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"Sometimes you're damn cold, Lieserl."
Lethe,she thought.People. "No," she said. "I just have a longer perspective than you." She sighed. "Oh,
come on, Mark. Show me the Ring," she said.
The sculpture of string, driving itself into the heart of the scarred galaxy, was not symmetrical. It was in
the form of a rough figure-of-eight; but each lobe of the figure was overlaid with more complex
waveforms a series of ripples, culminating in sharp, pointed cusps.
"Do you see it, Spinner?" Mark asked. "That is a loop of string nearly a thousand light-years wide."
Spinner smiled. "That's not a loop. That's aknot."
"It's moving toward the galactic core at over half the speed of light. It's got the mass of a hundred billion
stars... Can you believe that? It's as massive as a medium-size galaxy itself. No wonder it's cutting this
swathe through the stars; the damn thing's like a scythe, driving across the face of this galaxy."
Louise laughed."A knot. Knot-making is a skill, up there in the forest, isn't it, Spinner? I'll bet you'd
have been proud to come up with a structure like that."
"Actually," Mark said, "and I hate to be pedantic, but thatisn't a knot, topologically speaking. If you
could somehow stretch it out straighten up the cusps and curves you'd find it would deform into a
simple loop. A circle."
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Spinner heard Garry Uvarov's rasp. "And I hate to be a pedant, in my turn, but in fact a simple closed
loopis a knot called the trivial knot by topologists."
"Thank you, Doctor," Louise said drily.
Spinner frowned, peering at the detailed image of the string loop; in the false colors of her faceplate it
was a tracery of blue, frozen against the remote background of the galaxy core. She realized now that
she was looking at one projection of a complex three-dimensional object. Subvocally she called for a
depth enhancement and change in perspective.
The loop seemed to loom toward her, lifting away from the starry background, and the string was
thickened into a three-dimensional tubing, so that she could see shadows where one strand overlaid
another.
The image rotated. It was like a sculpture of hosepipe, rolling over on itself.
Mark commented, "But the string isn't stationary, of course. I mean, the whole loop is cutting through
this galaxy at more than half lightspeed but in addition the structure is in constant, complex motion.
Cosmic string is under enormous tension a tension that increases with curvature and so those loops
and cusps you see are struggling to straighten themselves out, all the time. Most of the length of the string
is moving at close to lightspeed indeed, the cusps are movingat lightspeed."
"Absurd," Spinner heard Uvarov growl. "Nothing material can reach lightspeed."
"True," Mark said patiently, "but cosmic string isn't trulymaterial, in that sense, Uvarov. Remember, it's
a defect in spacetime... a flaw."
Spinner watched the beautiful, sparkling construct turn over and over. It was like some intricate piece of
jewelry, a filigree of glass, perhaps. How could something as complex, asreal as this, be made of nothing
but spacetime?
"I can't see it move," she said slowly.
"What was that, Spinner?"
"Mark, if the string is moving at close to lightspeed how come I can'tsee it? The thing should be
writhing like some immense snake..."
"You're forgetting the scale, Spinner-of-Rope," Mark said gently. "That loop is over a thousand
light-years across. It would take amillennium for a strand of string to move across the diameter of the
loop. Spinner, itis writhing through space, just as you say, but on timescales far beyond yours or mine...
"But watch this."
Suddenly the three-dimensional image of the string came to life. It twisted, its curves straightening or
bunching into cusps, lengths of the string twisting over and around each other.
Mark said, "This is the true motion of the string, projected from the velocity distribution along its length.
The motion is actually periodic... It resumes the same form every twenty thousand years or so. This
graphic is running at billions of times true speed, of course the twenty millennia period is being covered
in around five minutes.
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"But the graphic is enough to show you an important feature of this motion. It'snon-intersecting... The
string is not cutting itself at any point in the periodic trajectory. If it did, it would bud off smaller
sub-loops, which would oscillate and cut themselves up further, and so on... the string would rapidly
decay, shrivelling through a thousand cuts, and leaking away its energy through gravitational radiation."
Spinner wished, suddenly, that she wasn'thuman: that she could watch the motion of this loop unfold,
without having to rely on Mark's gaudy projections. How wonderful it would be to be able to step out of
time!
...Close your eyes, Spinner.
"What?"
You can step out of time, just as you desire. Close your eyes, and imagine you are a god.
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