Today’s colloquium was Stuart Freedman on the latest results from KamLAND, one of the neutrino detection experiments. The experiment is basically a gigantic vat of liquid scintillator—an oil convenient for producing photons from exotic particles passing through—surrounded by high-efficiency photon detectors. Neutrinos are produced in huge quantities by the sun and nuclear reactors, but they rarely interact with matter, so to observe them one needs to construct a very large detector and wait for a while.
I’ve always enjoyed following the neutrino experiments, since they came online about when I started to study physics, and since then they have made steady progress understanding this particle. It’s a nice example of the incremental progress of science. Around my senior year in high school the story was “We’ve been assuming neutrinos are massless, but it’s been suggested they do have mass and experiments are being constructed to look for it.” (That was the year I went to IPhO, which was held in Sudbury, Canada, a town whose only distinction was that the Sudbury Neutrino Observatory was being built there, so we heard a lot on this subject.) Over the next few years the line became “Neutrinos might have mass,” then “Neutrinos probably have mass (but we don’t know what it is)”. And in today’s colloquium, the word was:
- Neutrinos totally have mass. There are three different varieties of neutrinos, named according to the lepton they’re associated with in weak-force interactions: for example, the basic nuclear beta decay produces an electron and an electron neutrino. But KamLAND looked at neutrinos produced in this way by nuclear reactors, and found that neutrinos that start out as electron neutrinos oscillate between this type and the other two types (the mu and tau neutrinos). This can happen only if neutrinos are massive.
- But we don’t know what it is. Measurements on neutrino oscillations only tell you the relationship between the masses of the three types of neutrinos, and not the masses themselves. There are estimates of the actual masses based on this, but they are not very precise.
- The electron, mu, and tau neutrinos are not mass eigenstates. Rather than having a single mass itself, the electron neutrino is actually a kind of mixture (technically, a superposition) of three neutrinos, each of which does have its own mass. The mass eigenstates have been creatively named ν1, ν2, and ν3. It’s known approximately how much of each mass eigenstate is present in the electron, mu, and tau mixtures, but not how the masses are arranged—so ν3 could be the heaviest or the lightest.
- There’s still an undetermined parameter in neutrino mixing. It’s a complex phase, and relates to a symmetry breaking? This is one of those things I’d be more informed about if I’d ever taken a course on the Standard Model.
Freedman also spent some time on another angle of this experiment, in geophysics rather than fundamental physics. (I know I have some geophysicists reading, so you can correct me if I get this wrong.) There’s a discrepancy between various estimates of the heat produced by the Earth, and one hypothesis (which is apparently not widely credited) is that the core of the Earth contains a natural nuclear reactor. Since KamLAND is built to detect neutrinos from man-made reactors, it could in principle look for one at the center of the planet as well. Except that KamLAND is (deliberately) built really close to a number of reactors in Japan, and any geophysical signal would be absolutely swamped by the signal from power plants. So in practice it looks like another detector would have to be built somewhere else to do this experiment.
Via Katie in e-mail, the NYTimes has excerpts from textbooks for “Christian schools”, published by (who else?) Bob Jones University.
And yes, there’s a Physics for Christian Schools. It’s disturbing that someone thought physics was too atheistic and needed to be all churched up. Physicists, on the other hand, are pretty godless compared to the general population. Anyway, here’s an excerpt:
Some people have developed the idea that higher mathematics and science have little to do with the Bible or Christian life. They think that because physics deals with scientific facts, or because it is not pervaded with evolutionary ideas, there is no need to study it from a Christian perspective. This kind of thinking ignores a number of important facts to the Christian: First, all secular science is pervaded by mechanistic, naturalistic and evolutionistic philosophy. Learning that the laws of mechanics as they pertain to a baseball in flight are just the natural consequences of the way matter came together denies the wisdom and power of our Creator God. … Second, physics as taught in the schools of the world contradicts the processes that shaped the world we see today. Trying to believe both secular physics and the Bible leaves you in a state of confusion that will weaken your faith in God’s Word.
I have this perverse curiosity as to how exactly they remedy the mechanistic and naturalistic approach in “secular science” (a redundant phrase, I believe). Perhaps the equations are presented in the form “F = ma, because of Jesus.”
Reminds me of the classic anti-evolution Chick tract in which it is asserted that the strong nuclear force is a falsehood, and that atomic nuclei are compelled to hold together by the power of Christ. And speaking of evolution, I can only imagine what their “biology for Christians” text is like. Good for the UC for not crediting some of these courses.
Those of you who come here for the physics blogging (which has been somewhat absent of late) may be interested in a couple of links I found recently, via referrals and Technorati:
Mixed States aggregates the RSS feeds of a number of physics blogs (including this one). Since the included bloggers are listed by their real name, it’s a nice way to see who else in the community is blogging (although I didn’t recognize any names that I knew from physics rather than from reading blogs).
Coherence * is a blog reviewing work in superconducting quantum computing, something that should be useful to me professionally (perhaps more so than the cond-mat RSS feed, which is high volume and a bit tough to sort by topic). Above their blogroll they list professors working in the field, including former Clarke group member and current collaborator Britton Plourde, but strangely not John Clarke himself. (However, there are at least four of John’s former students/postdocs there, among other familiar names.)
What happens in Vegas is supposed to stay there, but I should say a few words about what I did instead of blogging the last few days:
Cirque du Soleil: I saw “O”, which is their water-oriented show done at a special theater (in the Bellagio) with a pool taking up most of the stage. Mostly the show consists of fantastically beautiful acrobatics into, out of, and above the water. They use fire nicely too. I wasn’t really into the clown acts, but those at least provided a recovery period before something interesting happens again.
Blue Man Group: Another awesome show. I’m not sure how to describe it—comic performance art? You’ve probably seen them in Intel commercials and stuff but the real thing is about a million times better.
Food: Good. But expensive.
Gaming: I did best at video poker but felt classiest playing blackjack. I find slots pretty boring, where the only variety is found by pulling the lever instead of pushing the button. I prefer to have something to strategize on (even if the perfect strategy for the game is known, as in both of the aforementioned games).
Carpets of Death: The carpet at the Venetian could have powered the slot machines from the electrons it was stripping off my feet. I found myself bracing for the shock every time I touched a machine, which provided a deterrent from spending much money there (although that’s where I happened to win the most). The carpets at the Bellagio did a bit of this but much less than at the Venetian.
Overall, a good use of my Thanksgiving break.
Tomorrow I am leaving for my Thanksgiving vacation—but I will be dodging the traditional extended-family-and-turkey version in favor of losing money at blackjack. Yes! I’m headed out to a spiritual retreat in Las Vegas. Blogging may or may not occur, so here’s another open thread in case I get distracted by the lights.
Recommendations for what to do/see are welcome!
This morning’s Stinson Beach Trail Run would have been more aptly named the Mt. Tamalpais Trail Climb (Which Happens To Start At Stinson Beach). This was a course so steep that at one point it was necessary to climb a ladder to continue. The t-shirt depicts runners going up a gentle incline; this would be accurate if I wore it while lying on my side. It was a nice place to run, as it’s basically the same forest as Muir Woods. But next time I’m bringing a sherpa.
The open thread can be delayed no longer! Also, if you work in Birge Hall and were running electronic equipment yesterday evening that you turned off at 1 am, please leave a comment. Thanks.
Franz Ferdinand: You Could Have It So Much Better: This is a great album that happened to come out the same day as Ladytron’s Witching Hour, so I didn’t listen to it as much as I otherwise would have. It’s very much along the lines of Franz Ferdinand’s debut album, although there’s a subtle difference in the sound that I can’t quite put my finger on, but makes me like the new one even more. There are a couple of motifs that keep appearing in the songs: a bunch of them are about breaking up, and a bunch of others are about, well, being evil. Not that this is a depressing CD, it’s more of a revelling-in-darkness CD. This is exemplified by the first track, “The Fallen”, which has a “Sympathy for the Devil” thing going in the lyrics. Later on you’ve got “I’m Evil and a Heathen” and “I’m Your Villain” so they clearly had the dark side on their minds. Of course, villainy has always made for good rock and this album is no exception.
I’ve had like three posts I’ve wanted to put up today (including the open thread), and have been prevented from doing so by severe computer problems. Posting from the lab computer is somewhat more annoying (lacking my usual software and bookmarks) so I’ll write up the post with the fewest number of links.
So I’d decided to acquire the new album by My Morning Jacket, which ordinarily would have been a straightforward matter, but this time I ran into an ethical dilemma. The problem, of course, is that My Morning Jacket is on a Sony label. Hence:
- If I buy the CD, I am implicitly supporting Sony’s harmful DRM practices. I won’t personally be affected since I have AutoRun turned off on my computers, and Z has the comparatively mild Suncomm DRM rather than the rootkit version, but one still shouldn’t buy CDs with such software on them.
- Or I could buy the tracks off iTMS, forgoing CD quality, album art, and liner notes, and substituting Apple’s DRM for Sony’s. Well, at least Apple won’t try to hack my PC, but they do have a habit of unilaterally renegotiating the terms of the license agreement.
- Or I could download them off a peer-to-peer service (for all the damage it does to paying customers, the DRM is easily worked-around and the tracks will certainly be available), but once again I forgo the packaging and now the band doesn’t get any money.
- Or I could buy it on vinyl (if it exists in that format), but I still don’t own a turntable.
It seemed to me that there was no good solution, and I ended up buying the actual CD since this is my preferred medium anyway. But I’m still sort of conflicted about it.
This link is of course mean, cruel, and shallow, not to mention that it takes aim at some extremely easy targets. But when I was feeling frustrated by my experiment today, it’s amazing how much my spirits were lifted by The First Annual MySpace Stupid Haircut Awards. (Via memepool.)
Yesterday’s colloquium was entitled “String Theory and Cosmology”, usually a sign that I can safely spend that hour in the lab trying to get my qubits to work. If I had known that the speaker would be giving the talk from handwritten transparencies I definitely would have stayed away, figuring that the talk was so overly technical that Powerpoint couldn’t handle it, and the speaker would be running through some incomprensible morass of equations and text that had been lifted from the Necronomicon and then translated a couple times by Babelfish.
But fortunately I did go to the colloquium, which turned out to be pretty accessible. The speaker, Shamit Kachru, was very good and able to give sort of a hand-wavy outline of what string theorists are up to. String theory is a very difficult and jargon-heavy subject, and there was no way for him to get very technical without losing 95% of the audience (myself included), so I can’t say that I gained much understanding of what string theories are actually about. However, I did at least grasp where the boundaries of knowledge are in this field, which I think can best be classified using the epistemological scheme invented by philosopher/poet Donald Rumsfeld:
- Known knowns: The Standard Model of particle physics, which describes the behavior of particles in certain regimes (i.e. the experimentally accessible ones) to very high accuracy. And general relativity, which describes gravity in observable regimes.
- Known unknowns: What gravity does at energies where it’s comparable to the other three forces (it’s normally much weaker). Also, various mathematical quirks and inconsistencies in the Standard Model.
- Unknown knowns: Various string theories generate universes that look sort of like this one. But it’s unknown whether any of them do describe the actual universe, because they only make interesting predictions at energies much higher than could possibly be tested. (I believe the number cited in the talk was 1017 GeV; the best accelerators run at 103 GeV.) The connection to cosmology in the talk was in trying to explain the origins of the universe using string theory; out of all of the potential verieties of theories, a few do make testable predictions on observable phenomena like the cosmic microwave background due to how they address the Big Bang. So if we’re lucky enough to live in one of these universes, we could confirm it with certain astrophysical experiments.
- Unknown unknowns: And then there’s the possibilty that string theory isn’t the right answer, but rather something no one’s thought of yet. As Douglas Adams noted, “There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
There is another theory which states that this has already happened.” (String theory always reminds me of that quote.)
Now, for serious string theory blogging you should be reading Cosmic Variance, since I don’t really know much at all about the field beyond what can be communicated in an hour-long colloquium. However, I’m starting to understand why it’s interesting. (Also, it turns out that the guys shambling down the halls around here muttering about “braaaaanes” aren’t zombies but overworked string theorists. Oops.)
I just discovered that there are videos of the colloquia on the physics department website, here, so you can actually watch this talk if you’re interested. (It hasn’t been posted yet but probably will be within a week.) Another good one from this semester was “Cycles in Fossil Diversity” by Rich Muller, which was a study of what causes species to thrive or die out at apparently regular intervals in Earth’s history.