April 2006

Pandora’s box

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The Wikipedia article on countries with nuclear weapons is sobering reading. This map is from the article, although the color-coding is a bit misleading. (3quarksdaily points to more maps.)
Nuclear powers

  • The United States, Russia, United Kingdom, France and the People’s Republic of China are the five nuclear powers recognized by the Nuclear Non-Proliferation Treaty (NPT). Not coincidentally, they are also the five permanent members of the UN Security Council. The US and Russia have about 6,000 active warheads each, while the others have a few hundred each. According to the NPT, only these countries are permitted to have nuclear weapons, and they are prohibited from sharing weapons technology with other countries.
  • India did not sign the NPT, and exploded its first nuclear weapon in 1974 (in a test perversely named “Smiling Buddha“). In 1998 they tested “weaponized” nuclear warheads (I don’t know what that means) in Pokhran-II. Numerous complaints and sanctions followed, none of which had any appreciable effect, and the controversy eventually died down. Possession of nuclear weaponry is considered to be a crucial part of India’s self-image as a world power. They are now recognized by the US as a “responsible nuclear state.”
  • Pakistan is also not an NPT signatory. They performed their first nuclear test in 1998, in response to India’s test. In 1999 they signed accords with India, agreeing to a bilateral moratorium on nuclear testing. A.Q. Kahn, leader of the Pakistani program, confessed to being involved in a clandestine network to share nuclear weapons technology with Libya, Iran, and North Korea; he was pardoned by President Perez Musharraf in 2004. There is some evidence that his network was also collaborating with the Taliban and al-Qaeda.
  • Israel has not acknowledged possessing a nuclear arsenal, but it is an open secret; Israel is not an NPT signatory. (In fact, India, Pakistan, and Israel are the only sovereign states not to ratify the NPT — although see below.) They probably have several hundred warheads, comparable to the stockpiles of China, France, and the UK.
  • North Korea, in contrast to Israel, has publicly claimed to have nuclear weapons, although some analysts remain skeptical. After ratifying the NPT in 1985, they withdrew in 2003; no other countries have ever withdrawn from the treaty. In September 2005 they agreed to scrap their existing nuclear weapons and rejoin the NPT, but later stated that no such steps would be taken unless they were supplied with a light water reactor.
  • Iran is of course an interesting question.
  • South Africa produced a few nuclear weapons in the 1980’s, but later dismantled them. They are the only nation to build nuclear weapons themselves and later give up the capability.
  • Saudi Arabia has stated that they might need to develop nuclear weapons, although they deny actually having done so. Some recent reports claim that the Saudis have embarked on a weapons-development program, with aid from the Pakistani nuclear program.
  • Several republics of the former Soviet Union found themselves in possession of nuclear missiles upon the collapse of the USSR in 1991: Ukraine, Belarus, and Kazakhstan. All have subsequently transferred the weapons to Russia and signed the NPT, and are currently nuclear-free. Concerns persist over the possibility that weapons technology was sold through the black market; Ukraine, in particular, was known to be active in selling at least conventional technology.
  • Several industrialized nations are thought to be capable of putting together nuclear weapons with very little effort, including Canada, Italy, Germany, Lithuania, and Japan. For the most part there is no evidence that these countries have any desire to pursue such a course. However, former German defense minister Rupert Scholz has argued that Germany should consider nuclear weapons as a way to respond to terrorist attacks.
  • Iraq, of course, had a program to develop nuclear weapons that suffered a number of setbacks, notably the Israeli air strike on the Osirak nuclear facility in 1981. After the 2003 invasion, the Iraq Survey Group concluded that the nuclear program had been abandoned in 1991, along with most other WMD programs, but that Saddam Hussein had plans to re-start the program once multilateral sanctions were lifted.
  • As part of NATO agreements, the US provides tactical nuclear weapons for use by Belgium, Germany, Italy, the Netherlands, and Turkey.
  • A number of countries are known to have begun programs to develop nuclear weapons, only to abandon them and eventually sign the NPT; these include Sweden, Switzerland, Egypt, Philippines, Libya, Australia, Poland, Romania, South Korea, Brazil, Argentina, Taiwan, and Yugoslavia.

What are the chances, with all those weapons out there, that someone will use one, say in the next fifty years? Extremely high, I would guess. None has been used in the last fifty years, it’s true, but for most of that time we lived in a bipolar world with clearly defined lines of engagement and relatively symmetrical capabilities and liabilities. (The above list doesn’t even mention non-state groups, of course.) A more fragmented situation exponentially increases the number of events that could lead to a nuclear strike, including the possibility of accidents. And the number of nuclear-capable states shows little signs of decreasing in the near future.

For what it’s worth, Russia, India and China have officially adopted a No-First-Use policy regarding nuclear weapons; the United States, United Kingdom, France, Israel, Pakistan and North Korea have declined to do so. In the 2005 revised Doctrine for Joint Nuclear Operations, the Pentagon listed the conditions under which a nuclear first strike could be requested, which includes basically any situation in which someone might want to use them. The Doctrine itself was originally published freely on the Pentagon web site, before being cancelled — that is, removed from the site, but not necessarily revised as doctrine. The original document can be read here. Britain and France have similarly asserted the right to nuclear first-use. It is hard to imagine that countries generally thought of as less responsible than the US, UK and France would feel much compulsion against using nuclear weapons if they felt threatened.

Once any country strikes another using nuclear weapons, the presumption against further use will be considerably lowered. The consequences are hard to imagine, simply for being so terrifying.

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The Future of Theoretical Cosmology

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I’m back from an extraordinarily hectic yet unusually rewarding April Meeting of the American Physical Society in Dallas. The APS has two big meetings each year, the April meetings for very large- and small-scale types (particle physics, nuclear physics, gravitation, astrophysics), and the March meeting for medium-scale types (condensed matter, atomic physics, biophysics). The March meeting is a crucially important event for its constituency, while the April meeting suffers from too much competition and far less customer loyalty, and is correspondingly a much smaller conference (perhaps 1,000-1,500 attendees, as opposed to 6,000 at a typical March meeting). That’s a subject for another post, for those of you out there with an unhealthy interest in APS politics.

(For other reports from the meeting, see Jennifer Ouellette’s Cocktail Party Physics or the mysterious and anonymous Charm &c. Common refrain: “It’s 2006! Why isn’t there decent wireless in this hotel??!!”)

There’s a rule to the effect that any person can give no more than one invited talk at an APS meeting, but such rules are made to be broken and I sneaked in there with two talks. One was a general overview of the accelerating universe and its associated problems, at a special session on Research Talks Aimed at Undergraduates. Having a session devoted to undergrads was a splendid idea, although I suspect that the median age of attendees at my talk was something like 45. That’s because, when asked to pitch a talk to an audience of level of expertise x, most physicists will end up pitching it at a level of expertise x+3. So various people with Ph.D.’s concluded that their best chance of understanding a talk outside their specialty was to attend a session for undergraduates. Perhaps they were right. Before my talk they got to hear nice presentations by Florencia Canelli on particle physics and the top quark, and Paul Chaikin on packing ellipsoids. (Okay, “packing ellipsoids” doesn’t sound like the sexiest topic, but it was filled with fascinating tidbits of information. Did you know that both prolate and oblate ellipsoids pack more efficiently than spheres? That ordered crystalline packings are generally found to be more efficient than random packings, but nobody can prove it in general? That M&M’s are extremely reliable ellipsoids, to better than 0.1%? That the method by which the Mars Corporation makes their M&M’s so regular is a closely guarded secret?)

My other talk was at a joint double session on the past, present, and future of cosmology, co-sponsored by the Division of Astrophysics and the Forum for the History of Physics. Six talks naturally needed to be given: one each on the past/present/future of observational/theoretical cosmology, and organizer Virginia Trimble invited me to speak on The Future of Theoretical Cosmology. The observational session conflicted with my talk to the “undergrads,” but I got to hear the talks on the past and present of theory by Helge Kragh and David Spergel, respectively.

Of course nobody has any idea what the future of theoretical cosmology will be like, given that we know neither what future experiments will tell us, nor what ideas future theorists will come up with. So I defined “the future” to be “100 years from now,” by which time I figured (1) I won’t be around, or (2) if I am around it will be because we will all be living in pods and communicating via the Matrix, and nobody will be all that interested in what I said about the future of cosmology a century earlier.

interactive dark sector

With those caveats in mind, I did try to make some prognostications about how we will be thinking about three kinds of cosmological issues: composition questions, origins questions, and evolution questions. You can peek at my slides in html or pdf, although I confess that many were cannibalized from other talks. The abbreviated version:

  • Composition Questions. We have an inventory of the universe consisting of approximately 4% ordinary matter, 22% dark matter, and 74% dark energy. But each of these components is mysterious: we don’t know what the dark matter or dark energy really are, nor why there is more matter than antimatter. My claim was that we will have completely understood these questions in 100 years. In each case, there is an active experimental program aimed at providing us with clues, so I’m optimistic that the matter will be closed long before then.
  • Origins Questions. Where did the universe come from, and why do we find it in this particular configuration? Inflation, which received an important boost from the recent WMAP results, is a crucial ingredient in our current picture, but I stressed that there is a lot that we don’t yet understand. In particular, we need to understand the pre-inflationary universe to know whether inflation really provides a robust theory of initial conditions. Thinking about inflation naturally leads us to the multiverse, and I argued that untestable predictions of a theory are perfectly legitimate science, so long as the theory makes other testable predictions. We don’t yet have a theory of quantum gravity that does that, and I prevaricated about whether one hundred years would be sufficient time to establish one. (Naive extrapolation predicts that we won’t be doing Planck-scale experiments until two hundred years from now.)
  • Evolution Questions. Given the initial conditions, we already understand the evolution of small perturbations up to the point where they become large (“nonlinear”). That’s when numerical simulations become crucial, and here I was a little more bold. The very idea of a computer simulation is only about 50 years old, so there’s every reason to expect that the way in which computers are used will look completely different 100 years from now. Quantum computers will be commonplace, and enable parallel processing of enormous power. More interestingly, the types of computation that we’ll be doing will be dramatically different; I suggested that the computers will not only be running simulations to test theories against observations, but will be coming up with theories themselves. Such a prospect is a natural outgrowth of the idea of genetic algorithms, so I don’t think it’s as crazy as it sounds.

The next day I managed to catch no fewer than three sessions filled with provocative talks — one on ultra-high-energy cosmic rays, one on cosmology and gravitational physics, and one on precision cosmology. And I would tell you all about them if I hadn’t lost the keys to my special time-stretching machine that allows me to put aside my day job for arbitrarily long periods so that I can blog at leisure. Probably the most intriguing suggestions were those by Shamit Kachru from SLAC, who argued that considerations from string theory (and in particular the constraint that scalar fields cannot evolve by amounts greater than the Planck scale) imply that gravitational waves produced by inflation will never be strong enough to be observable in the CMB, and those by David Saltzberg from UCLA, who listed an amazing variety of upcoming experiments to detect high-energy astrophysical neutrinos, including listening for sound waves (!) produced when a neutrino interacts with ocean water off the Bahamas. If I decide to become an experimentalist, that’s the one I’m joining.

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Cafe Scientifique Chicago

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You may have read celebrated and successful bloggers such as Mark and PZ Myers enthusing about the “Cafe Scientifique” idea. It’s an attempt, international in scope but local in focus, to promote discussion about exciting scientific ideas between experts and non-experts in an informal environment. By “in an informal environment” we typically mean “in a bar,” although I suppose an actual cafe or similar venue would do just as well. The original Cafes were located in England, but the idea has subsequently taken off and spread around the world. It’s similar in spirit to KC Cole’s Categorically Not series that Clifford has mentioned.

So now it’s our turn. Randy Landsberg at the University of Chicago has taken up the challenge of organizing a Cafe Scientifique in the Windy City, and the first meeting will be this Wednesday at the Map Room, a neighborhood bar famous for its dizzyingly diverse beer list. I’ll be the speaker, although the speaking is not the focus of the event. I’ll talk for about twenty minutes, followed by a break to give everyone a chance to refill their drinks, culminating in an extensive discussion/Q&A session where everyone gets a chance to talk the ideas through. The particular idea to be discussed is one of my favorites: Why is the past different from the future? We’ll talk about entropy and the arrow of time in our everyday lives, and connect it to big speculative ideas about the origin of the universe. Should be fun! And if everyone gets along, this will undoubtedly be the first of many events, and before too long the El will be alive with intense discussions about dispatches from the frontiers of science.

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Physicists against the nuclear option

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Via digby: Jorge Hirsch at UC San Diego has gathered a few of his friends — Nobel Laureates, Boltzmann and Fields Medalists, Medal of Science winners, and past Presidents of the American Physical Society — to write a letter to President Bush, urging him not to use nuclear weapons against Iran. The signatories are:

  • Philip Anderson, professor of physics at Princeton University and Nobel Laureate in Physics
  • Michael Fisher, professor of physics at the Institute for Physical Science and Technology, University of Maryland and Wolf Laureate in Physics
  • David Gross, professor of theoretical physics and director of the Kavli Institute of Physics at the University of California, Santa Barbara and Nobel Laureate in Physics
  • Jorge Hirsch, professor of physics at the University of California, San Diego
  • Leo Kadanoff, professor of physics and mathematics at the University of Chicago and recipient of the National Medal of Science
  • Joel Lebowitz, professor of mathematics and physics, Rutgers, The State University of New Jersey and Boltzmann Medalist
  • Anthony Leggett, professor of physics, University of Illinois at Urbana-Champaign and Nobel Laureate, Physics
  • Eugen Merzbacher, professor of physics, University of North Carolina at Chapel Hill and former president, American Physical Society
  • Douglas Osheroff, professor of physics and applied physics, Stanford University and Nobel Laureate, Physics
  • Andrew Sessler, former director of Lawrence Berkeley Laboratory and former president, American Physical Society
  • George Trilling, professor of physics, University of California, Berkeley, and former president, American Physical Society
  • Frank Wilczek, professor of physics, MIT and Nobel Laureate, Physics
  • Edward Witten, professor of physics, Institute for Advanced Study and Fields Medalist

In reality, winning a Nobel Prize doesn’t make you an informed judge of geopolitical affairs. But anyone in their right mind can see it would be a bad idea to launch a nuclear first strike against Iran or anyone else, and these folks are in their right minds. Hopefully they can lend some heft and gather some publicity for the cause.

Part of me wonders whether the administration understands perfectly well that a nuclear strike would be madness, but they want to give the impression of being reckless cowboys so that Iran will dismantle their nuclear program — that’s a hopeless plan, of course, but at least not wildly irreponsible. Then I remember that they have consistently acted like reckless cowboys in every previous situation, and my heart sinks a little. Remember DeLong’s Law: “The Bush Administration is always worse than one imagines, even when taking into account DeLong’s Law.”

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String Theory, With a View Towards Reality

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The Arthur H. Compton Lectures are a great tradition at the Enrico Fermi Institute here at the University of Chicago. Twice each academic year, a postdoc (!) from the EFI gives a series of 8-10 lectures on Saturday mornings, aimed at the general public, on a topic of current scientific interest. The EFI focuses on research in particle physics, astrophysics, and gravitation, so that’s what the lectures tend to cover. They are a great resource, and it’s amazing to see over a hundred people from the community trudge to a lecture hall every Saturday morning to hear about modern physics.

This Spring’s lectures are being given by Nick Halmagyi, a string theorist whose office is right across from mine. The title is String Theory: With a View Towards Reality, and Nick is gradually putting notes and slides online. With two lectures gone by, reality itself has been the focus thus far, as Nick sets up the current state of particle physics. String theory will undoubtedly follow, and when the moment comes to draw the connection between the two time will probably have run out.

Previous Compton lecturers are a distinguished lot, including our very own Risa. The EFI does a terrible job at keeping them online, but I was able to dig up slides from a few recent lecture series.

Any recent ones with online slides that I missed, let me know. And if you’re in the neighborhood, anyone is welcome to come to Nick’s lectures, which are at 11 a.m. most Saturdays. He speaks with a distinct Australian accent, but it’s ususally possible to understand him.

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Experimental sociology

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A little late, but I didn’t want to let slip this interesting discussion about the agonizing process of making experimental particle physics results ready for public consumption from Tommaso Dorigo and Gordon Watts. You’ll recall that we mentioned a couple of weeks ago the new results from Fermilab’s Tevatron on B-mixing, a measurement that puts interesting new constraints on the possibilities for physics beyond the Standard Model. The first announcement was from the D0 (“D-Zero”) experiment; as Collin pointed out in the comments, the CDF experiment followed with their own results soon thereafter.

From the CDF point of view, this is not how things are supposed to be; CDF is supposed to get there first, and D0 is supposed to confirm their results. Speaking from the CDF side, Tommaso talks about the process:

The publication process of CDF data analyses is baroque, bordering the grotesque. Once a group finalizes their result and presents it at internal meetings, the result has to be blessed. This involves three rounds of scrutiny, the full documentation of the analysis in internal notes, and often the fight with skeptics who like to sit at meetings and play “shoot the sitting duck” with the unfortunate colleague presenting the result. Usually, when an important result is on, the physicists who produced it are asked to perform additional checks of various kinds, and defend it with internal referees. When all of that is through, and not a day earlier, the result can be shown at Physics conferences.

After that happens, one would like to get the result on a Physics journal as soon as possible – to be cited!!! But just then, another much longer nightmare starts, when a process called “godparenting” begins and three knowledgeable colleagues (the godparents) are designated to scrutinize every detail of the work. Then a draft paper is produced, and in the following two weeks all the collaborators can play “shoot the duck” in written form, by sending criticism and demanding yet more checks. Then a second draft follows, and the process repeats…. In the end, usually six months pass between the blessing of a result at the physics meeting and the forwarding of a paper to a journal.

Gordon, from the D0 side, agrees with the general outline.

I don’t think it is that much different than what CDF has to go through — perhaps a bit more streamlined. We are all afraid that something wrong will make it out; hence all the layers of cross checking that go on. All of the collaboration is on the author list; this is the way the collaboration makes sure that the results that get out are correct. It can be a pain!

Read the whole things.

Of course there’s a lot more to the sociology of particle physics experiments than deciding when to release results. Interestingly, there are a lot of great books that take high-energy experiments and experimenters as their source material. Even novels — I recently read A Hole in Texas by Herman Wouk (best known for The Caine Mutiny and The Winds of War). It’s a short book set in the aftermath of the cancellation of the Superconducting Super Collider, imagining the hysteria if China managed to beat us to the Higgs boson. As a novel, I’ve read better; the romantic and political plots are somewhat perfunctory and not very believable. (And obviously written by a man; where else can you find no fewer than three attractive and accomplished women throwing themselves at a somewhat over-the-hill and not especially charming male physicist?) But the physics is surprisingly good; Wouk really put some effort into getting it right, including field trips to Fermilab and the SSC site.

And then you have your honest social-science explorations of the anthropology of the tribe of particle physicists. Beamtimes and Lifetimes, by anthropologist Sharon Traweek, treats HEP experimenters the same way we would treat an isolated tribe in the Amazon jungle, trying to figure out what makes them tick. (I’m still not sure.) But for my money, far and away the most insightful book is Nobel Dreams by Gary Taubes, the story of how Carlo Rubbia smashed the competition, not always using the most fair-minded tactics, to discover the W boson and win the Nobel Prize. Oh yes, and how he then failed to win another Nobel for discovering supersymmetry, despite repeatedly suggesting that his UA1 experiment had found evidence for it. A fascinating read, one that makes you tremble at the ambition of Rubbia and his lieutenants, admire the superhuman dedication of the many physicists on the project, and thank your lucky stars that your own working hours are a bit more sensible.

Update: Tommaso and Gordon explain more about the physics of the result.

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Thank Stanislav Petrov Day

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Stanislav Evgrafovich Petrov is arguably the most influential person who ever lived, although I had never heard of him until seeing this post on Cynical-C and this tribute.

Our story unfolds on September 26, 1983. Lieutenant Colonel Petrov was the officer on duty at the Serpukhov-15 bunker near Moscow with the responsibility of alerting Soviet command if there was any indication that the U.S. had launched a nuclear missile strike against the U.S.S.R. The response, of course, would be massive retaliation, and the deaths of many millions of people.

Just after midnight, the computers indicated that an American missile had been launched. Petrov was skeptical, since it wouldn’t make much sense to just launch a single missile. However, soon thereafter, the computer indicated that another four missiles had been launched.

To make a long story short (see Wikipedia for more), Petrov decided that the multiple launches were still a computer error rather than a real attack, and declined to alert his superiors, putting the Soviet Union at risk if he were mistaken. As it turned out, Petrov was right, and he had certainly averted an accidental worldwide catastrophe. But he had disobeyed procedure in the process; his superiors gave him a reprimand and reassigned him to a lower-profile post. The entire incident was kept secret until 1998.

Stanislav Petrov

Forget Easter, here’s a guy who deserves our thanks.

The question is: what would you have done? Presume that you were in an equivalent situtation, responsible for the defense of your country, a mission in which you believed with all your heart. But you have no desire to have millions of people die unnecessarily. How certain would you have to be that an attack was actually occuring before you would set massive retaliation in motion? Fifty-fifty? 100-1? A million to one? Or would you never retaliate, knowing that your decision would lead to hundreds of nuclear warheads raining down on your homeland, and your mortal enemy presumably taking over the world?

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Defending science

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Greetings from New Mexico, where I selflessly rise early to share a couple of items on the fight-to-save-honest-science front:

  • At Daily Kos, DarkSyde has an interview with Representative Brad Miller (D-NC) about his efforts to ferret out instances of the overt politicization of science within the administration (as we mentioned before). He wants to gather enough evidence to hold an investigation by the House Science Committee.
  • Phil Plait points us to Defend Science, a group that is holding protests and circulating a petition decrying attacks on objective scientific thinking within the U.S. I personally wasn’t that fond of the way the petition itself was written — a little too overheated, with a lot of capital letters — but it’s absolutely a worthy cause, and I am happy to go along.

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Books!

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A couple of publishing events of possible interest to CV readers:

  1. As an interesting experiment in web publishing, Robert Frenay’s new book Pulse is being fully published online. The book is about the future of computers, technology, and complex systems, so its appearance in blog form makes a certain kind of sense.
  2. Morse and Feshbach’s Methods of Theoretical Physics, a classic textbook and reference, has been reprinted after being out of circulation for a while. At almost $300, it’s not really an impulse buy, but you do get two volumes of about 1000 pages each. The reprinting was done under the supervision of Mark Feshbach, son of co-author Herman Feshbach.

Truth in advertising compels me to admit that I have not read either of these books! Nor I am getting anything for mentioning them, so it’s not really “advertising.” But both events are interesting.

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