Hal Clement: Star Light

“Probably not much,” Seumas McDevitt admitted. “If you don’t like cynicism I’ll have to pick my words carefully; but the light on the screen there should be right within a few hundred miles, and I doubt that we can compute a precise enough forecast for that to make a significant difference.”

“I wasn’t sure you’d have enough material for any predictions at all,” Easy countered. “I understand that weather comes from the west even on this world, and the area to the west has been out of sunlight for days now. Can you see such places well enough to get useful data?”

“Oh, sure.” Benj’s sarcasm had vanished and the enthusiasm which had caused him to put down atmospheric physics as his post-primary tentative was taking over. “We don’t get much of our measurement from reflected sunlight anyway; nearly all is direct radiation from the planet. There’s a lot more emitted than it receives from the sun anyway; you’ve heard the old argument as to whether Dhrawn ought to be called a star or a planet. We can tell ground temperature, a good deal about ground cover, lapse rates, and clouds. Winds are harder—” he hesitated, seeing McDevitt’s eye on him and unable to read the meteorologist’s poker face. The man read the trouble in time and nodded him on before the rush of self-confidence had lost momentum. McDevitt had never been a teacher, but he had the touch.

“Winds are harder because of the slight uncertainty in cloud heights and the fact that adiabatic temperature changes often have more to say about the location of clouds than air mass identities do. In that gravity, the air density drops by half about every hundred yards of climb, and that makes for terrific PV changes in temperature—” he paused again, this time eyeing his mother. “Do you know about that sort of thing, or should I slow down?”

“I’d hate to have to solve quantitative problems on what you’ve just been saying,” Easy replied, “but I think I have a fair qualitative picture. I get the impression that you’re a little doubtful about telling Don to the nearest minute when his fog is going to clear. Would a report from him on surface pressures and winds be any help? The Kwembly has instruments, you know.”

“It might,” McDevitt admitted as Benj nodded silently. “Can I talk to the Kwembly directly? And will any of them understand me? My Stennish doesn’t exist yet.”

“I’ll translate if I can keep your technical terms straight,” replied Easy. “If you plan to do more than a one-month tour here, though, it would be a good idea to try to pick up the language of our little friends. Many of them know some of ours, but they appreciate it.”

“I know. I plan to. I’d be glad if you’d help me.”

“When I can, certainly; but you’ll see a lot more of Benj.”

“Benj? He came here three weeks ago with me, and hasn’t had any better chance to learn languages than I have. We’ve both been checking out on the local observation and computer nets, and filling in on the project background.” Easy grinned at her son.

“That’s as may be. He’s a language bug like his mother, and I think you’ll find him useful, though I admit he got his Stennish from me rather than the Mesklinites. He insisted on my teaching him something that his sisters wouldn’t be able to listen in on. Write as much of that off to parental pride as you like, but give him a try. Later, that is; I’d like that information for Dondragmer as soon as we can get it. He said the wind was from the west at about sixty miles an hour, if that helps at all.”

The meteorologist pondered a moment.

“I’ll run what we have through integration, with that bit added,” he said finally. “Then we can give him something when we call, and if the numerical details he gives us then are too different we can make another run easily enough. Wait a moment.

He and the boy turned to their equipment, and for several minutes their activities meant little to the woman. She knew, of course, that they were feeding numerical data and weighting values into computing devices which were presumably already programmed to handle the data appropriately. She was pleased to see Benj apparently handling his share of the work without supervision. She and her husband had been given to understand that the boy’s mathematical powers might not prove up to the need of his field of interest. Of course, what he was doing now was routine which could be handled by anyone with a little training whether he really understood it or not, but Easy chose to interpret the display as encouraging.

“Of course,” McDevitt remarked as the machine was digesting its input, “there’ll be room for doubt anyway. This sun doesn’t do very much to the surface temperature of Dhrawn, but its effect is not completely negligible. The planet has been getting closer to the sun almost ever since we really got going here three years ago. We didn’t have any surface reports except from half a dozen robots until the Mesklinite settlement was set up a year and a half later, and even their measurements still cover only a tiny fraction of the planet. Our prediction work is almost entirely empirical, no matter how much we want to believe in the laws of physics, and we really don’t have enough data for empirical rules yet.”

‘Easy nodded. “I realize that, and so does Dondragmer,” she said. “Still, you have more information than he does, and I guess anything is welcome to him at this point. I know if I were down there thousands of miles from any sort of help, in a machine which is really in the test stage, and not even able to see what was around me — well, I can tell you from experience that it helps to be in touch with the outside. Not just in the way of conversation, though that helps, but so they could more or less see me and know what I was going through.”

“We’d have an awful time seeing him,” put in Benj. “Even when the air at the other end is clear, six million miles is a long way for telescope work.”

“You’re right, of course, but I think you know what I mean,” his mother said quietly. Benj shrugged and said no more; in fact, a rather tense silence ensued for perhaps half a minute.

It was interrupted by the computer, which ejected a sheet of cryptic symbols in front of McDevitt. The other two leaned over his shoulders to see it, though this did Easy little good. The boy spent about five seconds glancing over the lines of information, and emitted a sound halfway between a snort of contempt and a laugh. The meteorologist glanced up at him.

“Go ahead, Benj. You can be as sarcastic as you like on this one. I’d advise against letting Dondragmer have these results uncensored.”

“Why? What’s wrong with them?” asked the woman.

“Well, most of the data, of course, was from shadow satellite readings. I did plug in your wind report, with a bit of uncertainty. I don’t know what sort of instruments the caterpillars have down there, or how precisely the figures were transmitted to you; and you did say about sixty for the wind speed. I didn’t mention the fog, since you didn’t tell me any more than the fact that it was there, and I had no numbers. The first line of this computer run says that visibility in normal light — normal to human eyes, that is, and about the same to Mesklinite ones, I gather — is twenty-two miles for a one-degree blur.”

Easy raised her eyebrows. “Just how do you account for something like that? I thought all the old jokes about weather men had gone pretty well out of date?”

“Actually, they just got stale. I account for it by the simple fact that we don’t and can’t have complete information for the machine. The most obvious lack is a detailed topographic chart of the planet, especially the couple of million square miles west of the Kwembly. A wind coming up or down a slope of six inches per mile at any respectable speed would change its air mass temperature rapidly just from PV change, as Benj pointed out a few minutes ago. Actually, the best maps we have of the topography were worked out from just that effect but they’re pretty sketchy. I’ll have to get more detailed measurements from Dondragmer’s people and give them another run. Did you say Aucoin was getting a more exact position for the Kwembly?”