“On the other side,” Cole answered quickly, hoping to move the story along. “No—” With his index finger extended, he drew a circle in the air in front of him and focused on it through his goggles. “You’d end up where you started. Right?”
“Only if you stopped there.” Byrne had taken the tone of a teacher guiding along a favored student. He smiled at Cole, and for the first time, Cole realized Byrne didn’t have on goggles and didn’t seem to need them.
“You could keep going forever, if you liked,” Byrne said. “And that’s how the universe is shaped, only one dimension higher—”
“Well, you’re wrong about our cosmology, then. We’ve known this for a long time. If you travel in a straight line anywhere in the universe, you’ll end up where you started. It curves around on itself.”
“Oh, you’ve got the shape right,” Byrne agreed. “You’ve had that nailed for hundreds of years. However, your cosmologists don’t seem to appreciate the consequences, even though it’s completely obvious.”
“Consequences?” Cole asked.
“Everything in the universe is indeed traveling in a straight line. Which means—” He frowned, pursing his thin lips as if formulating a dumbed-down version for a child. “Imagine we’re sitting on the North Pole of your planet.”
Cole looked up at the snow flurries, at the large spire behind him. His imagination hardly needed to exert itself. “Done,” he said.
“Now picture the matter of the universe spreading out from here, all of it heading in every direction possible around your planet. Where is it going?”
“Back to where it started, just like when I go walking in a straight line.”
“Except you were traveling alone,” Byrne pointed out. Cole could almost imagine the armless man wagging his finger like Professor Phister used to. “Don’t forget,” Byrne said, “that there’s a lot of stuff in this example. If it’s all moving roughly the same speed—”
“The South Pole!” As soon as Cole uttered the answer, a lot more fell into place; he could almost hear his brain click audibly. The leading theory of their day, hundreds of years old and mostly unchanged, remained the Big Bang theory. Even with the problems of inflationary theory and dark energy, it was still the best they had, as messy and patchwork as it had become.
Cole thought about all that matter spreading out across the surface of a sphere, all heading away from the North Pole. He could see it traveling through the dips and rises, thinning out as it moved away. And then he could see it starting to come back together. All of it—all of everything—meeting in a big crunch at the South Pole. He considered the expanding universe and pictured for the very first time where it was expanding to!