Starplex

“Good day, sir,” said the ever-polite Azmi, in a flat voice. Keith knew from old movies how musical Indian accents used to be; he missed the rich variety that human voices had had before instantaneous communications had smoothed out all the differences. Azmi gestured at the cube. “We’ve built the time capsule out of graphite composite with a few radioactives added. It’s solid except for the self-repairing hyperspatial sensor, which will lock onto the shortcut, and the starlight-powered ACS system for helping the cube hold position relative to it.”

“And what about the message for the future?” asked Keith.

Hek pointed to one of the cube’s sides. “We’ve incised it into the cube’s faces,” he said, his barking echoing in the bay. “It begins on this side. As you can see, it consists of a series of boxed examples. Two dots plus two dots equals four dots; a question with its answer. The second box, here, has two dots plus two dots, and a symbol. Since any arbitrary symbol would do, we just used the English question mark, but without the separate dot underneath; that might confuse one into thinking it was two symbols rather than one. Anyway, that gives us a question and a symbolic representation of the fact that the answer is missing. The third box shows the question symbol, the symbol I’ve established for ‘equals,’ and four dots, the answer. So that box says, “The answer to the question is four. Do you see?”

Keith nodded.

“Now,” continued Hek, “having established a vocabulary for our dialogue, we can ask our real question.” He waddled around to the opposite side of the cube, which was also incised with markings.

“As you can see,” said Hek, “we have two similar boxes here. The first one has a graphic representation of the shortcut, with a star emerging from it. See that scale mark showing the width of the star, and the series of horizontal and vertical lines beneath? That’s a binary representation of the star’s diameter in units of the box’s width, in case there’s any confusion about what the image represents. And then there’s the equals symbol, and the question symbol. So it says, ‘shortcut with star emerging from it equals what?’ And beneath it is the question symbol, the equals symbol, and a large blank space: “The answer to the above question is…” and a space implying that we want a reply.”

Keith nodded slowly. “Clever. Good work, gentlemen.”

Azmi pointed to one of the cube’s other faces. “On this face, we’ve incised information about the periods and relative positions of fourteen different pulsars. If the shortcut makers in the future—or whoever it is who finds this—have records going back this far in time, they’ll be able to identify the specific year in which the cube was created from that information.”

“Beyond that,” said Hek, “they might also assume, quite reasonably, that the cube had been created shortly after the green star emerged from this shortcut—and presumably they’ll know what date they sent that star back to, as well. In other words, they’ve got two independent ways of determining when to send any reply back to.”

“And this will work?” Keith asked.

“Oh, probably not,” said Azmi, smiling. “It’s just a bottle in the ocean. I don’t seriously expect any results, but I suppose it’s worth a try. Still, as Dr. Magnor has told me, if we don’t get a good explanation, and if we decided the stars are a threat, we can use the Waldahud space-flattening technique to evaporate the shortcuts. Granted, stars may be popping out of thousands of exit points, so we probably can’t do much to stop them. But if they know we have the capability to interfere to some degree, perhaps they’ll provide an explanation rather than have us do that.”

“Very good,” said Keith. “But what will make the cube conspicuous? How can you be sure someone will find it?”

“That’s the hardest part of all,” barked Hek. “There are only a few ways to get something to stand out. One is to make it reflective. But no matter what we make this box out of, it will have to endure perhaps ten billion years of scouring by interstellar dust. Granted, that’s only a few microscopic impacts per century, but the net effect over that much time would be to dull any reflective surface.

“The second possibility we’d considered was to make the time capsule big—so that it’s eye-catching; or heavy—so that it warps spacetime. But the bigger you make it, the more likely it is to be destroyed by a meteor collision.

“The final possibility was to make it loud—you know, by broadcasting a radio signal. But that requires a power source. Of course, right now the green star is close by, and we can use simple solar cells to generate electricity from it, but the star has a respectable proper motion relative to the shortcut. In just a few thousand years, it’ll be a full light-year from here, much too far away to provide significant power. And any internal power source we use would exhaust its fuel, or have most of its radioactives decay to lead, long before the target date.”