Friday, December 31, 2010

Welcome Lara and Gloria!

The babies are here! After 38 weeks waiting and 48 hours labor, Lara Lily and Gloria Sophie were born on Wednesday, Dec 29th, in Heidelberg.

We wish all our readers a great start into the year 2011!

Saturday, December 25, 2010

Merry Christmas!

In good tradition, we'll celebrate Christmas with a quiz. It isn't easy to come up with questions that Google won't answer for you! Below you see images of 5 currently operating physics experiments. Write down their names and enumerate the letters as indicated below the pictures, ie the first experiment's name has 7 letters, the second one 5 etc. I apologize that I'll have to temporarily violate some people's copyrights but it wouldn't be of any use did I link to the picture sources now, I'll add them later. Click on an image to get an enlarged version if available.





32-33-34-35-36 formerly known as 37-38-39-40-41.

The solution we are looking for is 9-7-30-15-5-12 32-14-37-21-41.

This year's price is a BackRe(Action) mug and it will go to the first who submits the right answer in the comments. (For the shipment, we'll need your snail-mail address. If you are not willing to provide your address anyway, please do not spoil the fun.)

If it seems the quiz is more difficult than I thought, I'll leave some hints in the comments later.


Here's the solution.

1) ICECUBE, a neutrino experiment at the South Pole, picture taken from here, more info here.

2) ATLAS, LHC's largest detector, picture taken from here, more info here.

3) Super-Kamiokande, a neutrino experiment in Japan, picture taken from here, more info here.

4) The Cryogenic Dark Matter Search CDMS in the Soudan Underground Lab, picture taken from here, more info here.

5) Fermi formerly known as GLAST, NASA's Gamma ray space telescope, picture taken from here, more info here

Thursday, December 23, 2010


The probably last update from my pregnancy: Contrary to all doctors' expectations I didn't have a preterm delivery. Instead, I'm still pregnant with a bump that's left behind adjectives like huge or enormous; it can now only be described as grotesque. It's not even round anymore because one baby butt hangs out to the left and on the other side one can frequently see feet kicking into my kidneys. I've outgrown even my largest maternity cloths. The trousers keep sliding down while the shirts slip up, flashing unsuspecting passers-by with blue-veined, tightly stretched skin akin the smile of the Cheshire's cat. I can't go anywhere without having to answer always the same questions about due date and gender and complete strangers enthusiastically report the pregnancy of their daughter/neighbor/sister etc.

Ironically, now that I've made it full term, the docs tell me that for the sake of my own health the pregnancy better not continue too much longer. The overstretched tissue, so they claim, brings a heightened risk of severe bleeding or uterine rupture which I'm admittedly not too keen on. Add to this that I've developed some late pregnancy complications that, while at present not of immediate concern, are not beneficial neither for mine nor for the babies' health when they persist longer. Luckily, the girls are both positioned head down, so I'm at least not a priori in need of a cesarean section. I am now scheduled for induction of labor the week after Christmas - unless something happens till then - and I hope this goes well. The babies' weight is now estimated above 2.5 kg each and they are all ready for their first own breath.

That means you'll have to expect it being quiet on this blog for some while till I've recovered and we've accommodated ourselves with the new situation. However, pregnant or not, we will of course still have our annual Christmas quiz! (See here for the ones from 2007, 2008 and 2009). This year's quiz is prescheduled for Dec. 25th, 5pm CET, in the hope that this is a convenient time for the majority of our readers. The price is a BackRe(Action) mug, so don't miss it.

We wish you all a happy season and a peaceful Christmas time.

Monday, December 20, 2010

Evidence of Eternal Inflation in the CMB?

Last week, I read on the physics arXiv blog a post titled Astronomers Find First Evidence Of Other Universes, claiming that
Our cosmos was "bruised" in collisions with other universes. Now astronomers have found the first evidence of these impacts in the cosmic microwave background.

This left me deeply puzzled because I had read the paper in question:
    First Observational Tests of Eternal Inflation
    By Stephen M. Feeney, Matthew C. Johnson, Daniel J. Mortlock, Hiranya V. Peiris
    arXiv:1012.1995 (see here for an extended version)

yet seemed to have read something completely different out of it. So what's this all about?


The cosmic microwave background (CMB) we measure today is a relic from the time when the universe was only 300,000 years old and radiation decoupled from matter. Since then, photons could travel almost undisturbed. Thus the radiation, especially the fluctuations around its mean temperature, contain valuable information about the history of the universe. The CMB temperature fluctuations have been measured with great precision by the, now completed, WMAP mission and I'm sure you've all seen their skymap.

This data from the CMB temperature fluctuations, often discussed in form of its power spectrum, has allowed us to extract parameters determining the expansion of the universe and complement other data. What we know today, among other things, is that the universe is not only big, but to excellent accuracy spatially flat. That's a feature not naturally achieved with every mode of expansion. It also requires explanation why the CMB temperature is so homogeneous and isotropic, ie essentially the same everywhere with only small fluctuations around it. The currently most widely accepted model that achieves all that easily is inflation. Inflation is basically a phase of early, very rapid expansion that succeeds in solving the problems of flatness and homogeneity (and some others in addition). Inflation then has to end at some time, so matter can form and after that the expansion of the universe proceeds in a more moderate form, allowing the structures to form that surround us today (filaments, galaxies, stars).

There are several models of inflation that differ in the detailed predictions, but the rapid expansion is what they have in common. A particular variant of inflation is called "eternal inflation." As the name says, in that case inflation does not end completely but continues eternally. The way this is thought to happen is that inflation only ends locally when a metastable "false" vacuum state decays into a "true" vacuum state and subsequently continues along a local inflation scenario that ends and results in matter formation and gives rise to a patch like our own, commonly called "bubble universe." However, the areas of false vacuum never decay away completely because they expand more quickly than they can decay. As a result, new bubble universes continue to be formed out of the false vacuum eternally.

Bubble Collisions

While eternal inflation has its proponents, the most well-known probably being Alan Guth, it hasn't been particularly popular, mostly because for what observations are concerned it's a superfluous overhead to the local inflation scenario. It increased in popularity somewhat with string theorists having to face a large number of possible vacuum states, a scenario that seems to fit nicely with the continuing creation of bubble universes that together form what's become known as the "multiverse." Still there remains the question what's it matter if we can't observe it anyway.

It turns out that there are circumstances in which we could find evidence for the existence of other bubbles because initially separate bubble universes might come to overlap during their expansion in a "bubble collision." The probability of there having been a bubble collision in our past, and that bubble collision being observable yet not fatal for the evolution of life in our universe, depends on the parameters of the model.

The Paper

That finally brings us to Feeney et al's paper. Inspired by earlier work by Aguirre et al (Towards observable signatures of other bubble universes, arXiv:0704.3473) they studied the possibility that a bubble collision in our past has left an imprint in the CMB. Their paper basically presents a particular analysis scheme for the CMB temperature fluctuations. Projected on the 2-dimensional surface of last scattering, the leftover signal would have azimuthal symmetry. They assume that a bubble collision has left a mark in the CMB that consists of a slightly different temperature in such an azimuthal patch.

They use an algorithm to analyze the temperature fluctuation that works in three steps. First, search for areas with azimuthal symmetry. Second, search for edges where the temperature makes a slight step. Third, if you've found that, look for the best parameters to reproduce what you've found. They then go on to create fake CMB fluctuations with signals of bubble collisions to quantify how well their algorithm works. The picture below, taken from Feeney et al's paper, depicts the stages of this simulation. Each quarter of the skymap is supposed to show the same area, just mirrored horizontally and vertically. The upper left part shows the patch with the temperature variation from the bubble collision without fluctuations superimposed (the Mollweide projection used to plot the map distorts the shape). The upper right part adds random fluctuations. Now the task is to get the signal back. The lower left part shows the result of looking for patches of azimuthal symmetry, the lower right one the result of looking for edges with temperature steps.

After testing out their algorithm with fake data to understand what features it is able to identify with certainty, they come to the interesting part and analyze the actual CMB data. Their algorithm doesn't find edges, but identifies 4 regions of interest whose features could possibly have been caused by bubble collisions. As the authors put it, these features are "compatible" with having been caused in that way. Two of these spots of interest btw have previously been discussed, one is the well-known CMB "cold spot," the other was identified in this paper which made use of a similar analysis as Feeney et al. It is important to emphasize though that the identification of these spots was based solely on the symmetry and they were not able to find the second identifier, the edge of the spot. For this reason the authors are careful to make clear:
"Without the corroborating evidence of a circular temperature discontinuity, we cannot claim a definitive detection [...] Azimuthally symmetric temperature modulations are not unique to bubble collisions."

Though it might be that better data from the Planck satellite will allow to extract a less ambiguous signal in the coming years, this is so far clearly no evidence for a bubble collision. Feeney et al's results are just once again evidence that there's some features in the CMB.

One also has to keep in mind that their paper already starts from the assumption that the signal of a bubble collision is of such a particular sort of merely resulting in a small temperature difference. It leaves entirely open the question how likely it is that a particular model of eternal inflation would result in such a signal that is just barely observable rather than in features entirely incompatible with what we've seen so far. It is entirely unclear to me for example what would happen if the vacuum in the other bubble or possibly even its physical constants were different from ours. It seems quite unlikely that a tiny temperature modulation is all that would come out of it. I don't think anybody has at this point a comprehensive picture of what might happen in a general bubble collision. The question is then if not it is extremely improbable that our bubble was subject to a collision and that collision, rather than wiping us out, was just nice enough to reveal itself in the upcoming Planck data.

In any case, the analysis put forward in Feeney et al's paper serves to rule out some regions of the parameter space in models that produce such an imprint in the CMB. Such constraints are always good to have. It is a nice and very straight-forward paper presenting an observer's take on eternal inflation. It's a very worthwhile analysis indeed - imagine how exciting it would be to find evidence for other universes! However, so far the evidence leaves waiting.

Update: See also one of the author's guest post at Cosmic Variance Observing the Multiverse.

Thursday, December 16, 2010

Time to democratize science?

Yesterday, I read this article in New Scientist
The argument Hind makes goes roughly as follows. There's something wrong with academic research in economics because they've been in favor of deregulation and been supportive of policies that eventually lead to the financial crisis, while the warning voices were not listened to. I'd agree on that. What's wrong with that research, according to Hind, is that "financiers paid [many university economists] handsomely." That certainly didn't help objective research, but I doubt it's the central problem. The streamlining that's troublesome in economics can also be seen in other fields, just that in economics mistakes cause real-world disasters. An insightful article on this is Colander et al's The Financial Crisis and the Systemic Failure of Academic Economics.

Anyway, given this troublesome bias allegedly caused by funding sources Hind concludes
"[I]t is surely time to consider an alternative. If we are serious about science as a public good, we should give the public control over the ways in which some - and I stress "some" - of its money is spent.

I propose taking a portion of the money that subsidises private industry and giving it to new bodies set up to allocate resources on the basis of a democratic vote. Scientists could apply to these bodies for funding and we could all have a say in what research is given support."

Well, a lot of science funding comes from the national science foundations. And their agenda is set by national politics for control of which we go and cast our vote on election day. That this didn't prevent the issue with economics research demonstrates there's shortcomings in the academic system which spoil objectivity other than bribery. So much about Hind's motivation for his argument.

Leaving aside the shaky reasoning, I am afraid then that what Hind means with "democratic vote" is not a representative democracy. If his "alternative" is supposed to be something new, he must be talking about a grassroots democracy; the wisdom of the masses and all. That interpretation of his proposition of "democratisation" also goes well with him being the author of a book called The Return of the Public that according to the blurb "outlines a way forwards for a new participatory politics." But back to the New Scientist article, Hind explains the benefits of letting the public decide on research funding by referendum:
"Think what such a system could achieve. With public support, the few economists that predicted the financial crash could have gained greater access to publicity as well as more research resources. Public concern with environmental degradation could guide much-needed funds into alternative energy research."

I have no clue why that should be. In fact, I suspect a public "voting" on what scientific research projects deserve funding would make matters significantly worse rather than better. The main reason is that it would set incentives for researchers to produce results the public wants to hear rather than rely on their own sense of what is important. Hind continues:
"There is no good reason I can see why science funding could not be made subject to democratic decision-making. Yes, it will hand power to non-experts, but so does the present system: non-experts in the state and private sector often have a decisive say in what scientists study."

The present system does give non-experts the power to set general guidelines, but the details are left to experts. And that is, imho, good as it is. The problem with the academic system is definitely not that "the taxpayer" has too little say in what researcher's study but rather that the system itself suffers from internal problems. I've written on that many times and don't want to repeat the details here. For more check e.g. my posts Science and Democracy III and We have only ourselves to judge each other. The title of the latter says it all: The only people who can plausibly have an informed opinion on what research projects are worth pursuing are working in the field themselves. The problem with the academic system is, in short, that their opinions are unfortunately influenced by all sorts of external pressures which has the result that the grants are not efficiently used. The cure isn't to replace expert's judgement with that of uninformed people, but to make sure the judgement is unbiased.

In contrast to Hind, I can see several good reasons why science funding should not be made subject to public vote, except for setting the general agenda by assigning funds to the respective agencies and their programs. The reasons are the same reasons why pretty much all democracies on the planet are representative democracies. First, the public opinion changes from one day to the next. That's no basis on which one can pursue research. Second, the public opinion is easily influenced by those who have enough money to spend on media relations and search engine optimization. This works completely against Hind's own argument that the problem is the influence of wealthy people and cooperations.

The third and most important point is that the very reason academic research is mostly funded as a public good rather than through individual investments is that despite its recognized relevance for the well-being and progress of our societies it's such a long-term investment that very few people would privately invest money in it. Asking them to then decide on where the money they wouldn't individually invest should be spent, one has zero reason to believe that the money would be well spent.

(A fourth reason why the public opinion may not be suitable to call upon directly for decision making is that it may be inconsistent, but that's not a relevant point here. For more on that see my post The Nature of Laws.)

Hind explains his opinion:
"Certainly the public will sometimes support research that seems fanciful to informed insiders. We won't always spend our money wisely. But the opportunity to exercise power is a great educator. The successes and failures of democratically funded science would promote a much more vigorous public debate about the purpose of research."

The big problem is that it may take decades or even centuries to figure out what a success or a failure is. The feedback loop in this education is way too long to be effective; it's not something that will lead to an optimization. That's the reason such a lot of research is pursued as public service to begin with.

Let me be very clear here. I write this as a taxpayer myself that I am not qualified to make certain judgements. I preferably delegate my voice to somebody who has the time and makes the effort to obtain and survey all the relevant information on some decision rather than making a sloppy and uninformed decision myself because, after all, I have a job. In other words, I believe representative democracies are a good system (though there's no doubt they could use some improvements). There is place in our societies for direct public votes and we have tools for exactly this purpose. The funding of research projects just clearly isn't one of them.

Wednesday, December 15, 2010

Book review: “Stiff” by Mary Roach

Stiff: The Curious Lives of Human Cadavers
By Mary Roach
W. W. Norton & Company; Reprint edition (May 2004)

After my previous read on the beginning of life, this one is about the end of it. Mary Roach has collected data, historical facts and curious anecdotes on the fates of human corpses. Despite the unappetizing topic, it is an entertaining read.

Roach discusses decay, burial and its alternatives, giving one's body to science for anatomical studies (where one might serve as a practice for face lifting), organ donation and brain death, plastination, preservation, embalming or becoming a post-mortem crash-test dummy. You, or at least parts of you, can also end up being shot at to study the stopping power of bullets. She further covers the examination of victims of fatal accidents, for example plane crashes, to obtain information about the accident's cause, cannibalism, and experiments that were done to determine whether the shroud of Turin is authentic.

She evidently did a lot of reading and in many cases went to visit the places where experiments were made and talked to the scientists. Roach also does not hold back with her opinion, neither on organ donation nor on the credibility of some scientists or their publications. Thomas Edison for example comes off as “a loopy individual” and she remarks about one author “[He] is not a doctor, or not, at least, one of the medical variety. He is a doctor of the variety that gets a Ph.D. and attaches it to his name on self-help book covers. I found his testimonials iffy as evidence...” One might or might not agree with her opinions, but I found it very refreshing that she speaks her mind and does not leave the reader with a white-washed who-said-what, an unfortunately wide-spread habit among science writers that is sold as balanced reporting but eventually is mostly useless reporting. She also doesn't swallow every story she's read but goes to try verify it herself, as for example in a case of cannibalism reported from China that turns out to be made up. While the report on her travel to China is somewhat pointless in that it doesn't contribute to the theme of the book, it speaks for Roache's fact checking.

The book is full with absurdities from the history of science, such as techniques used in the 18th and 19th century to verify death, among them putting insects into the corpse's ear or rhythmic tongue-pulling for three hours following the suspected death. The reader also learns that the average human stomach bursts when stretched over a volume of approximately 4 liters, and that the Urban Institute in 1991 calculated the value of one human life at US $ 2.7 million. (One is left to wonder whether that's the global average or the value of US citizens.) On some topics I found the coverage thin and would have expected more details, for example on the history of burial or the progress in organ transplantation. I was also surprised that the fate of Einstein's brain didn't even make it into a footnote.

I guess there's only two ways to approach the topic of decaying human remains, either with gravity and philosophy or with humor. Mary Roach does it with humor and she does well, though her jokes become quite foreseeable after a few chapters. A little disturbing I found her tendency to self-degradation and portraying herself as an annoying person who her interview partners must think badly about, reflected in sentences like “[He] throws me a look.... [The look] says I'm a petit bouchon fécal [French, roughly: little piece of shit]” or “She considers this fact. I am feeling more like last week's coleslaw than usual.” It's probably supposed to be funny-ha-ha, but it makes me wonder about the author's self-image.

Taken together, the book is smoothly written, entertaining and covers the topic well. If this was an amazon review, I'd give five stars for flawlessness. Having finished “Stiff” I have to say though that after all the topic isn't one I'm particularly interested in. The book has however provided me with plenty of useless knowledge that is certain to make me a memorable guest when offered at the next dinner party.

Friday, December 10, 2010

This and That

  • In my post It comes soon enough I speculated on some future developments, among them:

    “I've been thinking... that... it would be possible to grow meat suitable for consumption without having to bother with the whole animal. [A] century from now, we'll have factories with organ bags that resemble nothing like animals at all.”

    In an interview of Time Magazine with Ray Kurzweil I read last week:

    “We'll grow in vitro cloned meats in factories that are computerized and run by artificial intelligence. You can just grow the part of the animal that you're eating."

    For the complete interview, see 10 Questions for Ray Kurzweil

  • If you want more evidence that I have my thumb on the pulse of time: In my post Why'd you have to go and make things so complicated? I remarked on the the predictability of complex systems:

    “You don't need to predict the dynamics of the system. You just need to know what parameter space it will smoothly operate in so optimization works.”

    A recent article by Seed Magazine quotes Tom Fiddaman who, in collaboration with MIT and the Sustainability Institute, examines the policy implications of dynamic complexity in climate and economic models:

    “You are in a sort of dance with this complicated mess,” he says, explaining that it is impossible to determine the individual steps of this “dance”—and this is in some sense the error of current thinking. Instead, we need to be able to construct robust solutions that provide general guidelines for what style of dance we should be doing. They need to be flexible and capable of withstanding the inevitable unpredictable behaviors of complex systems.

    The whole article, titled Knowing sooner, is a very recommendable read.

  • I just learned that since July 1st, fast internet access is a legal right in Finland. Don't have much to say about it, just find it noteworthy.

  • Most concise paper ever: Unsuccessful treatment of writer's block.

  • I spoke to a science writer about What's at the center of black holes - and then forgot about it.

    “From a theoretical point of view, the singularity is something where something becomes infinitely large,” said physicist Sabine Hossenfelder at the Nordic Institute for Theoretical Physics. [That's not what she wrote, but what I actually said.]

    No one can be sure that their singularity doesn't describe a physical reality, Hoss[en]felder told Life's Little Mysteries. But most physicists would say that the singularity, as theorized by equations, doesn't really exist. If the singularity was “really real,” then it would mean that “energy density was infinitely large at one point,” exactly the center of the black hole, she said.

    However, no one can know for sure, because no complete quantum theory of gravity exists, and the insides of black holes are impossible to observe.

  • My recent paper with Xavier Calmet and Roberto Percacci just got published.

I wish you all a nice weekend and don't forget to light the 3rd candle.

Friday, December 03, 2010

The inevitable outcomes from basic research - ?

If you're trying to get into the Christmas mood, I can warmly recommend a recent article in Seed Magazine by Rolf Heuer, Director General of Cern, On Competitive Collaboration. The title is somewhat misleading though; the article is actually a praise of basic research and its merits for our societies. It doesn't really say anything new, and of course for the readers of our blog it's preaching to the choir that basic research was and will continue to be essential for progress. But the essay is such a nice piece of writing I'm sure it will put a smile on your face.
“[A] scientist involved in basic research is by definition motivated: We do what we do because we are passionate about understanding the universe...

Human ingenuity being what it is, the future will undoubtedly bring applications based on discoveries made with the LHC. Although, as with Newton’s gravity, it may be some time before we’re privy to all of them, and to their implications. For our children and grandchildren, however, I am sure that the wait will have been worthwhile.”

In my earlier post Knowledge for the sake of knowledge, I was complaining that all to often to make a case for the relevance of basic research the argument is that eventually some technology will come out of it. This leaves aside the relevance that knowledge itself has, whether or not it results in some new gadget that you'll find under the tree in a decade, despite the fact that most people working in the field are driven by the gain in knowledge since applications are often too remote to be a tangible personal goal. I think that insights on fundamental questions about the nature of reality themselves have a direct influence on our societies. Consider topics like free will or the multiverse-question whether the physics in our universe is the only one possible or just one of many possibilities. I was thus happy to see that Heuer didn't try to sell the LHC as something that obtains its value merely by its rôle in producing new technologies.

In Canada, basic research is doing well: As you might have read on Peter's blog or in the Globe & Mail, the Bank of Montreal has donated CAN $4 million to Perimeter Institute to establish “the BMO Financial Group Isaac Newton Chair in Theoretical Physics at Perimeter Institute.” Bill Downe, President and Chief Executive Officer of the BMO Financial Group said
“The Institute’s ambitious thirst for new knowledge places it at the very frontier of discovery. Its thinkers can change our world by boldly pushing the boundaries of our current understanding of physical laws. We couldn’t be more proud of this association and hope that our unique investment in the BMO Isaac Newton Chair in Theoretical Physics will enhance innovation in Canada and encourage other private sector donors to fund Chairs at PI.”

So, congratulations to PI! In PI's press release, one also finds a quotation from Mike Lazaridis, founder of Perimeter Institute, who repeats the usual justification for basic research with the prospect of technological applications. In fact, he goes so far to say:
“Theoretical physics has driven the most important insights and technological advances in the history of humankind. Although the outcomes from basic research may not be immediate, they are inevitable...”

That's quite a bold statement, don't you think?

I completely agree with Heuer that basic research is instrumental for progress, but I'm far from sure that basic research of any sort “inevitably” leads to technological advances. Take for example the recent media fuzz about the re-recycled idea that the universe did not start with the Big Bang, and consider for a moment this turns out to be correct. The question is clearly of high relevance for us to understand our place in the universe, but since the distinction between bang and bounce lies 14 billion years in the past I'm having some trouble imagining what technology might possibly come out of an experimental distinction. I can easily imagine what it might be good for to find superluminal propagation of information to be possible, and could come up with a dozen applications for antigravitation. I can imagine that the development of quantum gravity and/or string theory will one day be of relevance for quantum computing, and that finding the Higgs or some alternative mechanism to generate particle masses will in the remote future play a role for energy generation. But especially when it comes to cosmology, it seems to me the outcome is mainly in the realm of pure knowledge, addressing the eternal questions where we come from and where we go to.

But hey, my imagination is finite, so let your fantasy fly free and tell me what inevitable application a big bounce scenario might have one day. Even better, tell me what, in your wildest dreams, will be the outcome of some basic research of your choice in theoretical physics that is pursued today.