Book review: “Time Reborn” by Lee Smolin

Time Reborn: From the Crisis in Physics to the Future of the Universe
By Lee Smolin
Houghton Mifflin Harcourt (April 23, 2013)

This is a difficult review for me to write because I disagree with pretty much everything in Lee’s new book “Time Reborn,” except possibly the page numbers. To begin with there is no “Crisis in Physics” as the subtitle suggests. But then I’ve learned not to blame authors for title and subtitles.

Oddly enough however, I enjoyed reading the book. Not despite, but because I had something to complain about on every page. It made me question my opinions, and though I came out holding on to them, I learned quite something on the way.

In “Time Reborn” Lee takes on the seemingly puzzling fact that mathematical truth is eternal and timeless, while the world that physicists are trying to describe with that mathematics isn’t. The role of time in contemporary physics is an interesting topic, and gives opportunity to explain our present understanding of space and time, from Newton over Special and General Relativity to modern Cosmology, Quantum Mechanics and all the way to existing approaches to Quantum Gravity.

Lee argues that our present procedures must fail when we attempt to apply them to describe the whole universe. They fail because we’re presently treating the passing of time as emergent, but as emergent in a fundamentally timeless universe. Only if we abandon the conviction, held by the vast majority of physicists, that this is the correct procedure, then can we understand the fundamental nature of reality – and with it quantum gravity of course. Lee further summarizes a few recent developments that treat time as real, though the picture he presents remains incoherent, some loosely connected, maybe promising, recent ideas that you can find on the arXiv and I don’t want to promote here.

More interesting for me is that Lee doesn’t stop at quantum gravity, which for most people on the planet arguably does not rank very high among the pressing problems. Thinking about nature as fundamentally timeless, Lee argues, is cause of very worldly problems that we can only overcome if we believe that we ourselves are able to create the future:

“We need to see everything in nature, including ourselves and our technologies, as time-bound and part of a larger, ever evolving system. A world without time is a world with a fixed set of possibilities that cannot be transcended. If, on the other hand, time is real and everything is subject to it, then there is no fixed set of possibilities and no obstacle to the invention of genuinely novel ideas and solutions to it.”

I’ll leave my objections to Lee’s arguments for some other time. For now, let me just say that I explained in this earlier post that a deterministic time evolution doesn’t relieve us from making decisions, and it doesn’t prevent “genuinely novel ideas” in any sensible definition of the phrase.

In summary: Lee’s book is very thought provoking and it takes the reader on a trip through the most fundamental questions about nature. The book is well written and nicely embedded in the long history of mankind’s wonderment about the passing of time and the circle of life. You will almost certainly enjoy this book if you want to know what contemporary physics has to say, and not to say, about the nature of time. You will almost certainly hate this book if you're a string theorist, but then you already knew that.

The Enantiomers’ Swimming Competition

Image Source.

The spatial arrangement of some large molecules can exist in two different versions which are mirror images of each other, yet their chemical composition is entirely identical. These mirror versions of molecules are said to have a different “chirality” and are called “enantiomers.” The image to the right shows the two chiralities of alanine, known as L-alanine and D-alanine.

Many chemical reactions depend not only on the atomic composition of molecules but also on their spatial arrangement, and thus enantiomers can have very different chemical behaviors. Since organisms are not chirally neutral, medical properties of drugs made from enantiomers depend on which chirality of the active ingredient is present. One enantiomer might have a beneficial effect, while the other one is harmful. This is the case for example for Ethambutol (one enantiomer treats tuberculosis, the other causes blindness), or Naproxen (one enantiomer treats arthritis pain, the other causes liver poisoning).

The chemical synthesis of molecules however typically produces molecules of both chiralities in approximately equal amounts, which creates the need to separate them. One way to do this is to use chemical reactions that are sensitive to the molecules’ chirality. Such a procedure has the disadvantage though that it is specific to one particular molecule and cannot be used for any other.

Now three physicists have shown, by experimental and numerical analysis, that there may be a universal way to separate enantiomers

Separation of chiral colloidal particles in a helical flow field
Maria Aristov, Ralf Eichhorn, and Clemens Bechinger
Soft Matter, 2013,9, 2525-2530 

It’s strikingly simple: chiral particles swim differently in a stream of water that has a swirl to it. How fast they travel with the stream depends on whether their chirality is the same or the opposite of the water swirl’s orientation. Wait far enough downstream, and the particles that arrive first will almost exclusively be the ones whose chirality matches that of the water swirl.

They have shown this as follows.

Molecules are typically of the size of some nanometers or so, and the swimming performance for molecules of different chirality is difficult to observe. Instead, the authors used micrometer-sized three-dimensional particles made of a type of polymer (called SU-8) by a process called photolithography. The particles created this way are the simplest example of configurations of different chirality. They labeled the right-handed particles with a blue fluorescent dye, and the left-handed particles with a green fluorescent dye. This allows taking images of them by a fluorescent microscope. Below you see a microscope image of the particles

Next you need a narrow channel through which water flows under some pressure. The swirl is created by gratings in the wall of the channel. The length of this channel is about a meter, but its height and width is only of the order 150 μm. Then you let bunches of the mixed chiral particles flow through the channel and photograph them on a handful of locations. From the amount of blue and green that you see in the image, you can tell how many of each type were present at a given time. Here’s what they see (click to enlarge)

This figure is an overlay of measurements at 5 different locations as a function of time (in seconds). The green shade is for molecules with the chirality that matches the water swirl orientation, the blue shade is for those with the opposite chirality. They start out, at x=32.5mm, in almost identical concentration. Then they begin to run apart. Look at the left tail of the x=942.5 mm measurement. The green distribution is almost 200 seconds ahead of the blue one.

If you aren’t impressed by this experiment, let me show you the numerical results. They modeled the particles as rigidly coupled spheres in a flow field with friction and torque, added some Gaussian white noise, and integrated the equations. Below is the result of the numerical computation for 1000 realizations (click to enlarge)

I am seriously amazed how well the numerical results agree with the experiment! I’d have expected hydrodynamics to be much messier.

The merit of the numerical analysis is that it provides us with understanding of why this separation is happening. Due to the interaction of the fluid with the channel walls, the flow is slower towards the walls than in the middle. The particles are trying to minimize their frictional losses with the fluid, and how to best achieve this depends on their chirality relative to the swirl of the fluid. The particles whose chirality is aligned with the swirl preferably move towards the middle where the flow is faster, while the particles of the opposite chirality move towards the channel walls where the flow is slower. This is what causes them to travel at different average velocities.

This leaves the question whether this study of particles of micrometer size can be scaled down to molecules of nanometer size. To address this question, the authors demonstrate with another numerical simulation that the efficiency of the separation (the amount of delay) depends on the product of the length of the channel and the velocity of the fluid, divided by the particle’s diffusion coefficient in the fluid. This allows one to estimate what is required for smaller particles. If this scaling holds, particles of about 120 nm size could be separated in a channel of about 3cm length and 3.2 μm diameter, at a pressure of about 10⁸ Pa, which is possible with presently existing technology.

Soft matter is not anywhere near by my area of research, so it is hard for me to tell whether there are effects at scales of some hundred nanometers that might become relevant and spoil this simple scaling, or whether more complicated molecule configurations alter the behavior in the fluid. But if not, this seems to me a tremendously useful result with important applications.

Listen to Spacetime

Quantum gravity researcher at work.

We normally think about geometry as distances between points. The shape of a surface is encoded in the distances between the points on in. If the set of points is discrete, then this description has a limited resolution.

But there’s a different way to think about geometry, which goes back about a century to Hermann Weyl. Instead of measuring distances between points, we could measure the way a geometric shape vibrates if we bang it. From the frequencies of the resulting tones, we could then extract information about the geometry. In maths speech we would ask for the spectrum of the Laplace-operator, which is why the approach is known as “spectral geometry”. Under which circumstances the spectrum contains the full information about the geometry is today still an active area of research. This central question of spectral geometry has been aptly captured in Mark Kac's question “Can one hear the shape of a drum?”

Achim Kempf from the University of Waterloo recently put forward a new way to think about spectral geometry, one that has a novel physical interpretation which makes it possibly relevant for quantum gravity

Quantum Gravity on a Quantum Computer?
arXiv:1302.3680

The basic idea, which is still in a very early phase, is the following.

The space-time that we live in isn’t just a classical geometric object. There are fields living on it that are quantized, and the quantization of the fluctuations of the geometry themselves are what physicists are trying to develop under the name of quantum gravity. It is a peculiar, but well established, property of the quantum vacuum that what happens at one point is not entirely independent from what happens at another point because the quantum vacuum is a spatially entangled state. In other words, the quantum vacuum has correlations.

The correlations of the quantum vacuum are encoded in the Greensfunction which is a function of pairs of points, and the correlations that this function measures are weaker the further away two points are. Thus, we expect the Greensfunction for all pairs in a set of points on space-time to carry information about the geometry.

Concretely, consider a space-time of finite volume (because infinities make everything much more complicated), and randomly sprinkle a finite number of points on it. Then measure the field's fluctuating amplitudes at these points, and measure them again and again to obtain an ensemble of data. From this set of amplitudes at any two of the points you then calculate their correlators. The size of the correlators is the quantum substitute for knowing the distance between the two chosen points.

Achim calls it “a quantum version of yard sticks.”

Now the Greensfunction is an operator and has eigenvalues. These eigenvalues, importantly, do not depend on the chosen set of points, though the number of eigenvalues that one obtains does. For N points, there are N eigenvalues. If one sprinkles fewer points, one loses the information of structures at short distances. But the eigenvalues that one has are properties of the space-time itself.

The Greensfunction however is the inverse of the Laplace-operator, so its eigenvalues are the inverses of the eigenvalues of the Laplace-operator. And here Achim’s quantum yard sticks connect to spectral geometry, though he arrived there from a completely different starting point. This way one rederives the conjecture of (one branch of) spectral geometry, namely that the specrum of a curved manifold encodes its shape.

That is neat, really neat. But it’s better than that.

There exist counter examples for the central conjecture of spectral geometry, where the shape reconstruction was attempted from the scalar Laplace-operator's spectrum alone but the attempt failed. Achim makes the observation that the correlations in quantum fluctuations can be calculated for different fields and argues that to reconstruct the geometry it is necessary to not only consider scalar fields, but also vector and symmetric covariant 2-tensor fields. (Much like one decomposes fluctuations of the metric into these different types.) Whether taking into account also the vector and tensor fields is relevant or not depends on the dimension of the space-time one is dealing with; it might not be necessary for lower-dimensional examples.

In his paper, Achim suggests that to study whether the reconstruction can be achieved one may use a perturbative approach in which one makes small changes to the geometry and then tries to recover these small changes in the change of correlators. Look how nicely the physicists’ approach interlocks with thorny mathematical problems.

What does this have to do with quantum gravity? It is a way to rewrite an old problem. Instead of trying to quantize space-time, one could discretize it by sprinkling the points and encode its properties in the eigenvalues of the Greensfunctions. And once one can describe the curvature of space-time by these eigenvalues, which are invariant properties of space-time, one is in a promising new starting position for quantizing space-time.

I’ve heard Achim giving talks about the topic a couple of times during the years, and he has developed this line of thought in a series of papers. I have no clue if his approach is going to lead anywhere. But I am quite impressed how he has pushed forward the subject and I am curious to see how this research progresses.

Excuse me, where is the mainstream?

More than once I went away from a discussion, confused about what exactly my conversation partners meant with “physics mainstream”. The “mainstream,” it seems, is typically employed as reference point for why some research projects get funded and others not. If it’s not “mainstream physics”, I gather, it’s difficult to get it funded. But can we come up with a good explanation for what is “mainstream”?

My first attempt to define the “mainstream” would be by the context it is most often used, the ease by which a research topic can be funded: the easier, the more mainstream. But on second thought this is not a helpful definition because it’s not based on properties of the research itself, which makes it circular. We could as well say a topic attracts funding easily because it’s mainstream, and so we are none the wiser. What is it that puts a research area into the main of the stream to begin with?

Reference to “mainstream science” is often made by pseudoscientists who are using the term in an attempt to downgrade scientific research and to appear original. (Ironically they then often boldly use and abuse vocabulary from the unoriginal mainstream. Google for quantum healing to see what I mean.) In that case the “mainstream” is just all that deserves to be called scientific research.

The way that pseudoscientists use the expression is not what I want to discuss today. It’s the way that researchers themselves speak about the “mainstream” that has left me wondering if it is possible to make this a meaningful, and useful, terminology. The way the expression is used by researchers it seems to have connotations of popularity, fashionableness, timeliness, and attracting large numbers of people. Below I have tried to make sense of each of these properties, and then I’ll offer the best definition that I could come up with. I invite you to submit your own!

Public attention

At any given time, some topics are popular. In physics there is presently direct detection of dark matter, quantum computing, topologic insulators and cold atom gases, for just to mention a few. But in many cases these popular topics constitute only a small fraction of the research that is actually happening. The multiverse, to name another example, is in reality a fringe area of gr-qc that just happens to capture public attention. The same is the case for the black hole firewall. In fact, in many cases what makes headlines in the press are singular or controversial findings. It’s not the type of research that funding agencies have on their agenda, which is why popularity is not a good defining property for the mainstream.

Fashionableness

High energy physics is a very fad-driven area of physics and quite often you can see a topic appearing and gathering momentum within a matter of months, just to then exponentially decay and hardly be mentioned some years later. Anybody remembers unparticles? The pentaquark? The so-called OPERA anomaly? These fads aren’t as extreme in other areas of physics (or so I am told) but they exist, if less pronounced.

Fashionableness indeed seems to some extent correlated with the ease of getting funding. But a trend must have been around for a while and have attracted a base of research findings to appear solid and worthy of funding, so that cannot be the whole story. This brings me to the next point.

Occupation number

The more people work on a topic, the easier it is to make a case that the topic is relevant and deserves being funded. Thus the number of researchers in an area seems a plausible measure for it being mainstream. Or does it?

The total number of people is in fact a highly misleading quantity. A topic may attract many researchers because it’s very rich and there is a lot that can be done. Another topic might just not support such a large number of researchers, but this says more about the nature of research in an area than about its relevance or its promise.

String theory is an example of a research area that is very rich and supports many independent studies, which I believe is reason it has become so dominant in quantum gravity – there’s just a lot that can be done. But does that make it mainstream research? Nanoscience is another example of a research area that attracts a lot of people, but does so for an entirely different reason, that being the potential of developing patents and applications. Throwing them both together doesn’t seem to make much sense. The total number of people does not seem a good defining property for the mainstream either.

The important factor for the ease of obtaining funding is not so much the total number of people, but the amount of tangible open problems that can be attacked. This then leads me to the next point.

Saturation level

A refinement of the occupation number is the amount to which a research area attracts people that study presently open questions on the topic. Mainstream physics, then, would be those areas that attract at least as many researchers as are necessary to push forward on all presently open questions. Since this is a property relative to the number of possible research projects, a small research area can be mainstream as much as a large one. It has some aspects of fashionableness, yet requires a more solid base already.

This definition makes sense to me because ease of funding should have something to do with the availability of research projects as well as their promise, which would be reflected in the willingness of researchers to spend time on these projects.

Except that this definition doesn’t seem to agree with reality because funding usually lags behind, leaving research areas overpopulated: It is easy to obtain funding for projects in areas whose promise is already on the decline because funding decisions are made based on reports by people who work in the very same area. So this definition, though appealing at first sight, just doesn’t seem to work.

Timeliness

Thus, in the end neither popularity, fads, the number of people, nor the availability of promising research topics seem to make for a good definition of the mainstream. Then let me try something entirely different, based on an analogy I used in the Nordita video.

Knowledge discovery is like the mapping of unknown territory. At any time, we have a map with a boundary beyond which we do not know what to expect. Applied research is building on the territory that we have mapped. Basic research is planning expeditions into the unknown to extend the map and with it the area that we can build on.

In either case, building on known territory and planning expeditions, researchers can take small steps and stay close to the known base. Or they can aim high and far and risk both failure and disconnect from colleagues.

This image offers the following definition for mainstream research.

Mainstream research is the research that aims just far enough to be novel and contribute to knowledge discovery, but not so far as to disconnect from what is already known. It’s new, but not too new. It’s familiar, but not too familiar. It’s baby steps. It builds on what is known without creating uncomfortable gaps.  It uses known methods. It connects. It doesn’t shock. It’s neither too ambitious nor too yesterday. It’s neither too conservative nor too tomorrow. It is what makes the community nod in appraisal.

Mainstream research is what surprises, but doesn’t surprise too much.

We previously discussed the relevance of familiarity in an entirely different context, that of appreciating musing. There too, you want it to be predictable, but not too predictable. You want it to have just the right amount of complexity.

I think that’s really the essence of what makes a field mainstream: how tight the connection is to existing knowledge and how well the research is embedded into what is already known. If a new field comes up, there will be a phase when there aren’t many connections to anything. But over the course of time, given all goes well, research on the topic will create a map of new territory that then can be built upon.

Proximate and Ultimate Causes for Publication

I am presently reading Steven Pinker’s “Blank Slate”. He introduces the terms “proximate cause” and “ultimate cause,” a distinction I find enlightening:

“The difference between the mechanisms that impel organisms to behave in real time and the mechanisms that shaped the design of the organism over evolutionary time is important enough to merit some jargon. A proximate cause of behavior is the mechanism that pushes behavior buttons in real time, such as the hunger and lust that impel people to eat and have sex. An ultimate cause is the adaptive rationale that led the proximate cause to evolve, such as the need for nutrition and reproduction that gave us the drives of hunger and lust.” ~Steven Pinker, The Blank Slate: The Modern Denial of Human Nature, p 54.

It is the same distinction I have made in an entirely different context between “primary” and “secondary” goals, my context being the use of measures for scientific success. In Pinker’s terminology then, enhancing our understanding of nature is the “ultimate cause” of scientific research. Striving to excel according to some measure for scientific success – like the h-factor, or the impact factor of journals on one’s publication list – is a “proximate cause”.

The comparison to evolution illuminates the problem with introducing measures for scientific success. Humans do not, in practice, evaluate each of their action as to their contribution to the ultimate cause. They use instead readily available simplifications that previously proved to be correlated with the ultimate cause. Alas, over time the proximate cause might no longer lead toward the ultimate cause. Increasing the output of publications does no more contribute to our understanding of nature than does deep-fried butter on a stick contribute to health and chances of survival.

There is an interesting opinion piece, “Impacting our young” in the Proceedings of the National Academy of Sciences of the USA (ht Jorge) that reflects on the impact that the use of measures for scientific success has on the behavior of researchers:

“Today, the impact factor is often used as a proxy for the prestige of the journal. This proxy is convenient for those wishing to assess young scientists across fields, because it does not require knowledge of the reputation of individual journals or specific expertise in all fields… [T]he impact factor has become a formal part of the evaluation process for job candidates and promotions in many countries, with both salutatory and pernicious consequences.

Not surprisingly, the journals with the highest impact factor (leaving aside the review journals) are those that place the highest premium on perceived novelty and significance. This can distort decisions on how to undertake a scientific project. Many, if not most, important scientific findings come from serendipitous discovery. New knowledge is new precisely because it was unanticipated. Consequently, it is hard to predict which projects are going to generate useful and informative data that will add to our body of knowledge and which will generate that homerun finding. Today, too many of our postdocs believe that getting a paper into a prestigious journal is more important to their career than doing the science itself.”

In other words, the proximate cause of trying to publish in a high impact journal erodes the ultimate cause of doing good science.

Another example for a proxy that distracts from recognizing good science is paying too much attention to research coming out of highly ranked universities, “highly ranked” according to some measure. This case was recently eloquently made in Nature by Keith Weaver in a piece titled “Scientists are Snobs” (sorry, subscription only):

“We all do it. Pressed for time at a meeting, you can only scan the presented abstracts and make snap judgments about what you are going to see. Ideally, these judgments would be based purely on what material is of most scientific interest to you. Instead, we often use other criteria, such as the name of the researchers presenting or their institution. I do it too, passing over abstracts that are more relevant to my work in favor of studies from star universities such as Stanford in California or Harvard in Massachusetts because I assume that these places produce the “best” science…

Such snobbery arises from a preconceived idea that many scientists have –that people end up at smaller institutions because their science has less impact or is of lower quality than that from larger places. But many scientists choose smaller institutions for quality-of-life reasons…”

He goes on to explain how his laboratory was the first to publish a scientific finding, but “recent papers… cited only a more recent study from a large US National Institutes of Health laboratory. Losing this and other worthy citations could ultimately affect my ability to get promoted and attain grants.”

In other words, using the reputation of institutions as a proxy for scientific quality does not benefit the ultimate goal of doing good science.

Now let us contrast these problems with what we can read in another recent Nature article “Beyond the Paper” by Jason Priem. He wipes away such concerns as follows:

“[A] criticism is that the very idea of quantifying scientific impact is misguided. This really will not do. We scientists routinely search out numerical data to explain everything from subatomic physics to the appreciation of Mozart; we cannot then insist that our cogitations are uniquely exempt. The ultimate judge of scientific quality is the scientific community; its judgements are expressed in actions and these actions may be measured. The only thing to do is to find good measures to replace the slow, clumsy and misleading ones we rely on today. The great migration of scholarship to the Web promises to help us to do this.”

This argument implicitly assumes that making use of a quantifiable measure for scientific impact does not affect the judgement of scientists. But we have all reason to believe it does because it replaces the ultimate cause with a proximate cause, the primary goal with a secondary goal. (Priem's article is otherwise very interesting and readable, I recommend you give it a closer look.)

I’m not against using measures for scientific success in principle. But I wish people would pay more attention to the backreaction that comes from doing the measurements and providing people with a time-saving simplified substitute for the ultimate goal of doing good science.

Black holes and the Planck length

According to Special Relativity, an object in motion relative to you appears shortened. The faster it is, the shorter it appears. This is effect known as Lorentz-contraction. According to General Relativity, an object that has a sufficiently high mass-density in a small volume collapses to a black hole. Does this mean that if a particle moves fast enough relative to you it turns into a black hole? No, it doesn't. But it's a confusion I've come across frequently. Take Craig Hogan's recent "paper", where he writes:

"[B]elow the Planck length... it is no longer consistent to ignore the quantum character of the matter that causes space-time to curve. Even a single quantum particle of shorter wave-length has more energy than a black hole of the same size, an impossibility in classical relativity..."

The wave-length of a particle depends on the motion you have relative to it. For every particle there is a reference frame in which the wave-length of the particle appears shorter than the Planck length. If it was true what Hogan writes, this would imply that large relative velocities are a problem with classical general relativity. Of course they are not, for the following reasons.

A black hole is characterized by the existence of an event horizon. The event horizon describes the causal connectivity of space-time. It's a global property. Describing an object from the perspective of somebody moving relative to this object is a coordinate transformation. A coordinate transformation changes the way the physics appears, but not the physics itself. It just makes things look different. You cannot create an event horizon by a change of coordinates. Ergo, you cannot create a black hole just by looking at a particle that is moving rapidly relative to you.

There are three points I believe contribute to this confusion:

First, one can take the Schwarzschild metric for a black hole and describe it from the perspective of an observer moving relative to it. This is known as the Aichelburg-Sexl metric. The Aichelburg-Sexl metric is commonly used to handle black hole formation in particle collisions. The argument about the Planck length being a minimal length makes use of black hole formation too. But note that in these cases there isn't one, but at least two particles. These particles have a center-of-mass energy. They create a curvature which depends on the distance between them. They either do or don't form an horizon. These are statements independent on the choice of coordinates. This case should not be confused with just looking at one particle.

Second is forgetting that black holes have no hair. Leaving aside angular momentum, they're spherically symmetric which implies there are preferred frames. Normally one uses a frame in which the black hole is in rest, which then leads to the normal nomenclature with the Schwarzschild radius and so on.  But you better don't apply an argument about concentrating energy inside a volume that you'd have in the static case to the metric in a different coordinate system.

Third is a general confusion about the Planck length being called a "length". That the Planck length has the dimension of a length does not mean that it behaves the same way as a length of some rod. Neither is it generally expected that something funny happens at distance scales close by the Planck length - as we already saw above, this statement doesn't even have an observer-independent meaning.

The Planck length appears in General Relativity as a coupling constant. It couples the curvature to the stress-energy tensor. Most naturally, one expects quantum gravitational effects to become strong, not at distances close by the Planck length, but at curvatures close to one over Planck length squared. (Or higher powers of the curvature close to the appropriately higher powers of the inverse Planck length respectively.) The curvature is an invariant. This statement is therefore observer-independent.

What happens in the two particle collisions is that the curvature becomes large, which is why we expect quantum gravitational effects in this case. It is also the case that in the commonly used coordinate systems these notions agree with each other. Eg, in the normal Schwarzschild coordinates the curvature becomes Planckian if the radius is of Planck length. This also coincides with the mass of the black hole being about the Planck mass. (No coincidence: there is no other scale that could play a role here.) Thus, Planck mass black holes can be expected to be quantum gravitational objects. The semi-classical approximation (that treats gravity classical) breaks down at these masses. This is when Hawkings calculation for the evaporation of black holes runs into trouble.

For completeness, I want to mention that Deformed Special Relativity is a modification of Special Relativity which is based on the assumption that the Planck length (or its inverse respectively) does transform like the the spatial component of a four-vector, contrary to what I said above. In this case one modifies Special Relativity in such a way that the inverse of the Planck length remains invariant. I've never found this assumption to be plausible for reasons I elaborated on here. But be that as it may, it's an hypothesis that leads to consequences and that can then be tested. Note however that this is a modification of Special Relativity and not the normal version.

First Issue of the New Nordita Newsletter!

The Nordita Newsletter has gotten a major technical upgrade and the first issue of the new version is now online at

www.nordita.org/news 

Most notably, you can now subscribe and unsubscribe yourself and we have rss feeds for the different Newsletter categories.

Subscribing to the Nordita Newsletter might be interesting to you if you are interested in the research we do, want to be informed about job opportunities and other application deadlines like program proposals or PhD visiting fellowships, want timely information on which upcoming conferences, schools or programs you can now register for, or if you work in physics or related field anywhere in the Nordic countries and are interested in our "Nordic News" about research in this part of the world.

A big benefit of the upgraded Newsletter is that individual news items can now easily be shared, which we're hoping will make this information more useful to pass on via social media.

The highlight of this issue is this little video that we produced about the institute:


Part of the shots were made during last year's programs on holography in October and the on Cosmology program in November so you might recognize a few faces here or there. Jump to 2:42 and see if you recognize the guy to the right. 3:16 onward, anybody looks familiar? 3:08 and 5:22, that was during the program I organizied.

And in another video you can meet Oksana, who you got to know earlier in my blogpost about Nematic Films. Here she explains her research in her own words:

Twitter Enthusiasm Dwindling

I've spent Easter in bed with a high fever. After a few days of this my brain is deep fried, my inbox a disaster, and I'm not in the shape to do anything besides occasionally scrolling through my news feeds. On the search for something to write that doesn't require much brain use, let me offer a self-observation.

I've pretty much stopped using Twitter. Years ago it seemed like a useful platform to aggregate and share information quickly and easily. But it's turned out to be pretty much useless when it comes to organizing information. My Twitter feed is inevitably dominated by a handful of people who don't seem to be doing anything else than tweeting, at a frequency 100 times higher than everybody else. I did create a few lists to circumvent the problem, but it's cumbersome and also doesn't really solve the main issue, that most tweets are just not of interest to me. They're replies to somebody's reply, or comments on somebody's comment. Ordered by time, not by topic. And needless to say, there's things that don't fit into 140 characters. This guy has made a similar self-observation of Twitter tiredness.

Which is why, these days I'm pretty much relying on facebook for my social networking. I've looked at G+, but not much seems to be going on there, or at least not among the people in my circles. And that what's going on seems to be an echo of what they're doing on facebook. My main news source is still RSS feeds, but facebook does a good job with the interesting and amusing bits that pass through the network. And it has the big benefit that commenting is easy, so it's turned out to be a comfortable platform to discuss those recent news, more so than Twitter or Blogger.

So how about you? Still using twitter?

Opinions, Morals and What Science Could but Shouldn’t Tell Us

Headache. Image source: Mupso.

In an opinion piece from December, Brian Cox and Robin Ince argued that opinion must be separated from science when it comes to policy decisions:

“[T]here must be a place where science stops and politics begins, and this border is an extremely complex and uncomfortable one. Science can’t tell us what to do… The choice of policy response itself is not a purely scientific question, however, because it necessarily has moral, geopolitical and economic components.”

I used to say the same, that politics unfortunately mixes up scientific questions with unscientific ones, and that informed decision making requires us to first distinguish these. But then I went down a windy road trying to understand where science ends and where decision making begins. This eventually lead to my paper on the measurement of happiness. It also lead me to the conviction that the “extremely complex and uncomfortable border” doesn’t exist. Cox and Ince come to the right conclusion, but for the wrong reasons.

What is and what isn’t in the realm of science, and what is the role of science is in our political system are questions I care about deeply. And so I could not avoid noticing Sean Carroll and Lubos Motl recently discussed whether morals can be reduced to science. They come down, in rare agreement, on the side of “no”. It’s a variant of the “boundary” Cox and Ince touched on, so let us see what they had to say.

Sean and Lubos start by elaborating on what is and what isn’t a scientific statement. A scientific statement, they say, is one that could be false and whose truth value could at least in principle be empirically evaluated. The problem is then that the statement that morals can’t be reduced to science itself isn’t scientific. It isn’t because a definition for “moral” is lacking. Then, all answers to this question are just opinion so why bother with it? Lubos alludes to this by saying that whenever one could answer the question one way or the other somebody might just change the definition of moral

“Imagine that you find some quantity M encoded in the equations of M(orality)-theory in the future and you will claim that it measures morality… The problem is that even with this nice and well-defined formula, one may always legitimately refuse such a measure of morality and choose a completely different one.”

This lack of proper definition is an example for what I complained about in my recent post, that many philosophical questions are a waste of time if one doesn’t know what one is talking about to begin with. So let’s not debate the meaning of words and instead identify the real issue behind it.

What people really want to know is where science leaves them the freedom to make decisions. That’s why they are looking for a border between scientific and unscientific questions, the former can be answered by science, the latter presumably can only be answered by humans. In other words, they’re asking for their space to exercise free will.

Free will is an illusion that people hold on to quite stubbornly and that they protect vehemently, so the debate about the unscientificness of morals shouldn’t come as a surprise. The thought that science might tell people what they should or shouldn’t do is a great threat to free will, one that gets addressed in a forward defense. But that’s a misunderstanding. Science has never and will never tell anybody what should or shouldn’t be done because “should” is another one of these ill-defined words. “Should” implicitly necessitates a goal or a purpose.

“Science can’t tell us what to do”, as Cox and Ince write - correctly. But science can in principle tell us what we do. To understand how let’s have a look at what people mean when they refer to “morals” or “values”.

Humans are self-aware complex systems that have to process a lot of information to make informed decisions. Human self-awareness however is limited. We are not normally aware how the detailed processes of our thoughts proceed. In fact recent research in neuroscience seems to show that what we think of as “I” is primarily an aggregating mechanism of various deeper level systems whose detailed procedures the “I” does not normally take note of.

Thus, “we” don’t consciously know the details of how we make decisions. Moreover, a central element of human decision making is ignorance and oversimplification. The one thing that the human brain is really good at is energy efficiency. Which is why the default is to avoid thinking if unnecessary.

What we do instead of monitoring all that information from the input that we receive is learning to construct models of behavior that make use of simplified patterns and categories. Then we explain our decisions and those of others in terms of these simplified patterns. You chose this job because independence is important to you. You think polygamy is immoral and should be punished. These are rough summaries of longwinded thought processes which made use of experience, evolutionary traits, and random noise. They classify decisions in values like “independence” or morals like “faithfulness.”

Morals and values are thus just categories that people use to classify and explain the way they make decisions. Over time, using these simplified models, the higher level “I” system becomes good at predicting what will happen, and interprets this as an exercise of “free will.”

That having been said, if you believe in reductionism, morals and values are just emergent patterns in highly complex systems. It is clearly impractical and anyway presently impossible, but in principle one could define morals in this way. Imagine you’d do this. Now you have a definition for moral. An individual one, one that depends on cultural history as well as genetic ancestry. Here you have it. These are your morals.

You might then go and say that’s not what you mean with moral. And that would be fine with me because I don’t want to argue about words, so just call these emerging patterns something else. The point is that they’re what people make use of when they make decisions, and recall that this is the question we really want to address: What decisions are humans free to make because they’re allegedly unscientific?

If you have such a definition for morals then would science then tell you what you should do? No. It would in the best case simply tell you what you do. The best case being one in which scientists would be able to construct a complete model for human behavior. Depending on your attitude you might call that the worst case.

But while in principle possible, it is questionable that such a model is feasible to construct at all. It seems plausible to me that the process of thought is irreducible in the sense that if you tried to predict it you’d have to create an almost perfect copy of the original system and watch it in real time, in which case you’d just duplicate rather than predict decisions.

In other words, while the “border” between scientific and unscientific questions does not exist in principle, it does exist in practice. And it’s located where our ability to model complex systems ends, an end that might shift somewhat in the future but quite possibly will never entirely recede. The best way we presently know to find out what decisions humans make is to ask them. The best way we know to find out what the global climate does is not to ask humans but a computer model.

What does this have to do with happiness? Well, striving to achieve happiness is a human universal, so much so that you might want to raise the maximization of well-being of conscious beings to a universal goal. Having defined such a goal it would fill in the blank of the “purpose” and the “should” that was previously missing, or at least it seems so.

The problem is however that happiness is a byeffect of natural selection, it’s a simplified response to behavior that has in the past been beneficial for reproduction. Elevating happiness to an end unto itself is a circular definition of purpose, it’s fundamentally meaningless. Which is why, in my paper I argued we should forget about trying to define happiness and its maximization as a proxy to understand human behavior. Instead we should look for a properly defined quantity that has predictive power to describe the evolution of our economic, politic, and social systems, and the suggestion I made was maximizing the number of possible decisions that we (think we can) make. Which might or might not be correct. A scientific question that’s waiting to be answered.

Summary: Ill-defined questions are unscientific, but uninterestingly so. Once a question is well-defined science is in principle able to answer it, but not necessarily in practice. A scientific definition for morals might exist, but quite plausibly we will never be able to construct it. And even if we could, it wouldn’t tell us what should be done, but simply what is done. Opinion begins where our ability to model complex systems ends. This border will inevitably shift over time and it’s this “shift” that makes it uncomfortable. And no, I don’t believe in free will.

Apps I’d like to see

I learned this morning that in the drawer of pessimists, I lie in the corner of existential pessimists:

“Pessimists are of two types, the catastrophists, that is to say the types who look up in the starry heavens and see (metaphorically) only asteroids in the sky racing towards us to wipe us out as the dinosaurs were wiped out; and existential pessimists, that is to say those who see dissatisfaction as the permanent condition of mankind because of his inherent makeup, his contradictory desires and emotions, dissatisfaction that is perfectly compatible however with a great deal of enjoyment of life.” [Source]

Which is why I totally appreciate the internet in all its glory, and yet I am doomed to always complain about something that isn’t quite as good as it should be. Why, for example, doesn’t gmail mark messages that I have already replied to, which a program as dumb, clumsy, and stupid as Windows Mail could do for me? And why does facebook roll out a search function that nobody needs and nobody wants, instead of allowing me to simply search my timeline for a keyword. (Don’t tell me to use CTRL+F on the activity log while scrolling, I tried that and it didn’t work.) If I could assign tags to links posted on fb it might actually become a useful archiving system, but usefulness is clearly not Zuckerberg’s vision. And why, oh why, did Google have to kill the Google reader?

Leaving aside my complaints about current affairs, here’s something I would like to see in the future:

Scientific Seminar Channel

I’d really like to see that all institutes with a good AV equipment lifestream their seminars, and that all their seminar announcements are collected in some common channel. I could browse there for areas of interest, mark upcoming talks I’d like to listen to, and get a timely reminder, no matter where on the planet the talk takes place. And needless to say, there would be a way to log in and virtually “raise hand” to ask a question. I’m visualizing that in the back of the room there’s a screen showing avatars or video streams of people logged in from remote places. The technology is clearly there, so where’s my seminar channel?

Shopping cart for seminar speakers

Something that I’ve wished for whenever I organize a conference is a simple way to find people who could give talks on a specific topic, ideally filtered by location. The way I do this presently is by browsing my memory, personal referral, or searching the arxiv for keywords and then looking up author names on Google, hoping they have a descriptive webpage. This isn’t only time-consuming, but also ineffective. I am thinking this could be useful also for reasons of science outreach. You could look up on such a website speakers on topics of current interest in your area and invite them for a public lecture or a coffee house talk. Ideally, people could also upload slides or videos of some representive talks so you could form an impression on what to expect from them. Maybe one would want to add a possibility to rate speakers.

Remote Robot

This isn’t so much something I’d like to see, but something I think we will see. The intelligent robot that will do your household while you’re at work is still science fiction, and it will remain so for quite a while. But once you can construct a robot with a similar mobility as a human, it would be handy to have one at home that you could move around while you’re physically absent. Put the laundry from the washing machine into the dryer. Close the window. Water the plants. It seems to me that the technology for this is almost there. The economy probably isn’t.

Gamified PhD Life

You might have heard of the recent trend to gamification, inventing games around peoples’ self-set goals that they can use to collect points and virtual rewards whenever they make good decisions. Healthy living for example. You gained two points by not adding salt. The life of a PhD student would make for a good gamification. You gain points for each talk you give, conversation with your supervisor that you survived, group meeting that you didn’t fall asleep in, and if you have amassed 10.000 points you’re ready for the final battle.

Two apps that really exist and that you might appreciate: The particles app for the iPad and GmailTex.

What app would make your life a little better?

The Philosophie of Gaps

“And then there's the joke in which a young man told his mother he would become a Doctor of Philosophy and she said, “Wonderful! But what kind of disease is philosophy?”

~Steven Pinker in “The Blank Slate”

Philosophers and physicists, especially those working on fundamental questions of nature, have a difficult relationship. I know a lot of physicists who use the word philosophy as an insult, and even those who have sympathy for the quest of the philosopher tend to give them a hard time.

And understandably so. I’ve heard talks by philosophers about the “issue” of infinities in quantum field theory who had never heard of effective field theory. I’ve heard philosophers speaking about Einstein’s “hole argument” who didn’t know what a manifold is, and I’ve heard philosophers talking about laws of nature who didn’t know what a Hamiltonian evolution is.

But on the other hand, I’ve met remarkably sharp philosophers with the ability to strip away excess baggage that physicists like to decorate their theories with, and go straight to the heart of the problem. No wonder the relation between both sides can be uncomfortable.

This has left me wondering what is the role of philosophy in physics, or in modern science more general.

I will admit that I have a limited attention span for philosophical arguments. To begin with, philosophers (as apparently everybody in the humanities) have the annoying tendency to throw around names rather than proper definitions. The introduction of a cosmology paper in philosophy style would not contain the Friedmann equations, but instead two conflated paragraphs on the Friedmannian paradigm and its contextual appropriation of the cosmological principle, subsequently adapted as the concordance model.

Leaving aside the name-throwing and over-abundance of multi-syllable words, the issue of lacking definitions is a deep one for me. If somebody can’t write down a definition for expressions they are referring to, I lose interest. Because then their whole argument is in the end just empty words. I am interested in verbal arguments only to the point that they precede the construction of a mathematical model.

Having said that, here is where philosophy plays a role in physics: To develop these verbal arguments that have not yet been possible to cast in a more stringent form. This means though that when science progresses, when our knowledge expands, the room where philosophy is useful inevitably shrinks. The role of the observer in quantum mechanics, horizons in general relativity, or infinities in quantum field theory might once have been philosophical question. They no longer are. Presently popular topics for philosophers in physics seem to be the nature of time and the multiverse. Personally I think these are already topics that are close enough to existing theories that they can and should be cast into a mathematical language. Topics that are further off presently existing theories, and still more clearly playground for philosophers, are for example free will or the role of mathematics in science in general.

This tension between philosophers and scientists doesn’t only exist in physics. Another area where you find frequent displays of this confrontation is neuroscience. Consciousness used to be the field of the philosophers, but no longer so. Yet, philosophers are slow to get off the turf.

A recent display of this can be found in a NYT opinion piece that discusses “famous thought experiments” by philosophers. One of these famous arguments that philosophers discuss to make a living seems to be based on confusing the brain perceiving the color red as a result of photons of a certain wavelength hitting the retina, with the brain knowing about the process of perceiving the color. You might be forgiven for confusing knowledge about perception with the perception itself if you didn’t know anything about the brain, but in the last decade we have learned a lot about how the brain is wired and processes input. Or at least some of us have.

It seems clear to me that consciousness and self-awareness are areas that philosophers will have to clear in the soon future. That is correct: I don’t think there’s anything particularly mysterious about self-awareness, and nothing about it that we won’t be able to understand with some more research on complex systems and neural networks.

But what about science at large? Does this mean that we have a philosophy of the gaps much like we have a god of the gaps, filling in the spaces where currently knowledge is missing, but inevitably on the retreat?

For most of science this is a thorny question (previously discussed here), that being whether or not there is an end to the knowledge about nature that mankind can gather. It’s a question I don’t know how to answer.

But regardless of the answer to this question, for as long as there will be conscious beings thinking they will always be left with the question whether there are limits to what they can think of. And a more pragmatic, though related, question is how science works and how it progresses. These I believe are areas where philosophy will always play a role: to analyze the process of thought and inquiry, and its realization in the scientific endeavor. And as long as we have fundamental questions  about nature, it is good to keep philosophers around to catalyze the process of making soft science into hard science. Even if they are sometimes a little annoying.

Interna

Lara with her new glasses.

When you last heard from Lara and Gloria, they could utter a few single words. Within a couple of weeks, they have transitioned to speaking full sentences, answer to questions with "yes" and "no", and are very clear in expressing themselves. "Jacke an, Bagger gucke" (Jacket on, watch digger), they might say when they want to go for a walk. They still refer to each other as Gaakie and Gookie though. And they are struggling with German grammar, especially finding the right articles.

Lara now has glasses that are meant to help correct her squinting. She wears them without complaint. It probably helps for her acceptance that I too wear glasses.

The half-day daycare solution is working reasonably well, except that it's prohibitively expensive. The nanny has taught the kids to drink from a cup, to wash their hands, to paint and to jump. I'm sure our downstairs neighbors are as excited about the jumping as the kids. My commuting to Stockholm is not working quite so well. It leaves all of us terribly exhausted and is a huge waste of time, not to mention money. The time that I gain by having the kids in daycare is mostly spent on catching up on life's overhead, paperwork, the household, piles of unread papers and unanswered emails that wait for me upon return.

That having been said, I have a bunch of trips coming up. March 15 I'm in Bergen giving a seminar, apparently on the topic "Siste nytt om kvantegravitasjon". On April 12 I'm in Reykjavik. I haven't been able to find anything resembling a seminar schedule on the department website, but it's the same seminar as in Bergen. In May George and I are running the previously mentioned Workshop for Science Writers in Stockholm, and at the end of May I'll be attending a workshop on "Quantum Gravity in Perspective" in Munich. I have some more trips coming up, but plans haven't proceeded further than that. If you're located in any of these places and feel like  meeting up, send me a note.

Besides this, I've been told that the current issue of the Finnish magazine Tähdet ja avaruus ("Stars and Space") has an article by Laura Koponen about quantum gravity, featuring Renate Loll, Robert Brandenberger, and me. It's in Finnish so I have no clue what it says, but the photos look nice. Though... something about the photo of me didn't feel quite right, and after some forehead frowning it occurred to me that the NorthFace logo on my shirt fell victim to Finnish photoshopping. I actually like it better this way; I prefer my clothes without logos if possible. In any case, should you by any chance speak Finnish and have read the article, let me know what you think.

Upcoming Science Writers Workshop at Nordita

Recently, I've seen and heard a lot of talk about the relevance of science communication. Of course I totally believe it's relevant. I also totally believe Elvis was right asking for a little less conversation and a little more action. So George Musser and I, we decided to run a workshop that actually communicates science, physics in particular, astrophysics and cosmology specifically.

Our "Workshop for Science Writers: Astrophysics and Cosmology" will take place May 27-29, 2013, in Stockholm. It is is hosted and mainly funded by Nordita, and co-funded by the Swedish Research Council, Vetenskapsrådet. All the relevant information is on our website:

Workshop for Science Writers: Astrophysics and Cosmology

The organization is well under way, and we have meanwhile assembled a great list of lecturers, that we will bring together with a selection of excellent science writers. The details of the schedule aren't settled yet, but we are planning on lectures focused on recent developments and running and upcoming experiments, followed by question and answer session. I am very much looking forward to this workshop as I myself am not an expert in the area and I expect to learn a big deal.

Space for this meeting is limited but we will select some applicants among those who register online. The application deadline is March 31st. So if this sounds interesting to you, either as a physicist or as a science writer, you can fill in this application form.

This isn't the typical workshop that I normally organize. It's somewhat of a challenge for me to figure out the needs of science writers. George's suggestions have been invaluable while I've mostly taken care of the local issues. We're still in the midst of preparation though. I'll keep you updated on how it's going and you can expect some coverage of the event on this blog.

23 and Me

This is the century in which personal DNA sequencing became affordable. And so it was unavoidable that curiosity would finally have me sign up at 23andMe, spit in a plastic tube, and see what's in my genes. Primarily, I just wanted to know how it works. So here's how it works for those of you who share my curiosity and are thinking of having a look at their genetic information too.

How does it work?

First thing you do is order a spit kit. It contains a plastic tube with some preservative and exact instructions how to send it back to the lab. 23andMe is located in California. They ship outside the US, but not to all countries; you can find a full list here. Cost for the spit kit is presently at US$ 99. To this you have to add the shipping and customs cost for a "human sample" which comes at US$ 79,95.

I ordered the spit kit on January 4th. It was shipped January 10th and arrived in Germany within a few days. They ask for quite some amount of saliva, so it's not really done with "just spitting." It took me half an hour or so to fill the tube up to the mark.

There's a number on the spit kit that you have to register on the website. For this you have to set up an account if you haven't already done that anyway. Then close the tube and seal it into a plastic bag with a biohazard logo which goes into a padded envelope. The spit kit comes with customs forms that have to be filled in. (If you live in the US, the procedure is easier). To send it back  to the lab, you have to drop off the envelope at a DHL Express station. So if you think of doing this, you might want to check where you find the closest one to your place.

On January 18, I received an email saying the sample arrived in the lab.  They tell you the analysis takes on average 6 weeks. On March 4th, after exactly two months, I got the results. It should be said that that they don't actually sequence the whole DNA. They look for about a million SNPs that are known or suspected to be interesting for one or the other reason.

What do you get?

First thing you see when you log in to view your results is the question whether you want to opt out of receiving health information. If you do, you only get information about your genetic ancestry.

Once logged in, you can browse the raw data if you like, this will give you a long list with names of SNPs, their position, and your genotype. For the average user like me, who doesn't know a terrible lot about genetics, this isn't very useful though. What's more useful is the summary you get that tells you what's known about your genotypes, what this means, and how reliable this information is.

In the "Health" menu, you have the categories "Disease Risk," "Carrier Status," "Drug Response" and "Traits." Disease risk and drug responce is self-explanatory. Carrier status tells you if you carry any known mutations responsible for heritable genetic diseases (which you might not necessarily get yourself but just pass on to your kids). Disease risks come in percentage of likelihood to develop some disease, and they tell you whether your risk is higher or lower than average. In addition the results are labelled by stars telling you roughly how reliable the conclusion from existing research is. Drug response gives you a list of drugs you are likely to respond to more or less than average, which is valuable medical information.

The first three categories in the "Health" menu contain more details than I'm comfortable sharing publicly, so let me instead show you a screenshot of the "Traits" list, which you could summarize as fun facts

Blue eyes, curly hair, and, no, I don't use deodorant. I've always assumed the rest of the world is just somewhat weird when it comes to their arm pits.

Now let's look at the ancestry, which you see in the screenshot in the left menu. The "relative finder" isn't working yet, it says they're still processing my data. For all I know I haven't lost any relatives, so I'm not expecting to find many. The ancestry composition tells you where your genes came from 50 years ago, it looks like this:

So, I'm European, but then you already knew that. From what I know of my family, I'd have expected more East European and less North European though; I'm somewhat surprised about this. Who knows what my ancestors have been up to.

And then you can trace your maternal and paternal line. The maternal line comes down through mitochondrial DNA which is exclusively inherited from the mother. Allegedly, if you look back long enough, we all go back to the same woman, referred to as Mitochondrial Eve. But there have been a few mutations since and the line has split, which allows some localization. 23andMe lists your haplogroup and shows its estimated distribution about 500 years ago:

Again, it looks more nordic than I'd have expected.

The paternal line is traced via the Y-chromosome. So I'll have to convince a male relative to spit for this information. I think I know what my younger brother will get as a birthday present ;o)

The website

The website is very functional, readable, and works well. What I appreciate very much is that they don't just give you a likely correlation between your genotype and some trait, but, if you click on an item, you get a list of scientific papers and a short summary of the research status. So you don't have to believe what they tell you but can make up your own mind.

You can also, if you find the time, fill out some dozens of surveys that they use to find cross-correlations between what you report and your genetic information. The participation is entirely voluntary. They've found some links in this way, eg the "curly hair" SNP that you see in the first image (the one that appears with the 23andMe logo) is such a case. So you can actively contribute to research in the area, which I find a nice twist.

Taken together I'd say it's worth the money. I had previously toyed with the idea to sign up with 23and Me, but before January 2013 you had to get a subscription for the webpage in addition to the cost for the sequencing and the shipment.

It is btw entirely coincidental that my favicon looks pretty much like the 23andMe logo. I've used this icon since 1997 I believe, it's supposed to be a mixture of an x and a lightcone.

The simulation hypothesis and other things I don’t believe

Some years ago at SciFoo I sat through a session by Nick Bostrom, director of the Future of Humanity Institute, who elaborated on the risk that we live in a computer simulation and somebody might pull the plug, thereby deliberately or accidentally erasing all of mankind.

My mind keeps wandering back to Bostrom’s session. You might think that discussing the probability of human extinction due to war, disease or accident is a likely cause of insomnia. The simulation hypothesis in particular is the stuff that dreams and nightmares are made of - a modern religion with an omnipotent programmer. In this light, it is not so surprising that the simulation hypothesis is popular on the internet, though Keanu Reeves clearly had a role in this popularity, which now gives me an excuse to decorate my blog with his photo.

But while I do sometimes get headaches over questions concerning the nature of reality, the simulation hypothesis is not among the things that keep me up at night (neither is Keanu Reeves, thanks for asking).  After some soul searching I realized that I don’t believe in the simulation hypothesis for the same reason I don’t believe in alien abductions. Before science fiction literature and its alien characters became popular, there was no such thing as alien abduction. Instead, people commonly thought they were possessed by demons. It is believed today that sleep paralysis is a likely origin of hallucinations and out-of-body experiences, an interesting topic on its own right, but the point here is that popular culture creates hypotheses, and present culture is a collective limit to our imagination.

People today ponder the idea that reality is a computer simulation in the same way that post-Newtonian intellectuals thought of the universe as a clockwork. The clockwork universe theory seems bizarre today, now that we know many things that Newtonian mechanics cannot describe. But then people used to wear strange wigs and women stood around in dresses barely able to walk, let alone breathe, so what did they know. And chances are, 200 years from now the simulation hypothesis will seem equally bizarre as the idea to transfer fat from the butt to the lips or take notes by rubbing graphite on paper.

A more scientific way to phrase this is that the simulation hypothesis creates a coincidence problem, much like the coincidence problem for the cosmological constant. For the cosmological constant the coincidence problem is this: Throughout the expansion of the universe, matter dilutes and the constant stays constant. Why do we just happen to live in a period when both have about the same value? For the simulation hypothesis the coincidence problem is this: Why do we just happen to live in a period where we discover the very means by which the universe is run?

To me, it’s too much of a coincidence to be plausible. I will put this down as a corollary of the Principle of Finite Imagination “Just because humans do not or cannot imagine something doesn’t mean it does not or cannot exist.” Corollary:  “If humans put forward a hypothesis based on something they have just learned to imagine, it is most likely a cultural artifact and not of fundamental relevance.” Though the possibility exists that present day human imagination is the eclipse of scientific insight, the wish to be special vastly amplifies believes in this possibility.

That having been said, another way to approach the question is to ask for scientific evidence of the simulation hypothesis. There has been some work on this, and occasionally it appears on the arxiv, such as this paper last year which studied the possibility that The Simulator runs state-of-the art lattice QCD. I find it peripherally interesting and applaud the authors for applying scientific thought to vagueness (for other attempts at this, check their reference list). Alas, the scenario that Bostrom has in mind is infinitely meaner than theirs. As he explains in this paper, to save on calculational power only that part of reality is simulated that is currently observed:

“In order to get a realistic simulation of human experience, much less [than simulating the entire universe] is needed – only whatever is required to ensure that the simulated humans, interacting in normal human ways with their simulated environment, don’t notice any irregularities.”

So you’d never observe any effects of finite lattice spacing because whenever you look all symmetries are restored. Wicked. It also creates other scientific problems.

To begin with, unless you want to populate the simulation by hand, you need a process in which self-awareness is created out of simpler bits. And to prevent self-aware beings from noting the simulation’s limits, you then need a monitoring program that identifies when the self-aware parts attempt to make an observation and exactly which observation. Then you need to provide them with this observation, so that the observation is the same as they would have gotten had you run the full simulation. This might work fine in some cases, say, vacuum fluctuations, because nobody really cares what a vacuum fluctuation does when you’re not looking. If you have a complex system however, reducing the complexity systematically and blowing it back up is difficult if not impossible.

Take a system that’s still fairly simple, like a galaxy. If nobody is pointing a telescope at it, you don’t want to bother with its time evolution. But then how do you make sure that observations at different times are consistent? And then there’s the possibility that somewhere in the galaxy that humans weren’t observing intelligent life developed that would one day land on planet Earth. If your simulation by design doesn’t take into account events like this, it’s strangely anthropocentric. It also then raises the question why bother with 7 billion people to begin with? Would not an island do, and the rest of us pop in and out of existence to amuse the islanders? This reminds me, I have to book a flight to Iceland.

To avoid these problems, The Simulator would use a much simpler method: deter observations that might test the limits, much like it is difficult to reach the boundary of Dark City. And suddenly it makes sense, doesn’t it? All the recent budget cuts to research funding, even in areas like theoretical physics, the possibly most cost-efficient insight engine running on little more than graphite rubbing on paper. It’s all to deter us from discovering the boundaries of our simulation. Now if saying hello to the programmer who runs the simulation we live in isn’t an argument to support basic research, then I don’t know what is. I’ll leave you with this thought and book my flight before I pop out of existence again.

Book review: "The Theoretical Minimum" by Susskind and Hrabovsky

The Theoretical Minimum: What You Need to Know to Start Doing Physics
By Leonard Susskind, George Hrabovski
Basic Books (January 29, 2013)

Susskind made his lecture notes into a book and did a great job. His book is explicitly not aimed at students but at everybody with an interest in physics who wants to expand their toolkit and start speaking the language of physicists.

The book primarily covers classical mechanics: momentum and forces, energy and potentials, up to the principle of least action, Hamiltonian mechanics and poisson brackets. In content it is very similar to the lecture notes that I learned from, it might also remind you of Goldstein's classical book on classical mechanics. However, what's special about Susskind's book is that he introduces along the way all the mathematical concepts that are needed, starting with vectors and functions to integration and differentiation. The book is thus very self-contained and yet really brief and to the point, which is quite an achievement.

It seems pretty obvious that there will be a sequel to this book that continues this educational effort.

I appreciate this book very much. It would have been dramatically useful for me when I was a teenager, because there is a gap in the physics literature between high school level and the level aimed at students, a gap this book can bridge. However, if you think this book will bring to up to speed with modern physics, you got it wrong. It's a long way to quantum field theory and there really are no shortcuts. Susskind's book, and the ones that will probably follow, however might be the shortest route, the one of least action so to say.

That having been said, I'm not a teenager anymore and frankly don't have much use for the book. Which is why I'll give away my copy for free. The book will go to the first person who has a mailing address in Europe and leaves a comment to this blogpost telling us why you want the book and what is your interest in physics.

Update: The book is gone.

Thumbs up for the Cambridge University Press Customer Service

Some years ago, I bought a copy of Stephani et al's book "Exact Solutions of Einstein's Field Equations" from Cambridge University Press. It's pretty much an encyclopedia of all that's known about Einstein's Field Equations. It's the type of book you turn to for advice when you've got a problem, not a textbook you read front to back. So I hope you'll forgive me when I say it took me a few months to notice that the copy I bought was a misprint with several empty pages towards the middle. These are the obscurer parts of the book whose physical applications are at least to me somewhat unclear, and I thought I would just never need whatever should have been printed on these pages anyway.

Over the years however I developed the distinct paranoia that whenever I was looking for something that I could not find in Stephani's book, it was certainly printed on the missing pages. Some time last week, frustrated by yet another intractable set of equations one gets without a good ansatz for the metric, I wrote to Cambridge University Press customer service, complaining about the misprint, with the above photo attached.

Needless to say, several years after purchasing the book I don't have a receipt. Nevertheless, I got a reply within 24 hours, with an apology for the misprint. Alas, the hardcover version that I have is out of print, if a paperback would be okay. "Sure", I wrote back. They asked for my shipping address and a week later I have a brand new copy, all for free. Now if I don't find an answer to a problem I was looking for, I have no empty pages to blame any more.

The Future of Peer Review

This week's cover of The Economist.

A year ago, I told you what I think is the future of scientific peer review: Peer review that is conducted independently from the submission of a manuscript to a journal. You would get a report from an institution offering such a service, possibly some already existing publisher, possibly some new institution specifically created for this purpose. This report you could then use together with submission of your paper to a journal, but you could also use it with open access databases. You could even use it in company with your grant proposals if that seems suitable. I call it pre-print peer review.

I argued earlier that, irrespective of what you think about this, it's going to happen. You just have to extrapolate the present situation: There is a lot of anger among scientists about publishers who charge high subscription fees. And while I know some tenured people who simply don't bother with journal publication any more and just upload their papers to the arXiv, most scientists need the approval stamp that a journal publication presently provides: it shows that peer review has taken place. The easiest way to break this dependence on journals is to offer peer review by other means. This will make the peer review process more to the point and more effective.

The benefit of this change over other, more radical, changes that have been proposed is that it stays very close to the present model in that the procedure of peer review itself need not be changed. It's just the provider that changes.

I am thus really excited that the recent issue of Nature reports that one such service exists now and another one is about to be created:

Company offers portable peer review
Author-pays service cuts down on redundant reviews.
By Richard Van Noorden

The one that already exists is called Peerage of Science, based in Jyväskylä, Finland. Yeah, right, the Nordic people, they're always a little faster than the rest of the world. Peerage of Science seems to have launched a little more than a year ago, but this is the first time I've heard of it. The one in the making is US based and the project is managed by a guy called Keith Collier.

Of course it's difficult to say whether such a change will catch on. Academia has a large inertia, and it depends a lot on whether people will accept independent reviews. But I am confident, so let me make a prediction, just for the fun of it: In 5 years there will be a dozen of such services, some run by publishers. In ten years, most of peer review will take place this way.