It wasn’t easy. Despite the fact that Stringer often worked under hypnosis to further slow his already slowed time sense, despite the fact that he often fasted for beclads to increase his perception, it still wasn’t easy. The training took weeks or months or teclads, none of which meant much now. Neberdjer, the central control, rotated into night, but Stringer and Valyavar and Barbalan hardly noticed. An entire city lay before Stringer waiting to be explored, but he rarely moved from his desk at the information center while he learned everything he could about the planet he was to save.
He often despaired, often swore to Neberdjer that he would give up. And in these moments, when learning anything seemed hopeless, he would envisage the Time Keeper at his own desk, silver hair draped over a mass of difficult calculations, refusing always to concede defeat until the resistive problem crumbled beneath his onslaught. Then Stringer would sigh, marveling at the older man’s infinite energy, and return to work, still never believing that he and his companions could ever save a planet.
Stringer saw his friends rarely, but he looked forward to the time he could spend with them. On one of these occasions he entered his sleeping quarters, an almost bare room with a couch taken from the information center to serve as a bed, and saw Barbalan sitting there stiffly and breathing heavily. Her skin was shades lighter and infinitely softer now than in the Bannk, almost the only sign that beyond the city was total darkness.
What’s the matter?
Stringer asked as he
approached her.
Barbalan just shook her head absently and blinked her eyes. Stringer, I don’t think I can go on with this.
Stringer, puzzled, stretched out on the couch and pulled her head down on
his chest. With what?
With all of this. I think I am going crazy—
That doesn’t sound like the confident Barbalan I
have always known.
Barbalan sighed deeply. A great failing in my life
is that people always mistake my actions for confidence.
An easy mistake with you, don’t you think?
Barbalan shook her head. I do what I feel should
be done. Mostly I am not confident of the outcome at all, but what does
that have to do with it? I do not act because I am confident but because I
am not afraid to fail. I think about the problem until it is clear that
further thinking will only confuse. Then I stop thinking and do.
Stringer nodded. A great talent, I think, to know
when to stop thinking, and an even greater one to not be afraid to
fail.
It is very simple. But this is not
simple. Neberdjer shows me and Valyavar how to get from here to there. He
says,
These controls won’t fit your hands, so use
these if you want to do this.
I am shown how to operate other devices
and still more. But, Stringer, I don’t even know what any of them do. I
don’t know what Neberdjer is. The devices it shows us might as well be
magic and it a god. It isn’t, is it?
Stringer didn’t laugh. Barbalan, I think I
understand what you are going through. I’m amazed that you’ve been able to
withstand it. Look, at Konndjlan you have clockmakers and scientists,
right?
Yes.
Do you understand what they do?
Some. Not all of it.
Well, I think that what surrounds us is only a
great extension of the work they are doing. I don’t understand it all
myself, but that doesn’t stop me from using it. The point is to accept it
without having to understand it all. Have faith that there is some logic
behind it.
But when Neberdjer says,
Here is a display of the neutrino flux on the inside
of the collection sphere to monitor the decay rate of the black hole,
I
hear words that have no meaning. I don’t even know what a neutrino is. Is
Neberdjer playing games with me? Could you read a book all the way through
that was in a foreign language? I feel as if I am trying to live in a world
that is in a foreign language. Why do I have to be so important all of a
sudden? It was much easier before.
Stringer held her head gently in his hands. Barbalan, listen to me. The only difference between
you and me is that I was brought up in a world where I could believe that
two plus two equals four. I don’t understand why two plus two equals four
any better than you do. I’m just used to the words and concepts floating
around all the time. When somebody hands me a graser and says that it
shoots coherent gamma rays, I don’t balk because I’ve heard the words
before. But I’m just now learning what a coherent gamma ray really is. You
can do it. I’ll help you all I can.
Barbalan smiled faintly and nodded.
But now…for some basics.
Stringer began
unfastening her shirt.
Sometime later, deep in the Patra, Stringer was disturbed by a huge hand on his shoulder. Since there were only two other pairs of hands in all of Neberdjer, it did not take much of a guess to know this was Valyavar.
I think we have something that you’d like to
see. To go?
Yes, and I think I have something you’d like to
know.
I’d not wager that yours is as good as this. Let’s
go.
Valyavar took Stringer beneath the city and pulled him into a room. At the first step Stringer recoiled and dove for the exit; there was no floor in the room and three walls were absent also.
Come on, Stringer,
Barbalan called from the
other side. The floor’s there, really.
Gingerly, Stringer stepped across and found that there was indeed something to walk on.
Now watch.
Barbalan put her hand on a hidden control and the light went out.
Other than not being able to see anything, what am
I supposed to see?
Watch.
Suddenly the sky around him lit up. To his right and to his left were lines, luminous, streaking across the blackness. Farther out were stars; some seemed near, others far and isolated. Still others were arranged in rosettes and pentagons. There were hundreds, thousands, or tens of thousands, creating an artificial heaven beneath their feet.
The inside of Patra-Bannk,
said Valyavar.
Those lines must be some of the tunnels. I wonder
why they’re lit up.
With such a spectacle as this, do you ask for a
better reason, my friend?
The three of them stood quietly for a long time, simply watching and
enjoying the silent peace. Eventually Stringer said, Now I have something to tell you. I think I finally
understand what a stability correction mechanism is.
That means you can fix it?
No, that’s your department. I just think I
understand the problem. And yes, it is quite a problem—one big enough to
destroy this entire planet.
I’ve wondered about it, too. Has something to do
with that black hole? They’re supposed to be powerful things, those holes,
and Neberdjer mentioned tides.
Stringer shook his head, but Valyavar didn’t see this in the dark.
What did you say?
Valyavar asked, not seeing.
I’m sorry, the answer to your question is no. That
object there—do you see that one right below us, that bright orange one,
the size of Two-Bit’s moon? I’ll bet that’s it, or rather the energy
collection sphere around it. Do you believe that the object that is holding
us to the surface of this planet is hardly bigger than the size of this
room? More than twenty-five hundred Two-Bit masses crushed into a ball less
than fifty meters in diameter, crushed into a ball so dense that light
can’t escape from it, or virtually anything else, either. You’re right,
it’s a powerful thing when you get close enough to it. Nearby, as it pulled
you in, it would rip you apart, collapse you to nothing, and stretch you to
infinity all at once. But we’re far enough away from it here. After all, on
the planet’s surface we feel only a little more than one Two-Bit gravity
from it.
So what’s the problem, then?
I’m getting to that. It isn’t a simple matter,
exactly. The problem is that this world is round.…That ball you see lit up,
floating there, is doing exactly that: floating. And there is no reason for
it to stay in the center. Patra-Bannk is a spherical shell built around the
energy collection sphere, built around the small black hole in the center,
right?
The others nodded, unseen.
That’s what causes the whole problem. You see,
because this planet is a spherical shell, the gravitational force it exerts
on anything on the inside cancels out. On the inside of a hollow sphere you
find there isn’t any gravity. Anything on the inside will pretty much float
where it’s put. Neutral stability, Neberdjer calls it. Rings are unstable;
they tend to collide with the central object—
But back to spheres. If there is no gravity on the
inside and things will stay pretty much where put, what is the problem?
Won’t the hole stay centered?
That
pretty much
is
the whole problem. The basic thing to keep in mind is that neutral
stabilities don’t last. Exactly why is a little complicated. Patra-Bannk is
in orbit around a sun. To a very good approximation, the sphere and the
hole travel in the same orbit, everything is fine, and the hole stays
centered. That’s because, according to Neberdjer, an orbit is independent
of the mass of the orbiting body. But suppose the sphere has irregularities
in it: more mountains on one side; mass concentrations here and there. Then
the sphere is no longer really a sphere and slight gravitational forces
appear between parts of the shell and the black hole. A slight additional
problem is caused by the fact that both the hole and Patra-Bannk are
rotating, thus bending slightly, and, again, are no longer spheres. Both
effects cause the black hole to drift relative to the shell.
But the most important
problems are those caused by the tidal forces between Patra-Bannk and the
sun. Because Patra-Bannk is so huge and one side so much closer to the sun
than the other, that side gets attracted to the sun slightly more than the
far side. So Patra-Bannk is bent by
tidal forces,
the same forces
that raise ocean tides. The bending is, to a good approximation,
symmetrical, but not quite. Thus, the planet’s center of mass shifts ever
so slightly. Then the shell and the hole begin to follow slightly different
orbits and the neutral stability is upset.
And we’re still not
through. There are even more tidal force problems. The black hole raised
tidal bulges on the sun which, in turn, exert a force back on the shell and
the hole. These forces tend to circularize the orbits, and synchronize the
rotation period of the planet with its period of revolution around the
sun. This might be why Patra-Bannk is spinning so slowly: Since the control
mechanism broke, it has been slowing down. Anyway, because the
circularization rates for the hole and the shell are slightly different,
the center of mass again is slightly shifted and again the hole drifts a
little. And there is even the possibility that Patra-Bannk could begin to
start resonating and fly apart because of these forces, so you have to be
careful about that too.
The point is, that Patra-Bannk is a very
complicated system. You need some sort of mechanism—a stability-control
mechanism or a centering mechanism—to correct for all these problems and
keep the black hole in the center of the planet.
How is it done?
The two shells are moved slightly to keep the
black hole centered.
Valyavar whistled. Must take a lot of push to move
this monster. Not to mention all the energy needed to keep twenty-five
hundred planets’ worth of planet operating. Where does it come from?
Not as much as you’d think for corrections, but
look. I always wondered why I saw ocean tides on this planet when I didn’t
see any moon. I was just looking in the wrong place.
Coming into view, lit up just for show, was a moon. It moved noticeably quickly, traveling toward them, emerging from the light-streaked darkness of the giant inverted ball beneath their feet.
Fuel enough to run a civilization for a good many
years. A convenient storage place, you must admit. Crumble it up into
little bits, throw it into the hole, and it heats up so much that it
radiates a fair portion of its mass as energy. Throw in your garbage—throw
in anything, for that matter—and before it disappears you’ve put it to its
best advantage. You don’t need oil, coal, uranium, or anything else. Only
the black hole and garbage.
Valyavar was impressed. Where did they get the
black hole?
Stringer shrugged. Neberdjer doesn’t know because
it was here when Neberdjer was born. But it has several likely
mechanisms.
Such as?
Well, black holes are usually formed by
supermassive stars collapsing and crushing themselves out of existence by
the force of their own weight. This one is much too small for that, a
thousand times too small.
I’d think, then, it would have to be
manufactured.
Stringer shook his head. It
might have been, but that seems pretty pointless, at least in the present
state. More energy would be needed to manufacture this one than you could
ever get from it. But in some sense you’re right. You could first make a
very small one, maybe a fraction of a centimeter in diameter. That one,
too, would require more energy to make than could be gotten from it. But
you could use that tiny one as a seed and let it gobble up surrounding
matter until it got to its present state. You could breed your holes.
The other mechanism would be to find one left over
from the big bang, the beginning of the Universe. There might have been a
lot created then, of all sizes. All you have to do is find one.
Valyavar was impressed again. Still, it seems to
me a lot of trouble to go to for a derelict planet.
Unless…
The conclusion was obvious.
Barbalan turned off the sky and switched back on the lights. So, we must fix this…centering mechanism. How long do
we have?
A good question. Maybe it is time to find out.
How long do we have, Neberdjer?
That is unclear. The problem is both intermittent
and spreading. I have been overcompensating for the sensors. You see, the
sensors send me information that tells me exactly where the black hole is,
and I send out correction signals to adjust the position of the
planet. Some of the sensors stop sending me signals, so I must interpolate
from data received by nearby sensors. However, the problem is spreading
erratically. Many of the sensors are now out and the black hole has drifted
dangerously far, thousands of kilometers, setting up unbalanced stresses
and strains on the shell, which I am trying to adjust for.
Stringer nodded; he understood earthquakes.
If this continues to happen, the planet will
ultimately be destroyed. Although my auxiliary units have checked every
possible source of the problem, millions of times, the difficulty has
escaped me. So you must succeed. Do you understand that? You must
succeed.
The three gulped collectively.
I am printing out a list of the faulty correction
centers. For a start, you will visit them and see if you can locate the
problem. Valyavar and Barbalan have been trained to operate what is
necessary.
Stringer took the list that appeared from a slot near his desk. Where are these places?
All over the planet—and elsewhere. The first is
on the energy collection sphere.
We can’t go down there!
Stringer shouted.
Not exactly, but there are other ways.