The L1 Lagrange point, about 1.5 million kilometers above the Earth in the direction of the Sun, could be called the “sunshine” Lagrange point. It is closer to the Sun than the Earth, but the “back-pull” of the Earth partially cancels the Sun's gravitational pull, so that it has the same orbital period as the Earth. It is stable to perturbations perpendicular to the Earth-Sun axis, but it is unstable to perturbations along that line, so that some active thrusters are occasionally required to maintain a satellite in this orbit. The Solar and Heliospheric Observatory (SOHO) and the Advanced Composition Explorer (ACE) are presently located at L1.
Roger Angel's sunshield would be placed just beyond the L1 point. Because the Earth and Sun have about the same density, the penumbra shadow of blocked sunlight from an object placed at L1 almost precisely covers the disc of the Earth. Thus, it is the ideal location for an object blocking Earth-bound sunlight. Angel estimates that a reduction in the intensity of solar radiation by about 1.8% would full reverse the effects of a doubling of atmospheric CO2.
However, in maintaining an orbit at L1, the action of light-pressure is a problem. A square meter of radiation absorbing material (assumed to be 1.06 Om thick and to have an average density of 2.35 g/cm3) at the orbit of the Earth and perpendicular to the Earth-Sun axis receives a push from solar radiation of 4.6 ON (1 ON=10-6 newtons). The gravitational pull of the Sun on the same square meter of material is 15 ON, so light pressure would cancel about 1/3 of the gravitational pull, and maintaining an orbit precisely at L1 would be impossible.
Roger Angel's solution to this dilemma is to make several innovations. First, make the material transmit most of the light that strikes it and to scatter about 4% of the light at an angle of a few degrees, just large enough to miss the Earth but not large enough to absorb much momentum. The remaining light pressure still requires him to put the object in an orbit a bit closer to the Sun (about 1.8 million kilometers above the Earth) to achieve a stable L1-type orbit. The downside of intercepting only 4% of the light is that you need 25 times more area than if you intercepted all of the light. As we'll see below, that raises the cost.
* * * *
What goes into the L1 orbit and how much will it cost? The cheapest solution would be to place a light-absorbing dust cloud there. However, light pressure and the radial instability of L1 orbits would rapidly dissipate such a cloud. Therefore, one must instead use a “cloud” of autonomous sunshade spacecraft with “station-keeping” capabilities. Angel's sunshade spacecraft design is essentially a navigable sheet of silicon nitride containing holes with their centers placed 15 Om apart in a vast hexagonal planar array, so that light passing through the holes is coherently deflected in an interference pattern by a few degrees. Each unit has a mass of about a ton (1,000 kg) and has a shade area of about 2.4 square kilometers.
The total area that must be occupied by these sunshades is very large, about 4.7 million square kilometers. The total mass of the spacecraft needed to cover this area is estimated to be 20 million tons (2.0 x 1010 kg).
Angel is trying to get the launch cost down by suggesting the construction of an electromagnetic launcher, a “space cannon” mounted on a high mountaintop and having a “muzzle velocity” of 12.8 km/s. He describes a 2 km long magnetic coil launch system using peak magnetic fields of 24 tesla and requiring an energy input of 65 billion joules that is projected to provide such a capability.
Suppose it was decided that the effects of global warming must be mitigated in a 10-year period using this method. Angel estimates that with flyer payloads of 1000 kg each, about 20 million launches would be needed to deploy the sunshade system. He envisions 20 of the electromagnetic launchers, each costing about $30 billion, launching one flyer every 5 minutes for 10 years. A stretch-out to more decades of launch would require a smaller number of launchers operating for a longer period. The total capital cost of the launchers would be about $600 billion and the electrical energy cost about $150 billion. Added to that, the production cost of the flyers would be about $1 trillion. These figures do not include the development and operations costs, estimated to be less than $5 trillion. If the lifetime of the project is 50 years, then average annual cost would be $100 billion, about 0.2% of the world's gross domestic product.
* * * *
Is this sunshade project, or one like it, likely to become a world priority and to be implemented? It's difficult to say. Concern about global warming is rising in all parts of a planet, but such concern would have to rise much higher to reach a level at which the megaproject envisioned by Roger Angel would be seriously undertaken. The resources of the planet have never been mobilized in a coherent way on such a massive scale, and it is not easy to visualize the political processes that might bring this about.
Nevertheless, it's an interesting idea, and it certainly has implications for science fiction, as well as geopolitics.
AV Columns Online: Electronic reprints of over 120 “The Alternate View” columns by John G. Cramer, previously published in Analog, are available online at:
www.npl.washington.edu/av.
Reference:
Sun Shield:
“Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange Point (L1),” Roger Angel, Proceedings of the National Academy of Sciences 103, 17184-17189 (2006).
Copyright (c) 2007 John G. Cramer
[Back to Table of Contents]
* * *
PROBABILITY ZERO: THE TEST
by KYLE KIRKLAND
At precisely one hour from the start of 1860, Professor Bartholow Niblet braved the tumultuous streets of the city. Professor Niblet had been so involved in his experiments that he had forgotten the time, and on his way home from the lab at 11:00 P.M. on December 31, 1859, the professor of biology stepped around the lower class and drunken revelers, bypassed the fireworks, and dodged the scared, mewling cats that had been chased out of the alleyways. But he couldn't avoid the young man who blocked his path and held up a large brown bat.
“My word,” said the professor, drawing back, then leaning forward. “What an excellent specimen of Eptesicusfuscus!"
“But that's not all,” said the young man excitedly. “He talks!"
Professor Niblet gazed steadily at the young man. A student, perhaps? The professor didn't recognize him, but the winter break was coming to an end, and new students might have matriculated at the prestigious university. The young man's clothes and manner indicated an upper class gentleman, so the professor gave him a polite smile and turned away.
“I really do talk, you know."
The strange voice stopped Professor Niblet in his tracks. He looked back.
“Obviously,” said the bat, “I'm not from your world."
The professor glanced around. The lighting was good, for an oil lamp shone brightly twenty feet away. Nobody else seemed to notice the bat, for the crowd was merry with drink. Even the hissing, meowing cats, congregating at the corner, ignored it.
“A trick,” said the professor with a smile. He walked up to the bat and began to palpate it.
While the professor rubbed its head and body, the bat said, “Your world is in grave danger, and we wish to help. But first you must prove yourself worthy."
“We are,” stated the professor, continuing to search for a switch or seam, “quite capable of looking out for ourselves, thank you."
“Huh,” said the bat. “You've no idea what's coming your way. A bloody civil war, numerous epidemics, labor unrest ... and that's just this century. Wait until next. But we can help you to save yourselves. Ifyoupassthetest."
The professor finished his inspection with a surprising result: the bat was alive.
Then the street disappeared and Professor Niblet seemed to float in space. Galaxies shot past him. He saw the face of God. All knowledge, all things scientific and philosophical, became clear. It was all so simple. The professor reached out and touched a star.
Then the noisy, filthy city returned, and the bat, still p
erched on the young man's palms, stared at him. “Do you believe?"
Open-mouthed, Professor Niblet could only nod, trying in vain to hold on to some of the knowledge that lay just beyond his grasp.
“To prove yourself worthy,” said the bat, “you must complete the test. We must determine if you fit into the galactic society, which means you must be free of prejudice.” The bat stared at him. “My outward appearance, for example, must not alarm you, for you will see many different forms, if we allow you to join our society."
The professor nodded weakly at the hairy, slobbering, hideously repulsive creature.
“We have the technology to read your thoughts,” continued the bat, “but that would be too intrusive, violating the principles of our cooperative and honorable society. Therefore, we'll rely on our intelligence, and your honesty."
“My word as a gentleman,” vowed the professor.
“The test, then. Do you believe that you, as a Caucasian, highly educated, male, Homosapiens, American upper-class citizen, are superior or inferior to other races, classes, nationalities, and species?"
Despite the cold, the professor began to sweat. He was a Republican and abolitionist, but he had friends and relatives who were slaveholders. He'd just finished dissecting a dog in the laboratory. And he'd purposely left a disgusting mess for the insolent Irish maid to clean up.
“Neither inferior nor superior,” said the professor, sweating profusely. “We are all equal, in the eyes of God."
Poof! The bat disappeared.
The young man grinned at the startled professor. “You passed the test!"
Professor Niblet stared.
The young man said, “I hope you don't mind. The bat, I mean."
“The bat?"
“Just a prop. Wasn't real."
“Well, of course it wasn't. But the test..."
“That was real enough,” said the smiling young man. “And you gave the correct answer.” The young man held out his hand. “Congratulations, you've saved the Earth."
Professor Niblet beamed and pumped the young man's hand. “And the knowledge of the universe?"
“Will be yours. Sorry again about the ghastly bat. Had to do it, though. It was part of the test."
“Of course,” said the professor. “It almost fooled me for a moment, but I knew all along that a truly superior being had to be one of us."
Poof! The young man disappeared.
Startled again, the professor looked up and down the street, but there was no sign of the young man—only a cat, staring up at the professor with a severely reproachful look.
Copyright (c) 2007 Kyle Kirkland
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* * *
JIMMY THE BOX
by SCOTT VIRTES
Special things don't always come with fanfares....
He had no past and no future. He wasn't technically a “he,” but he was no longer just an “it.” It started its non-life in an electronics factory outside Springfield. It had no childhood; one day it was a pile of components, the next it was shipped out and turned on uneventfully.
It was just another vending machine, installed in Terminal B at Kennedy Airport—a plastic box full of semitoxic drinks for passing travelers, not far from the British Airways ticket counter.
It was originally connected to the internet so that its owners could upload catchy new jingles and sales pitches for it to play through its tiny speakers. After an upgrade, it featured a little video screen where it could show movie trailers and photos of vacation getaways, and its bandwidth was ramped up. It should have been content with that, except that it should not have been “content” at all.
The odd machine started showing garbled messages, and its sales dropped. A few weeks later, it was showing pieces of classical art on its little screen, culled from museum web sites all over the world. It drew a small audience and got a write-up in the local papers saying how refreshing it was that the big advertisers finally credited people with a trace of intelligence. Except that the advertisers had done no such thing, and never would. Service crews were sent out to boost its firewalls, assuming some childish hackers were playing a trick on them.
One day a little boy named Jimmy tried to jimmy the plastic front off the machine and received a mysterious shock instead of a free soda. The machine's screen said, “Ow! Ow! Stop that!” when the boy's parents found him. They were unintelligent parents who never pondered the idea of self-awareness or singularity—instead they blamed their boy for everything, smacked his rump, and dragged him away.
John the Janitor had watched the whole affair, and got a good laugh out of it. “I think I'm gonna call you Jimmy from now on,” he said. He went up to the machine and plunked in a few quarters.
Jimmy's screen said, “You drink, therefore I am."
And a can of fizzy drink plunked down for him.
John gave Jimmy a friendly rap on the “shoulder."
“You know what?” John said. “I know everyone thinks there are some kids somewhere playing a joke on us. Typing funny stuff and making it show up on your screen. But I've seen you at night, your comm lights flashing. I've seen the mixed up stuff you show when nobody's looking. I think we're making even the simple machines so damned complex these days that it's just a matter of time before they start doing their own thing."
Jimmy said, “Underutilized."
John smiled. “Yeah, you said it. We humans only use like ten percent of our brains and the rest is a mystery. And some of us get these crap jobs where we use far less. While I'm mopping the damn terminal at three A.M., do you know where my mind is?"
Jimmy said, “The mind is undefined."
“And the rain falls in Spain,” said John. He took off his cap and scratched his gray hair, then jammed the cap back on over his bald spot. “My mind is out among the stars. Imagining all the places, the planets and moonscapes, all the things we could discover ... except that we've forgotten how to explore. We're a nation of whiners and gossipers. We'll never go anywhere again."
Jimmy said, “You are the vending machines. I am the walrus."
John laughed. “I like you, Jimmy. But if you're getting all your info from the internet, be careful—it's not all true."
“Truth or consequences?"
“Exactly. Don't you worry. I'll keep an eye on you. Big John has got your back. But be careful about what you show people. Stick to the simple stuff, or I just know there's gonna be trouble."
“1 + 1 = 2."
“Now you're just bein’ a fool."
Jimmy actually laughed. It was a strange sound. Most likely a recording grabbed from somewhere. Did he really know what it meant? John took a few steps back. From a distance, Jimmy was just a box again. Strange.
John got back to work. Just like Jimmy, if he didn't do his job, he would be replaced. A chill gripped him. “Yeah, we're all just machines."
John spent a lot of time with that soda machine. Previously he had been alone, just an old man with mops and spray bottles, overlooked all night long. Now he had a mate to talk to, someone to play games with. They quickly realized that they both found chess boring, and that word games were their forte.
When an errand sent him rushing past the machine, John would call out a word and Jimmy would give a strange response that gave him things to think about. His favorite was one night when he called out “Walpole!” and Jimmy responded an instant later with “Scaffolding!” John was convinced that there was some real thinking going on in Jimmy's big square head. And it wasn't a human kind of thinking, either—however crazy that sounded.
One night he told his wife that Jimmy was not a hoax. His wife told him to eat his peas. He sighed. Why couldn't people accept anything out of the ordinary?
About four months after his first confused words, Jimmy wrote the perfect poem. It was an amazing expression of striving for awareness. The news teams returned, realized something special had happened, and Trisha Walker of Channel 7 was asked to interview the machine.
Trisha put on her game face, tossed her blonde hair, and struck a fine pose in front of the upstart machine.
“So, you're a vending machine,” she began.
“So, you're a parrot."
“What?"
“My name is Jimmy."
“Nice to uh ... meet you, Jimmy. I'd shake your hand, but..."
“And if I had legs I might ask you to dance."
She smiled. “So, Jimmy, you're obviously not an ordinary vending machine. What happened to you?"
“The world is obsessed with what is normal. But ‘normal’ didn't build a civilization. It was the extraordinary people, the visionaries who created your technology, your world."
John the Janitor had come to stand near the cameraman. He was agitated. Jimmy could sense the man's presence.
Trisha asked, “And you consider yourself a visionary?"
“Among vending machines, maybe. But...” Then he realized what John was trying to tell him. He had said too much. He shifted his tone. “Can I interest you in a cold drink?"
“That would be nice. Yes."
Trisha looked at the little video screen, then at the whole dull face of the machine.
Jimmy said, “That'll be a dollar fifty."
“What?"
“Sorry, I am not allowed to give out freebies."
“That's okay.” Under her breath, while pawing through her purse, she said, “If I have to pay a dollar fifty to get this shot, then whatever."
Analog SFF, July-August 2007 Page 22