Jaydium by Deborah J. Ross

a zipper could have landed without my alarms sounding. So how did you get here?”
    â€œWe don’t really know,” Eril said. “But one thing is sure, we didn’t travel through space. Kithri and I started out on Stayman, a world of great arid plains with only a few marginal settlements, nothing even remotely like the crystal city. We were mining in the Manitous, that mountain range on the eastern side of the forest, and Lennart there fell out of an interdimensional time gap.”
    â€œOh, is that what happened to me?” Lennart said, rubbing the back of his neck.
    â€œAn interdimensional time gap ?” Brianna raised one eyebrow, although her expression remained perfectly serious.
    Praying he wouldn’t sound totally unbelievable, Eril related how Lennart had been caught up in a time-space disturbance and had appeared suddenly in the tunnel.
    â€œActually,” said Lennart, “I was outside the ship, repairing the medial ramscoop struts. We were travelling at a significant fraction of light-speed and if a lightstorm had caught us crooked like that... I’ve seen what was left of the Verne , half the tail blasted into nothing and no sign of the crew. Anyway, one moment everything was going fine, the next I looked up and there was the storm. I was sure I was dead but the next moment these two were welcoming me to the future.”
    â€œThe...future?” Brianna repeated.
    â€œBy all the geological and astronomical evidence, we’re still on the same planet, in the same time,” Eril said. “Lennart’s been frozen — suspended you might say — for millenia.”
    Brianna folded her arms over her chest and pursed her lips. “I see what you’re suggesting. It’s never been proven, of course, but it’s not impossible by the current theory of temporal mechanics. If Lennart were ‘suspended’ in a mass-space-time anomaly, then whatever factor released him would experience an equivalent vectorial displacement.”
    â€œHuh?” said Lennart and Eril together.
    â€œWhen Lennart fell out of the thing, we got knocked sideways,” Kithri said. When they all stared at her, she added, “I think.”
    â€œTheoretically — and I must stress the hypothetical nature of this line of reasoning,” Brianna gestured with her hands as she talked, “time isn’t linear but divergent. At each intersection point, each crucial event, two or more subsidiary time-lines are produced.”
    â€œLike the world where the dinosaurs didn’t become extinct and went on to explore space?” said Lennart.
    â€œIt’s all speculation at this point,” Brianna said. “And if you tried it again with Lennart, since he’s the focal point of the displacement, you might just as easily travel linearly instead of horizontally. Back to his own time, I’d guess. But if you did come from an alternate probability world...and we could find some way to reverse the process...and open a door between our two worlds...”
    She raised her shoulders in a little shiver of excitement. “The Institute scientists will be crawling over each other to help you get back, not to mention creating a two-way portal.”
    â€œIt’s my guess all we have to do to return to our own world is to retrace our steps,” Eril said, ignoring Kithri’s snort of derision. “But if that doesn’t work, we’d be grateful for your help.”
    Brianna’s green eyes narrowed speculatively. “What were you mining here? There were no commercial options when the Institute issued the excavation permits.”
    For a moment, Eril considered keeping the jaydium a secret. It might make a powerful bargaining tool, yet Kithri had been so damned sensitive about his even mentioning it to Lennart.
    That was just conversation, but this is important! To hell with her paranoia.
    â€œWe were chipping jaydium, deep in the