Events on the world lines of two theoretical physicists, from the horizon to timelike infinity. A scientifically minded blog with varying amounts of entertainment, distractions, and every day trivialities.
By Bee on
Monday, February 08, 2010
Why, oh why, is the Psi called Psi?
I'm currently reading Sean Carroll's book "From Eternity to Here" and stumbled over this remark
In Newtonian mechanics, the space of states is called "phase space" for reasons that are pretty mysterious.
A mystery that hadn't occurred to me before, probably because the German word "Zustandsraum" means literally "state space," so no mystery there. Stefan and I were guessing Gibbs, who introduced the word, might have generalized the terminology from the harmonic oscillator where the location in phase space does indeed tell you the phase of the oscillation. (You find a nice applet depicting the phase-space diagram of the damped and undamped oscillator here).
In any case, this caused me to ponder what other words with funny origin physicists like to use. (Both funny ha-ha, and funny peculiar.) Why, for example, is the recombination in the early universe called recombination if there was no prior combination? Not that I was the first to ask that question. Sean offered the explanation that the word is borrowed from nuclear physics. But then why don't nuclear physicists call the fragmentation refragmentation?
There are more interesting nomenclatures though than presence or absence of prefixes.
A particularly well known oddity is the name "quarks" introduced by Gell-Mann, who couldn't decide how to spell the sound ducks make:
In 1963, when I assigned the name "quark" to the fundamental constituents of the nucleon, I had the sound first, without the spelling, which could have been "kwork". Then, in one of my occasional perusals of Finnegans Wake, by James Joyce, I came across the word "quark" in the phrase "Three quarks for Muster Mark". Since "quark" (meaning, for one thing, the cry of the gull) was clearly intended to rhyme with "Mark", as well as "bark" and other such words, I had to find an excuse to pronounce it as "kwork".
~M. Gell-Mann, The Quark and the Jaguar, via Wikipedia
Had Gell-Mann read a German dictionary instead of Joyce, he'd have noticed "Quark" is the German word for a milk product (often mistakenly translated as "cottage cheese" which is something entirely different). Besides this, "Quark" is a frequently used colloquial expression for nonsense.
But at least we know how that word came along. A mystery remained to me why the English adaption of the German word "Eigenvektor" came out to be "eigenvector." The German word "eigen" simply means "innate," and could easily have been translated.
A better example fo imaginative nomenclature is the Psi-particle (now known as J/Psi) whose cloud-chamber pictures frequently have the shape of a Psi (see picture above).
Then there is the "Penguin diagram", which owes its name to a lost bet and some illegal substances, and the "tadpole diagram" which once run risk of turning into a "spermion." Probably a good thing the tadpoles kept their name - just imagine what issues the anti-abortionists would have had with spermion cancellation.
In General Relativity, we have the conjecture of "cosmic censorship" to prevent us from seeing "naked singularities," and "wormholes" are already a classic. Cosmologists have further blessed us with MACHOs and WIMPs, acronyms for MAssive Compact Halo Object and Weakly Interacting Massive Particles respectively. Loop Quantum Gravity features a LOST theorem, after the last names of its authors. The large gap between the energy scale of currently known physics and the scale where grand unification is thought to occur is also known as "desert." We have a seesaw mechanism, play with Mexican hat potentials, have ghosts and talk about stop particles. There's a swiss cheese universe and neutron stars have pasta-antipasta layers with a spaghetti-phase. The most stupid nomenclature I so far have come up with is a "pullover". Yes, I know, not terribly original, but then I didn't expect a Nobelprize for it ;-)
Last time, we finally arrived at the diagram of the evaporating black hole:
More precisely, it's a non-rotating uncharged black hole.
The most important features of this spacetime are that it has a (spacelike) singularity and an event horizon. The blue line indicates the surface of some collapsing matter configuration [1]. Let me remind you that since we've chosen radial coordinates, curves that pass through r=0 (where it is non-singular) look like they are reflected back. These segments of curves are also referred to as in- and outgoing in an obvious terminology.
Shown in the figure is v0, the last ray of light that passes through the collapsing matter and still manages to escape [2]. In the background depicted in the diagram, particle creation takes place at the horizon, which causes the black hole to lose mass. It then shrinks until it has finally completely evaporated, leaving behind nothing but thermal Hawking radiation [3].
Another important fact is that this spacetime is "asymptotically flat" or "asymptotically Minkowski," which means that at an infinite distance from the black hole spacetime is flat (flat as in "the curvature tensor vanishes"). This doesn't necessarily have to be the case (i.e. it could be asymptotically AdS instead), but it will make our discussion leaner. The reason for this asymptotic flatness is simply that in the beginning as well as in the end the matter is arbitrarily thinly dispersed.
To wrap up the summary, note that this diagram depicts a highly idealized situation. It's an evaporating black hole in an otherwise entirely empty spacetime. Realistic black holes are surrounded by matter and accrete mass, and occasionally Bob sends one of his Alices behind the horizon. But, as so often in physics, the uncluttered idealized version will help us understand the situation better without spoiling the conclusions.
Evolution
To understand the black hole information loss problem you need one further ingredient, that's what physicists mean with time-evolution. Intuitively, it means that one specifies a system at one moment in time, known as "initial conditions" and from this determines the status of that system at any other time by the help of a differential equation [4]. The most basic example is throwing a ball. The initial conditions needed are the location and velocity at one moment. The equation you use is Newton's law (or something equivalent).
In General Relativity the situation is more complicated but conceptually similar. You specify the initial conditions of your matter configuration at one moment in time and use Einstein's field equations to determine what space-time and matter are doing at any other time [5]. The attentive reader might remark that already in Special Relativity "one moment in time" is ambiguous. Indeed, and this is also the case in General Relativity. Point is, you can use any "moment in time" for you initial conditions, as long as it's at one moment, but everywhere in space (this is not the only option, but the most commonly used one). We call that a "complete spacelike hypersurface." Complete means basically it doesn't have holes and no expandable boundaries.
Almost there now. In the below picture I've added two complete spacelike hypersurfaces denoted Σ1 and Σ2
Information Loss
The evolution of a quantum mechanical state is unitary. That means in particular it is time-reversible [6]. You can evolve the status of your system back and forth how you like. There are many ways to think about information, and when talking about the black hole evolution some people like to hang themselves up on the exact meaning of information. That's a very interesting topic, but we'll cut this discussion short because it's irrelevant to understand the problem. Consider you have an initial state and you evolve it into a final state. If your final state does not uniquely specify the initial state we'll consider this loss of information. It means you can't tell what happened.
Black hole evaporation causes a loss of information because the outgoing radiation depends only on the total mass. Once the black hole is evaporated, all states with the same initial mass are converted into the same endstate. There are many ways a system can be composed if you only know the total mass [7]. There's only one way it will look after evaporation. This process is thus not reversible: it is not possible to reconstruct the initial state from the final state. But if it's not reversible, it can't be unitary. And for beginners that's the problem: The formation and complete evaporation of the black hole seems to be incompatible with quantum mechanics. On the advanced level it's more complicated since we know the computation leading to Hawking radiation breaks down when quantum gravity becomes important. In this case the problem is that this quantum gravitational contribution doesn't help you to get enough information out.
There are several points that people tend to misunderstand about the problem already on the beginner's level, so let me mention some pitfalls. First, note that the problem is not that the information is inaccessible behind a horizon. There is no horizon in the endstate, look at the diagram. It's flat Minkowski space with infinitely thinly dispersed thermal radiation. Think of the black hole as a black box. You start with flat Minkowski space, something happens in between, you end with flat Minkowski space. Yet, this evolution cannot be described by quantum mechanics as we know it. Second, to lay out the problem I didn't have to refer to measurement at all. It's a fundamental incompatibility in the evolution, you don't solve that incompatibility by waving your hands and yelling "measurement problem." Third, we are talking about the microscopic laws. Yes, on macroscopic scales we do have an arrow of time and entropy tends to increase anyway, but the problem is to accommodate the black hole evolution with the fundamentals of quantum mechanics prior to coarse graining. Fourth, yes, it is possible to cover the the Schwarzschild geometry by what is known as "nice slices," hypersurfaces that avoid the singularity for any finite time. (You find some very good graphics for that here, on slide 10). That doesn't solve the problem either because no matter how you turn it, your black hole evaporates away and you'll finally have to face that all you have left at scri minus is thermal radiation.
If you want to argue that the problem is a thought-experiment and unobservable, please read my earlier post on Thoughts and Experiments. We have to pay attention to inconsistencies even if they are not observable since they document a gap in our knowledge. While troubelsome, they also offer us opportunities to improve our understanding of Nature, which is why physicists turn problems like this upside-down and inside-out.
The value of the causal diagram once again is that it captures a lot of physics in one simple picture. If you look at it one more time you can see the problem. At the singularity matter gets crushed to infinite density and absent non-local effects everything that crossed the horizon has to fall into the singularity. Recall that curves on 45° angles depict the trajectories light travels on. You'd have to be faster than light to avoid the singularity once you've passed the horizon. All information about the initial state that evolves into the singularity is thus not available on the final slice. And that's exactly what happens in the calculation. You have to finally let go of the part of the initial wave-function that vanished behind the horizon, because it cannot avoid the singularity.
Now what
This then opens the playground for solutions to the problem. You either have to get the information out before it hits the singularity or avoid that it crosses the horizon at all. Lee and I argued in our last year's paper (see previous post for details) that the easiest way to avoid hitting the singularity is if there is no singularity. This by itself doesn't mean information behind the horizon becomes accessible again for the observer outside the horizon. But if you recall, this wasn't the problem to begin with. The problem was to achieve compatibility with unitary evolution, and this doesn't require information to be accessible to everybody as long as it exists.
In any case, since the black evaporation is and will likely remain elusive to experiment, everybody has their favorite solution. String theorists like the idea that information never gets lost because the evolution of the black hole is equivalently described by a dual, unitary, theory formulated on the boundary of the space-time which has been shown to encode regions of the bulk both inside and outside the horizon. People working on other approaches to quantum gravity seem to favor the idea that the singularity is avoided and the information somehow makes it out of the horizon, though at least to me it's remained unclear how so. (I sometimes suspect they'll finally reinvent and adopt the string theory solution.) Scenarios with stable or quasi-stable remnants that keep information or slowly release it also occasionally reoccur, and then there's parallel- and baby universes and a long list of miscellaneous other. The idea that black holes can't be formed to begin with lies in a shadowy fringe-area and is not considered plausible by the vast majority of researchers in the field.
I personally am somewhat agnostic on the how of information release, but am certain it can eventually only be achieved if the singularity is avoided (in the sense explained in mentioned paper.)
So. *wiping sweat off forehead* If you still haven't enough let me know.
[1] Modulo the question where it hits the singularity, see comments to previous post, but that's not relevant for our purposes. [2] To be more precise, since we have assumed spherical symmetry to be able to draw a 4 dimensional manifold, a point in the figure is actually a sphere, but this distinction isn't so relevant. One can decompose the solutions to the wave-equation in spherical harmonics as usual. We are then talking here only about the s-wave state. States with higher angular momentum have a more complicated behavior.
[3] In the upheaval around the alleged risk of black holes at the LHC, some people ridiculed the fact that Hawking's calculation does not "automatically" decrease the mass of the black hole but that energy conservation is "put in by hand." That is in fact true. But that in this calculation the radiation does not "automatically" carry away the mass of the black hole is an artifact of doing the analysis in a fixed background, which "by hand" prohibits the mass from changing. There is absolutely nothing wrong with the argument that taking into account the energy loss through radiation the mass is not in fact constant. This in turn does not render the calculation false, it merely sets limits to its accuracy, and Hawking's calculation can be shown to be an excellent approximation as long as the ratio of mass loss is small. It is only in the end stage of evaporation when quantum gravity is important that the mass loss becomes relevant for the properties of the emitted radiation. This phase is thus still a matter of discussion. [4] Note that it is entirely irrelevant the "initial" conditions are indeed the beginning of the evolution from which you determine the past. You could equally well specify the state of your system in the future and evolve it into the past. [5] Note that this means once you've specified an equation of state for the matter, General Relativity does not allow you to specify what you want the matter to do over the course of time. [6] The reverse is not true. A reversible evolution is in general not also unitary. [7] Even if it's spherically symmetric. You lose all information in the radial direction.
Yesterday, we had a very nice colloquium by Jonas Strandberg from the University of Michigan on "The startup of the LHC and the very first collisions in the ATLAS detector" (abstract and video here). If you have an hour time, watching the video is a good way to spend it. Here, I just want to pick out one image he showed because it got stuck in my head.
As you might know the protons the LHC is circulating are accelerated in various stages. From a duoplasmatron, they are first injected into a linear accelerator (up to 50 MeV), then in the first small circular accelerator, the Proton Synchroton Booster (50 MeV -> 1.4 GeV), then in the Proton Synchroton (1.4 GeV -> 26GeV) and then in the Super Proton Synchroton (26 GeV -> 450 GeV). Only after this are they injected into the LHC tunnel for the real kick (450 GeV -> 7 TeV).
This year, the laser will turn 50! On May 16, 1960, at the Hughes Research Laboratories in Malibu, California, Theodore Maiman realized for the first time "Light Amplification by Stimulated Emission of Radiation", using a tiny ruby crystal.
Actually, Maiman and his small group of coworkers was back then just one of several teams, all at industrial laboratories, intensely searching for ways to create laser beams. At the end of the year, the ruby laser was replicated and improved, and lasing was realized using other crystals, and helium-neon gas mixtures. So, it's just fair that the American Physical Society, the Optical Society, SPIE, and the IEEE Photonics Society have decided to organize a yearlong celebration of the 50th anniversary of the laser - that's LaserFest.
But in fact, the path to the laser had begun much earlier.
Berlin, 1916
In the summer of 1916, Albert Einstein took a break from general relativity and cosmology and tried to make sense, once more, of the riddle of the quantum. Specifically, he thought about ways to combine the recent ideas of Bohr on discrete energy levels in atoms with the Planck spectrum of blackbody radiation.
Atoms in thermal equilibrium with radiation can absorb radiation, thereby transiting to a state of higher energy, and they can drop from an excited state to a state with lower energy spontaneously, thereby emitting radiation. Could it be, so Einstein's idea, that atoms also will transit from an excited to a lower-energy state when they are hit by radiation with suitable energy?
Indeed, assuming a thermal Boltzmann distribution for the states of the atoms interacting with radiation, and equal rates for absorption on the one hand and spontaneous and stimulated emission – as the newly stipulated process came to be called – on the other hand, as one would expect for a thermal equilibrium between the atoms and radiation, Einstein could reproduce the Planck formula for the spectrum of blackbody radiation. "A splendid light has dawned on me about the absorption and emission of radiation," he wrote in a letter to his friend Michele Besso on August 11, 1916.
Einstein's "splendid light" of stimulated emission of radiation: An atom in a state with energy E2 is hit by a photon with energy hν = E2−E1. This can trigger a transition of the atom to the lower energy level E1, accompanied with the emission of a photon with energy hν, in phase with the initial photon. After this so-called stimulated emission, there are two photons instead of one, both in the same state – a nice manifestation of the "bunching" Bose character of photons.
It was recognized in the 1920s that theoretically the process of stimulated emission could result in "negative absorption", that is, amplification, of radiation, but nobody had a good idea how to demonstrate this effect in practice.
New York, 1954
To achieve amplification of radiation via stimulated emission, it is necessary to have more atoms in the high-energy state than in the low-energy state. Otherwise, a photon hitting an atom will more likely just be absorbed than trigger stimulated emission, and there is no gain in radiation. This requirement for amplification is called "population inversion".
In 1951, Charles Townes had an idea how to create "population inversion" in an ensemble of ammonia molecules. The ammonia molecule comes with two states which are separated by an energy corresponding to microwave frequencies. A beam of ammonia molecules can be split into two in an inhomogeneous electric field, separating molecules in the higher and the lower energy states, respectively, with an arrangement similar to a Stern-Gerlach apparatus.
In April 1954, Townes and his students Jim Gordon and Herbert Zeiger at Columbia University piped a beam of ammonia molecules in the higher-energy state into a microwave cavity resonating at the frequency of the energy difference between the two states, and obtained "microwave amplification by stimulated emission of radiation" - this was the birth of the maser.
Townes soon started to think about ways how to extend the maser principle to infrared or optical frequencies. With graduate student Gordon Gould, he discussed arrangements of mirrors around the medium in which population inversion is created, replacing the microwave cavity. These mirrors make sure that a beam of light is going back and forth through the medium many times, thus being able to "collect" ever more photons every time it crosses the medium.
Gould realized that such an arrangement, for which he coined the term "laser", could create sharply focussed light beams of extreme intensity, which could be used for communication, as a tool, or as a weapon.
As soon as the concept of the "optical maser", as Townes continued to call it, was explained in detail in a paper written together with Arthur Schawlow, many groups embarked on a race to be the first to actually construct such a device.
Malibu, 1960
Theodore Maiman had received his doctorate in Physics from Stanford University in 1955 to take a job at the Hughes Research Laboratories, which moved to Malibu in 1960. At Hughes, Maiman had constructed masers using ruby crystals, and when he learned of the possibility of the laser, he convinced himself that it should be possible to build a laser using ruby as the "lasing" medium.
Ruby is, chemically speaking, a crystal of aluminum oxide doted with chromium ions. The chromium ions have several energy levels which can be excited by irradiation with light, two of which are metastable and can be used as the upper level of a lasing medium. The energy of the transition to the ground state corresponds to red light with a wavelength of 694 nm.
Maiman's idea was to take a rod of ruby with parallel faces, to coat these faces with silver to realize the mirrors, and to put the rod inside a helical flashlight tube. The flashlight then excites the chromium atoms and creates population inversion, and the spontaneous emission of one photon can trigger an avalanche of photons by stimulated emission.
On the afternoon of May 16, 1960, Maiman and his assistant Irnee D’Haenens saw for the first time directed beams of intense red light emerging from the ruby - they had realized the first laser.
Theodore Maiman holding the first laser. It consists of a small ruby crystal and a helical flashlight which serves to stimulate the chromium ions of the ruby, thus creating the population inversion necessary for laser action. The ends of the ruby rod have been coated with silver to mirror back and forth the light stemming from stimulated emission, thus producing sufficient gain. The whole device is placed in the small white casing. (Source)
Maiman is reported to have said that “A laser is a solution seeking a problem”, Gould's visions notwithstanding. I have no specific idea how fast the laser was used for commercial or industrial purposes, but it immediately grasped public imagination.
When the movie Goldfinger is released in 1964, James Bond has to face a huge laser, looking similar to a scaled-up version of Maiman's first tiny ruby device, and replacing the buzz saw of Ian Flemings original 1959 novel. As Auric Goldfinger explains:
l, too, have a new toy, but considerably more practical. You are looking at an industrial laser, which emits an extraordinary light, unknown in nature. It can project a spot on the moon. Or, at closer range, cut through solid metal. I will show you.
If you want to know more about the history of the laser, there are two books I can recommend:
The history of the laser, by Mario Bertolotti, actually tells much more than just the story of the laser: It starts back at the beginning of the 20th century with the early atom models and the puzzle of blackbody radiation, and traces the path to the laser via spectroscopy, magnetic resonance, and the maser.
Beam: the race to make the laser, by Jeff Hecht, focusses on the developments of the late 1950s and 1960, beginning with just two brief chapters on the early history of stimulated emission and the maser. If you get lost in between all the names, there is a list of dramatis personae at the end of the book which I, unfortunately, discovered only after reading the text.
If you have Feynman's lectures at hand, there is a discussion of Einstein's derivation of the blackbody spectrum using stimulated emission and the Einstein coefficients in Section 42-5 of Volume I, and the whole Chapter 9 of Volume III is devoted to explain the principle of the ammonia maser.
First: As some of you (Steven,Phil) have noticed, we have turned on comment moderation for all posts older than 14 days. Blogger only allows such selective comment moderation since recently. I've tried it for some weeks and it saves me a lot of time and effort, thus I will keep it.
Thing is that the vast majority of comments on posts older than 2 weeks are spam comments. You will occasionally have noticed them appearing in the comment feed. They typically come in bulks of 5-10, sometimes several a day. With the old settings, we had to visit every post separately and delete them. With the comment moderation on, they now go into the moderation queue without appearing in the feed, and I can check the queue when I please and hit "delete all."
For you this brings the inconvenience that on posts older than 14 days you might have to wait for your comment to appear till I come around to publish it. Let me add that I get all comments by email, so while the risk is not zero that I miss one, it is small.
Second: The number of comments on this blog has steadily been increasing and it has reached a level where Stefan and I don't come around to adequately handling them. I made a count on two days last week, and I came up to more than 50 comments per day (including my own). This has finally convinced me to take the step I've been hesitating to take for several years now: I have disabled anonymous comments.
The reason is simply that I am sick of the all too common Web2.0 drive-by anonymity. More often than not, it's the analogue of dropping into my living room with a Mickey-Mouse mask, spitting on the floor and then running away. I have previously told you that yes, anonymity has its place, but it should not be used unnecessarily. However, in reality, almost all anonymous comments are anonymous simply for the reason of cowardice, because somebody finds it okay to bother me with what just went through their head but then doesn't want to be brought in connection with it. You all know who I am. If somebody feels like they have to utter words without thinking and waste my time, I at least want the crap to stick to them. I am also sick of complaining about it.
It is clear to to me that requiring a Blogger ID won't exactly prevent that problem, but at least it's a hurdle that I hope will improve things. Please note that most blogs meanwhile either require registration, or that you submit an email address with your comment. This is not the case at blogspot, which literally invites anonymity.
Practically, for you this means you can no longer post comments without a Blogger ID or an Open ID. This affects some of our more frequent commenters, George and Kay come to mind. You do not need to write a blog to get a blogger ID. With a Google-account it takes you like 30 seconds to get one. It is 100% spam free. I've had my Blogger account since more than 4 years and have not received one single spam mail/news/updates etc. The Open ID you get with any of the participating services, including Wordpress, Facebook and Flickr.
I hope that our readers will benefit from these decisions.
We've had some more snow the last days. Sweden is very family friendly, but some restrictions do apply ;-)
This reminded me that when I was moving to Stockholm I joked the trajectory I'm on, Santa Barbara - Waterloo - Stockholm, is not good. If I continue this way, I'll get tenure in Novosibirsk. I was terribly wrong with this because Novosibirsk is in fact more south than Stockholm. No kidding. The extrapolation looks in fact like this:
Uuh-ooh. Looks more like the Siberian Islands than Novosibirsk. But of course that's all a matter of perspective.
My Swedish hasn't made significant progress. There's bits and pieces that I understand in the news on the radio. "Olycka" (accident), "kallt väder" (cold weather) "flygbombade" (air bombing). Do I really want to know more? So far I have encountered a total of two Swedes who didn't speak English, one of them an elderly lady who answered my question where to find the exit with "I love you," followed by what I believe meant "This is the only English sentence I know." I found out of the garage anyway, thus the pressure to learn Swedish is low. Only problem is the mail I receive, since I'm typically not in the mood to get a dictionary and find out what exactly it says. Such it turned out that I have happily thrown away letters containing forms about my pension fund, thinking they were advertisements. On the other hand, I received a letter from the German Society in Stockholm, kindly offering me German lessons.
In fact, many Swedes speak English so well that I, not being a native speaker myself, sometimes can't tell whether they are British or Swedish. Tale-telling though is the melody of the language. Meanwhile, my English that used to be American English with a German accent and lately some Canadian impact, threatens to pick up that melody too. The Uncyclopedia kindly offers "Eeengleesh vid de Sveeedeeesh acky-centy eees de moost hilariooos dialectas of de Eeengleeesh lengveeege." If anybody has a good advice how to get rid of the Canadian "ou" pls let me know (watch this, min 1:07, listen to "anything abOUt Newfoundland"). These two Newfoundlanders of course give you a totally wrong picture of Canada. Watch the below to see how successfully they've been working on their inferiority complex...
It started when I was an undergraduate. In his email he explained he had found a theory for the indeterminism in quantum mechanics. I spent 2 weeks trying to explain that dividing both sides of an equation by zero does not create a non-deterministic measurement outcome, but simply nonsense. He insisted I misunderstand his idea and accused me of being narrow-minded.
This was 15 years ago when the internet was young. Since then, I've received hundreds of emails from self-declared geniuses who urgently want me to read their attached paper or visit their website. Some are trying to politely convince (with your qualifications... I would be honored...), some are outright offensive (intellectual elitism!), some are asking for pity (I have nobody to talk to.) Most of them write emails, some write letters, others send their self-printed books. I guess everybody with a PhD in physics has received one or the other such "theory." Baez' crackpot index tells this tale. Writing a blog makes you a preferred target. And during the last week, my inbox has seen a sharp increase in unsolicited mailings which I totally blame on winning a 2nd price in the FQXi essay contest.
I realize that some fraction of this blog's readership very likely consists of people who have themselves written such emails and who are hoping that I recognize their ingenuity. Not despite but exactly because of this I want to offer you some open words. I will not read your paper. I will not visit your website. And, no, I am not interested in your "theory." That's for several reasons. First, I generally will not open any attachments or click on links in emails from people I don't know, period. Second, I have no lack on interesting things to read and don't need your inspiration either. If I add your paper to the pile, I might get around to reading it sometime in the next century, so forget about it. Third, it is entirely obvious from your email that you have never read any of my papers, and have no clue who I am or what I am working on. Why should I waste a single second of my day reading what you wrote?
Let me be clear on this. I totally acknowledge the possibility that your theory is indeed groundbreaking and will fundamentally change our understanding of Nature. Not having read what you wrote, I am not judging your work whatsoever. But I am crucially aware my time on this planet is finite and I select the information that I pipe into my brain carefully. And yes, this means I use the most common crap-filters, peer review and personal connections. It is not impossible your work is groundbreaking. But it's unlikely. More likely, it's just a waste of my time. You can call that ignorant if you like, but it's effective. Tell me a better filter and I'll use it. You can go and complain about the arrogance of PhD holders. But I hope you realize that you and your spiritual brothers (if you have sisters, they are rare) have to blame yourself for this protective wall. If you wouldn't constantly bother us with immature ideas, we'd maybe take you more seriously.
The point is you have to know the rules before you break them. That's true in politics, in the arts, and it's also true in the sciences. No, you don't need a PhD to contribute to research in theoretical physics. But whether you have a title or not, you need the equivalent knowledge. You're not getting there by reading blogs, or posting in a forum. It takes time, it takes effort. And it is abundantly clear if your educational background is insufficient. You're not fooling anyone. You wouldn't go tell your doctor you have a great new idea for how he's supposed to do your bypass, would you? And why not? Because you know he has more education and experience than you. Time to realize that it also takes education and experience to write a paper in theoretical physics.
Having said that, let's look at the lighter side of things. I frequently scribble notes on papers. Most often used are "?" and "!," closely followed by "Check this!" and "nice." Inspired by this site with funny rubber stamps, you'll see in this post a few stamps I'd sometimes like to use ;-) Click to enlarge. And here's for the sisters:
Layout and design: yours truly. We also meanwhile have a few abstracts and a new one coming in every couple of days, so check out the website for more details.
Last week I was in Great Britain (as you'll know if you follow me on Twitter). Even when you're flying long-distance Westbound a commercial plane doesn't catch up with the setting sun. Eg the flight from Frankfurt to Toronto takes 9 hours while you gain only 6 time-zones. But when flying South-West from Sweden on a winter afternoon one can amazingly enough see the sun rise again above the horizon. Winters here in Stockholm are cold and dark. Plenty of time to be reminded that life on earth would not be possible without a gigantic ball of hot plasma that our planet happens to be orbiting around.
We're so used to the sun that we often forget what a fascinating object it really is. Far from being the dull blob that it appears from far away, it's 1030 kg of nuclear matter with temperatures ranging from 5,000 K at the surface to 107 K at the core. Some months ago, during Nordita's program on "Solar and stellar dynamos and cycles" in a talk on Helioseismology, I saw this video showing a solar quake, waves on the sun's surface:
This quake from July 1996 was triggered by a solar flare in its center that was recorded just prior to the quake. Not the newest news, but I still think this is totally amazing. There's also a lot of physics in here. Unfortunately, I wasn't able to find the real-time scale is for the video, but I think it's roughly an hour. The actual size of the image shown is 100,000 km in each direction. The data was taken with the Michelson Doppler Imager of NASA's Solar and Heliospheric Observatory (SOHO) mission which basically measures the velocity perpendicular to the sun's surface by use of the Doppler shift in spectral lines. You can find a better resolution of the picture with a brief description of the event on this website.
It is interesting to note, and you can see this on the crappy video already, that unlike water waves you'd see in a puddle, the waves on the sun's surface increase their velocity with time (by roughly factor 10 for what is shown in the video). The explanation for this is that the waves are not surface waves, but pressure waves propagating into the sun's interior. Unlike the puddle the sun is a ball and its density increases towards the middle. With increasing density, the velocity of the waves (essentially the sound velocity) increases. The waves are reflected (similar to light-reflection/refraction on planar surfaces) and appear back on the sun's surface as outgoing rings whose outward velocity increases due to the geometry of the wavefronts and the density gradient. (For more details, the interested reader is referred to astro-ph/0601006 and references therein.)
So next time you look at the sun recall it's a giant ball of plasma held together by gravity, an every-day display of fascinating physics.
Some bits of information that crossed my way recently:
The upcoming deadline for applications to Perimeter Institute's master course, Perimeter Scholars International, is February 1st, 2010. Details are available at www.perimeterscholars.org.
Planck 2010, the Thirteenth European Meeting "From the Planck scale to the electroweak scale", will take place at CERN from May 31 to June 4, 2010. The conference website is here.
The International Union of Pure and Applied Physics (IUPAP) is conducting a global survey to study the situation of physicists. The aim is to assess conditions of education and research and family support in international comparison. This is the third time this survey is made. It is available in 8 different languages on this website. (Thanks to Achim.)
The Foundational Questions Institute (FQXi) runs an annual Essay Contest, and last year's installment asked for papers on the question: "What is Ultimately Possible in Physics?"
The essay of Sabine attacks our presumption that anyone could answer the essay question, arguing that we can never know if we have hit a limit of scientific knowledge. Judges praised the witty and logical style and the author's creative questioning of the question.
Congratulations, Sabine!
At the Frontier of Knowledge
At any time, there are areas of science where we are standing at the frontier of knowledge, and can wonder whether we have reached a fundamental limit to human understanding. What is ultimately possible in physics? I will argue here that it is ultimately impossible to answer this question. For this, I will first distinguish three different reasons why the possibility of progress is doubted and offer examples for these cases. Based on this, one can then identify three reasons for why progress might indeed be impossible, and finally conclude that it is impossible to decide which case we are facing.
I've never been much into video games. While I am stunned by the high quality of today's virtual worlds I tend to lose interest in human-created puzzles quickly. On the rare occasions I've played one or the other game (TombRaider, Half-Life) I shamelessly used walkthroughs. Why spend 2 hours opening all the graves when some teenager in Mississippi knows which contains the mummy? In addition, when I'm traveling, I sometimes feel like my days are a bizarre piece of software with unclear purpose. The walkthrough would go something like this:
Doubleclick the basket next to the coffee machine. Inspect the items it contains by hovering over each. One of them is labeled Coffee Dreamer. Put it into your inventory. Leave the hotel and take the bus to Euston Station. Find the ticket machine in the far left corner. Punch in your code and obtain an orange-colored card. Take the escalator right behind you and wait for the blue line Southbound, exit at Victoria Station.
At Victoria Station you have to find platform 23. A security officer will appear and tell you there is no platform 23. To your left you will see a Burger King and next to it two restroom doors. Enter the restroom for the gender that is not your character's. Use the orange card to open the inner door and walk right through the mirror. It will bring you to platform 23. Enter the blueish gleaming train standing there.
On the train you will meet a group of teenagers costumed as cats. Offer them the Coffee Dreamer. In exchange you will get a magic mushroom. Exit the train at Brighton. In front of the station, wait for bus 8 and get off at the Pier. This is not where you need to go, but it will save you a detour. Walk down the seashore to an old railway station. Above it you will see some words written on the wall. This is your code for the University, so write them down. They are different every time. In my case they read "I have great desire - My desire is great."
Continue down the seashore until you see a "Hotel" sign and ask for a room. The receptionist will show you a list with available rooms. Chose the one marked as emergency exit. Rest for some hours. On the next morning, make a safety backup. Take off your chainmail, you will not need it today, but make sure to wear running shoes. Take the bus number 8 again (this doesn't make sense) it will bring you to the university. Enter the grey building across the street. Take the elevator to the uppermost floor. When you step out of the elevator, go down three doors to the right and knock. This is your contact person. No matter what he says, reply with the keywords you found at the pier. He will then give you the number to the secretary's room (a different number every time).
Go down the corridor till you find the right room. Give the secretary your Bank information, then continue down the corridor to the seminar room (a blue double-winged door). Time now to pop the smart-pill you found in the mummy's grave. Open your inventory, double click the pill and confirm. You should make it through the seminar safely. If not, reload your morning backup and try again. Upon completion of the seminar you will gain 4 skill points.
Head back to the hotel (bus number 8 again) and enter your room. Rest some hours to recharge energy, but not more than 3 because the hotel will start burning during the night. Once the fire alarm goes off, open the window and climb up the latter to the roof. Above you there is a helicopter waiting...
I can't say the internet is changing or has changed the way I think. It has however changed the way I post-process what I think in several ways. This has pros and cons.
Pro: The most obvious change is that I share my thoughts with many more people than before. This has frequently resulted in very interesting feedback, opened my eyes to issues I neglected or points of view I wasn't previously aware of. This is one of the prime reasons I'm writing this blog.
Con: On the flipside, while writing down my thoughts I'll typically do some Google searches and come across previous articles on related topics. This likely affects my own opinion, and I'm not sure this is entirely a good thing. And, needless to say, some of the feedback I got has merely taught me that the world is full with ignorant, hostile, and simply crazy people. Knowledge I could I have lived without.
Pro: Clearly, the internet provides a vast amount of easily accessible resources. 15 years ago reading a journal article required going to the library, erring around in search of the right aisle, not finding the ladder, waiting half an hour till the guy with the ladder is done erring around, then realizing that the very volume you're looking for is missing, etc etc. Nowadays, it's a click on a link (unless your acrobat reader has crashed again). If it would take much more than that I probably wouldn't read articles in any other field than physics, so the internet has certainly broadened my horizon.
Con: On the flipside, this is a hard time for perfectionists. If you're trying to read everything available on a topic, you'll never finish anything. So when I'm writing I'm constantly trying to balance the amount of input with the expected benefit of the output, meaning I have to find the right point to stop reading. This typically will leave me with a bad consciousness. All these people, they had something to say too, and lazy me didn't read it.
Generally, the internet has changed what knowledge I regard relevant, and I suspect this is a quite widespread change. Now that you can fast and easily look up a lot of facts, learning them by heart is totally yesterday. Like, who cares if I can't name all presidents of the USA? What's the capital of Qatar again and when was the transistor invented? The problem is though that if you don't have any factual knowledge you won't even know what to look for. So I just hope that modern school education carefully selects what knowledge is really necessary to pipe into children's brains.
Another clearly noticeable change is the obsession with the present that the internet has brought upon us. A week from now, this post will have wandered down the "recent" list and nobody wil recall what I wrote. Maybe it's my European genes that object on the idea that only the Now really exists, but if we don't honor the past we'll just repeat our mistakes. Why does Google return recent entries first? What is it that makes Americans believe what's newer is necessarily better?
Maggie Jackson in her book "Distracted" warns, backed up by research studies, that this "Now-Culture" severely affects the capability of children (meanwhile teenagers) to sustain attention. We're now seeing the first generation grow up that was born with the Internet. If there's any major impact on human cognitive processes caused by the overflow of information we're faced with and the amount of tasks we have to simultaneously deal with then this development can become an obstacle to progress. Something to have an eye on. There's mistakes you only make once.
"English novelist George Orwell was remarkably prescient about many things, and one of the most disturbing aspects of his masterpiece 1984 involved the blatant perversion of objective reality, using constant repetition of propaganda by a militaristic government in control of all the media.
Centrally coordinated and fully effective reinvention of reality has not yet come about in the U.S. (even though a White House aide in the past administration came chillingly close when he said to a New York Times reporter, “We’re an empire now, and when we act, we create our own reality”). I am concerned, however that something equally pernicious, at least to the free exercise of democracy, has."
So, for now my conclusion is that while I doubt the internet has yet actually changed thought processes, it has certainly affected what we think about. And in the long run, the latter is going to affect the former.
“Es ist mir ein prächtiges Licht über die Absorption und Emission der Strahlung aufgegangen ‒ es wird Dich interessieren. Eine verblüffend einfache Ableitung der Planck’schen Formel, ich möchte sagen die Ableitung. Alles ganz quantisch.”
“A splendid light has dawned on me about the absorption and emission of radiation ‒ it will be of interest to you. A stunningly simple derivation of Planck's formula, I might say the derivation. All completely quantical.”
Albert Einstein in a letter to his friend Michele Besso on August 11, 1916.
The “splendid light” refers to Einstein's insight that stimulated emission (also called induced emission) of light from excited atoms occurs in nature, and that this yields an elementary explanation of Planck's formula for the spectrum of black body radiation.
And, of course, some 46 years later and 50 years ago this May, the “splendid light” of Einstein's idea became a real “splendid light” with the construction of the Laser, based on the principle of stimulated emission of radiation.
"Scenarios for the future of the Higher Education sector: Where will we be in 25 years' time?" is the title of a short paper by Eddie Blass, Anne Jasman, and Steve Shelley. One should add they are concerned with the Higher Education sector in the UK in particular. The authors offer 5 dystopian future scenarios as a warning, and with this hope to prevent the developments outlined. The paper is so short it's pointless to summarize it, you can read the PDF here, it's only 2 pages. If that's still too long, The Times Higher Education offers a 1 page summary of the 2 page paper.
The authors say they wrote in a "deliberately provocative language to evoke an emotional response." Maybe there's something wrong with me, but my only "emotional response" is that Brits have a funny idea of what's "provocative." They could probably learn a thing or two from reading certain blogs, but let's not name names. Anyway, this inspired me to come up with a worst case scenario. And since that depressed me, I'll add a best case scenario. Feel free to offer your scenario in the comments. Or, even better, post it on your blog, I'll add a link below. Rules of the game are: One utopian and one dystopian future scenario for academia in 25 years from now in less than 500 words each. (You can count words online here.)
Dystopia
Global competition of universities and research institutes is ranked by a tightly defined metric for scientific success (that grows out of the UK's Research Assessment Exercise). University departments turn into clubs that make deals on recruitment of star scientists. The universities have professional marketing departments that hype every paper, patent, award, and conference. Research performance as defined by The Metric becomes a prime interest of national politics and with that public accountability for all and every pen stroke spells the death for academic freedom. International companies pour money into the leading places to improve their company's image and get a hand on those scientists willing to join the industrial workforce.
Since success becomes a matter of attention rather than quality, public outreach departments schmooze their way into major newspapers and magazines. Star scientists host talkshows and give public lectures in front of thousands of people with lots of technical finesse and no content. Bribery of editors of high impact journals frequently makes headlines. Extreme competitive pressure renders unbiased peer review impossible, so it becomes replaced by "external review" from so-called "unbiased independent experts" frequently recruited among science journalists and research departments of major companies . The media wants its share of the money and eternally celebrates progress that is none, causing frustration and cynicism among the public. Like on the fish market, the winner is who screams the loudest and smells the least. Leading scientists find their private life rewritten in cheap magazines next to Hollywood starlets and members of the royal families.
One part of researchers conforms to the new rules and accordingly optimizes their output, connections and social skills. However, a small but increasing fraction of researchers finds higher education has turned into a farce. They refuse to participate in what they argue will eventually entirely stifle knowledge discovery and cause a breakdown of modern societies who are in need of constant innovation. These researchers form a scientific underground, a globally operating association of scientists most of which have to finance themselves from non-research jobs. Belittled by the star scientists, the scientific underground is helped by a few philanthropists' generous donations that allows to maintain online networks and occasional meetings. The resentment on both sides grows.
John had just handed out the second hot-dog when Lisa's cab came to a screeching halt directly under the no-parking sign. She jumped out and waved her flexiscreen: "Look at this!" John focused on the mustard to prevent his eyes from rolling heavenward. "That's 1.99," he said.
Getting a little carried away here ;-)
Utopia
Fed up with the inefficient use of resources in academia, scientists decide to take matters of management into their own hand. Instead of further conforming to nonsensical policies and wasting time being swept away by emergent community trends, they systematically study and monitor the dynamics of knowledge discovery itself. Based on scientific models that are constantly refined, they put into place a decentralized application- and hiring system that makes only moderate use of metrics and instead relies on accountability of peer's judgement. All research results are available open access, and suggested research projects and proposals are frequently openly available too, though many of these feature remain subject to constant flow and debate.
Transformative research is implemented depending on the field and stage of research where a community sees the need, and measures are taken to balance competition with collaboration. Social networking tools are refined to optimally filter information and connect dispersed knowledge and researchers all over the globe. Not only national boundaries dissolve: also the educational boundaries of academia soften and participation in research projects more often encompasses a variety of contributors with different background.
But most importantly, scientists' skills and interests become individually recognized, supported, and put to best use. The earlier one-size-fits-all positions that combined the duties of teaching, researching, reviewing, communicating, mentoring, administrating and managing are broken down into different education and career paths. This way, duties other than research are significantly reduced and talents are optimally utilized.
These improvements unleash innovative power that overhauls some sleepy research areas and creates several new ones. Inspired by this success, leaders of a few future-oriented democracies decide to base their increasingly dysfunctional opinion- and decision making processes on modern scientific models. This results in particular in a dramatically different approach to the communication of information, the aggregation of opinions, and significant changes to the content and structure of the educational system.
This era would later become known as the 2nd scientific revolution, but John didn't know that. He was sitting in a seminar and had just decided the women speaking was clearly insane. But he liked the theme she used for the slides; he had not seen it before and wondered where to get it. She flipped to the next slide. "I'm not insane," John read "The theme is called "Sparkles in red" and is shareware."
“Surfing the Universe” is a unique new reality series that blurs the lines between scientist and athlete, breaking the popular perception of both. These are inspirational stories of young scientists at the forefront of their fields, who also love playing outside -- people living life to the fullest both intellectually and physically.
We call them ‘Scientific Adventurers’.
Host Garrett Lisi (a PhD in theoretical physics who’s also an avid surfer) is the epitome of a Scientific Adventurer. Having reached a high level of academic achievement in physics, Garrett discovered long ago the best way to balance his demanding life in science is with a constant stream of fun and adventure.
Part personal profiles, part science, mixed with sports adventures and travel, each episode will profile a new ‘scientific adventurer’ whose work includes anything from uncovering the mysteries of the human brain, finding a cure for AIDS, or a look inside the high energy particle collisions created by the Large Hadron Collider (LHC) in Geneva.
Then we’ll accompany our ‘scientific adventurer’for an exotic sports adventure: skiing the Alps, surfing in Tahiti, snowboarding in Alaska, kite surfing in Maui, paragliding in Chile, mountain climbing in Thailand, scuba diving in the Great Barrier Reef, and many, many more.
Recently we discussed the question “What is natural?” Today, I want to expand on the key point I was making. What humans find interesting, natural, elegant, or beautiful originates in brains that developed through evolution and were shaped by sensory input received and processed. This genetic history also affects the sort of question we are likely to ask, the kind of theory we search for, and how we search. I am wondering then may it be that we are biased to miss clues necessary for progress in physics?
It would be surprising if we were scientifically entirely unbiased. Cognitive biases caused by evolutionary traits inappropriate for the modern world have recently received a lot of attention. Many psychological effects in consumer behavior, opinion and decision making are well known by now (and frequently used and abused). Also the neurological origins of religious thought and superstition have been examined. One study particularly interesting in this context is Peter Brugger et al’s on the role of dopamine in identifying signals over noise.
If you bear with me for a paragraph, there’s something else interesting about Brugger’s study. I came across this study mentioned in Bild der Wissenschaft (a German popular science magazine, high quality, very recommendable), but no reference. So I checked Google scholar but didn’t find the paper. I checked the author’s website but nothing there either. Several Google web searches on related keywords however brought up first of all a note in NewScientist from July 2002. No journal reference. Then there’s literally dozens of articles mentioning the study after this. Some dorefer to, somedon’t refer to the NewScientist article, but they all sound like they copied from each other. The article was mentioned in Psychology Today, was quoted in Newspapers, etc. But no journal reference anywhere. Frustrated, I finally wrote to Peter Brugger asking for a reference. He replied almost immediately. Turns out the study was not published at all! Though it is meanwhile, after more than 7 years, written up and apparently in the publication process, I find it astonishing how much attention a study could get without having been peer reviewed.
Anyway, Brugger was kind enough to send me a copy of the paper in print, so I know now what they actually did. To briefly summarize it: they recruited two groups of people, 20 each. One were self-declared believers in the paranormal, the other one self-declared skeptics. This self-description was later quantified with commonly used questionnaires like the Australian Sheep-Goat Scale (with a point scale rather than binary though). These people performed two tasks. In one task they were briefly shown (short) words that sometimes were sensible words, sometimes just random letters. In the other task they were briefly shown faces or just random combination of facial features. (These both tasks apparently use different parts of the brain, but that’s not so relevant for our purposes. Also, they were shown both to the right and left visual field separately for the same reason, but that’s not so important for us either.)
The participants had to identify a “signal” (word/face) from the “noise” (random combination) in a short amount of time, too short to use the part of the brain necessary for rational thought. The researchers counted the hits and misses. They focused on two parameters from this measurement series. The one is the trend of the bias: whether it’s randomly wrong, has a bias for false positives or a bias for false negatives (Type I error or Type II error). The second parameter is how well the signal was identified in total. The experiment was repeated after a randomly selected half of the participants received a high dose of levodopa (a Parkinson medication that increases the dopamine level in the brain), the other half a placebo.
The result was the following. First, without the medication the skeptics had a bias for Type II errors (they more often discarded as noise what really was a signal), whereas the believers had a bias for Type I errors (they more often saw a signal where it was really just noise). The bias was equally strong for both, but in opposite directions. It is interesting though not too surprising that the expressed worldview correlates with unconscious cognitive characteristics. Overall, the skeptics were better at identifying the signal. Then, with the medication, the bias of both skeptics and believers tended towards the mean (random yes/no misses), but the skeptics overall became as bad at identifying signals as the believers who stayed equally bad as without extra dopamine.
The researcher’s conclusion is that the (previously made) claim that dopamine generally increases the signal to noise ratio is wrong, and that certain psychological traits (roughly the willingness to believe in the paranormal) correlates with a tendency to false positives. Moreover, other research results seem to have shown a correlation between high dopamine levels and various psychological disorders. One can roughly say if you fiddle with the dose you’ll start seeing “signals” everywhere and eventually go bonkers (psychotic, paranoid, schizoid, you name it). Not my field, so I can’t really comment on the status of this research. Sounds plausible enough (I’m seeing a signal here).
In any case, these research studies show that our brain chemistry contributes to us finding patters and signals, and, in extreme, also to assign meaning to the meaningless (there really is no hidden message in the word-verification). Evolutionary, type I errors in signal detection are vastly preferable: It’s fine if a breeze moving leaves gives you an adrenaline rush but you only mistake a tiger for a breeze once. Thus, today the world is full of believers (Al Gore is the antichrist) and paranoids who see a tiger in every bush/a feminist in every woman. Such overactive signal identification has also been argued to contribute to the wide spread of religions (a topic that currently seems to be fashionable). Seeing signals in noise is however also a source of creativity and inspiration. Genius and insanity, as they say, go hand in hand.
It seems however odd to me to blame religion on a cognitive bias for Type I errors. Searching for hidden relations on the risk that there are none per se doesn’t only characterize believers in The Almighty Something, but also scientists. The difference is in the procedure thereafter. The religious will see patterns and interpret them as signs of God. The scientist will see patterns and look for an explanation. (God can be aptly characterized as the ultimate non-explanation.) This means that Brugger’s (self-)classification of people by paranormal beliefs is somewhat besides the point (it likely depends on the education). You don’t have to believe in ESP to see patterns where there are none. If you read physics blogs you know there’s an abundance of people who have “theories” for everything from the planetary orbits, over the mass of the neutron, to the value of the gravitational constant. One of my favorites is the guy who noticed that in SI units G times c is to good precision 2/100. (Before you build a theory on that noise, recall that I told you last time the values of dimensionful parameters are meaningless.)
The question then arises, how frequently do scientists see patterns where there are none? And what impact does this cognitive bias have on the research projects we pursue? Did you know that the Higgs VEV is the geometric mean of the Planck mass and the 4th root of the Cosmological Constant? Ever heard of Koide’s formula? Anomalous alignments in the CMB? The 1.5 sigma “detection?” It can’t be coincidence our universe is “just right” for life. Or can it?
This then brings us back to my earlier post. (I warned you I would “expand” on the topic!) The question “What is natural” is a particularly simple and timely example where physicists search for an explanation. It seems though I left those readers confused who didn’t follow my advice: If you didn’t get what I said, just keep asking why. In the end the explanation is one of intuition, not of scientific derivation. It is possible that the Standard Model is finetuned. It’s just not satisfactory.
For example Lubos Motl, a blogger in Pilsen, Czech Republic, believes that naturalness is not an assumption but “tautologically true.” As “proof” he offers us that a number is natural when it is likely. What is likely however depends on the probability distribution used. This argument is thus tautological indeed: it merely shifts the question what is a natural from the numbers to what is a natural probability distribution. Unsurprisingly then, Motl has to assume the probability distribution is not based on an equation with “very awkward patterns,” and the argument collapses to “you won't get too far from 1 unless special, awkward, unlikely, unusual things appear.” Or in other words, things are natural unless they’re unnatural. (Calling it Bayesian inference doesn’t improve the argument. We’re not talking about the probability of a hypothesis, the hypothesis is the probability.) I am mentioning this sad case because it is exactly the kind of faulty argument that my post was warning of. (Motl also seems to find the cosine function more natural than the exponential function. As far as I am concerned the exponential function is very natural. Think otherwise? Well, zis why I’m saying it’s not a scientific argument.)
But more importantly it is worthwhile to as ask what formed our intuitions. On the one hand they are useful. On the other hand we might have evolutionary blind spots when it comes to scientific theories. We might ask the wrong questions. We might be on the wrong path because we believe to have seen a face in random noise, and miss other paths that could lead us forward. When a field has been stuck for decades one should consider the possibility something is done systematically wrong.
To some extend that possibility has been considered recently. Extreme examples for skeptics in science are proponents of the multiverse, Max Tegmark with his Mathematical Universe ahead of all. The multiverse is possibly the mother of all Type II errors, a complete denial that there is any signal.
In Tegmark’s universe it’s all just math. Tegmark unfortunately fails to notice it’s impossible for us to know that a theory is free of cognitive bias which he calls “human baggage.” (Where is the control group?) Just because we cannot today think of anything better than math to describe Nature doesn't mean there is nothing. Genius and insanity...
For what the multiversists are concerned, the “principle of mediocrity” has dawned upon them, and now they ask for a probability distribution in the multiverse according to which our own universe is “common.” (Otherwise they had nothing left to explain. Not the kind of research area you want to work in.) That however is but a modified probabilistic version of the original conundrum: trying to explain why our theories have the features they have. The question why our universe is special is replaced by why is our universe especially unspecial. Same emperor, different clothes. The logical consequence of the multiversial way is a theory like Lee Smolin’s Cosmological Natural Selection (see also). It might take string theorists some more decades to notice though. (And then what? It’s going to be highly entertaining. Unless of course the main proponents are dead by then.)
Now I’m wondering what would happen if you gave Max Tegmark a dose of levodopa?
It would be interesting if a version of Brugger’s test was available online and we could test for a correlation between Type I/II errors and sympathy for the multiverse (rather than a believe in ESP). I would like to know how I score. While I am a clear non-believer when it comes to NewScientist articles, I do see patterns in the CMB ;-)
The title of this post is of course totally biased. I could have replaced physics with science but tend to think physics first.
Conclusion: I was asking may it be that we are biased to miss clues necessary for progress in physics? I am concluding it is more likely we're jumping on clues that are none.
Purpose: This post is supposed to make you think about what you think about.
Reminder: You're not supposed to comment without first having completely read this post.
I've been sick the last few days, thus my silence. Stefan has lovingly fed me with chicken soup and porridge, so I now feel like a bag of oatmeal and am starting to cluck.
We wish all our readers a good start into the year 2010! We want to use this last day of the year to thank you all (yes, you all) for your visits, comments, feedback, links, and for making this blog so interesting!
Here's our 2009 visitor statistic, shown is the weekly average:
And here is the country share for an average day (not an annual average). Shown are only countries with a share larger than 1%:
Perc.
Country Name
34.25%
United States
8.45%
Germany
7.31%
Canada
5.25%
India
4.79%
Australia
4.11%
United Kingdom
4.11%
Hungary
3.20%
Singapore
2.51%
Unknown
-
2.05%
Poland
1.37%
Sweden
1.37%
Taiwan
1.37%
Austria
1.37%
Turkey
1.14%
Philippines
1.14%
United Arab Emirates
1.14%
Saudi Arabia
1.14%
France
Seems the Swedes have still somewhat to catch up :-)
And here's Backreaction's Best of 2009. If you have some hours of 2009 left to kill, check these out:
Had Gell-Mann read a German dictionary instead of Joyce, he'd have noticed "Quark" is the German word for a milk product (often mistakenly translated as "cottage cheese" which is something entirely different). Besides this, "Quark" is a frequently used colloquial expression for nonsense.
Then there is the "Penguin diagram", which owes its name to a lost bet and some illegal substances, and the "tadpole diagram" which once run risk of turning into a "spermion." Probably a good thing the tadpoles kept their name - just imagine what issues the anti-abortionists would have had with spermion cancellation.
