* * * *
A Snapshot of the Landscape
In the late 1990s, despite lots of books on the subject being published, string theory was pretty much dead. The theory promised a unique solution (a TOE, Theory of [almost] Everything)—and delivered it. But the solution (a Calabi Yau manifold) didn't seem to describe our universe, and it was supersymmetric (sneutrinos, gluinos, etc.). Soon thereafter, not one, but about a dozen solutions were found—and then a million or so. So there went one of the major promises of the theory: uniqueness. Not long after that, the number of solutions rose to 10500 or thereabouts.
The various solutions implied pretty much all possible (discretized) values of the standard model parameters and of the cosmological constant, and even different numbers of physical dimensions. Each of these solutions is essentially a specification for a universe.
One might (almost) visualize these solutions, the Calabi Yau topologies, as hunks of clay with lots of holes in them threaded by fluxes—that is to say lines of force.
For Susskind, the 10500fold abundance of solutions was not a failure, but a stunning success for string theory; the solutions collectively are a “landscape” of possible universes, the “megaverse” as Susskind calls it. It is made up of “pocket universes” (Alan Guth's name for them).
Armed with Guth's (largely accepted) theory of cosmic inflation, particularly eternal inflation, the “landscape architects” were able to generate a theory where these universes would actually be produced.
Alan Guth had theorized that the very early universe (when the entire universe was the size of an elementary particle) would undergo a period of very rapid expansion (a result of a repulsive force acting against gravity, and acting for about 10-35 seconds, ending when the universe was about the size of a marble). Andre Linde (among others) expanded on that, asserting inflation was eternal—that there was not just one Big Bang, but a series of pocket universes, continuously being created. Susskind (using the M-brane version of string theory) avers that most of the 10500 universe possibilities will actually come to exist. He encapsulates the idea as, “A landscape of possibilities populated by a megaverse of actualities.” The landscape theory is controversial in the extreme. It will be interesting to see how it develops and is accepted over the next few years. And incidentally, Joseph Polchinski did not quit physics.
* * * *
Speculations
I'm reminded of the old Cambridge University exam question “Define the Universe and give three examples.” I used to think that was funny.
Just what is a universe? Perhaps we could think of universes as isolated, non-interacting space-times. But I'm not sure we can. Some years back, there was a heated argument (that went on for years) between Susskind and Kip Thorne on one side and Stephen Hawking on the other. The issue was whether information is lost when matter falls into a black hole (Hawking said yes). Eventually Thorne and Susskind prevailed—sort of. The resolution was that the information isn't lost. It does come back out, but in a scrambled form where the key to unscrambling it (probably) cannot exist. Strange! (To paraphrase Arthur Dent in the Hitchhiker's Guide: Ah, this is obviously some strange use of the word information that I wasn't previously aware of.) The point is that the description of universes is much like the description of black holes. Universes then might be able to exchange information; they need not be isolated and non-interacting (although Alex Vilenkin says they cannot possibly interact). The concept of “universe” then becomes, at least for me, rather fuzzy.
While the richness of the landscape model appeals to me, I must admit to a (probably cultural) bias that if a quantity has a value exceedingly close to zero, then either it is zero or there's got to be a good theoretical reason for its near-zero value. Perhaps useful would be an “uberphysics” (hopefully not metaphysics) describing interactions between pocket universes—maybe a physics without Newton's zeroth law. Perhaps the laws governing, say, the value of the cosmological constant are trans-universe laws. Maybe the value of Lambda tends towards but doesn't reach zero. Perhaps Lambda is a kind of normalization—a mechanism whereby universes communicate with each other to attempt to evolve Lambda ultimately to zero.
I would guess that it is not an either/or situation of the landscape, macho physics calculations, or Lee Smolin's evolution ideas. The universe (whatever that means) seems to have the complexity to encompass all three approaches.
There's a paradigm playfully called (Murray) Gell-mann's Law (derived from T.H. White's The Once and Future King), which asserts, “anything not expressly forbidden by physics, must exist.” It was arguably a good guide for hunting new elementary particles. I guess it might apply as much to universes as to particles—or even to theories of physics.
* * * *
Einstein famously said, “Raffiniert ist der Herrgott aber boshaft ist er nicht.” ("Subtle is the Lord, but malicious he is not.")
I wonder.
Copyright (c) 2008 Carl Frederick
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* * *
Novelette: THE EXOANTHROPIC PRINCIPLE
by Carl Frederick
Those who ask big questions must be prepared to accept the answers....
Colin plopped the last of the cardboard boxes onto his desk at the Institute for Distant Communication: Alien Intelligence Group. He smiled. If Bing, his new colleague, was to be believed, the IDC:AIG had more syllables in its name than it had research scientists. Not that his presence would make a difference in that regard; he was a mathematician in a den of physicists.
He cast a glance at his bookcase—empty, depressing, like a deserted beehive—then pulled open a few boxes of books and populated a shelf and a half. In one of the boxes, he found his Brigit's Cross plaque. Kicking off his shoes, he grabbed the plaque, climbed onto his desk, and set the Brigit Cross on the molding above the window.
Just then, the phone rang. Colin dropped to his knees and rummaged on the cardboard-strewn desk for the phone. He found and answered it.
“Colin!” came Bing's voice, his excitement apparent in even one word. “I think maybe at long last we've got something. Come on down, if you would.”
“Of course,” said Colin. “Where?”
“Farcast lab.”
Colin chuckled. “As I said, where?”
“Oh, right! One flight down. Room 302.”
* * * *
Darting through the door into the Farcast lab, Colin saw Bing Robinson and two others whom he didn't recognize standing over a desk gazing intently at a large computer display. From a speaker on the monitor came a pervasive hum, as if from a defective fluorescent fixture. A chirping sound, like the twittering of finches, interrupted the hum at regular intervals. Although Colin couldn't identify much of the room's instrumentation, he did notice an old line printer in the rear of the lab. Buzzing in rhythm with the chirps, it disgorged a waterfall of continuous-feed paper to the floor. He was surprised that a modern laboratory would still use a line-printer. But then, this lab didn't look particularly modern.
The scene, particularly the hum, brought to mind his visit as a boy to his mother in the hospital. He pushed away the memory and walked forward.
Bing turned at his approach. The others did as well—but only briefly before returning their gazes to the monitor. Bing drew them away to make introductions. Katya Shirova was an experimental physicist and Neville Fox, a theorist. The two were cordial but clearly had other things on their minds.
Bing grabbed a sheet of printout from the desk and thrust it into Colin's hands. The sheet held only rows of dots. Colin stared at them:
... ..... ....... ........... ............. ................. ...................
... ..... ....... ........... ............. ................. ...................
... ..... ....... ........... ............. ................. ...................
“I'll save you counting them,” said Bing. “They're three, five, seven, eleven, thirteen, seventeen, and nineteen.” He nodded toward
the speaker. “The chirps you hear are that sequence at high frequency. Blips separated by short pauses and longer pauses between the numbers.”
“Are you...” Colin struggled to take it in. “Are you saying you're receiving extraterrestrial signals?”
“Certainly looks like it,” said Bing.
“Maybe not be so quick with conclusion,” said Katya, turning from the monitor. “You remember LGM.”
“LGM?” said Colin.
Neville swiveled into the conversation. “LGM. Little Green Men. That's what some astronomers called pulsars when they thought that only an intelligence could be the source of such regular pulses.”
“I think,” said Bing, “that these prime number sequences are from an intelligence.”
Smiling, Neville glanced at the monitor. “Actually, so do I.”
“This is wonderful!” said Colin. “Absolutely fantastic!”
Bing and Neville gave slow, shy smiles, the way children might when given an unexpected compliment. Katya looked pleased as well.
“We really don't have much,” said Neville with a self-deprecating shrug. “Some prime numbers, only seven of them.” He shrugged. “The sequence repeats approximately every 15.5 seconds. The hum frequency is 142 Hz, almost exactly—”
“The hum?” said Colin. “Is it from the same source?” Again, he pushed that long ago hospital visit from his mind.
“Most likely,” said Bing. “Sort of a carrier—or an indicator that we should stick to this wavelength.”
“And that wavelength?” said Colin, eager to show he was conversant in SETI matters, “Twenty-one-centimeter, neutral hydrogen, I imagine.”
“No, not radio waves,” said Neville. “Actually we scan through frequencies and polarizations of coherent gravity waves.”
“What?” Colin felt his eyes widen in wonder. “I didn't know you could do that.”
“Oh, we physicists can do a lot,” said Neville, lifting a cup from the desk, “given enough money—and enough coffee.” He pointed at the printout Colin held. “And voila!"
Colin looked down at the printout. “Interesting that they don't consider one or two as prime.” He blew out a slow breath. “They probably define a prime as an integer with no integral divisors less than itself. Makes Fermat's Last Theorem easier to state.”
In thought, he gazed absently at the monitor speaker. “I wonder if the hum frequency is arbitrary.”
Katya cocked her head. “Arbitrary?”
“Let's assume it is,” said Colin. “And also assume the time between transmissions is also arbitrary. By arbitrary, I mean chosen for convenience, or rather for ease of representation. And further, assume the Axiom of Choice.”
Bing and Neville exchanged puzzled glances.
“You know,” said Colin, softly as if to himself. “We might be able to deduce something.” He fingered an imaginary piece of chalk. “Let's call their basic unit of time a ... a ‘woof’ and take that as the time between transmissions. A transmission every woof.” He looked away at an imaginary blackboard. “Then in cycles per woof, the hum frequency would be 142 times 15.5, approximately.” He narrowed his eyes in thought. “Which would be ... 2201.” He paused. “Ah, how about this?” he said after a few seconds. “If they picked an easy number for the frequency, as we might pick 100hz or 1000hz then, if we let A be the base of their number system, their equivalent would be A squared or A cubed or perhaps A to the fourth—which would have to be approximately 2201.”
Stealing a glance at his listeners, he saw signs of their eyes glazing over. He had to admit taking some small satisfaction in getting that result from physicists.
“So,” Colin continued. “Trying base six, we'd have 6, 36, 216, 1296. Nope. Nothing anywhere close to 2201. Trying seven, 7, 49, 343,"—he paused—"and 2401. Closer, but still no cigar. Eight gives 8, 64, 512, 4096. No good. For nine, 9, 81, 729, and"—again a pause—"6561. A strong no. Ten won't work of course. Eleven gives 11, 121, 1331. Not even close—”
“That's fine,” said Neville, taking off his glasses. “We get the idea.”
“And twelve,” said Colin, ignoring the interruption but noting the little furrows of bite marks on the temple-tips of Neville's glasses, “gives 12, 144, 1728. Closer, but no. Thirteen gives 13, 169,"—yet another pause—"and 2197. Ah good. That's only four off from 2201. Well within measurement error, I should think.” He let out a long breath. “Yes,” he said, with finality. “My guess is that they have a base thirteen number system.”
“You're kidding,” said Bing.
“It would imply an odd biology,” said Neville. “A fingers per hand issue.”
“It's the best I can do, I'm afraid,” said Colin with a smile to Bing. Again he gazed at the printout. “3, 5, 7, 11, 13, 17, 19,” he said, distantly. “It's too bad we can't send them 23 as a reply and see what happens.”
“Oh, but we can,” said Bing. “Or we will be able to once we've cooled down the Farcaster.”
“We just don't have enough liquid nitrogen left to cool the gallium arsenide emitter,” said Neville. “Jake, our lab technician, has taken the van and a Dewar to the university to borrow thirty liters or so. He should be back in half an hour.”
“What I meant,” said Colin with a chuckle, “is send a reply and see how they react—without waiting the, I don't know, the hundreds of years of light travel time.”
“Not a problem,” said Bing in an amused voice. “Round-trip signal delay is negligible.”
“Excuse me?” Colin, wide-eyed, wondered if Bing was kidding.
“I do hope they keep transmitting,” said Neville.
“Wait a minute. Wait a minute.” Colin felt suddenly thrust into the Alice in Wonderland tea party. “What do you mean, the delay is negligible?”
Katya gave Bing a puzzled look.
“Sorry,” said Bing. “I didn't have time to brief him yet.” He turned to Colin. “Primitive as this place looks,” he said, “we're actually doing some cutting-edge physics here.”
Colin threw a glance at the printer.
“Our legacy printer?” said Bing. “Yeah, primitive, but there's something comforting about hard copy you can tack to a wall.”
“Please,” Katya cut in. “Perhaps brief him in your office. I need do transmitter calibration before Jake comes with nitrogen.” She smiled at Colin. “I will enjoy to talk later.”
Bing stood. “Fair enough.” Turning to Colin, he said, “But let's use your office. Mine's a mess. And maybe I can help you move in.”
* * * *
“I would have imagined,” said Colin as he walked back to his office with Bing, “that having detected an alien intelligence, you'd be much more excited.”
“I'm afraid to be excited,” said Bing. “We've been burned before. We're pretty sure we've eliminated all mechanisms for pranks now, but...” He shrugged. “Katya almost died from the embarrassment—which is why she's so cautious now. It's lucky we hadn't released the news to the media.”
“And that's why you're not doing it now,” said Colin. “Yes?”
“That and not wanting the project taken away from us just when we start chatting with our aliens.”
“Speaking of chatting,” said Colin, “you were kidding, right? When you said the signal delay was negligible.”
Bing shook his head. “I wasn't.”
For the sake of conversation, Colin slowed his walk toward the stairs. “But Einstein said nothing can exceed the speed of light—not even information.”
“Well ... yes and no.” Bing gave a grunt of a chuckle. “You have to be very, very careful when making a statement about physics. It's as if the universe takes any little loophole it can find and acts on it.”
“But what does this have to do with the speed of light?”
“Well, ‘nothing goes faster than light’ was first taken to mean matter.” Bing spoke in synchrony with his tromping up the flight of stairs. “But the distant galaxies in our expanding universe go, in effect, faster than light. Of
course they're going directly away from us so we can't see any light from them.” He looked over his shoulder, as if to see if Colin was following him, both literally and figuratively, then went on, “So then people said the idea applied to information.” They went through the fire door to the fourth floor. “But quantum entanglement,” said Bing, scarcely pausing for breath, “implies instantaneous transmission of information of some strange sort. So now one says that no message can be transmitted faster than light.”
Bing waited as Colin opened the door to his office. “But even here there's wiggle room.” Bing followed Colin into the room, took a quick glance around, and then laughed. “And that's not a comment on the clutter in your office.”
“You're most kind,” said Colin as he cleared off a chair for Bing.
Bing sat. “Anyway,” he said with the enthusiasm of a kid, “if the information is stochastic in nature, which means we're not certain of the message contents, then there's the possibility of superluminal transmission. But the big loophole, the one Project Farcast makes use of, is that if the receiver of the message can't tell where the message came from, then it's allowed to have traveled faster than light.”
Colin circled around his desk to its chair. “That's a little hard to believe,” he said as he sat.
“It doesn't violate Einstein,” said Bing. “Tachyons and all that.”
Analog SFF, July-August 2008 Page 13
