Sean Carroll

Blog

  • Dept. of Energy Support for Particle Theory: A “Calamity”

    One of the nice things that governments do is support basic scientific research — work that might help us better understand how the world works, but doesn’t have any direct technological or economic application. Particle physics and cosmology are great examples. In the U.S., much of the funding for these fields comes from the Office of High Energy Physics within the Office of Science at the Department of Energy (DOE).

    Now that support is crumbling — drastically. In the last couple of years, the DOE has radically changed how it carries out reviews of different university theory groups, to decide how much grant support each will get. All for ostensibly good reasons — leveling the playing field and all that. But, without much fanfare, the actual result has been a significant drop in funding for almost every major theory group in the country.

    Laurence Yaffe of the University of Washington, a respected particle and nuclear theorist, just released an analysis he informally carried out after serving a temporary assignment at the DOE. Here is his abstract (emphasis mine):

    Impacts of Recent Comparative Review Cycles on DOE-funded High Energy Theory
    L.G. Yaffe, University of Washington
    February 19, 2014

    A summary is presented of data obtained from a grass-roots effort to understand the effects of the FY13 and FY14 comparative review cycles on the DOE-funded portion of the US high energy theory community and, in particular, on graduate students and postdoctoral researchers who are beginning their careers. For a sample comprised of nearly all of the larger groups undergoing comparative review, total funding declined by an average of 23%, with numerous major groups receiving reductions in the 30–55% range. Funding available for postdoc or graduate student support declined over 30%, with many reductions in the 40–65% range. The total number of postdoc positions in this large sample of theory groups is declining by over 40%. The impacts on young researchers raise grave concerns regarding continued U.S. leadership in high energy theory.

    A 20% cut in funding in one year is kind of a big deal. A picture is worth a thousand words, so here are two of them; overall funding changes for all the different groups:

    calamity1

    and changes specifically in support for graduate students and postdocs:

    calamity2

    Obviously this is unsustainable, unless as a society we make the decision that particle physics just isn’t worth doing. But hopefully things can be rectified at least a bit, to restore some of that money. Everyone I know is bemoaning the cuts, complaining that they have been turning away prospective grad students and postdocs more than ever before. I’m not necessarily against decreasing the number of postdocs (as opposed to grad students); the pipeline has to narrow somewhere, and there’s a sensible argument to be made to do it at that point. But we should do it deliberately and after thinking and talking about it, not as the haphazard result of some new bureaucratic procedures. It would be a shame to destroy our future prospects in this centrally important area of science.

  • Chat With Hans Halvorson

    Here’s the video for the dialogue I mentioned earlier, a discussion with Princeton philosopher Hans Halvorson on physics, philosophy, and religion.

    It was a friendly and substantive chat, moderated by Katie Galloway of the Veritas Forum. Most of the scientists and philosophers who work in fields close to mind are either agnostics or committed atheists; Hans is one of the exceptions. (Even closer to my own research area, Don Page is well known as an evangelical Christian.) Our ontologies are quite different, but many of our conclusions about the everyday macroscopic world are quite compatible.

  • Greetings from Bangkok

    Where you will find a welcoming Ronald MacDonald,

    ronald

    a monk checking his iPhone,

    monk

    and a stone temple guardian in a top hat:

    guard

    That’s all for now. Probably radio silence until I get back next week.

  • The Many Worlds of Quantum Mechanics

    Greetings from Sihanoukville, Cambodia, or at least the waters immediately off. I’m here as part of Bright Horizons 19, a two-week cruise on the Holland American ship Vollendam, in collaboration with Scientific American. We started in Hong Kong and have been working our way south, stopping a few times in Vietnam, and after this we’ll briefly visit Thailand before finishing in Singapore. A fascinating, once-in-a-lifetime experience, even if two weeks is an amount of time I can’t honestly afford to be taking off. Been getting a touch of work done here and there, but not as much as I would have liked, in between dashes ashore to sample the local cuisine. Although the local cuisine has been pretty spectacular, I have to admit.

    My job here is to give a few talks about physics and cosmology to the folks who signed up for the package — a public audience, but the kind of people whose idea of a good time while sailing the South China Sea is hearing talks about molecular biology or world history. Mostly my talks are variations of themes I’ve spoken on frequently before — the Higgs boson, the arrow of time, dark matter and dark energy. But to spice things up I decided to throw in something new, so I wrote up a talk on The Many Worlds of Quantum Mechanics.

    And here it is — the slides, at least. The content is roughly based on my explanation in From Eternity to Here, with a few improvements thrown in.

    Two basic goals here. One is to introduce QM to people who don’t know much more about it than a vague notion of “uncertainty” or “fluctuations.” And in particular, to focus on the conceptual foundations, rather than any of the other perfectly legitimate angles one could take: the historical development, the calculational basics, the experimental evidence, the role in modern technology, and so on. Hey, it’s my talk, I might as well concentrate on the parts I’m most fascinated by. So there’s a discussion of entanglement and decoherence that is a bit more specific and detailed than one would often get in a talk of this type, even if it is enlivened by silly pictures of cats and dogs.

    The second goal was to give a subtle sales pitch for the Many-Worlds interpretation. Really more damage control than full-on hard sell; the very idea of many worlds is so crazy-sounding and counterintuitive that my job is more to let people know that it’s actually quite a natural implication of the formalism, rather than a bit of ad hoc nonsense tacked on by theorists who have become unmoored from reality. I’m happy to bring up the outstanding issues with the approach, but I do want people to know it should be taken seriously.

    Comments welcome, especially since I’ve never tried this approach in a talk before. Of course by only seeing the slides you miss all the witty asides, but the basic substance should come through.

  • Reality, Pushed From Behind

    “Teleology” is a naughty word in certain circles — largely the circles that I often move in myself, namely physicists or other scientists who know what the word “teleology” means. To wit, it’s the concept of “being directed toward a goal.” In the good old days of Aristotle, our best understanding of the world was teleological from start to finish: acorns existed in order to grow into mighty oak trees; heavy objects wanted to fall and light objects to rise; human beings strove to fulfill their capacity as rational beings. Not everyone agreed, including my buddy Lucretius, but at the time it was a perfectly sensible view of the world.

    These days we know better, though the knowledge has been hard-won. The early glimmerings of the notion of conservation of momentum supported the idea that things just kept happening, rather than being directed toward a cause, and this view seemed to find its ultimate embodiment in the clockwork universe of Newtonian mechanics. (In technical terms, time evolution is described by differential equations fixed by initial data, not by future goals.) Darwin showed how the splendid variety of biological life could arise without being in any sense goal-directed or guided — although this obviously remains a bone of contention among religious people, even respectable philosophers. But the dominant paradigm among scientists and philosophers is dysteleological physicalism.

    However. Aristotle was a smart cookie, and dismissing him as an outdated relic is always a bad idea. Sure, maybe the underlying laws of nature are dysteleological, but surely there’s some useful sense in which macroscopic real-world systems can be usefully described using teleological language, even if it’s only approximate or limited in scope. (Here’s where I like to paraphrase Scott Derrickson: The universe has purposes. I know this because I am part of the universe, and I have purposes.) It’s okay, I think, to say things like “predators tend to have sharp teeth because it helps them kill and eat prey,” even if we understand that those causes are merely local and contingent, not transcendent. Stephen Asma defends this kind of view in an interesting recent article, although I would like to see more acknowledgement made of the effort required to connect the purposeless, mechanical underpinnings of the world to the purposeful, macroscopic biosphere. Such a connection can be made, but it requires some effort.

    Of course loyal readers all know where such a connection comes from: it’s the arrow of time. The underlying laws of physics don’t work in terms of any particular “pull” toward future goals, but the specific trajectory of our actual universe looks very different in the past than in the future. In particular, the past had a low entropy: we can reconcile the directedness of macroscopic time evolution with the indifference of microscopic dynamics by positing some sort of Past Hypothesis (see also). All of the ways in which physical objects behave differently toward the future than toward the past can ultimately be traced to the thermodynamic arrow of time.

    Which raises an interesting point that I don’t think is sufficiently appreciated: we now know enough about the real behavior of the physical world to understand that what looks to us like teleological behavior is actually, deep down, not determined by any goals in the future, but fixed by a boundary condition in the past. So while “teleological” might be acceptable as a rough macroscopic descriptor, a more precise characterization would say that we are being pushed from behind, not pulled from ahead.

    The question is, what do we call such a way of thinking? Apparently “teleology” is a word never actually used by Aristotle, but invented in the eighteenth century based on the Greek télos, meaning “end.” So perhaps what we want is an equivalent term, with “end” replaced by “beginning.” I know exactly zero ancient Greek, but from what I can glean from the internet there is an obvious choice: arche is the Greek word for beginning or origin. Sadly, “archeology” is already taken to mean something completely different, so we can’t use it.

    I therefore tentatively propose the word aphormeology to mean “originating from a condition in the past,” in contrast with teleology, “driven toward a goal in the future.” (Amazingly, a Google search for this word on 3 February 2014 returns precisely zero hits.) Remember — no knowledge of ancient Greek, but apparently aphorme means “a base of operations, a place from which a campaign is launched.” Which is not a terribly bad way of describing the cosmological Past Hypothesis when you think about it. (Better suggestions would be welcome, especially from anyone who actually knows Greek.)

    We live in a world where the dynamical laws are fundamentally dysteleological, but our cosmic history is aphormeological, which through the magic of statistical mechanics gives rise to the appearance of teleology in our macroscopic environment. A shame Aristotle and Lucretius aren’t around to appreciate the progress we’ve made.

  • William Lane Craig Debate

    Last week I participated in a dialogue with Princeton philosopher Hans Halvorson, sponsored by the Veritas Forum here at Caltech. We were talking about “physics and philosophy,” but the primary issue was theism and naturalism — Hans’s research specialty is philosophy of physics, especially quantum field theory, but he’s also a theist and often writes about science and religion. It was a fruitful discussion (I like to think), as we ended up agreeing about many points, even though we started from very different premises. He agreed with me, for example, that purported fine-tuning of cosmological parameters isn’t a very good argument in favor of the existence of an intelligent designer.

    Next month I’ll be doing something related, although under quite different circumstances. On February 21 I’ll be debating William Lane Craig at the Greer-Heard Forum, an event sponsored by the New Orleans Baptist Theological Seminary. It will actually be a two-day event; a debate between Craig and me on Friday night, and follow-ups on Saturday from other speakers — Tim Maudlin and Alex Rosenberg for Team Naturalism, Robin Collins and James Sinclair for Team Theism. Registration is open! I believe the whole thing will be streamed live online, and it will certainly be recorded for posterity. [Update: Here is the video.]

    greer

    William Lane Craig (or WLC as we call him in the business) is of course a very well-known figure, largely for his many public debates, on theism/atheism as well as on various other specific theological issues. As far as debating goes: he’s very good at it! If his debates were being judged by a panel of experts as in an intercollegiate debate tournament, he would have a very good record indeed. This has led many people to conclude that atheists just shouldn’t debate him at all, or at least not until they have devoted 10,000 hours to learning how to be a good debater.

    Daniel Dennett warned me that, as soon as word got out that I would be debating WLC, I would be deluged with opinions and unsolicited advice. Which is great! Always happy to hear other perspectives, although I don’t promise to actually follow any of the advice. I won’t reproduce the various emails I’ve received, but here are a few very different perspectives online: Jerry Coyne, Luke Barnes (and another), and Wintery Knight. (WK is relatively restrained, but others predict “pummelings,” presumably for me.)

    Just so we’re clear: my goal here is not to win the debate. It is to say things that are true and understandable, and establish a reasonable case for naturalism, especially focusing on issues related to cosmology. I will prepare, of course, but I’m not going to watch hours of previous debates, nor buy a small library of books so that I may anticipate all of WLC’s possible responses to my arguments. I have a day job, and frankly I’d rather spend my time thinking about quantum cosmology than about the cosmological argument for God’s existence. If this event were the Final Contest to Establish the One True Worldview, I might drop everything to focus on it. But it’s not; it’s an opportunity to make my point of view a little clearer to a group of people who don’t already agree with me.

    The guy is a very polished public speaker, and he is certainly an expert in this format. But I have the overwhelming advantage of being right. If I thought WLC were right, I would just change my views. Since I don’t, my goal is to explain why not, as clearly as possible.

    The general consensus in some corners seems to be that I will be crushed. I guess we shall see.

  • Searching for the Science of Self

    memywhy_cover Book release day! Not by me — I’ve gone on quasi-hiatus from book-writing, and for that matter from blogging, while I am happily getting some actual science done. But the brilliant and talented Jennifer Ouellette has come out with her best book yet — Me, Myself, and Why: Searching for the Science of Self.

    Jennifer’s last book was The Calculus Diaries: How Math Can Help You Lose Weight, Win in Vegas, and Survive a Zombie Apocalypse. The idea behind that one stemmed from her conviction that, despite having been an English major who did badly in math, it was important that she learn the basics of calculus in order to appreciate the way it alters how we experience the world. But in doing the research for that book, she discovered something surprising: according to her high-school transcripts, she hadn’t done badly in math at all. In fact she got all A’s. But she left school with a conviction that she was bad in math.

    Where did that conviction come from? Was it society’s fault, man? Or did it come from her parents? And since she was adopted, which set of parents should be blamed? Clearly there was an science question here: what were the crucial influences that made her the person she eventually became?

    Thus, the new book. Here Jennifer traces various scientific strands that weave together to make us the people that we are. Starting with some of the obvious strategies — genome sequencing, brain scans — and working up to some more (literally) brain-bending ideas about sexual identity, addiction, virtual reality, and the origins of consciousness.

    Me, Myself and Why (book trailer)

    Jennifer even convinced her innocent, straight-arrow husband to experiment briefly with hallucinogenic substances, in order to better understand how a temporary alteration in brain chemistry affects the self/other boundary. See Chapter Seven for the scandalous details.

  • Particle Fever: Catch It!

    A brief search of the archives reveals that I truly have not done my job in plugging Particle Fever, the new documentary about particle physics and the Large Hadron Collider. I guess it would have been a bit premature, as the movie hasn’t technically been released yet. But here it comes! And the trailer captures a bit of the excitement:

    PARTICLE FEVER Official HD Trailer Premiere

    Particle Fever is the brainchild of David Kaplan, a young (younger than me, anyway) particle theorist at Johns Hopkins who was crazy enough to think he could make a feature film in his spare time. (Actually David told me that his first idea was to write a book, but the act of writing was just too painful, so obviously he decided to take an easier route.) Readers of The Particle at the End of the Universe will be familiar with David’s story, which I told as part of exploring how physics proceeds in our ever-more-complicated media landscape.

    Some people will doubtless feel that a movie about particle physics is self-indulgent and unnecessary. The polite term for such people is “poopyheads.” (You can imagine some of the impolite terms.) The experimentalists and technicians who built the LHC, and the theorists who built the theories that the machine tests, are human beings who have devoted their lives to a rather esoteric pursuit — but one that is truly universal, uncovering the basic rules of the cosmos in which we all live. This is an important story to tell.

    Long a labor of love on the part of David and his intrepid crew of filmmakers, Particle Fever was picked up for distribution the same day the Nobel Prize was announced for Englert and Higgs, and will be officially released on March 5. Early reviews have been glowing. Depending on where you live, you might be able to catch a theatrical release, but before too long I’m sure you will be able to see the film using one of those gizmos that beams media content straight to your living room. What a world we live in.

  • What Scientific Ideas Are Ready for Retirement?

    Every year we look forward to the Edge Annual Question, and as usual it’s a provocative one: “What scientific idea is ready for retirement?” Part of me agrees with Ian McEwan’s answer, which is to unask the question, and argue that nothing should be retired. Unasking is almost always the right response to questions that beg other questions, but there’s also an argument to be made in favor of playing along, so that’s what I did.

    My answer was “Falsifiability.” More of a philosophical idea than a scientific one, but an idea that is bandied about by lazy scientists far more than it is invoked by careful philosophers. Thinking sensibly about the demarcation problem between science and non-science, especially these days, requires a bit more nuance than that.

    Modern physics stretches into realms far removed from everyday experience, and sometimes the connection to experiment becomes tenuous at best. String theory and other approaches to quantum gravity involve phenomena that are likely to manifest themselves only at energies enormously higher than anything we have access to here on Earth. The cosmological multiverse and the many-worlds interpretation of quantum mechanics posit other realms that are impossible for us to access directly. Some scientists, leaning on Popper, have suggested that these theories are non-scientific because they are not falsifiable.

    The truth is the opposite. Whether or not we can observe them directly, the entities involved in these theories are either real or they are not. Refusing to contemplate their possible existence on the grounds of some a priori principle, even though they might play a crucial role in how the world works, is as non-scientific as it gets.

    I’m also partial to Alan Guth’s answer: “The universe began in a low-entropy state.” Of course we all know that our observable universe had a relatively low entropy at the Big Bang; Alan is making the point that the observable universe might not be the whole thing, and the Big Bang might not have been the beginning, so it’s completely possible that the universe as a whole was never in what one might call a “low-entropy” state. Instead, starting from a generic state, entropy could increase in both directions, leading to a two-sided arrow of time. This has been one of my favorite ideas for a while now, and Alan and I are writing a paper with Chien-Yao Tseng that examines toy models with such behavior.

    Here are some other interesting/provocative answers, picked unsystematically out of over 100,000 words overall. Remember that the titles are what the person wants to retire, not something they’re in favor of.

  • Buchalter Cosmology Prize

    Ari Buchalter is one of the many people who has successfully made the transition from graduate student and researcher in physics (Columbia PhD, Caltech postdoc) to the business world, where he is currently the CEO of MediaMath. But he never lost his interest in theoretical cosmology, which is completely appropriate — how our universe works is something everyone should be interested in, no matter what their day job might be.

    In order to promote innovative thinking in cosmology (experimental as well as theoretical), Ari has founded the Buchalter Cosmology Prize, which was just announced at the meeting of the American Astronomical Society. It will be an annual award, given to the best cosmology papers to have appeared on the arxiv, as decided by a panel of esteemed judges. (I’m one of the esteemed judges, which is a mixed blessing — should be a lot of fun, but it means I can’t win.) Any PhD or current graduate student in physics or astronomy is eligible to submit papers for consideration; this year’s deadline is 30 September. The winner will walk away with $10,000, and even third place will bag you $2,500.

    Currently, cosmology is in a situation where the dominant theoretical framework (Big Bang, Hubble expansion, dark energy and dark matter, possibly primordial inflation) is pretty darn good at fitting the data, but nevertheless has some worrisome conceptual issues. (Was there really inflation? Is there a multiverse? Is the dark energy a cosmological constant, and is the dark matter a WIMP? Why is the vacuum energy so small? Etc.) Hopefully a prize like this will help spur people to be just a tiny bit more bold and imaginative in tackling these issues than they would otherwise be.