Sean Carroll

Author: Sean Carroll

  • Leaking Wikis

    Obviously everyone in the world has heard about Wikileaks and its associated controversies. It seems like the site itself has to keep moving to avoid various attacks, but at the moment it can be found here.

    My strong first impulse is to be in favor of shining light in secret places. This can be taken to extremes, of course; there is such a thing as appropriate privacy, for governments and corporations as well as for individuals. But the natural tendency on the part of governments (or bureaucracies more generally) is to go too far to the other extreme, making secrecy routine where it should be exceptional — and using it to cover up embarrassment rather than protecting people’s lives. Something like Wikileaks is a great corrective to this tendency.

    I don’t really see, however, how something like the wholesale release of diplomatic cables helps this cause. Some of the cables might have been covered up for pernicious reasons, but for the most part diplomats should have an expectation of privacy in these kinds of communications, as much as an ordinary citizen would when making a phone call. This doesn’t seem like a brave strike against government corruption as much as a bit of leering Peeping-Tommery. I’d personally be happier if Wikileaks were a bit more selective in what it shared with the world.

    Personally, the most depressing aspect of the whole affair — even more than the cartoonish responses from craven politicians — has been the attitude of the established media. Sure, they will publish the stories, although usually accompanied by some sort of meek apologia. But on TV and in the op-ed pages, there is enormously more discussion about Julian Assange and Wikileaks itself than about what we have actually learned from the documents. A lot of people in the media these days consider themselves to be more like partners with government, rather than respectful adversaries. I’d love to see more thoughtful pieces about what we’ve learned from all these documents about how the world actually works.

    Regardless of the ambiguities, I certainly hope Wikileaks keeps going. As Thomas Jefferson put it, “The press, confined to truth, needs no other legal restraint.” Or as Ruben Bolling more recently tweeted: “If a journalist is walking down the street, and happens to find a box of secret government documents, what should he do?” Telling the truth is always a good first strategy.

  • Interview on Static Limit

    David Reffkin is a radio host at KUSF in San Francisco. His usual gig is classical music, but once a month he hosts a special called Static Limit where he delves into physics and cosmology. Here’s an interview he did with me a short while back. Right at the beginning we’re talking about this very blog, which I am now using to plug the interview, which is mostly about my book. This is what’s known as “synergy.”

    (Those viewing in an RSS reader, you have to visit the page to click the audio link.)

    David assumes the listeners have been following along previous shows, so we don’t spend too much time defining general relativity and the Big Bang; we go right for the cutting edge. But we also covered a lot of meta ground, about the process of doing physics. He also gave me the most comprehensive list of errata (mostly minor typos) for my book, so I know he read the whole thing!

  • Penrose’s Cyclic Cosmology

    Update: Gurzadyan and Penrose have very quickly put up a response to the analysis papers quoted below. And another paper critical of G&P has appeared, by Amir Hajian.

    Gurzadyan & Penrose Roger Penrose and his collaborator Vahe Gurzadyan made a splash recently by claiming that there was evidence in the cosmic microwave background for a pre-Big-Bang era in the history of the universe. (Here’s the paper.) The evidence takes the form of correlated circles in the cosmic microwave background anisotropies, as pictured here. They claim that they have found such circles at a level of significance much higher than would be predicted in a conventional scenario, where perturbations were random and uncorrelated on various scales.

    That would be pretty amazing, if true. But it looks like it isn’t. Here are two skeptical papers that just appeared on the arxiv. (Hat tip to David Spergel. Peter Coles was an early skeptic.)

    A search for concentric circles in the 7-year WMAP temperature sky maps

    Authors: I. K. Wehus, H. K. Eriksen

    Abstract: In a recent analysis of the 7-year WMAP temperature sky maps, Gurzadyan and Penrose claim to find evidence for violent pre-Big Bang activity in the form of concentric low-variance circles at high statistical significance. In this paper, we perform an independent search for such concentric low-variance circles, employing both chi^2 statistics and matched filters, and compare the results obtained from the 7-year WMAP temperature sky maps with those obtained from LCDM simulations. Our main findings are the following: We do reproduce the claimed ring structures observed in the WMAP data as presented by Gurzadyan and Penrose, thereby verifying their computational procedures. However, the results from our simulations do not agree with those presented by Gurzadyan and Penrose. On the contrary we obtain a substantially larger variance in our simulations, to the extent that the observed WMAP sky maps are fully consistent with the LCDM model as measured by these statistics.

    No evidence for anomalously low variance circles on the sky

    Authors: Adam Moss, Douglas Scott, James P. Zibin

    Abstract: In a recent paper, Gurzadyan & Penrose claim to have found directions on the sky centred on which are circles of anomalously low variance in the cosmic microwave background (CMB). These features are presented as evidence for a particular picture of the very early Universe. We attempted to repeat the analysis of these authors, and we can indeed confirm that such variations do exist in the temperature variance for annuli around points in the data. However, we find that this variation is entirely expected in a sky which contains the usual CMB anisotropies. In other words, properly simulated Gaussian CMB data contain just the sorts of variations claimed. Gurzadyan & Penrose have not found evidence for pre-Big Bang phenomena, but have simply re-discovered that the CMB contains structure.

    The basic message is simple: sure, you can find some circles in the sky if you look there. But they are simply what you would expect from random alignments, not a new signal over and above the usual predictions. The authors here are respected CMB analyzers, and I strongly suspect that they are correct. Which reminds us of an important lesson: analyzing the CMB is hard! It’s a very messy universe out there, and if you don’t take every single source of error correctly into account, you can convince yourself of all sorts of things.

    Just because this particular signal is there doesn’t mean the underlying model — Penrose’s Conformal Cyclic Cosmology (CCC) — isn’t right. I’m all in favor of pre-Big-Bang cosmologies myself, and Penrose more than anyone has been correct in insisting that the low entropy of our early universe is a crucial problem that is not well-addressed in modern cosmology. But I’ve been hesitant because, frankly, I don’t really get it.

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  • Is Al Gore Responsible for Destroying the Planet?

    Among the many depressing aspects of our current political discourse is the proudly anti-science stance adopted by one of our major political parties. When it comes to climate change, in particular, Republicans are increasingly united against the scientific consensus. What’s interesting is that this is not simply an example of a conservative/liberal split; elsewhere in the world, conservatives are not so willing to ignore the findings of scientists.

    Republicans are alone among major parties in Western democracies in denying the reality of climate change, a phenomenon that even puzzles many American conservatives. Denialism is growing among the rank and file, and the phenomenon is especially strong among those with college degrees. So it doesn’t seem to be a matter of lack of information, so much as active disinformation. Republican politicians are going along willingly, as they increasingly promote anti-scientific views on the environment. After the recent elections, GOP leaders are disbanding the House Select Committee on Global Warming.

    What makes American conservatives different from other right-wing parties around the world? Note that it wasn’t always this way — there was a time when Republicans wouldn’t have attacked science so openly. I have a theory: it’s Al Gore’s fault.

    Actually it’s not my theory, it comes from Randy Olson. For a while now Randy has been vocally skeptical about An Inconvenient Truth, Gore’s critically-acclaimed documentary about global warming. I was initially unconvinced. Surely the positive effects of informing so many people about the dangers of climate change outweigh the political damage of annoying some conservatives? But Randy’s point, which I’m coming around to, was that for all the good the movie did at spreading information about climate change, it did equal or greater harm by politicizing it.

    By most measures, Al Gore has had a pretty successful career. Vice-President during an administration characterized by peace and prosperity, winner of the popular vote total during his Presidential run, co-founder of Current TV, winner of an Emmy, a Grammy, and a Nobel Prize. But to Republicans, he’s a punchline. It’s an inevitable outcome of the current system: Al Gore was the Democratic nominee for President; therefore, he must be demonized. It’s not enough that their candidate is preferable; the other candidate must be humiliated, made into a laughingstock. (Ask John Kerry, whose service in Vietnam was somehow used as evidence of his cowardice.) The conclusion is inevitable: if Al Gore becomes attached to some cause, that cause must be fought against.

    Here is some evidence. You may think of Jay Leno as a completely vanilla and inoffensive late-night talk-show host. But he’s a savvy guy, and he knows his audience. Which is mostly older, white, suburban middle-class folks. Which political party does that sound like? Between January and September of 2010, Jay Leno made more jokes about Al Gore than about Sarah Palin. You read that right. This is while Palin was promoting books, making TV specials, stumping for candidates, and basically in the news every day, while Gore was — doing what exactly?

    Once Al Gore became the unofficial spokesperson for concern about climate change, it was increasingly inevitable that Republicans would deny it on principle. This isn’t the only reason, not by a long shot (there’s something in there about vested interests willing to pour money into resisting energy policies that are unfriendly to fossil fuels), but it’s a big part. Too many Republicans have reached a point where devotion to “the truth” takes a distant back seat to a devotion to “pissing off liberals.” With often nasty implications.

    What the United States does about climate change will be very important to the world. And what the U.S. does will be heavily affected by what Republicans permit. And Republicans’ views on climate change are largely colored by its association with Al Gore. As much as I hate to admit it, the net real impact of An Inconvenient Truth could turn out to be very negative.

    Gore himself doesn’t deserve blame here. Using one’s celebrity to bring attention to an issue of pressing concern, and running for office in order to implement good policies, are two legitimate ways a person can help try to make the world a better place. In a healthy culture of discussion, they shouldn’t necessarily interfere; if any issue qualifies as “bipartisan,” saving the planet should be it. But in our current climate, no discussion of political import can take place without first passing through the lens of partisan advantage. Too bad for us.

  • Book Review: Jonathan’s Franzen’s Freedom

    Sorry for the radio silence — Thanksgiving really took it out of me. (The food was excellent — may have eaten too much.) Just got back from a workshop at Stanford, where we had a mini Cosmic Variance gathering, since I saw both Daniel and Risa. Had JoAnne not been delayed on her flight back to California, we might have been able to get four co-bloggers in the same room for probably the first time ever.

    Since today is Casual Friday, I’d like to put science aside and do a review of Jonathan Franzen’s new book, Freedom: A Novel. I am hampered in that goal by the fact that I haven’t read the book, and don’t plan to any time soon. (I think Franzen is a great writer, but I’m very behind in my reading list.)

    So instead I’ll outsource this one to Washington Post book reviewer Ron Charles, who delivers his critique in video format. It gives me some ideas. (Hat tip to Ariel Kalil.)

  • Special Relativity, Simply Explained

    Here’s how it starts. Click over to Abstruse Goose to see the exciting conclusion.

    AbstruseGoose

    Message to science journalists: if this actually happened, it would be pretty awesome.

  • Thanksgiving

    This year we give thanks for an idea that is absolutely crucial to how our understanding of nature progresses: effective field theory. (We’ve previously given thanks for the Standard Model Lagrangian, Hubble’s Law, the Spin-Statistics Theorem, and conservation of momentum.)

    “Effective field theory” is a technical term within quantum field theory, but it is associated with a more informal notion of extremely wide applicability. Namely: if we imagine dividing the world into “what happens at very short, microscopic distances” and “what happens at longer, macroscopic distances,” then it is possible to consistently describe the macroscopic world without referring to (or even understanding) the microscopic world. This is not always true, of course — our macroscopic descriptions have very specific domains of applicability, past which the microscopic details begin to matter — but it’s true very often, for a wide variety of situations with direct physical relevance.

    The most basic examples are thermodynamics and fluid mechanics. You can talk about gasses and liquids very well without having any idea that they are made of atoms and molecules. Once you get deep into the details, we start talking about effects for which the atomic granularity really matters; but there is a very definite and useful regime in which it is simply irrelevant that air and water are “really” made of discrete units rather than being continuous fluids. Fluid mechanics is the “effective field theory of molecules” in the macroscopic domain.

    How awesome is that? If it weren’t for the idea of effective field theory, it’s hard to imagine how we would ever make progress in physics. You wouldn’t be able to talk about atmospheric science without knowing all the details of microscopic physics (known in the trade as the ultraviolet completion), all the way down to the Planck scale! Fortunately, the universe is much more kind to us.

    In particle physics, this idea is absolutely central. Protons, neutrons, and pions constitute an effective field theory that describes how quarks and gluons behave over sufficiently large distances. Another great example comes from Enrico Fermi’s theory of the weak interactions. Back in the 1930’s, Fermi proposed a theory that made use of the new “neutrino” particle. It involved processes that looked like this interaction of a proton plus electron converting into a neutron plus neutrino.

    Fermi interaction

    Nowadays we know better. What’s really going on is that the proton is made of two up quarks and a down quark, while the neutron is made of two downs and an up. The electron exchanges a W boson with one of the quarks, converting into an electron neutrino in the process.

    Electroweak interaction

    But the miracle is: it doesn’t matter. Knowing that the weak interactions are “really” carried by W bosons is completely irrelevant, as long as we are concerned only with large distances. In quantum mechanics, large distances correspond to low energies. (Remember that the energy of a wave decreases as its wavelength increases; quantum mechanics is all about waves.) So for low-energy processes, the effective field theory provided by Fermi is all you need to know about the weak interactions.

    The universe is kind, but that kindness comes at a price. Sometimes you want to care about the microscopic realm — for example, if you’re a physicist trying to figure out what is going on down there. When we look at spacetime on length scales of 10-33 centimeters, do we see vibrating strings, or noncommuting matrices, or spin networks, or what? Hard to tell, because it makes no difference at all to the large-distance/low-energy physics we can actually observe.

    That’s okay. A world described by a succession of effective field theories of ever-higher resolution helps us make sense of the world, while leaving physicists plenty of puzzles to think about. Very deserving of our thanksgiving.

  • Lost in Fourier Space

    It’s guest week at XKCD, as Randall Munroe deals with a family illness. (Fortunately for the guest artists, it’s relatively easy to mimic his style.) Today’s contribution came from Bill Amend of Foxtrot fame, who gives us what might be the best Heisenberg’s Uncertainty Principle joke I’ve seen.

    xkcd_ Guest Week_ Bill Amend (FoxTrot)

    There are more.

  • Using Information to Extract Energy

    There was some excitement last week about a Maxwell’s-Demon-type experiment conducted by Shoichi Toyabe and collaborators in Japan. (Costly Nature Physics article here; free arxiv version here.) It’s a great result, worth making a fuss about. But some commentators spun it as “converting information into energy.” That’s not quite right — it’s more like “using information to extract energy from a heat bath.”

    Say you have a box of gas with a certain temperature at maximum entropy — thermodynamic equilibrium. That is, the gas is smoothly spread throughout the box. (We can safely ignore gravity.) There’s certainly energy in there, but it’s not very useful. Indeed, one way of thinking about entropy is as a measure of how useless a certain amount of energy is. If we have a low-entropy configuration, we can extract useful work from the energy inside, such as pushing a piston. If we have a high-entropy configuration, the energy is useless; there’s nothing we can do to consistently extract it.

    Here’s an example from my book. Consider two pistons with the same number of gas particles inside, with the same total energy. But the top container is in a low-entropy state with all the gas on one side of the piston; the bottom container is in a high-entropy state with the gas equally spread out.

    extracting energy from a piston

    You see the difference — from the top configuration we can extract useful work by simply allowing the piston to expand. In the process, the total energy of the gas goes down (it cools off). But in the bottom piston, nothing’s going to happen. There’s just as much energy inside there, but we can’t get it out because it’s in a high-entropy state.

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  • A Mystery Box Full of Red Matter

    Here is a fantastic TED talk by JJ Abrams, the guy behind many of the most interesting genre movies and TV shows in recent years (Alias, Lost, Star Trek, Cloverfield, Fringe). It’s about the fundamental role played by mystery and the unknown in storytelling.

    I’m posting it here because, as wonderful as the talk is, I disagree with it at a deep level. Yes, indeed, the concept of “mystery” is absolutely crucial to what makes a story compelling. But I think Abrams takes the idea too far, valorizing mystery for its own sake, rather than as motivation for the characters and the audience to try to solve the mystery. The reason why mysteries are interesting is because we want to figure them out! If they are simply irreducibly mysterious — if there is no sensible explanation that ultimately makes sense of all the clues — then it’s simply frustrating, not magical.

    This isn’t just jousting with words — it has consequences for how stories are told. That’s why I chose Star Trek as my one movie to complain about in our Comic-Con panel last summer (as much as I enjoyed the movie overall). The dangerous planet-killing substance in that case was “red matter.” Shiny, red, and ominous-looking, red matter is not anything known to modern science. Which is fine; modern science doesn’t know about warp drive or Vulcans, either, but they work well in this particular fictional context. The problem is that red matter wasn’t associated with any sensible properties even within this fictional world. We never knew where it came from, why it did what it did, how it would react to different circumstances, etc. (Why did it have to be deposited in the exact middle of a planet, rather than just splashed on the surface?) It was simply “mysterious.” But this particular bit of mystery didn’t make it more compelling — it prevented the audience from engaging with the menace that the red matter presented. If we knew something about it, we wouldn’t just be going “okay, that’s the bad stuff, gotcha”; we’d be following along as Kirk and Spock tried to defuse the danger, understanding what might and might not do the trick. Not all mystery is good storytelling — sometimes a bit of understanding helps grab the attention.

    Just to draw the distinctions even more carefully, let me come out in favor of ambiguity as opposed to mystery. The end of Inception is quite famously amenable to more than one interpretation. (To go back further, ask whether Deckard was a replicant.) This drives people crazy, trying to figure out which one is “right,” an impulse I think is misguided. It’s okay to accept that we don’t know all the answers! But in theses cases we understand quite well the space of all possible answers. There is no black box whose operation is simply mysterious. We don’t need to know all the final answers once and for all; but it’s better storytelling if we understand what the answers could be, and that they make sense to us.

    Hopefully it’s not too hard to read between the lines here, and see the consequences for science as well as for movies. There are those who argue that science destroys the magic of the world by figuring things out. That’s exactly backwards — the scientific quest to solve the world’s puzzles is one of the things that makes the story of our lives so interesting.