Sean Carroll Blog

Month: April 2006

  • How quickly can Iran get the bomb?

    Obviously a lot of smart and well-informed people have been thinking about this. Many, like Juan Cole, think that the Iranians are nowhere close to a bomb; ThinkProgress is slightly less sanguine. They are taking the trouble to make this argument because the US is claiming that it would only take 16 days for Iran to make a bomb. There are all sorts of reasons to disbelieve this particular claim: a history of crying wolf, an apparent misunderstanding of the concept of significant figures… Still, is it more like ten days, or ten years?

    Steinn Sigurðsson looks at the problem as a physicist, and isn’t optimistic.

    I don’t know Iran; I don’t have access to any classified information on nuclear weapons.
    I do know something about physics…

    First of all, Iran is clearly been working on putting together a full nuclear cycle for about 20 years

    That means they want to be able to do it all in-house: mining, enrichment, burning, plutonium extraction, power generation and bomb production.

    It is clear that they did the science in the early-to-mid-90s, they tested centrifuges, built small high neutron flux reactors and got small amounts of plutonium extracted.

    So, they learned Pu chemistry, what isotopes you get with different burns, and maybe some metallurgy.

    They then set up centrifuge halls and played with an AVLIS (laser isotope separator).

    They also ordered a 1GW reactor from the russians, and refined uranium oxide (aka “yellowcake”) into both uranium tetrafluoride, uranium hexafluoride and uranium metal.
    Supposedly several tons of uranium oxide were processed.

    Now: there are two ways to make bombs, at the basic level.
    Get highly refined uranium-235 metal; or, fairly pure plutonium-239. In kilogram quantities.
    U-235 bombs are simple and need not be tested. “A grad student could make one of those”.
    Pu-239 bombs are notoriously fickle and are said to need testing (although maybe not so much any more…)

    Read the whole thing.

    Hofstadter’s Law says “It always takes longer than you think, even when taking into account Hofstadter’s Law.” For nuclear weapons, unfortunately, the word “longer” should be replaced by “shorter.” Historically, we always underestimate the proximity of other nations to full nuclear capability (unless we’re trying to cook up reasons to invade them). I don’t know what to do about it, but there’s every reason to believe that, left to its own devices, Iran will have some sort of bomb sooner rather than later.

  • Just This

    By W.S. Merwin.

    When I think of the patience I have had
    back in the dark before I remember
    or knew it was night until the light came
    all at once at the speed it was born to
    with all the time in the world to fly through
    not concerned about ever arriving
    and then the gathering of the first stars
    unhurried in their flowering space
    and far into the story the planets
    cooling slowly and the ages of rain
    then the seas starting to bear memory
    the gaze of the first cell at its waking
    how did this haste begin this little time
    at any time this reading by lightning
    scarcely a word this nothing this heaven

  • The language of Science

    From a footnote on page 69 of Seth Lloyd’s new book Programming the Universe (about which more later):

    I happened to be in [Nobel Laureate Norman Ramsey’s office in Paris] when two members of the Academie Francaise came to call. “Why, Professeur Ramsey,” they inquired, “is French not the international language of Science?” Ramsey immediately answered them in his fluent French, with a thick midwestern accent. Horrified, they dropped the subject. In fact, the French Academy of Sciences caused the adoption of English as the international language of science in the seventeenth century by being the first national academy to abandon the previous international language, Latin, and publish their proceedings in their own language. The English and the Germans followed suit. The rest is just an accident of history.

  • Religious kids have all the fun

    From Ernie’s 3D Pancakes, perhaps the best holiday gift ever — the Plush Plagues Bag for Passover!

    Plush Plagues
    Yes, you can have soft fuzzy representations of each of the ten plagues sent by Yahweh to annoy the Egyptians into letting Moses and his people go. Types of pestilence represented include:

    • A spooky eyed drop of blood
    • A Frog — for frogs, of course
    • A Giant Lice for lice.
    • Cow for cattle disease
    • Black Locust for locusts
    • A white satin lump of hail
    • A black cube of darkness
    • An icky boil on a piece of flesh!
    • A snarling lion’s head for wild beasts
    • and last of all a very sad head – for death of the first born.

    Descriptions taken verbatim from the vendor, who goes on to say — “The frog, lice, cow and locust wriggle and roll their eyes, quiver, buzz and move when you pull their string and are apx 4.5″ long.” With toys like this, how come Judaism isn’t the world’s most popular religion?

    I mean, seriously. A black cube of darkness! With eyes. Nothing could be more awesome than that.

  • Going to California

    Some of you may know that I’ve been on the job market. The good news is that I’ve officially accepted a position at Caltech, starting in September. It’s a fantastic research environment, and they are building up in cosmology at the moment. Also I understand the weather is pretty nice, so I’m excited about the move.

    The job itself requires a little explication: I’ll be a Senior Research Associate in Physics. According to Caltech’s classification system, this is a faculty job (“Caltech’s equivalent of a research full professor,” as they put it to me) but not actually a “professor” job. Basically I get to concentrate on doing research — no teaching required, although I’m allowed to volunteer — and can apply for grants and hire postdocs (and even serve on committees!) just like any other faculty member. The downside is that there is no tenure, although it’s not a term-limited job; I can in principle stay forever if the money holds out and they don’t want to fire me. In the meantime, I’ll have the freedom to work on some of the more ambitious cosmology ideas that have been percolating in the back of my mind for a while.

    I have to express my gratitude to everyone who has been incredibly supportive during the entire process, from my close friends to strangers on the internet to famous scientists around the world to Marc Kamionkowski and the others who did such a good job recruiting me to Caltech. I’m sure I will miss Chicago at times, but the future looks really bright, and I can’t wait to get it started.

  • Dr. Doom

    This story is so amazing/silly/horrifying that it’s taken a few days to sink in. Short version: Dr. Eric Pianka of the University of Texas, an internationally recognized ecologist, goes around giving talks warning that the Earth is in major trouble. We’re headed for an ecological disaster, and human beings in particular are in serious danger of being wiped out by a deadly virus like Ebola, perhaps leading to the death of 90% of our current population. It might even be good for the environment over all (although bad for us, obviously). He’s an alarmist, no doubt about it, but it’s better to hear about such disaster scenarios than to simply ignore them.

    And then — and here’s the part that is so bizarre that it takes a while to really believe it — “citizen scientist” and creationist Forrest Mims apparently heard Pianka give a talk, and decided that Pianka is advocating that we release a virus to kill 90% of the Earth’s population. Completely untrue, of course; just a simple-minded and mean-spirited twisting of the guy’s words. Even from the original story, you could tell that there was a serious disconnect between portrayal and reality — the actual quotes from Pianka didn’t measure up to the surrounding alarmist hysteria.

    But the right-wing/creationist blogosphere has gone completely nutso over this. I thought my fellow left-wing/scientific friends might be exaggerating the reaction a bit, but it’s true — dozens of posts about the crazy “Dr. Doom” who longs to bring down our civilization through bioterrorism. ID advocate (and tireless defender of academic freedom!) William Dembski has taken the obvious step for someone who is unhinged but nevertheless concerned — he has reported Pianka to the Department of Homeland Security. A good summary of the craziness has been written by Nick Matzke at the Panda’s Thumb; more coverage from PZ Myers (and here), Ed Brayton, Wesley Elsberry (and here), and DarkSyde (and here).

    There’s a lesson here, although damned if I can figure out what it is. PZ thinks that these people are just anti-academic, and that it’s part of a campaign to discredit the very notion of expertise. But I suspect that it’s less calculated than that — we’re talking about folks who find it completely plausible to imagine that liberal biology professors are eager to wipe out most of the human race. The basic cognitive short-circuit seems to be an inability to understand the difference between a sentiment of the form “A human population of one billion is more ecologically sustainable than one of six billion” and something like “I would like to personally murder five out of every six living people.” It’s the right-wing equivalent of people who think that the 9/11 attacks were orchestrated by Halliburton and/or the Mossad. Except that it’s not a fringe movement; the buzz is all over the right hemiblogosphere, and was straightforwardly reported by Matt Drudge and others.

    Next time I mention that a decay of our vacuum state via bubble nucleation could wipe out life on Earth, I’ll make sure there aren’t any creationists in the audience. I can’t imagine explaining that to the Department of Homeland Security.

  • Either/Orchestra

    I’ve been a fan of the Either/Orchestra for over ten years now, since first hearing them on a public radio station in Boston. This Cambridge-based jazz ensemble, a “little big band” in the tradition of the Mingus band, is one of my absolute favorite musical groups. (Whether the name is indebted to Kierkegaard is somewhat ambiguous.) Unfortunately, I moved away from Massachusetts soon after discovering their music, so I haven’t had a chance to hear them live. Until, that is, this last Friday, when they played Chicago’s historic Green Mill. Suffice to say, a decade’s worth of expectations were not disappointed.

    Either/Orchestra

    The singular genius of the E/O is to simultaneously stimulate the pleasure centers of the right brain and left brain in equal measure. They are a ten-piece group at the moment — bass, piano, drums, six horns, and congas. Past configurations have varied, with personnel changing fairly frequently; distinguished alumni include John Medeski. But the spirit of the group has remained constant: sophisticated arrangements of eclectic music, played with an enthusiastic fervor that carries you along for the ride. Each of the band members is an accomplished soloist, and they work together in intricate configurations that certainly appeal to the intellectual side of one’s musical appreciation — but at no time could they be accused of being stuffy. Each song is generally constructed around a catchy hook, whose possibilities are thoroughly explored rhythmically and harmonically. These guys rock, groove, and swing.

    The E/O’s repertoire has always been wide-ranging, from original tunes to classics by Monk and Ellington and Miles to quirky covers of pop songs from the Beatles and Dylan to — wait for it — King Crimson. In the last few years they have been heavily influenced by Ethiopian music, culminating in a recent live album from Addis Ababa. One of the songs performed Friday night will give you an idea of a “typical” E/O tune. It was a suite in two parts, both of which were influenced by the Azmari music of Ethiopia. The first movement originated when saxophonist/leader Russ Gershon became intrigued by the massinko, a kind of one-string violin played in Ethiopian clubs. He composed a Western-style string quartet (“of all things”) inspired by this music, with the playful idea of getting classical musicians with incredibly expensive instruments to try their best to sound like cheap one-string violins you might hear in Addis Ababa. He later arranged the quartet for ten-piece jazz ensemble (don’t ask me how you do that), to form the first movement. The second movement came from bass player Rick McLaughlin, who had taken Thelonious Monk’s classic Well You Needn’t and arranged it with a Azmari-style rhythm. And voila — a suite that only the Either/Orchestra could possibly come up with, or for that matter perform. And it was beautiful.

    Besides getting the chance to hear the band play live, I finally had the opportunity to meet Russ Gershon, the founder of the group, in person. A few years ago I sent an email to their record label, asking to be put on the mailing list, and was pleasantly suprised to receive a personal reply from Russ himself. In my response I mentioned that he should let me know if he had any questions about cosmology; this led to a few back-and-forth emails, along these lines:

    Date: Mon, 10 Sep 2001 13:00:25 -0700
    To: Sean Carroll
    From: Russ Gershon
    Subject: Re:

    So the dark matter is not atoms, protons, quarks – it’s something
    else? That’s kind of alarming, what with it being 96% of the whole
    thing!

    Russ
    —
    Russ Gershon
    Accurate Records
    288 Norfolk St.
    Cambridge MA 02139 USA

    Well, yeah, it is kind of alarming, I have to admit. As you might guess from the date, our conversation was derailed by events. Still, jazz musicians with an interest in cosmology should be rewarded, don’t you think? Maybe someday we will get a Dark Energy Suite. So go buy the records already. My first discovery was The Calculus of Pleasure, so I have a soft spot for that one, but they’re all good.

    I arrived a bit early to the show to grab a good seat, since the Green Mill is always crowded. Naturally I grabbed some napkins and started writing equations, as one is wont to do — six cocktail napkins were sacrificed, but for a good cause, as I figured out something important about auxilliary scalar fields. The bartender, Jill, noticed my scribblings and asked me what they were about. As it turns out, she is currently taking a class on differential equations, working toward her Master’s degree to someday be a high-school math teacher. And she gave me a free glass of wine to demonstrate solidarity between we equation-oriented types. The guys sitting next to me also noticed, and between sets I ended up explaining dark energy and the accelerating universe to a bunch of jazz fans. See, another good reason to go to grad school in physics — it opens doors in the most unlikely venues.