She said, "I’m listening."

"For special events like this, we sometimes go nuclear.So I thought I’d ask whether you’d like to join us."

Cass froze, and stared at him. "Nuclear? How?Has someone solved all the problems?" Femtomachines built from exoticnuclei had been employed as special-purpose computers ever since thebasic design had been developed, six thousand years before. For sheerspeed, they left every other substrate in the dust. But as far as Cassknew, no one could make a femtomachine stable for more than a fewpicoseconds; they could perform a great many calculations in that time,but then they blew themselves apart and left you hunting through thedebris for the answer. Gamma-ray spectroscopy could only extract a fewhundred kilobytes, which was orders of magnitude too small even for adifferential memory — a compressed description of experience that couldbe absorbed by a frozen reference copy of the person who’d actuallylived through it. Cass might have missed the news of a breakthroughwhile she’d been on her way here from Earth, but if word had reachedMimosa Station at all she should have heard by now.

"Nothing’s changed in the technology," Rainzi said. "Wedo it freestyle. One-way."

Freestyle meant implementing yourmind on a substrate that underwent quantum divergence. One-waymeant none of the end products of any version of the computation couldbe retrieved, and transferred back into your usual hardware. Rainzi wasasking her to clone herself into a nuclear abacus-cum-time-bomb thatwould generate a multitude of different versions of her, while holdingout no prospect of even one survivor.

Cass said haltingly, "No, I’m sorry. I can’t join you."So much for feeling smugly unshockable for daring to contemplatecross-modal sex. She joked, "I draw the line at any implementationwhere I experience detectable weight changes every time I learnsomething." Femtomachines shuffled binding energies equivalent to asignificant portion of their own mass; it would be like gaining orlosing half a kilogram several times a second, from the sheer gravityof your thoughts.