Critical Difference

II

The sun was halfway toward mid-sky, and still attended by its sun-dogs, though they were fainter than at the horizon. The sky was darker. The mountain peaks reached skyward, serene and utterly aloof from the affairs of man. This was a frozen world, where there should be no inhabitants. The city was a fleet of metal hulks, neatly arranged on the valley floor, emptied of the material they had brought for the building of the colony. At the upper end of the valley the landing-grid stood. It was a gigantic skeleton of steel, rising from legs of unequal length bedded in the hillsides, and reaching two thousand feet toward the stars. Human figures, muffled almost past recognition, moved about a catwalk three-quarters of the way up. There was a tiny glittering below where they moved. They were, of course, men using sonic ice-breakers to shatter the frost which formed on the framework at night. Falling shards of crystal made a liquidlike flashing. The landing-grid needed to be cleared every ten days or so. Left uncleared, it would acquire an increasingly thick coating of ice. In time it could collapse. But long before that time it would have ceased to operate, and without its operation there could be no space travel. Rockets for lifting spaceships were impossibly heavy, for practical use. But the landing-grids could lift them out to the unstressed space where Lawlor drives could work, and draw them to ground with cargoes they couldn't possibly have carried if they'd needed rockets.

Massy reached the base of the grid on foot. It was not far from the village of drone-hulls. He was dwarfed by the ground-level upright beams. He went through the cold-lock to the small control-house at the grid's base.

He nodded to the man on standby as he got painfully out of his muffling garments.

"Everything all right?" he asked.

The standby operator shrugged. Massy was Colonial Survey. It was his function to find fault, to expose inadequacies in the construction and operation of colony facilities. It's natural for me to be disliked by men whose work I inspect, thought Massy. If I approve it doesn't mean anything, and if I protest, it's bad. He had always been lonely, but it was a part of the job.

"I think," he said painstakingly, "that there ought to be a change in maximum no-drain voltage. I'd like to check it."

The operator shrugged again. He pressed buttons under a phone-plate.

"Shift to reserve power," he commanded when a face appeared in the plate. "Gotta check no-drain juice."

"What for?" demanded the face in the plate.

"You-know-who's got ideas," said the grid operator scornfully. "Maybe we've been skimping something. Maybe there's some new specification we didn't know about. Maybe anything! But shift to reserve power."

The face in the screen grumbled. Massy swallowed. It was not a Survey officer's privilege to maintain discipline. But there was no particular virtue in discipline here and now. He watched the current-demand dial. It stood a little above normal day-drain, which was understandable. The outside temperature was down. There was more power needed to keep the dwellings warm, and there was always a lot of power needed in the mine the colony had been formed to exploit. The mine had to be warmed for the men who worked to develop it.

The demand-needle dropped abruptly, and hung steady, and dropped again and again as additional parts of the colony's power-uses were switched to reserve. The needle hit bottom. It stayed there.

Massy had to walk around the standby man to get at the voltmeter. It was built around standard, old-fashioned vacuum tubes—standard for generations, now. Massy patiently hooked it up and warmed the tubes and tested it. He pushed in the contact plugs. He read the no-drain voltage. He licked his lips and made a note. He reversed the leads, so it would read backward. He took another reading. He drew in his breath very quietly.

"Now I want the power turned on in sections," he told the operator. "The mine first, maybe. It doesn't matter. But I want to get voltage-readings at different power take-offs."

The Operator looked pained. He spoke with unnecessary elaboration to the face in the phone-plate, and grudgingly went through with the process by which Massy measured the successive drops in voltage with power drawn from the ionosphere. The current available from a layer of ionized gas is, in effect, the current-flow through a conductor with marked resistance. It is possible to infer a gas's ionization from the current it yields.

The cold-lock door opened. Riki Herndon came in, panting a little.

"There's another message from home," she said sharply. Her voice seemed strained. "They picked up our answering-beam and are giving the information you asked for."

"I'll be along," said Massy. "I just got some information here."

He got into his cold-garments again. He followed her out of the control-hut.

"The figures from home aren't good," said Riki evenly, when mountains visibly rose on every hand around them. "Ken says they're much worse than he thought. The rate of decline in the solar constant's worse than we figured or could believe."

"I see," said Massy, inadequately.

"It's absurd!" said Riki fiercely. "It's monstrous! There've been sun spots and sunspot cycles all along! I learned about them in school! I learned myself about a four-year and a seven-year cycle, and that there were others! They should have known! They should have calculated in advance! Now they talk about sixty-year cycles coming in with a hundred-and-thirty-year cycle to pile up with all the others—But what's the use of scientists if they don't do their work right and twenty million people die because of it?"

Massy did not consider himself a scientist, but he winced. Riki raged as they moved over the slippery ice. Her breath was an intermittent cloud about her shoulders. There was white frost on the front of her cold-garments.

He held out his hand quickly as she slipped, once.

"But they'll beat it!" said Riki in a sort of angry pride. "They're starting to build more landing-grids, back home. Hundreds of them! Not for ships to land by, but to draw power from the ionosphere! They figure that one ship-size grid can keep nearly three square miles of ground warm enough to live on! They'll roof over the streets of cities. Then they'll plant food-crops in the streets and gardens, and do what hydroponic growing they can. They are afraid they can't do it fast enough to save everybody, but they'll try!"

Massy clenched his hands inside their bulky mittens.

"Well?" demanded Riki. "Won't that do the trick?"

Massy said: "No."

"Why not?" she demanded.

"I just took readings on the grid, here. The voltage and the conductivity, of the layer we draw power from, both depend on ionization. When the intensity of sunlight drops, the voltage drops and the conductivity drops, too. It's harder for less power to flow to the area the grid can tap—and the voltage-pressure is lower to drive it."

"Don't say any more!" cried Riki. "Not another word!"

Massy was silent. They went down the last small slope. They passed the opening of the mine—the great drift which bored straight into the mountain. They could look into it. They saw the twin rows of brilliant roof-lights going toward the heart of the stony monster.

They had almost reached the village when Riki said in a stifled voice:

"How bad is it?"

"Very," admitted Massy. "We have here the conditions the home planet will have in two hundred days. Originally we could draw less than a fifth the power they count on from a grid on Lani II."

Riki ground her teeth.

"Go on!" she said challengingly.

"Ionization here is down ten per cent," said Massy. "That means the voltage is down—somewhat more. A great deal more. And the resistance of the layer is greater. Very much greater. When they need power most, on the home planet, they won't draw more from a grid than we do now. It won't be enough."

They reached the village. There were steps to the cold-lock of Herndon's office-hull. They were ice-free, because like the village walk-ways they were warmed to keep frost from depositing on them. Massy made a mental note.

In the cold-lock, the warm air pouring in was almost stifling. Riki said defiantly:

"You might as well tell me now!"

‘We could draw one-fifth as much power, here, as the same-size grid would yield on your home world," he said grimly. "We are drawing—call it sixty per cent of normal. A shade over one-tenth of what they must expect to draw when the real cold hits them. But their estimates are nine times too high." He said heavily, "One grid won't warm three square miles of city. About a third of one is closer. But—"

"That won't be the worst!" said Riki in a choked voice. "Is that right? How much good will a grid do?"

Massy did not answer.

The inner cold-lock door opened. Herndon sat at his desk, even paler than before, listening to the hash of noises that came out of the speaker. He tapped on the desktop, quite unconscious of the action. He looked almost desperately at Massy.

"Did she…tell you?" he asked in a numb voice."They hope to save maybe half the population. All the children, anyhow—"

"They won't," said Riki bitterly.

"Better go transcribe the new stuff that's come in," said her brother dully. "We might as well know what it says."

Riki went out of the office. Massy laboriously shed his cold-garments. He said uncomfortably:

"The rest of the colony doesn't know what's up yet. The operator at the grid didn't, certainly. But they have to know."

"We'll post the message on the bulletin board," said Herndon apathetically. "I wish I could keep it from them. It's not fun to live with. I…might as well not tell them just yet.'

"To the contrary," insisted Massy. "They've got to know right away! You're going to issue orders and they'll need to understand how urgent they are!"

Herndon looked absolutely hopeless.

"What's the good of doing anything?" When Massy frowned, he added as if exhausted: "Seriously, is there any use? You're all right. A Survey ship's due to take you away. It's not coming because they know there's something wrong, but because your job should be finished about now. But it can't do any good! It would be insane for it to land at home. It couldn't carry away more than a few dozen refugees, and there are twenty million people who're going to die. It might offer to take some of us. But…I don't think many of, us would go. I wouldn't. I don't think Riki would."

"I don't see—"

"What we've got right here," said Herndon, "is what they're going to have back home. And worse. But there's no chance for us to keep alive here! You are the one who pointed it out! I've been figuring, and the way the solar-constant curve is going—I plotted it from the figures they gave us—it couldn't possibly level out until the oxygen, anyhow, is frozen out of the atmosphere here. We aren't equipped to stand anything like that, and we can't get equipped. There couldn't be equipment to let us stand it indefinitely! Anyhow, the maximum cold conditions will last two thousand days back home—six Earth-years. And there'll be storage of cold in frozen oceans and piled-up glaciers. It'll be twenty years before home will be back to normal in temperature, and the same here. Is there any point in trying to live—just barely to survive—for twenty years before there'll be a habitable planet to go back to?"

Massy said irritably:

"Don't be a fool! Doesn't it occur to you that this planet is a perfect experiment-station, two hundred days ahead of the home world, where ways to beat the whole business can be tried? If we can beat it here, they can beat it there!"

Herndon said detachedly:

"Can you name one thing to try here?"

"Yes," snapped Massy. "I want the walk-heaters and the step-heaters outside turned off. They use power to keep walkways clear of frost and doorsteps not slippery. I want to save that heat!"

Herndon said without interest:

"And when you've saved it, what will you do with it?"

"Put it underground to be used as needed!" Massy said angrily. "Store it in the mine! I want to put every heating-device we can contrive to work in the mine! To heat the rock! I want to draw every watt the grid will yield and warm up the inside of the mountain while we can draw power to do it with! I want the deepest part of the mine too hot to enter! We'll lose a lot of heat, of course. It's not like storing electric power! But we can store heat now, and the more we store the more will be left when we need it!"

Herndon thought heavily. Presently he stirred slightly.

"Do you know, that is an idea—" He looked up. "Back home there was a shale-oil deposit up near the icecaps. It wasn't economical to mine it. So they put beaters down in bore-holes and heated up the wholeshale deposit! Drill-holes let out the hot oil vapors to be condensed. They got out every bit of oil without disturbing the shale! And then…why…the shale stayed warm for years. Farmers bulldozed soil over it and raised crops with glaciers all around them! That could be done again. They could be storing up heat back home!"

Then he drooped.

"But they can't spare power to warm up the ground under cities. They need all the power they've got to build roofs. And it takes time to build grids."

Massy snapped:

"Yes, if they're building regulation ones! By the time they were finished they'd be useless! The ionization here is dropping already. But they don't need to build grids that will be useless later! They can weave cables together on the ground and hang them in the air by helicopters! They wouldn't hold up a landing ship for an instant, but they'll draw power right away! They'll even power the helis that hold them up! Of course they've defects! They'll have to come down in high winds. They won't be dependable. But they can put heat in the ground to come out under roofs, to grow food by, to save lives by. What's the matter with them?"

Herndon stirred again. His eyes ceased to be dull and lifeless.

"I'll give the orders for turning off the sidewalks. And I'll send what you just said back home. They should like it."

He looked very respectfully at Massy.

"I guess you know what I'm thinking right now," he said awkwardly.

Massy flushed. It was not dignified for a Colonial Survey officer to show off. He felt that Herndon was unduly impressed. But Herndon didn't see that the device wouldn't solve anything. It would merely postpone the effects of a disaster. It could not possibly prevent them.

"It ought to be done," he said curtly. "There'll be other things to be done, too."

"When you tell them to me," said Herndon warmly, "they'll get done! I'll have Riki put this into that pulsecode you explained to us and she'll get it off right away!"

He stood up.

"I didn't explain the code to her!" insisted Massy. "She was already translating it when you gave her my suggestion!"

"All right," said Herndon. "I'll get this sent back at once!"

He hurried out of the office. This, thought Massy irritably, is how reputations are made, I suppose I'm getting one. But his own reaction was extremely inappropriate. If the people of Lani II did suspend helicopter-supported grids of wire in the atmosphere, they could warm masses of underground rock and stone and earth. They could establish what were practically reservoirs of life giving heat under their cities. They could contrive that the warmth from below would rise only as it was needed. But...

Two hundred days to conditions corresponding to the colony-planet. Then two thousand days of minimum heat conditions. Then very, very slow return to normal temperature, long after the sun was back to its previous brilliance. They couldn't store enough heat for so long. It couldn't be done. It was ironic that in the freezing of ice and the making of glaciers the planet itself could store cold.

And there would be monstrous storms and blizzards on Lani II as it cooled. As cold conditions got worse the wire grids could be held aloft for shorter and shorter periods, and each time they would pull down less power than before. Their effectiveness would diminish even faster than the need for effectiveness increased.

Massy felt even deeper depression as be worked out the facts. His proposal was essentially futile. It would be encouraging, and to a very slight degree and for a certain short time it would palliate the situation on the inner planet. But in the long run its effect would be zero.

He was embarrassed, too, that Herndon was so admiring. Herndon would tell Riki that he was marvelous. She might—though cagily—be inclined to agree. But he wasn't marvelous. This trick of a flier-supported grid was not new. It had been used on Saril to supply power for giant peristaltic pumps emptying a [polder] that had been formed inside a ring of indifferently upraised islands.

All I know, thought Massy bitterly, is what somebody's showed me or I've read in books. And nobody's showed or written how to handle a thing like this! He went to Herndon's desk. Herndon had made a new graph on the solar-constant observations forwarded from home. It was a strictly typical curve of the results of coinciding cyclic changes. It was the curve of a series of frequencies at the moment when they were all precisely in phase. From this much one could extrapolate and compute. Massy took a pencil, frowning unhappily. His fingers clumsily formed equations and solved them. The result was just about as bad as it could be. The change in brightness of the sun Lani would not be enough to be observed on Kent IV—the nearest other inhabited world—when the light reached there four years from now. Lani would never be classed as a variable star, because the total change in light and heat would be relatively minute. But the formula for computing planetary temperatures is not simple. Among its factors are squares and cubes of the variables. Worse, the heat radiated from a sun's photosphere varies not as the square or cube, but as the fourth power of its absolute temperature. A very small change in the sun's effective temperature, producible by sunspots, could make an altogether disproportionate difference in the warmth its worlds received. Massy's computations were not pure theory. The data came from Sol itself, where alone in the galaxy there had been daily solar-constant measurements for three hundred years. The rest of his deductions were based ultimately on Earth observations, too. Most scientific data had to refer back to Earth to get an adequate continuity. But there was no possible doubt about the sunspot data, because Sol and Lani were of the same type and nearly equal size.

Using the figures on the present situation, Massy reluctantly arrived at the fact that here, on this already frozen world, the temperature would drop until CO2 froze out of the atmosphere. When that happened, the temperature would plummet until there was no really significant difference between it and that of empty space. It is carbon dioxide which is responsible for the greenhouse effect, by which a planet is in thermal equilibrium only at a temperature above its surroundings—as a greenhouse in sunlight is warmer than the outside air.

The greenhouse effect would vanish soon on the colony world. When it vanished on the mother planet, Massy found himself thinking, if Riki won't leave when the Survey ship comes, I'll resign from the Service. I'll have to if I'm to stay. And I won't go unless she does.