Robin B., I can't speak for Eliezer's characters, but I believe the fashionability of skepticism about string theory has come from the lack of falsifiable predictions, after so many years. No-one has been able to say "this is the ground state". Instead string theorists have studied a large number of possible ground states (distinguished by background geometry), most of them looking nothing like what we see, as they try to get a grip on the theory. The hope used to be that all but one would prove on further study to be unstable. Now there's an interest in anthropic predictions, though that's just one school of thought.
I have read that no-one has ever exhibited a string-theory ground state exactly reproducing the Standard Model, though you can get close. That has to be significant. If such a place can be found in the space of ground states ("moduli space"), you could then try to reason out why it was dynamically favored. And we'll get more information within a few years from the Large Hadron Collider, which will establish whether there's a Higgs boson or something else (I bet on something else; the Higgs was just the simplest way to make a tractable theory and lingers by default).
In string theory's favor is that it generically has spin-1/2 particles (fermions), spin-1 particles (gauge bosons), and spin-2 particles (gravitons). That's a neat trick. So I tend to think either that it is the answer, or that it is just a beast of so many parts that anything you might look for is in there somewhere. In the latter case, it could be compared to the Monster group, the "largest sporadic simple finite group". There are infinitely many finite simple groups, just as there are infinitely many possible field theories, and most of those groups resemble some subgroup of the Monster, just as string theory has spin-1/2, spin-1, and spin-2 fields, just like the real world. It could be that string theory is just the "maximally complicated field theory" (and in fact, mathematically, it has a relationship to the Monster) and that it derives this generic pseudo-predictiveness solely from that. It has a little bit of everything, so anything looks a little bit like it. It would certainly be a mistake to take some real object, like Rubik's cube, discover a few facts about its symmetry group, and then announce that its symmetry group must be the Monster, just because the Monster has subgroups with those properties. It could be that string theorists are making a mistake like that.
On the other hand, what's the alternative? The phenomenological approach to particle physics is just to postulate enough fields with enough properties to explain what you see. You can treat gravity as just another field, contingently present, but then your theory becomes mathematically intractable. Part of string theory's appeal is that you can calculate graviton-graviton scattering, etc., unlike any previous theory of quantum gravity. But the price is that you buy into the unification philosophy. Recently, there have been claims that "contingent" theories of quantum gravity - according to which reality is just a bunch of fields plus gravity, and there's no deeper reason as to why it's that combination of fields - can be made to work; this is the "loop quantum gravity" research program. It's my judgement that string theory is mathematically much more solid. The loop quantum gravity researchers have had to backtrack several times, after making ambitious claims about the construction of consistent "gravity-plus-anything" quantum theories. Right now the evidence (in my semi-lay opinion) points in the other direction, that gravity needs to be part of a larger ensemble of fields with special properties if it is to be quantizable. Which suggests string theory.
"Do as well as Einstein?" Jeffreyssai said, incredulously. "Just as well as Einstein? Albert Einstein was a great scientist of his era, but that was his era, not this one! Einstein did not comprehend the Bayesian methods; he lived before the cognitive biases were discovered; he had no scientific grasp of his own thought processes. Einstein spoke nonsense of an impersonal God—which tells you how well he understood the rhythm of reason, to discard it outside his own field! He was too caught up in the drama of rejecting his era's quantum mechanics to actually fix it. And while I grant that Einstein reasoned cleanly in the matter of General Relativity—barring that matter of the cosmological constant—he took ten years to do it. Too slow!"
"Too slow?" repeated Taji incredulously.
"Too slow! If Einstein were in this classroom now, rather than Earth of the negative first century, I would rap his knuckles! You will not try to do as well as Einstein! You will aspire to do BETTER than Einstein or you may as well not bother!"
Jeffreyssai shook his head. "Well, I've given you enough hints. It is time to test your skills. Now, I know that the other beisutsukai don't think much of my class projects..." Jeffreyssai paused significantly.
Brennan inwardly sighed. He'd heard this line many times before, in the Bardic Conspiracy, the Competitive Conspiracy: The other teachers think my assignments are too easy, you should be grateful, followed by some ridiculously difficult task—
"They say," Jeffreyssai said, "that my projects are too hard; insanely hard; that they pass from the realm of madness into the realm of Sparta; that Laplace himself would catch on fire; they accuse me of trying to tear apart my students' souls—"
Oh, crap.
"But there is a reason," Jeffreyssai said, "why many of my students have achieved great things; and by that I do not mean high rank in the Bayesian Conspiracy. I expected much of them, and they came to expect much of themselves. So..."
Jeffreyssai took a moment to look over his increasingly disturbed students, "Here is your assignment. Of quantum mechanics, and General Relativity, you have been told. This is the limit of Eld science, and hence, the limit of public knowledge. The five of you, working on your own, are to produce the correct theory of quantum gravity. Your time limit is one month."
"What?" said Brennan, Taji, Styrlyn, and Yin. Hiriwa gave them a puzzled look.
"Should you succeed," Jeffreyssai continued, "you will be promoted to beisutsukai of the second dan and sixth level. We will see if you have learned speed. Your clock starts—now."
And Jeffreyssai strode out of the room, slamming the door behind him.
"This is crazy!" Taji cried.
Hiriwa looked at Taji, bemused. "The solution is not known to us. How can you know it is so difficult?"
"Because we knew about this problem back in the Eld days! Eld scientists worked on this problem for a lot longer than one month."
Hiriwa shrugged. "They were still arguing about many-worlds too, weren't they?"
"Enough! There's no time!"
The other four students looked to Styrlyn, remembering that he was said to rank high in the Cooperative Conspiracy. There was a brief moment of weighing, of assessing, and then Styrlyn was their leader.
Styrlyn took a great breath. "We need a list of approaches. Write down all the angles you can think of. Independently—we need your individual components before we start combining. In five minutes, I'll ask each of you for your best idea first. No wasted thoughts! Go!"
Brennan grabbed a sheet and his tracer, set the tip to the surface, and then paused. He couldn't think of anything clever to say about unifying general relativity and quantum mechanics...
The other students were already writing.
Brennan tapped the tip, once, twice, thrice. General relativity and quantum mechanics...
Taji put his first sheet aside, grabbed another.
Finally, Brennan, for lack of anything clever to say, wrote down the obvious.
Minutes later, when Styrlyn called time, it was still all he had written.
"All right," Styrlyn said, "your best idea. Or the idea you most want the rest of us to take into account in our second components. Taji, go!"
Taji looked over his sheets. "Okay, I think we've got to assume that every avenue that Eld science was trying is a blind alley, or they would have found it. And if this is possible to do in one month, the answer must be, in some sense, elegant. So no multiple dimensions. If we start doing anything that looks like we should call it 'string theory', we'd better stop. Maybe begin by considering how failure to understand decoherence could have led Eld science astray in quantizing gravity."
"The opposite of folly is folly," Hiriwa said. "Let us pretend that Eld science never existed."
"No criticisms yet!" said Styrlyn. "Hiriwa, your suggestion?"
"Get rid of the infinities," said Hiriwa, "extirpate that which permits them. It should not be a matter of cleverness with integrals. A representation that allows infinity must be false-to-fact."
"Yin."
"We know from common sense," Yin said, "that if we stepped outside the universe, we would see time laid out all at once, reality like a crystal. But I once encountered a hint that physics is timeless in a deeper sense than that." Yin's eyes were distant, remembering. "Years ago, I found an abandoned city; it had been uninhabited for eras, I think. And behind a door whose locks were broken, carved into one wall: quote .ua sai .ei mi vimcu ty bu le mekso unquote."
Brennan translated: Eureka! Eliminate t from the equations. And written in Lojban, the sacred language of science, which meant the unknown writer had thought it to be true.
"The 'timeless physics' of which we've all heard rumors," Yin said, "may be timeless in a very literal sense."
"My own contribution," Styrlyn said. "The quantum physics we've learned is over joint positional configurations. It seems like we should be able to take that apart into a spatially local representation, in terms of invariant distant entanglements. Finding that representation might help us integrate with general relativity, whose curvature is local."
"A strangely individualist perspective," Taji murmured, "for one of the Cooperative Conspiracy."
Styrlyn shook his head. "You misunderstand us, then. The first lesson we learn is that groups are made of people... no, there is no time for politics. Brennan!"
Brennan shrugged. "Not much, I'm afraid, only the obvious. Inertial mass-energy was always observed to equal gravitational mass-energy, and Einstein showed that they were necessarily the same. So why is the 'energy' that is an eigenvalue of the quantum Hamiltonian, necessarily the same as the 'energy' quantity that appears in the equations of General Relativity? Why should spacetime curve at the same rate that the little arrows rotate?"
There was a brief pause.
Yin frowned. "That seems too obvious. Wouldn't Eld science have figured it out already?"
"Forget Eld science existed," Hiriwa said. "The question stands: we need the answer, whether it was known in ancient times or not. It cannot possibly be coincidence."
Taji's eyes were abstracted. "Perhaps it would be possible to show that an exception to the equality would violate some conservation law..."
"That is not where Brennan pointed," Hiriwa interrupted. "He did not ask for a proof that they must be set equal, given some appealing principle; he asked for a view in which the two are one and cannot be divided even conceptually, as was accomplished for inertial mass-energy and gravitational mass-energy. For we must assume that the beauty of the whole arises from the fundamental laws, and not the other way around. Fair-rephrasing?"
"Fair-rephrasing," Brennan replied.
Silence reigned for thirty-seven seconds, as the five pondered the five suggestions.
"I have an idea..."