will we in our little ship feel a last pang of leave-taking as we 
say good-bye to this corner of the universe, with its trillions of 
suns, in the light of one of which we came into being?  Or has this 
already become too strange and remote to retain any of the warmth of 
home?  We rocket past the Leo I dwarf galaxy and head out of the Local
Group.


III / A Journey Through Intergalactic Space

We accelerate out of the Local Group.  As our speed edges ever closer 
to that of light, time on board passes ever more slowly by comparison 
to that of the universe at large.  Seen through our eyes, the cosmos 
up ahead conducts its affairs with crazy haste.  Planets whirl in 
their orbits.  Stars are formed and die between breakfast and supper.  
We speed on.
    We have entered upon the deep spaces that intervene between groups 
of galaxies.  The familiar spirals of Andromeda and the Milky Way have 
shrunk until smaller than a fingernail at the distance of an 
outstretched hand.  Free from nearby distractions, we are left for 
once in the sole and equitable company of everything -- all the 
galaxies -- floating in space in all directions.  We while away our 
time by examining them through the ship's telescope.
    What we see reminds us of home.
    Back on Earth, we recall, all the things of nature shared a deep 
kinship.  Objects as dissimilar as snowflakes and stones proved to be
made up of combinations of atoms drawn from a common pool of elements.  
Living things as diverse as a boll weevil and a human being were found 
not only to be made from the same common stock of atoms, but to have 
been built to the design of a single sort of molecule, that of DNA.  
All the creations of our planet could be understood as having been 
formed within the parameters of a few fundamental principles of 
physics.  Yet for all their kinship, no two things could be found 
exactly alike -- no two identical snowflakes or stones, boll weevils 
or people.  Nature's way seemed to be to try everything without ever 
doing the same thing twice.
    Now we find this way at work among the galaxies as well.  All 
function within the purview of basic physical principles.  Each 
galaxy, for example, must move through space along the trajectory 
dictated by its gravitational interaction with its neighbors and with 
the matter of the universe at large; no galaxy can pick up its skirts 
and scamper away in violations of those laws.  And the material 
kinship of galaxies runs deep.  All the stuff of all of them is made, 
so far as we can see, from various mixtures of the same sorts of atoms 
that we came to know back on Earth.
    Indeed, order and regularity are sufficiently manifest in the 
appearance of galaxies that we can sort them into categories.
    About half the galaxies we see are spiral in form, like the Milky 
Way.  Some among our crew take chauvinistic pride in learning that 
their home galaxy is the sort most widespread in the cosmos.  Others 
more dispassionate point out that since most stars are to be found in 
spiral galaxies, the odds are that any given species evolving on a 
given planet circling a star will find itself in a spiral, as did we.
    About one-quarter of the prominent galaxies are ellipticals.  Here 
the stars are arranged not in the flattened disk characteristic of 
spirals, but within a more nearly-spherical volume of space.  At first 
the ellipticals may look rather bland to our spiral-accustomed eyes, 
but as we study them further we come to appreciate their symmetry of 
form, their purity of content (ellipticals contain little interstellar 
gas and are made chiefly of stars and space), and the magnificence of 
their most exemplary representatives, which number among the largest 
galaxies in the universe.
    Scattered among the many other galaxies we find the SO, or 
lenticular, galaxies, much like spirals in form but lacking spiral 
arms.  They combine some of the quantities of both spirals and 
ellipticals.
    A few percent of the major galaxies are irregular.  Their virtues 
are those of individuality, even of eccentricity.  In their splayed
and contorted forms they offer us endlessly-varied perspectives on the 
star fields and nebulae they contain, like translucent sea-creatures, 
whose interiors and exteriors may at once be seen.
    Dwarf galaxies abound, most of the ellipticals and irregulars.  
Frequently we find them ranged around larger galaxies.  If they seem 
negligible by comparison, we need consider that even a dwarf contains 
millions of stars.
    If no two galaxies are identical, no two stars or planets 
identical, then how can we imagine the variety manifest in the 
universe on a planetary level?  Is there to be found across the whole 
sweep of creation a single insect, flower, raindrop or mud puddle that 
somewhere has a twin?  And where thoughtful life has arisen, to what 
degree do its imaginings converge with that of other intelligences, in 
consequence of nature's predilection for order and form, and to what 
degree do they diverge, in consequence of nature's predilection for 
variety?
    _What is the cosmology of imagination?_ we wonder, as our 
imaginary ship wanders on.


IV / A Journey Between Interacting Galaxies

A high-point in our intergalactic journey comes when we steer our ship 
between a pair of interacting galaxies.  We have chosen to fly through 
the relatively-narrow corridor separating two major spirals.  They 
constitute a binary system, two galaxies bound together 
gravitationally as are the Milky Way Galaxy and the Andromeda Galaxy.  
For most of their history they have stayed well apart, but now they 
are passing within only a couple of galactic diameters of each other, 
and it as at this dramatic stage in their interaction that we are to 
come between them. 
    The first mate is nervous, he points out that if we could see 
where we are headed in terms of Einstein's space-time continuum, we 
would perceive that our course lies along a precariously-narrow ridge 
between two enormous wells created by the gravitational potential of 
the two galaxies.  "We are steering between Scylla and Charybdis," he 
warns, "or rather, Charybdis and Charybdis, for we'll have whirlpools 
to either side."
    The galaxies are passing at an orientation that brings them almost 
face-on to each other, like a pair of cymbals.  From a distance we see 
them edge-on.  As the months pass and we draw closer, our perspective 
makes them appear to swing open like a pair of doors.  The doors do
not open evenly, but remain somewhat closer together near the top, 
where the relative inclination of the galaxies to each other has 
brought them closest together.  Luminous tendrils bridge the gap 
between them there.  Soon we will be amid the spectacle. 
    Thin clouds of hydrogen gas pervade the intergalactic space 
surrounding the two galaxies, and as we plunge through these their 
friction produces a sustained high-pitched wail from the ship's hull.  
To ward off nervousness we take solace in determinism:  It is 
comforting to reflect that the cymbals cannot choose to clash when we 
pass between them, but will continue to follow the orbits dictated by 
Newton's and Einstein's laws.  We have watched the projected course of 
the pair many times in computer simulation -- a do-si-do, the two 
galaxies turning sharply around their common center of gravity and 
then parting, a hundred-million years from now.  We ought to be able 
to sail between them without mishap.  Still, we keep a cautious eye on 
our course; none among us wants us to attempt to be the first to fly 
nearly at the speed of light through a spiral galaxy _edgewise._ 
    To further comfort ourselves we discuss interacting galaxies in 
general.  We remind ourselves that they are not rare.  All galaxies, 
we reassure one another, may be said to be interacting, in that all 
respond to the general gravitational field of the universe, to which
millions of galaxies contribute.  Didn't all the galaxies come from an 
undifferentiated soup of matter that permeated the universe long ago?  
And wasn't their formation a story of vortexes arising from the 
primordial soup, condensing to form the pairs, groups and clusters of 
galaxies we see today?  And isn't the structure of galaxies, which we 
find so lovely a sight, but the visible message written by the 
invisible hand of these gravitational interactions?
    There have been many close interactions of galaxies in the past, 
some perhaps involving the Milky Way and the Andromeda spiral, and the 
galaxies survived them in good order.  They were merely twisted, 
distorted, their disks distended, their nuclei banked into fire, 
millions of their stars blasted into space. . . . Whole galaxies 
wrenched out of shape. . . .
    We fall silent.  The ship's hull moans.
    Ultimately we find ourselves between them.  One spiral galaxy 
hangs to port, the other to starboard; two celestial wheels, ourselves 
at the axle.  Their starlight flooding through the ports bathes the 
interior of our ship in a light such as none before us has known.
    We view the spectacle from the overhead observation room, a 
transparent bubble that the ship's designers whimsically modeled after 
the domed railroad passenger cars once popular in North America.  We
turn out the interior lights and look above us to view the parts of 
the spirals where their mutual inclination has brought the disks 
closest together.
    There the intergalactic gap is bridges by luminous tendrils that 
hang far above us like vines in an arbor.  We can see that they are 
composed of gas and millions of stars being stripped from the lesser 
of the spiral galaxies and transferred to the more massive.
    "A stellar caravan," remarks the first mate.  "'The dogs; the 
caravan moves on.'"
    We gag the first mate with an antimacassar, and resume watching, 
in silence, the transactions of galaxies.
    The stars of a globular cluster flash past at close quarters, 
frightening us all.  Amid screams, someone thinks to ungag the first 
mate.  He bids us not be afraid.  Our course is taking us through the 
outskirts of one of the globular clusters that belongs to the halo of 
one of the galaxies, he shouts.  Stars are flashing by the windows 
like balls from a Roman candle.  He had intended to warn us, he 
shouts.
    Still, we are quick to descend the ladder.  It is days before 
anyone goes back up there.
    Weeks pass and the twin galaxies crawl away aft.  We welcome the
sight of the dark intergalactic spaces we once had feared.


V / A Journey Through the Local Supercluster

Our old ship has gone far.  We have edges so close to the speed of 
light that sometimes we feel we have become like light, fleet and 
insubstantial, velocity itself our only home.  Decades have passed on 
board.  There have been deaths and births, happiness and sadness, 
success and failure -- in short, decades of life.  The string quartet 
broke up years ago.  The cook has grown grumpy from the ebbing of both 
praise and blame.  Scholars complain about the limitations of the 
ship's vast library.  We who set out on this journey when so young 
have become the elders.  Occasionally we talk of putting in at a 
planet like Earth, near a star like the Sun, in a galaxy like the 
Milky Way, there to make a new start.  But we are going so fast that 
just to decelerate would take the work of many years.  So we fly on, 
like light.
    Where previously we studied the form of galaxies, now our 
attention is drawn to the form of clusters of galaxies.  Here we find 
order, intelligibility, a deep coherence underlying the diversity of
the universe.
    Clusters of galaxies, we see, display varieties of forms within a 
general pattern.  The most straightforward way to arrange them is 
along a continuum in terms of structure, with the most regular 
clusters of galaxies toward one end and the most seemingly-chaotic 
toward the other.  The regular clusters are spherical or elliptical in 
shape, their galaxies concentrated at the center of the cluster.  The 
irregular clusters, at the other end of our spectrum, are shambling 
and clumpy, often taking the form of extended chains of galaxies, they 
show little or no concentration toward the center.  Intermediate 
between the two extremes are clusters that display some of the 
characteristics of both regular and irregular clusters; in some 
instances these consist of a central elliptical concentration 
surrounded by a halo or disk of more thinly-distributed galaxies.
    The forms of the clusters unavoidably call to mind the analogous 
forms of galaxies themselves:  To some degree spherical clusters 
resemble spherical galaxies, irregular clusters resemble irregular 
galaxies, and intermediate clusters are not wholly-unlike spiral 
galaxies, with their mixture of characteristics of both types.  Our 
curiosity about this parallel deepens when we learn that the sort of 
galaxies predominant in each cluster is closely-related to the form of
the cluster itself.  The spherical clusters have the largest plurality 
of elliptical and SO galaxies, while irregular clusters are dominated 
by spirals there and have relatively-few ellipticals and SOs.  And 
what spiral galaxies there are in spherical clusters tend to 
segregated toward the out regions, or halo, of the cluster -- much as 
globular clusters occupy halos surrounding elliptical galaxies.  The 
evidence seems compelling that the form taken on by a galaxy cannot 
have been determined solely by forces internal to that galaxy, but 
must reflect something of the milieu of the cluster to which it 
belongs.
    Having taken this step up the hierarchical ladder, we are 
inclined to take an additional step and inquire whether clusters of 
galaxies belong to still-larger associations.  Here again our 
curiosity is rewarded.  Many of the clusters prove to be members of 
superclusters -- clusters of clusters of galaxies.
    Clusters of galaxies typically occupy volumes of space with 
diameters of roughly thirty- or forty-million light-years.  The 
diameters of supercluster are ten times greater, on the order of 
three hundred to four hundred-million light-years.  Even on this scale 
we find evidence of order and consistency.  Some of the superclusters 
consist of a central zone where clusters of galaxies are relatively-
concentrated, surrounded by a flattened disk of more thinly-
distributed clusters, an arrangement at least faintly-reminiscent of 
the structure of spiral galaxies.  And possible superclusters, too, 
are rotating.
    Now when we look back to our home galaxy we may view it in a 
supergalactic context.  The Local Group is a small cluster of galaxies 
located in the outskirts of the Local Supercluster.  Many of our 
neighboring small clusters -- the M81 Group, the M101 Group, the 
Sculptor Group -- are likewise members of the Local Supercluster.  The 
supercluster consists of a concentrated core, designating the Virgo 
Cluster, and an extended halo to which the Local Group and its 
neighboring groups belong.
    A few of us gather in the observation dome after dinner.  We trace 
out for one another the structure of the Local Supercluster spread out 
before us, as once long ago we mapped the disk of our home galaxy.  We 
talk of the old mystery that closes the circle of life -- that the 
incomprehensible thing about nature, in Einstein's phrase, is our 
ability to comprehend it.  However fast we go or far we travel, we 
have not fled one micron from this mystery.  We can feel its breath, 
touch its face; it is our breath, our face.
    The first mate stand and quotes a sentence from Carl Friedrich von
Weizacker, a physicist and philosopher of science who lived millions 
of years ago on Earth.  "All our thinking about nature must 
necessarily move in circles or spirals, for we can only understand 
nature if we think about her, and we can only think because our brain 
is built in accordance with nature's laws."
    The captain runs a hand through his white hair.
    "Spirals," he says.  "Our thinking expands as it circles.  It 
moves in spirals."


VI / A Journey Toward the Edge of the Universe

Now comes an end to our journeying.  Millions of years have passed on 
the planet of our birth; decades aboard.  Clusters of galaxies pass 
abeam and are recorded in the logbooks as once we recorded the passing 
of stars and later of galaxies.  The time has come to turn the ship 
around and decelerate until it can be brought to rest on a planet.  We 
owe this much to the younger generations, who never saw the Earth and 
have known only this life of ceaseless exploration.  But for us elders 
it is the beginning of the end.  Deceleration will take a long time, 
and we cannot hope to live to see the day when our crew will step out
onto planetary soil, under planetary skies.
    On the day when the deceleration order is to be given, we few 
survivors of the original crew gather in the observation dome fr a 
last look at the cosmos while our ship is at its peak velocity.  Few 
visit the observation dome any longer -- to swim among the galaxies is 
unremarkable to those who have known no other surroundings -- but to 
our old eyes the view remains awesome and a little frightening.  The 
time-dilation effect having sped up the workings of the spiral 
galaxies that lie ahead of us by a factor of several million, they 
spangle with the light of millions of newly-formed stars, and still 
more brilliant supernovae flash and crackle across them by the 
hundreds.
    The captain rises with difficulty and proposes a toast.  "To the 
unattainable goal," he calls, his glass raised toward the dome and to 
the galaxies in array.  "To the edge of the universe."
    "Hear, hear," we respond.  How often we have talked about the edge 
of the universe, mapped it with our telescopes, saluted it with this 
same toast.  The phenomenon is as familiar to us as our names.
    When we look across space we are also looking back in time.  At 
distances of up to a few billion light-years, we see galaxies as they 
were recently in cosmic history, looking much like those that lie
nearby.  At distances of five- to ten-billion light-years we are 
seeing younger galaxies whose light set out on its journey when the 
universe was about half its present age.  At distances approaching 
fifteen-billion light-years what we see are the brilliant beacons of 
galaxies being formed; they pour out huge quantities of energy, by 
comparison to which the births of stars in the contemporary cosmos 
seem but a bland resemblance, like fire-crackers set off to celebrate 
the anniversary of a revolution.  At these distances we are seeing the 
denizens of a young cosmos, all light and noise.
    The captain, projecting into cosmic time the tendency of the old 
to aggrandize the historical, sometimes speaks of events fifteen-
billion years ago as if he had been alive then, rather than having 
only witnessed them vicariously by telescope.  "That was when galaxies 
were _galaxies,"_ he likes to say.  "The juice squeezed out of ten-
thousand stars in a year.  Stars blowing up with every tick of the 
clock.  Energy aplenty -- you could singe your hair just by steeping 
outdoors -- and galaxies crowded so close together there was scarcely 
room to pass between them.  A pilot had to keep on his toes in those 
days.
    If we search with our telescopes for galaxies more distant than 
those at some fifteen-billion light-years, we see nothing.  At these
distances we are looking back to a time before the primordial stuff of 
the universe had cooled sufficiently to congeal into stars and 
galaxies.  That is what we mean by the edge of the universe -- a 
temporal threshhold marking the point in cosmic history before which 
darkness prevailed.  It is an edge not of space but of time, and to 
visit it we would need not our spaceship, but a timeship able to 
travel into the past.
    "To the unattainable goal."  The first mate echoes the toast.  
"Faster than the galaxies."
    This is a traditional riposte, one that refers to the expansion of 
the universe.  The farther away a given galaxy we observe, the faster 
it is receding from us (or us from it, as you prefer) as it takes part 
in the universal expansion.  In all directions we see galaxies on the 
threshhold of the universe hurtling away from us, trains out of the 
past running on rails of the past, their lights the markers of the 
unattainable past.
    The captain orders the ship brought about.
    "Faster than the galaxies," the first mate repeats.  "Fast as 
light."  A mathematical witticism contained in special relativity 
prescribes that the fuel bill to accelerate any particle of matter to 
the speed of light would be infinite, would include the conversion of
everything -- itself included -- into energy.
    "Maybe the young folks are right to want to stop," the captain 
says.  "They probably figure that otherwise we'd go on forever, that 
we'd burn up the whole universe in order to cross it.  They figure 
we'd be firing up the boilers with tables and chairs when we'd left 
not one star shining in the sky."
    "Don't worry, Captain," says the mate.  "There will always  be 
space travelers."
    "Always have been," the captain replies.  "We were space travelers 
before we ever left Earth.  See that galaxy over there?"  He extends a 
gaunt finger.  "When _they_ look at the Milky Way, don't they see it 
speeding away at ten per cent the speed of light?  And that galaxy 
over there, don't they see it moving at twenty per cent the speed of 
light?  And those millions of galaxies off near the edge, don't they 
see our galaxy moving almost fast as light itself, just as we see 
them?  Aren't we teetering on the edge of the universe, so far as 
they're concerned?  Isn't it _our_ part of the universe that's young 
and blinding brilliant, so says the old light that left here so long 
ago and only now is reaching them? 
    "We are all space travelers, gentlemen.  We are.  They are.  All 
are."
    The galaxies wheel across the sky as the ship is turned end-for-
end.
    "Let us show a light," says the captain.  He produces a kerosene-
burning ship's lantern, a treasured antique.  He lights the wick, 
replaces the glass, and holds the brass lantern up to the windows of 
the dome.  Its yellow flame mingles with the light of the galaxies.
    "In a moment this flame will belong to our past," he says.  "But 
it belongs to _their_ future.  Maybe one day an astronomer in one of 
those galaxies whose telescope is pointed the right way at the right 
time will catch this flicker from our little lantern.  Just a couple 
of million miles' worth of light falling into the telescope, gone in 
a couple of seconds."
    The captain blows out the lantern, sets it on the floor, takes 
the con and gives the order to fire the engines.
    "It's not so bad to be old, gentlemen," he says.  "We're part of 
the future of most of the universe."

                                                    -- Timothy Ferris,
                                            an excerpt from _Galaxies_



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