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wondered if you'd like to join me. I've got a wok in my apartment; I
could make that stir-fry I promised you."
Keith looked at . . . at the girl, he thought. Twenty-seven.
Two decades younger than himself. He felt a slight shifting in his
shorts. It was probably just an innocent invitation. She felt sorry
for the old guy, or maybe was trying to ingratiate herself with the
boss. Just some stir-fry, mayhe some wine, maybe . . .
"You know, Lianne," said Keith, "you are a very beautiful woman. He held
up a hand. "I know, I'm not supposed to say things like that, but we're
both off duty. You're a very beautiful woman." She lowered her eyes:
He paused and chewed on his bottom lip. And a thought welled up in his
brain.
Don't hurt Rissa.
You'll only hurt yourself.
"But," he said at last, "I think it's better if I just admire you from
afar."
She met his eyes for a moment, then dropped hers again.
"Rissa is a very lucky woman," Lianne said.
"No," said Keith, "I'm a very lucky man. See you tomorrow, Lianne."
She nodded. "Good night, Keith."
He went home, made himself a sandwich, read a few chapters in an old
Robertson Davies novel, then went to bed early.
And slept like a log, absolutely at peace with himself.
Alpha shift the next day started uneventfully. Rhombus had arrived
precisely on time, of course; Thor came in, put his feet up on the helm
console, and started dictating instructions into the navigational
computer; Lianne was hard at work briefing little holographic heads of
her engineers on the day's proposed work. In the back row, Keith was
talking quietly to Rissa, who had just returned from Grand Central.
But then the starscape split, and Jag came in, moving with more of a run
than a waddle.
"I've got it!" he said--although from the excited waving of his fur,
perhaps "Eureka!" would have been a more appropriate translation.
Keith and Rissa turned to look at Jag. He didn't go to his workstation;
instead, he moved to the front of the room, standing about two meters
ahead of Thor's console.
"What have you got?" asked Keith, resisting the potential straight
line.
"The answer!" barked Jag excitedly. "The answer!" He caught his
breath. "Bear with me for a moment; this will take some explaining.
But I'll tell you one thing up front--we do matter! We do make a
difference. Gods of the mountains, rivers, valleys, and plains--we make
all the difference!" His eyes diverged, one falling on Lianne, a second
on Rhombus, a third on Rissa, and the fourth on Thor and Keith, who were
lined up one behind the other from Jag's point of view.
"We know now that time travel from the future into the past is
possible," he said. "We've seen it happen with the fourth-generation
stars, and with the time capsule Hek and Azmi built. But consider the
implications of that. Suppose that at noon tomorrow, I used a time
machine to send myself back in time to today. What would we have then?"
Keith said, "Well, there'd be two of you, right? The Jag from today,
and the Jag from tomorrow."
"That's right. Now think about that: if you have two of me, you've
doubled the mass. I mass one hundred and twenty-three kilograms, but if
there were two of me here, then there'd be two hundred and forty-six
kilos of ]ag-mass aboard this ship."
"But I thought that was impossible," said Rissa, "because of the law of
conservation of mass and energy. Where did the extra hundred and
twenty-three kilos come from?"
Jag looked triumphant. "From the future! Don't you see? Time travel
is the only conceivable way to overcome that law. It's the only way to
increase the total mass in the system." His fur continued to dance.
"And what about the stars from the future? As each arrives, the mass of
the present-day universe is increased. After all, even
fourth-generation stars are made up of preexisting recycled subatomic
particles. Pushing them back in time means that those particles have
essentially been duplicated, doubling their total mass."
"An interesting side effect no doubt," said Rhombus. "But it still
doesn't explain why the stars are being sent back."
"Oh, yes it does. The doubling of mass is not just a side effect--not
at all! Rather, it's the whole point of. the operation."
"Operation?" said Keith.
"Yes! The operation to save the universe! These stars are being pushed
back in time to increase the mass of the entire universe."
Keith felt his jaw dropping. "Good God."
All four of the Waldahud's eyes converged on Keith.
"Exactly!" barked Jag. "We've known for over a century that the
visible matter in the universe accounts for less than ten percent of the
total that must be present. The rest is neutrinos and dark matter, like
our giant friends outside the ship. We now know what all the matter in
the universe is, but we don't know how much there is in total. And the
fate of the universe depends on how much mass it has, on whether the
total is above, below, or precisely at the so-called critical density."
"Critical density?" asked Rissa.
"That's right. The universe is expanding--and has been ever since the
big bang. But will that expansion go on forever?
That depends on gravity. And how much gravity there is, of course,
depends on how much mass there is. If there isn't enough--if the mass
of the universe is less than the critical density--gravity will never
overpower the original explosion, and the universe will continue to
expand forever, all the matter in it spreading out farther and farther.
Everything will grow cold and empty, with light-years separating
individual atoms."
Rissa shuddered.
"I suppose," said Keith. -"But what a project!"
"Indeed," said Jag. "And it might be even greater in scope than it
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