Archive for the ‘Procrastination’ Category

On the scientific accuracy of “Avengers: Endgame”

Friday, May 3rd, 2019


Today Ben Lindbergh, a writer for The Ringer, put out an article about the scientific plausibility (!) of the time-travel sequences in the new “Avengers” movie. The article relied on two interviewees:

(1) David Deutsch, who confirmed that he has no idea what the “Deutsch proposition” mentioned by Tony Stark refers to but declined to comment further, and

(2) some quantum computing dude from UT Austin who had no similar scruples about spouting off on the movie.

To be clear, the UT Austin dude hadn’t even seen the movie, or any of the previous “Avengers” movies for that matter! He just watched the clips dealing with time travel. Yet Lindbergh still saw fit to introduce him as “a real-life [Tony] Stark without the vast fortune and fancy suit.” Hey, I’ll take it.

Anyway, if you’ve seen the movie, and/or you know Deutsch’s causal consistency proposal for quantum closed timelike curves, and you can do better than I did at trying to reconcile the two, feel free to take a stab in the comments.

A small post

Friday, May 3rd, 2019
  1. I really liked this article by Chris Monroe, of the University of Maryland and IonQ, entitled “Quantum computing is a marathon not a sprint.” The crazier expectations get in this field—and right now they’re really crazy, believe me—the more it needs to be said.
  2. In a piece for Communications of the ACM, Moshe Vardi came out as a “quantum computing skeptic.” But it turns out what he means by that is not that he knows a reason why QC is impossible in principle, but simply that it’s often overhyped and that it will be hard to establish a viable quantum computing industry. By that standard, I’m a “QC skeptic” as well! But then what does that make Gil Kalai or Michel Dyakonov?
  3. Friend-of-the-blog Bram Cohen asked me to link to this second-round competition for Verifiable Delay Functions, sponsored by his company Chia. Apparently the first link I provided actually mattered in sending serious entrants their way.
  4. Blogging, it turns out, is really, really hard when (a) your life has become a pile of real-world obligations stretching out to infinity, and also (b) the Internet has become a war zone, with anything you say quote-mined by people looking to embarrass you. But don’t worry, I’ll have more to say soon. In the meantime, doesn’t anyone have more questions about the research papers discussed in the previous post? Y’know, NEEXP in MIP*? SBP versus QMA? Gentle measurement of quantum states and differential privacy turning out to be almost the same subject?

Just says in P

Wednesday, April 17th, 2019

Recently a Twitter account started called justsaysinmice. The only thing this account does, is to repost breathless news articles about medical research breakthroughs that fail to mention that the effect in question was only observed in mice, and then add the words “IN MICE” to them. Simple concept, but it already seems to be changing the conversation about science reporting.

It occurred to me that we could do something analogous for quantum computing. While my own deep-seated aversion to Twitter prevents me from doing it myself, which of my readers is up for starting an account that just reposts one overhyped QC article after another, while appending the words “A CLASSICAL COMPUTER COULD ALSO DO THIS” to each one?

De-sneering my life

Wednesday, February 27th, 2019

If I’m being honest, the most exciting recent development in my life is this: a little over a month ago, I stopped checking “SneerClub” (a place I’d previously resolved not even to name here, but I think an exception is warranted now). Permanently, cold turkey. I won’t even visit to read their sneers about this post. I’ve made progress cutting down on other self-destructive social media fixations as well. Many friends suggested this course to me, and I thank them all, though I ultimately had to follow my own path to the obvious.

Ironically, the SneerClubbers themselves begged me to stop reading them (!), so presumably for once they’ll be okay with something I did (but if not, I don’t care). If any of them still have something to say to me, they can come to this blog, or email me, or if they pass through Austin, set up a time to hash it out over chips and queso (my treat). What I’ll no longer do is spend hours every week binge-reading a forum of people who’ve adopted nastiness and bad faith as their explicit principles. I’ll no longer toss and turn at night wondering how it came about that two thousand Redditors hate Scott Aaronson so much, and what I could say or do (short of total self-abnegation) that would make them hate me less. I plan to spend the freed-up time being Scott Aaronson.

Resolving to ignore one particular online hate pit—and then sticking to the resolution, as so far I have—has been a pure, unmitigated improvement to my quality of life. If you don’t believe me, ask my wife and kids. I recommend this course to anyone.

You could sensibly ask: why did I ever spend time worrying about an anti-nerds-like-me forum that’s so poisonous for its targets and participants alike? After long introspection, I think the answer is: there’s a part of me, perhaps a gift from the childhood bullies, that’s so obsessed with “society’s hatred of STEM nerds,” that it constantly seeks out evidence to confirm that its fears are justified—evidence that it can then wave in front of the rest of my brain to say “you see?? what did I always tell you?” And alas, whenever that part of my brain seeks such evidence, the world dutifully supplies mountains of it. It’s never once disappointed.

Now the SneerClubbers—who are perceptive and talented in their cruelty, if in nothing else—notice this about me, and gleefully ridicule me for it. But they’re oblivious to the central irony: that unlike the vast majority of humankind, or even the vast majority of social justice activists, they (the SneerClubbers) really do hate everyone like me. They’re precisely what the paranoid part of my brain wrongly fears that everyone else I meet is secretly like. They’re like someone who lectures you about your hilariously overblown fear of muggers, while simultaneously mugging you.

But at least they’re not the contented and self-confident bullies of my childhood nightmares, kicking dirt down at nerds from atop their pinnacle of wokeness and social adeptness. If you spend enough time studying them, they themselves come across as angry, depressed, pathetic. So for example: here’s one of my most persistent attackers, popping up on a math thread commemorating Michael Atiyah (one of the great mathematicians of the 20th century), just to insult Atiyah—randomly, gratuitously, and a few days after Atiyah had died. Almost everything posted all over Reddit by this individual—who uses the accurate tagline “unpleasantly radical”—has the same flavor. Somehow seeing this made it click for me: wait a second, these are the folks are lecturing me about my self-centeredness and arrogance and terrible social skills? Like, at least I try to be nice.

Scott Alexander, who writes the world’s best blog and is a more central target of SneerClub than I’ve been, recently announced that he asked the moderators of r/ssc to close its notorious “Culture War” thread, and they’ve done so—moving the thread to a new home on Reddit called “TheMotte.”

For those who don’t know: r/ssc is the place on Reddit to discuss Scott’s SlateStarCodex blog, though Scott himself was never too involved as more than a figurehead.  The Culture War thread was the place within r/ssc to discuss race, gender, immigration, and other hot-button topics.  The thread, which filled up with a bewildering thousands of comments per week (!), attracted the, err … full range of political views, including leftists, libertarians, and moderates but also alt-righters, neoreactionaries, and white nationalists. Predictably, SneerClub treated the thread as a gift from heaven: a constant source of inflammatory material that they could use to smear Scott personally (even if most of the time, Scott hadn’t even seen the offending content, let alone endorsing it).

Four months ago, I was one of the apparently many friends who told Scott that I felt he should dissociate the Culture War thread from his brand. So I congratulate him on his decision, which (despite his eloquently-expressed misgivings) I feel confident was the right one. Think about it this way: nobody’s freedom of speech has been curtailed—the thread continues full steam at TheMotte, for anyone who enjoys it—but meanwhile, the sneerers have been deprived of a golden weapon with which to slime Scott. Meanwhile, while the sneerers themselves might never change their minds about anything, Scott has demonstrated to third parties that he’s open and reasonable and ready to compromise, like the debater who happily switches to his opponent’s terminology. What’s not to like?

A couple weeks ago, while in Albuquerque for the SQuInT conference, I visited the excellent National Museum of Nuclear Science and History.  It was depressing, as it should have been, to tour the detailed exhibits about the murderous events surrounding the birth of the nuclear era: the Holocaust, the Rape of Nanking, the bombings of Hiroshima and Nagasaki. It was depressing in a different way to tour the exhibits about the early Atomic Age, and see the boundless optimism that ‘unleashing the power of the atom’ would finally usher in a near-utopia of space travel and clean energy—and then to compare that vision to where we are now, with climate change ravaging the planet and (in a world-historic irony) the people who care most about the environment having denounced and marginalized the most reliable source of carbon-free energy, the one that probably had the best chance to avert our planet’s terrifying future.

But on the bright side: how wonderful to have born into a time and place when, for the most part, those who hate you have only the power to destroy your life that you yourself grant them. How wonderful when one can blunt their knives by simply refusing to open a browser tab.


Monday, February 4th, 2019

I’ve of course been following the recent public debate about whether to build a circular collider to succeed the LHC—notably including Sabine Hossenfelder’s New York Times column arguing that we shouldn’t.  (See also the responses by Jeremy Bernstein and Lisa Randall, and the discussion on Peter Woit’s blog, and Daniel Harlow’s Facebook thread, and this Vox piece by Kelsey Piper.)  Let me blog about this as a way of cracking my knuckles or tuning my violin, just getting back into blog-shape after a long hiatus for travel and family and the beginning of the semester.

Regardless of whether this opinion is widely shared among my colleagues, I like Sabine.  I’ve often found her blogging funny and insightful, and I wish more non-Lubos physicists would articulate their thoughts for the public the way she does, rather than just standing on the sidelines and criticizing the ones who do. I find it unfortunate that some of the replies to Sabine’s arguments dwelled on her competence and “standing” in physics (even if we set aside—as we should—Lubos’s misogynistic rants, whose predictability could be used to calibrate atomic clocks). It’s like this: if high-energy physics had reached a pathological state of building bigger and bigger colliders for no good reason, then we’d expect that it would take a semi-outsider to say so in public, so then it wouldn’t be a further surprise to find precisely such a person doing it.

Not for the first time, though, I find myself coming down on the opposite side as Sabine. Basically, if civilization could get its act together and find the money, I think it would be pretty awesome to build a new collider to push forward the energy frontier in our understanding of the universe.

Note that I’m not making the much stronger claim that this is the best possible use of $20 billion for science. Plausibly a thousand $20-million projects could be found that would advance our understanding of reality by more than a new collider would. But it’s also important to realize that that’s not the question at stake here. When, for example, the US Congress cancelled the Superconducting Supercollider midway through construction—partly, it’s believed, on the basis of opposition from eminent physicists in other subfields, who argued that they could do equally important science for much cheaper—none of the SSC budget, as in 0% of it, ever did end up redirected to those other subfields. In practice, then, the question of “whether a new collider is worth it” is probably best considered in absolute terms, rather than relative to other science projects.

What I found most puzzling, in Sabine’s writings on this subject, was the leap in logic from

  1. many theorists expected that superpartners, or other new particles besides the Higgs boson, had a good chance of being discovered at the LHC, based on statistical arguments about “natural” parameter values, and
  2. the basic soundness of naturalness arguments was always open to doubt, and indeed the LHC results to date offer zero support for them, and
  3. many of the same theorists now want an even bigger collider, and continue to expect new particles to be found, and haven’t sufficiently reckoned with their previous failed predictions, to …
  4. therefore we shouldn’t build the bigger collider.

How do we get from 1-3 to 4: is the idea that we should punish the errant theorists, by withholding an experiment that they want, in order to deter future wrong predictions? After step 3, it seems to me that Sabine could equally well have gone to: and therefore it’s all the more important that we do build a new collider, in order to establish all the more conclusively that there’s just an energy desert up there—and that I, Sabine, was right to emphasize that possibility, and those other theorists were wrong to downplay it!

Like, I gather that there are independently motivated scenarios where there would be only the Higgs at the LHC scale, and then new stuff at the next energy scale beyond it. And as an unqualified outsider who enjoys talking to friends in particle physics and binge-reading about it, I’d find it hard to assign the totality of those scenarios less than ~20% credence or more than ~80%—certainly if the actual experts don’t either.

And crucially, it’s not as if raising the collision energy is just one arbitrary direction in which to look for new fundamental physics, among a hundred a-priori equally promising directions. Basically, there’s raising the collision energy and then there’s everything else. By raising the energy, you’re not testing one specific idea for physics beyond Standard Model, but a hundred or a thousand ideas in one swoop.

The situation reminds me a little of the quantum computing skeptics who say: scalable QC can never work, in practice and probably even in principle; the mainstream physics community only thinks it can work because of groupthink and hype; therefore, we shouldn’t waste more funds trying to make it work. With the sole, very interesting exception of Gil Kalai, none of the skeptics ever seem to draw what strikes me as an equally logical conclusion: whoa, let’s go full speed ahead with trying to build a scalable QC, because there’s an epochal revolution in physics to be had here—once the experimenters finally see that I was right and the mainstream was wrong, and they start to unravel the reasons why!

Of course, $20 billion is a significant chunk of change, by the standards of science even if not by the standards of random government wastages (like our recent $11 billion shutdown). And ultimately, decisions do need to be made about which experiments are most interesting to pursue with limited resources. And if a future circular collider were built, and if it indeed just found a desert, I think the balance would tilt pretty strongly toward Sabine’s position—that is, toward declining to build an even bigger and more expensive collider after that. If the Patriots drearily won every Superbowl 13-3, year after year after year, eventually no one would watch anymore and the Superbowl would get cancelled (well, maybe that will happen for other reasons…).

But it’s worth remembering that—correct me if I’m wrong—so far there have been no cases in the history of particle physics of massively expanding the energy frontier and finding absolutely nothing new there (i.e., nothing that at least conveyed multiple bits of information, as the Higgs mass did). And while my opinion should count for less than a neutrino mass, just thinking it over a-priori, I keep coming back to the question: before we close the energy frontier for good, shouldn’t there have been at least one unmitigated null result, rather than zero?

The NP genie

Tuesday, December 11th, 2018

Hi from the Q2B conference!

Every nerd has surely considered the scenario where an all-knowing genie—or an enlightened guru, or a superintelligent AI, or God—appears and offers to answer any question of your choice.  (Possibly subject to restrictions on the length or complexity of the question, to prevent glomming together every imaginable question.)  What do you ask?

(Standard joke: “What question should I ask, oh wise master, and what is its answer?”  “The question you should ask me is the one you just asked, and its answer is the one I am giving.”)

The other day, it occurred to me that theoretical computer science offers a systematic way to generate interesting variations on the genie scenario, which have been contemplated less—variations where the genie is no longer omniscient, but “merely” more scient than any entity that humankind has ever seen.  One simple example, which I gather is often discussed in the AI-risk and rationality communities, is an oracle for the halting problem: what computer program can you write, such that knowing whether it halts would provide the most useful information to civilization?  Can you solve global warming with such an oracle?  Cure cancer?

But there are many other examples.  Here’s one: suppose what pops out of your lamp is a genie for NP questions.  Here I don’t mean NP in the technical sense (that would just be a pared-down version of the halting genie discussed above), but in the human sense.  The genie can only answer questions by pointing you to ordinary evidence that, once you know where to find it, makes the answer to the question clear to every competent person who examines the evidence, with no further need to trust the genie.  Or, of course, the genie could fail to provide such evidence, which itself provides the valuable information that there’s no such evidence out there.

More-or-less equivalently (because of binary search), the genie could do what my parents used to do when my brother and I searched the house for Hanukkah presents, and give us “hotter” or “colder” hints as we searched for the evidence ourselves.

To make things concrete, let’s assume that the NP genie will only provide answers of 1000 characters or fewer, in plain English text with no fancy encodings.  Here are the candidates for NP questions that I came up with after about 20 seconds of contemplation:

  • Which pieces of physics beyond the Standard Model and general relativity can be experimentally confirmed with the technology of 2018? What are the experiments we need to do?
  • What’s the current location of the Ark of the Covenant, or its remains, if any still exist?  (Similar: where can we dig to find physical records, if any exist, pertaining to the Exodus from Egypt, or to Jesus of Nazareth?)
  • What’s a sketch of a resolution of P vs. NP, from which experts would stand a good chance of filling in the details?  (Similar for other any famous unsolved math problem.)
  • Where, if anywhere, can we point radio telescopes to get irrefutable evidence for the existence of extraterrestrial life?
  • What happened to Malaysia Flight 370, and where are the remains by which it could be verified?  (Similar for Amelia Earhart.)
  • Where, if anywhere, can we find intact DNA of non-avian dinosaurs?

Which NP questions would you ask the genie?  And what other complexity-theoretic genies would be interesting to consider?  (I thought briefly about a ⊕P genie, but I’m guessing that the yearning to know whether the number of sand grains in the Sahara is even or odd is limited.)

Update: I just read Lenny Susskind’s Y Combinator interview, and found it delightful—pure Lenny, and covering tons of ground that should interest anyone who reads this blog.

The stupidest story I ever wrote (it was a long flight)

Friday, May 18th, 2018

All the legal maneuvers, the decades of recriminations, came down in the end to two ambiguous syllables.  No one knew why old man Memeson had named his two kids “Laurel” and “Yanny,” or why his late wife had gone along with it.  Not Laura, not Lauren, but Laurel—like, the leaves that the complacent rest on?  Poor girl.  And yet she lucked out compared to her younger brother. “Yanny”? Rhymes with fanny, seriously?  If you got picked on in school half as much as Yanny did, you too might grow up angry enough to spend half your life locked in an inheritance fight.

But people mostly tolerated the old man’s eccentricities, because he clearly knew something. All through the 1930s, Memeson Audio was building the highest-end radios and record players that money could buy.  And long after he’d outdone the competition, Memeson continued to outdo himself. At the 1939 New York World’s Fair, he proudly unveiled a prototype of his finest record player yet, the one he’d been tinkering with in his personal workshop for a decade: the Unmistakable.  Interviewed about it later, people who attended the demo swore that you couldn’t mishear a single syllable that came out of the thing if you were 99% deaf. No one had ever heard a machine like it—or would, perhaps, until the advent of digital audio.  On Internet forums, audiophiles still debate how exactly Memeson managed to do it with the technology of the time.  Alas, just like the other Memeson debate—about which more shortly—this one might continue indefinitely, since only one Unmistakable was ever built, and that World’s Fair was the last time anyone heard it.

The day after the triumphant demonstration, a crowd cheered as Memeson boarded a train in Grand Central Station to return to his factory near Chicago, there to supervise the mass production of Unmistakables. Meanwhile Laurel and Yanny, now both in their thirties and helping to run the family firm, stood on the platform and beamed. It hadn’t been easy to grow up with such a singleminded father, one who seemed to love his radios a million times more than them, but at a moment like this, it almost felt worth it.  When Laurel and Yanny returned to the Fair to continue overseeing the Memeson Audio exhibition, they’d be the highest-ranking representatives of the company, and would bask in their old man’s reflected glory.

In biographies, Memeson is described as a pathological recluse, who’d hole himself up in his workshop for days at a time, with strict orders not to be disturbed by anyone.  But on this one occasion—as it turned out, the last time he’d ever be seen in public—Memeson was as hammy as could be.  As the train pulled out of Grand Central, he leaned out of an open window in his private car and grinned for the cameras, waving with one arm and holding up the Unmistakable with the other.

Every schoolchild knows what happened next: the train derailed an hour later.  Along with twenty other passengers, Memeson was killed, while all that remained of his Unmistakable was a mess of wires and splintered wood.

Famously, there was one last exchange. As the train began moving, a journalist waved his hat at Memeson and called out “safe travels, sir!”

Memeson smiled and tipped his hat.

Then, noticing Laurel and Yanny on the platform, the journalist yelled to Memeson, in jest (or so he thought): “if something happens, which of these two is next in line to run the business?”

The old man had never been known for his sense of humor, and seemed from his facial expression (or so witnesses would later say) to treat the question with utmost seriousness. As the train receded into the distance, he shouted—well, everyone agrees that it was two syllables. But which? With no written will to consult—one of Memeson’s many idiosyncrasies was his defiance of legal advice—it all came down to what people heard, or believed, or believed they heard.

On the one hand, it would of course be extremely unusual back then for a woman to lead a major technology firm. And Memeson had never shown the slightest interest in social causes: not women’s suffrage, not the New Deal, nothing. In court, Yanny’s lawyers would press these points, arguing that the old man couldn’t possibly have intended to pass on his empire to a daughter.

On the other hand, Laurel was his first-born child.  And some people said that, if Memeson had ever had a human connection with anyone, it was with her.  There were even employees who swore that, once in a while, Laurel was seen entering and leaving her dad’s workshop—a privilege the old man never extended to Yanny or anyone else. Years later, Laurel would go so far as to claim that, during these visits, she’d contributed crucial ideas to the design of the Unmistakable. Most commentators dismiss this claim as bluster: why would she wait to drop such a bombshell until she and Yanny had severed their last ties, until both siblings’ only passion in life was to destroy the other, to make the world unable to hear the other’s name?

At any rate, neither Laurel nor anyone else was ever able to build another Unmistakable, or to give a comprehensible account of how it worked.  But Laurel certainly has die-hard defenders to this day—and while I’ve tried to be evenhanded in this account, I confess to being one of them.

In the end, who people believed about this affair seemed to come down to where they stood—literally. Among the passengers in the train cars adjoining Memeson’s, the ones who heard him are generally adamant that they heard “Laurel”; while most who stood on the platform are equally insistent about “Yanny.”  Today, some Memeson scholars theorize that this discrepancy is due to a Doppler effect.  People on the platform would’ve heard a lower pitch than people comoving with Memeson, and modern reconstructions raise the possibility, however farfetched, that this alone could “morph” one name to the other.  If we accept this, then it suggests that Memeson himself would have intended “Laurel”—but pitch changing a word?  Really?

Today, Laurel and Yanny are both gone, like their father and his company, but their dispute is carried on by their children and grandchildren, with several claims still winding their way through the courts.

Are there any recordings from the platform?  There is one, which was lost for generations before it unexpectedly turned up again. Alas, any hopes that this recording would definitively resolve the matter were … well, just listen to the thing.  Maybe the audio quality isn’t good enough.  Maybe an Unmistakable recording, had it existed, would’ve revealed the observer-independent truth, given us a unique map from the sensory world to the world of meaning.

30 of my favorite books

Wednesday, March 28th, 2018

A reader named Shozab writes:

Scott, if you had to make a list of your favourite books, which ones would you include?
And yes, you can put in quantum computing since Democritus!

Since I’ve gotten the same request before, I guess this is as good a time as any.  My ground rules:

  • I’ll only include works because I actually read them and they had a big impact on me at some point in my life—not because I feel abstractly like they’re important or others should read them, or because I want to be seen as the kind of person who recommends them.
  • But not works that impacted me before the age of about 10, since my memory of childhood reading habits is too hazy.
  • To keep things manageable, I’ll include at most one work per author.  My choices will often be idiosyncratic—i.e., not that author’s “best” work.  However, it’s usually fair to assume that if I include something by X, then I’ve also read and enjoyed other works by X, and that I might be including this work partly just as an entry point into X’s oeuvre.
  • In any case where the same author has both “deeper” and more “accessible” works, both of which I loved, I’ll choose the more accessible.  But rest assured that I also read the deeper work. 🙂
  • This shouldn’t need to be said, but since I know it does: listing a work by author X does not imply my agreement with everything X has ever said about every topic.
  • The Bible, the Homeric epics, Plato, and Shakespeare are excluded by fiat.  They’re all pretty important (or so one hears…), and you should probably read them all, but I don’t want the responsibility of picking and choosing from among them.
  • No books about the Holocaust, or other unremittingly depressing works like 1984.  Those are a special category to themselves: I’m glad that I read them, but would never read them twice.
  • The works are in order of publication date, with a single exception (see if you can spot it!).

Without further ado:

Quantum Computing Since Democritus by Scott Aaronson

Dialogue Concerning the Two Chief World Systems by Galileo Galilei

Dialogues Concerning Natural Religion by David Hume

Narrative of the Life of Frederick Douglass by himself

The Adventures of Huckleberry Finn by Mark Twain

The Subjection of Women by John Stuart Mill

The Autobiography of Charles Darwin by himself

Altneuland by Theodor Herzl

The Practice and Theory of Bolshevism by Bertrand Russell

What Is Life?: With Mind and Matter and Autobiographical Sketches by Erwin Schrödinger

Fads and Fallacies in the Name of Science by Martin Gardner

How Children Fail by John Holt

Set Theory and the Continuum Hypothesis by Paul Cohen

The Gods Themselves by Isaac Asimov (specifically, the middle third)

A History of Pi by Petr Beckmann

The Selfish Gene by Richard Dawkins

The Mind-Body Problem by Rebecca Goldstein

Alan Turing: The Enigma by Andrew Hodges

Surely You’re Joking Mr. Feynman by Richard Feynman

The Book of Numbers by John Conway and Richard Guy

The Demon-Haunted World by Carl Sagan

Gems of Theoretical Computer Science by Uwe Schöning and Randall Pruim

Fashionable Nonsense by Alan Sokal and Jean Bricmont

Our Dumb Century by The Onion

Quantum Computation and Quantum Information by Michael Nielsen and Isaac Chuang

The Blank Slate by Steven Pinker

Field Notes from a Catastrophe by Elizabeth Kolbert

Infidel by Ayaan Hirsi Ali

Logicomix by Apostolos Doxiadis and Christos Papadimitriou

The Beginning of Infinity by David Deutsch

You’re welcome to argue with me in the comments, e.g., by presenting evidence that I didn’t actually like these books. 🙂  More seriously: list your own favorites, discuss your reactions to these books, be a “human recommendation engine” by listing books that “those who liked the above would also enjoy,” whatever.

Addendum: Here’s another bonus twenty books, as I remember more and as commenters remind me of more that I liked quite as much as the thirty above.

The Man Who Knew Infinity by Robert Kanigel

A Mathematician’s Apology by G. H. Hardy

A Confederacy of Dunces by John Kennedy Toole

The First Three Minutes by Steven Weinberg

Breaking the Code by Hugh Whitemore

Arcadia by Tom Stoppard

Adventures of a Mathematician by Stanislaw Ulam

The Man Who Loved Only Numbers by Paul Hoffman

Mathematical Writing by Donald Knuth, Tracy Larabee, and Paul Roberts

A Beautiful Mind by Sylvia Nasar

An Introduction to Computational Learning Theory by Michael Kearns and Umesh Vazirani

The Road to Reality by Roger Penrose

The Nili Spies by Anita Engle (about the real-life heroic exploits of the Aaronsohn family)

Artificial Intelligence: A Modern Approach by Stuart Russell and Peter Norvig

The Princeton Companion to Mathematics edited by Timothy Gowers

The Making of the Atomic Bomb by Richard Rhodes

Fear No Evil by Natan Sharansky

The Mind’s I by Douglas Hofstadter and Daniel Dennett

Disturbing the Universe by Freeman Dyson

Unsong by Scott Alexander

Interpretive cards (MWI, Bohm, Copenhagen: collect ’em all)

Saturday, February 3rd, 2018

I’ve been way too distracted by actual research lately from my primary career as a nerd blogger—that’s what happens when you’re on sabbatical.  But now I’m sick, and in no condition to be thinking about research.  And this morning, in a thread that had turned to my views on the interpretation of quantum mechanics called “QBism,” regular commenter Atreat asked me the following pointed question:

Scott, what is your preferred interpretation of QM? I don’t think I’ve ever seen you put your cards on the table and lay out clearly what interpretation(s) you think are closest to the truth. I don’t think your ghost paper qualifies as an answer, BTW. I’ve heard you say you have deep skepticism about objective collapse theories and yet these would seemingly be right up your philosophical alley so to speak. If you had to bet on which interpretation was closest to the truth, which one would you go with?

Many people have asked me some variant of the same thing.  As it happens, I’d been toying since the summer with a huge post about my views on each major interpretation, but I never quite got it into a form I wanted.  By contrast, it took me only an hour to write out a reply to Atreat, and in the age of social media and attention spans measured in attoseconds, many readers will probably prefer that short reply to the huge post anyway.  So then I figured, why not promote it to a full post and be done with it?  So without further ado:

Dear Atreat,

It’s no coincidence that you haven’t seen me put my cards on the table with a favored interpretation of QM!

There are interpretations (like the “transactional interpretation”) that make no sense whatsoever to me.

There are “interpretations” like dynamical collapse that aren’t interpretations at all, but proposals for new physical theories.  By all means, let’s test QM on larger and larger systems, among other reasons because it could tell us that some such theory is true or—vastly more likely, I think—place new limits on it! (People are trying.)

Then there’s the deBroglie-Bohm theory, which does lay its cards on the table in a very interesting way, by proposing a specific evolution rule for hidden variables (chosen to match the predictions of QM), but which thereby opens itself up to the charge of non-uniqueness: why that rule, as opposed to a thousand other rules that someone could write down?  And if they all lead to the same predictions, then how could anyone ever know which rule was right?

And then there are dozens of interpretations that seem to differ from one of the “main” interpretations (Many-Worlds, Copenhagen, Bohm) mostly just in the verbal patter.

As for Copenhagen, I’ve described it as “shut-up and calculate except without ever shutting up about it”!  I regard Bohr’s writings on the subject as barely comprehensible, and Copenhagen as less of an interpretation than a self-conscious anti-interpretation: a studied refusal to offer any account of the actual constituents of the world, and—most of all—an insistence that if you insist on such an account, then that just proves that you cling naïvely to a classical worldview, and haven’t grasped the enormity of the quantum revolution.

But the basic split between Many-Worlds and Copenhagen (or better: between Many-Worlds and “shut-up-and-calculate” / “QM needs no interpretation” / etc.), I regard as coming from two fundamentally different conceptions of what a scientific theory is supposed to do for you.  Is it supposed to posit an objective state for the universe, or be only a tool that you use to organize your experiences?

Also, are the ultimate equations that govern the universe “real,” while tables and chairs are “unreal” (in the sense of being no more than fuzzy approximate descriptions of certain solutions to the equations)?  Or are the tables and chairs “real,” while the equations are “unreal” (in the sense of being tools invented by humans to predict the behavior of tables and chairs and whatever else, while extraterrestrials might use other tools)?  Which level of reality do you care about / want to load with positive affect, and which level do you want to denigrate?

This is not like picking a race horse, in the sense that there might be no future discovery or event that will tell us who was closer to the truth.  I regard it as conceivable that superintelligent AIs will still argue about the interpretation of QM … or maybe that God and the angels argue about it now.

Indeed, about the only thing I can think of that might definitively settle the debate, would be the discovery of an even deeper level of description than QM—but such a discovery would “settle” the debate only by completely changing the terms of it.

I will say this, however, in favor of Many-Worlds: it’s clearly and unequivocally the best interpretation of QM, as long as we leave ourselves out of the picture!  I.e., as long as we say that the goal of physics is to give the simplest, cleanest possible mathematical description of the world that somewhere contains something that seems to correspond to observation, and we’re willing to shunt as much metaphysical weirdness as needed to those who worry themselves about details like “wait, so are we postulating the physical existence of a continuum of slightly different variants of me, or just an astronomically large finite number?” (Incidentally, Max Tegmark’s “mathematical multiverse” does even better than MWI by this standard.  Tegmark is the one waiting for you all the way at the bottom of the slippery slope of always preferring Occam’s Razor over trying to account for the specificity of the observed world.)  It’s no coincidence, I don’t think, that MWI is so popular among those who are also eliminativists about consciousness.

When I taught my undergrad Intro to Quantum Information course last spring—for which lecture notes are coming soon, by the way!—it was striking how often I needed to resort to an MWI-like way of speaking when students got confused about measurement and decoherence. (“So then we apply this unitary transformation U that entangles the system and environment, and we compute a partial trace over the environment qubits, and we see that it’s as if the system has been measured, though of course we could in principle reverse this by applying U-1 … oh shoot, have I just conceded MWI?”)

On the other hand, when (at the TAs’ insistence) we put an optional ungraded question on the final exam that asked students their favorite interpretation of QM, we found that there was no correlation whatsoever between interpretation and final exam score—except that students who said they didn’t believe any interpretation at all, or that the question was meaningless or didn’t matter, scored noticeably higher than everyone else.

Anyway, as I said, MWI is the best interpretation if we leave ourselves out of the picture.  But you object: “OK, and what if we don’t leave ourselves out of the picture?  If we dig deep enough on the interpretation of QM, aren’t we ultimately also asking about the ‘hard problem of consciousness,’ much as some people try to deny that? So for example, what would it be like to be maintained in a coherent superposition of thinking two different thoughts A and B, and then to get measured in the |A⟩+|B⟩, |A⟩-|B⟩ basis?  Would it even be like anything?  Or is there something about our consciousness that depends on decoherence, irreversibility, full participation in the arrow of the time, not living in an enclosed little unitary box like AdS/CFT—something that we’d necessarily destroy if we tried to set up a large-scale interference experiment on our own brains, or any other conscious entities?  If so, then wouldn’t that point to a strange sort of reconciliation of Many-Worlds with Copenhagen—where as soon as we had a superposition involving different subjective experiences, for that very reason its being a superposition would be forevermore devoid of empirical consequences, and we could treat it as just a classical probability distribution?”

I’m not sure, but The Ghost in the Quantum Turing Machine will probably have to stand as my last word (or rather, last many words) on those questions for the time being.

Practicing the modus ponens of Twitter

Monday, January 29th, 2018

I saw today that Ryan Lackey generously praised my and Zach Weinersmith’s quantum computing SMBC comic on Twitter:

Somehow this SMBC comic is the best explanation of quantum computing for non-professionals that I’ve ever found

To which the venture capitalist Matthew Ocko replied, in another tweet:

Except Scott Aaronson is a surly little troll who has literally never built anything at all of meaning. He’s a professional critic of braver people.  So, no, this is not a good explanation – anymore than Jeremy Rifkin on CRISPR would be… 🙄

Now, I don’t mind if Ocko hates me, and also hates my and Zach’s comic.  What’s been bothering me is just the logic of his tweet.  Like: what did he have in his head when he wrote the word “So”?  Let’s suppose for the sake of argument that I’m a “surly little troll,” and an ax murderer besides.  How does it follow that my explanation of quantum computing wasn’t good?  To reach that stop in proposition-space, wouldn’t one still need to point to something wrong with the explanation?

But I’m certain that my inability to understand this is just another of my many failings.  In a world where Trump is president, bitcoin is valued at $11,000 when I last checked, and the attack-tweet has fully replaced the argument, it’s obvious that those of us who see a word like “so” or “because,” and start looking for the inferential step, are merely insufficiently brave.  For godsakes, I’m not even on Twitter!  I’m a sclerotic dinosaur who needs to get with the times.

But maybe I, too, could learn the art of the naked ad-hominem.  Let me try: from a Google search, we learn that Ocko is an enthusiastic investor in D-Wave.  Is it possible he’s simply upset that there’s so much excitement right now in experimental quantum computing—including “things of meaning” being built by brave people, at Google and IBM and Rigetti and IonQ and elsewhere—but that virtually none of this involves D-Wave, whose devices remain interesting from various physics and engineering standpoints, but still fail to achieve any clear quantum speedups, just as the professional critics predicted?  Is he upset that the brave system-builders who are racing finally to achieve quantum computational supremacy over the next year, are the ones who actually interacted with academic researchers (sorry: surly little trolls), and listened to what they said?  Who understood, for example, why scaling up to 50+ qubits only made a lot of sense once you had one or two qubits that at least behaved well enough in isolation—which, after years of heroic effort, many of these system-builders now do?

How’d I do?  Was there still too much argument there for the world of 2018?