The Protectors war

"This is what they called a Stirling-cycle engine-sort of like a steam engine without the water, using a gas as the working fluid in a closed cycle. This one comes from a museum in Eugene; I traded some moonshine to a scavenger who had it in a load of miscellaneous junk. I wanted it because it doesn't depend on fast combustionexplosions-like IC engines. Result: It doesn't work anymore either."

"Why am I not surprised?" Havel said.

He sounded patient, in a heavy sort of way. But then, he puts up with Astrid, too.

Larsson went on: "A Stirling engine is like the theory of heat engines made manifest. Put concentrated heat in here, raise the temperature of the gas, and you get mechanical work out there. OK, mechanical work and diffuse heat. All you need to make it work is a temperature gradient between one end and the other. And like all heat engines since the Change it just doesn't work to any useful degree."

"What about guns?"

"Guns are heat engines-first ones to be widely used. But."

He swung the lamp out from under the cylinder, engaged a crank and worked it with his good hand. Crankshaft and piston and flywheel spun up with a subdued hum; after a moment he released it to run down.

"You see, one of the interesting things about a Stirling engine is that if you run it in reverse-if you put mechanical work in -it acts as a refrigerator. You get cold out the other end. They were used for that in labs and some manufacturing back before the Change. And that still does work."

Havel 's brows went up. "Well, that could be very useful," he said. "We could really use some refrigerated storage for food, particularly if we could do it in bulk. It just doesn't get cold enough in the Willamette to make icehouses practical-one of the few advantages we had back when I was growing up on the Upper Peninsula, and man, did we have ice and to spare. We could run this Stirling thingie in reverse off a waterwheel or a windmill?"

"Yes, or the sort of horse gin we use for threshing machines now. But think about it for a moment. Why would the heat-to-work cycle not function, while the work-to-cold cycle does? And when you're cranking it, it works exactly the way it did pre-Change. It's like you can only play a film backward."

Havel shrugged again. "Presumably your Alien Space Bats, or Juney's gods, or the Reverend Abbot's Lord Jehovah wanted it that way. I never did think the Change just happened. "

"Neither did I. It's too: focused. A random change in natural law would most likely just collapse everything into quark soup. And everything is too neatly scaled, the effects kick in at the precise level necessary and no earlier; it lets any biological process go on just fine, our nervous systems work, fish can still use their swim bladders, but that"-he pointed at the engine-"is screwed. Somebody did this to us."

Havel slapped a hand against the brass bars that made a protective basket around the hilt of his backsword, "Give me a clear run at whoever did it, and I'll carve them a new one."

"Yes, yes," Larsson said, a testy edge to his voice. "But this gives me a handle on how the Arbitrarily Advanced ASB's are screwing it up-the heat engine side, at least, that's easier to get a grip on without instruments than the electrical problems. It isn't nanobots with unobtanium force-field generators watching our every move and selectively intervening whenever we try to fire a gun or run a generator. What's happened is a change in the Ideal Gas laws-or more accurately, a forced change in the behavior of near-ideal gasses-"

"Whoa, partner," Mike said, raising a hand. There was a rustling chink as the elbow-length mail sleeve of his hauberk brushed the vambrace on his forearm. "I knew my way around a motorcycle engine, but that's about it, tech-wise. You're talking to a high school graduate who just squeaked by in math and fudged a lot to get his pilot's license."

"OK, it's a change in the way gas molecules act under certain very specific circumstances, so there's no increase in pressure with heat beyond a low threshold. Like there's some added force that glues molecules together, so instead of producing work, the heat energy or the work put into mechanical compression gets locked into some weird form of potential energy."

He pointed to another apparatus, a cylinder with a gauge attached, a piston rod sticking above it, and a framework for dropping weights on that.

"This is the one that's really been driving me nuts. It turns out the pressure limitation is same-same with pumping air mechanically into a reservoir. After a certain point, all you get for more pumping is sweat-same glue-the-molecules effect."

Havel looked at the apparatus and frowned. "You mean if you drop that weight, it doesn't compress the air in the cylinder? OK, we've got infinitely efficient shock absorbers?"

"Oh, yeah, it does compress it-up to a point. Then the volume of air keeps getting smaller as you push, same-same as it would have before the Change if you exerted the same force, and it resists a push just as it would have before, but more like a liquid or solid than a compressed gas. The pressure doesn't get any higher after that cutoff point. There's a falloff in the extra push-back pressure you get for each input of energy applied; it starts small and then goes up in an asymptotic curve-ever-steeper curve, to you scientifically illiterate types. Pretty soon it reaches something close to infinity-like trying to go faster than light with a rocket."

Havel ran his hands over his hair. "That's crazy."

"Well, duh, my armor-plated son-in-law. Of course it's crazy. It simply fucks parts of the laws of thermodynamics, just for starters. That's what confirmed my mental certainty about the glue-the-molecules effect. Watch."

He walked over to the cylinder and tripped a release.

Whank!

The weight slammed down, and the gauge twitched. Ken jerked a thumb at it.

"OK, as far as I can tell, the piston went down exactly as far as it would have before the Change under the same weight. But see the pressure gauge? Barely a fraction of what it would have been with that reduction in volume. As far as I can tell, what happens is the air gets sort of: thicker: as it gets compressed: the molecules get closer together and the energy input goes into mashing them tighter and tighter, but they don't leap apart when it's removed. They just expand again, they fill additional volume but they don't push at it the way they should. The same thing happens with any other compressible gas, by the way, but not with non-compressible liquids like water. Which means you can use hydraulic systems just fine."

Larsson rubbed his good hand on the leather support of his multitool. "You know, if you could get that energy back quickly, this would make a hell of a battery, or an explosive."

"You can't get the energy back? It's gone? Conservation of energy I have heard of-"

"Oh, you can get it back; thermodynamics isn't totally screwed up. You just can't get it back very fast, or in any form that's any fucking use at all."

He turned a valve, and there was a long hiss; the piston rod sank down. "When you do this, the exit valve and the air around it heat up more than they should. For that matter, the air in the cylinder gets hotter than it should when you drop the weight; not much hotter, just barely enough difference that I can detect without electronic instruments. I think the potential energy trapped by the glue-together effect leaks away gradually in the form of diffuse low-level heat as the molecules 'unbind.' The slow burning with explosives is probably part of the same effect; the extra force keeps the molecules of a fuel from spreading fire as fast. There seems to be a relation between pressure and: never mind. I think something similar was done to set an upper limit on permitted voltages, too, maybe by increasing the degree of electron localization in solids. That would-"