Michael Swanwick's Periodic Table of Science Fiction

Cesium

132.9054

Castles in the Air

Cesium is the most reactive of all metals. It burns in air and reacts

violently in water. For which reason, it is best stored in interstellar

vacuum.

The Precursors, that most mysterious of (presumably) extinct alien races,

built cesium castles as large as moons in the emptiest reaches of

intergalactic space. We'd been prospecting for hard vacuum when we found

one. One minute the readings were down to a single atom per cubic mile,

and the next they were off the meters. We went in to look.

The castle was so spacious as to have an average density equivalent to

that of a light fog. We drifted through rooms as large as cities using

tiny puffs of steam for propellant. Wherever we went, walls burned behind

us. It didn't matter. There was a lot more where they came from.

At last, sated with wonders, godlike architecture, and miles-long statues

that looked like they'd been forged by Michelangelo's more talented

brother, we gathered in the exploration ship's conference room to decide

what to do.

"It's a hundred percent cesium," the Ship's Chemist said. "No impurities

at all. I can't imagine how they refined it, much less how they shaped

it."

"The art is magnificent," the Ship's Xenologist observed. "But where

could we display it? It's all volatile as hell and the best of it is so

large and delicate that if we put it in orbit around a planet, tidal

forces would tear it apart."

"I'm skunked," the Captain said. "I have no ideas whatsoever. It's

magnificent. But what practical use is it?"

I cleared my throat.

"In nineteenth century Egypt," I said, "mummies from looted tombs were

burned by the coal-tender load to power steam locomotives. Dry as they

were, they made excellent fuel, far better than coal."

"Mummies?" the Ship's Biologist asked, appalled. "You mean, like real

mummies?"

I nodded. "A century later this was considered a terrible cultural crime,

of course. But by then the entrepreneurs who had opened the graves and

sold the mummies in lots of thousands, had retired rich, died old, and

left prosperous dynasties behind them."

"So you're proposing ? that we ?" The Ship's Physicist could not quite

finish the thought.

"Break it and sell it as starship fuel, that's right. There's got to be a

billion quads worth of power out there. Enough to make every one of us

richer than Croesus."

The vote was quick and unanimous.

There's a good reason why I was included in the science vessel's crew.

Sometimes you need the kind of perspective that only a Ship's Historian

can provide.