Cheng Xin and AA locked gazes. They each saw in the eyes of the other the same thing: the excitement of enlightenment dancing within. Cheng Xin looked away. “I don’t have time to waste on silly games. If you want a bubble bath, go for it.” She left the bathroom.
AA followed. They poured themselves two glasses of wine and began to chat about random topics. First, they discussed the future of the Halo Group in the Bunker Project. Then they recalled their college lives in different centuries. Then they talked about life in the present. AA asked Cheng Xin why she had not found a man she liked after living in the new age for so long, and Cheng Xin replied that she couldn’t live a regular life, not yet. Then she pointed out that AA’s problem was that she dated too many men—of course she was welcome to bring her boyfriends to visit Cheng Xin, but it was best to bring only one at a time. They also discussed the fashions and tastes of the women of their respective eras, their similarities and differences….
Language was merely the vehicle through which they expressed their excitement. They dared not stop, lest the silence rob them of their hidden joy. Finally, in a break in the meandering conversation that would not be noticed by a listener, Cheng Xin said, “Curvature—”
She finished her sentence with her eyes:
AA nodded. Her eyes said,
Space wasn’t flat, but curved. If one imagined the universe as a large, thin membrane, the surface would be shaped like a bowl. The entire membrane might even be an enclosed bubble. Though at the local scale, the membrane seemed flat, the curvature of space was omnipresent.
During the Common Era, many ambitious ideas for spaceflight were proposed. One of them involved folding space. The idea was to imagine an increase in the curvature of space and fold it like a sheet of paper so that two spots tens of millions of light-years apart could touch each other. Strictly speaking, this wasn’t a plan for spaceflight, but “space-dragging.” It didn’t involve navigating to the destination, but pulling the destination over to you by bending space.
Only God could have carried out such a plan—and once the limitations of basic theory were taken into account, perhaps not even God.
Later, there was a more moderate and localized proposal for taking advantage of curved space for navigation. Supposing a spaceship could somehow iron flat the space behind it and decrease its curvature, the more curved space in front of it would pull it forward. This was the idea of curvature propulsion.
Unlike folding space, curvature propulsion couldn’t get a spaceship to its destination instantaneously, but it would be possible to drive it asymptotically to the speed of light.
Until Yun Tianming’s message had been correctly interpreted, curvature propulsion remained a dream, like hundreds of other proposals for lightspeed spaceflight. No one knew whether it was possible at either a theory or practice level.
A jubilant AA said to Cheng Xin, “Before the Deterrence Era, clothes with animated images were popular. Back then, everyone looked like blinking Christmas trees, but now, only children dress like that. Classical looks are in vogue again.”
But AA’s eyes were saying something else entirely. Her eyes dimmed.
Cheng Xin said, “I’m most surprised that precious metals and gems no longer exist! Gold is now a common metal, and both of our drinking glasses are made of diamonds…. Did you know that where—er, when—I come from, owning a tiny diamond—like this big—would have been an unattainable dream for most girls.”
Her eyes were saying,
“Well, at least you had cheap aluminum. Before the invention of electrolysis, aluminum was a precious metal as well. I’ve heard that some kings even had crowns made of aluminum.”
Cheng Xin couldn’t express what she wanted with only her eyes. IDC had once offered to build her a sophon-free room in her apartment. That would have involved a large amount of noisy equipment, so she had turned them down. Now she regretted that decision.
“Snow-wave paper,” she whispered.
AA’s eyes lit up again. The flame of excitement burned even brighter than before.
