Amazon.com: more junk-science than science?

(This article was originally posted on blogger.com on Aug 29, 2005)

As described earlier in Lubos’ blog, Anthony Kirmis’ 1-star review of the crackpot book The Final Theory (by Mark McCutcheon) did not survive for much more than one week. As of today, there are 34 reviews of the book, with an amazing 5-star average. I commented on this book earlier here. Basically, the book claims to describe the “final” theory of everything, ignoring – for example – the existence of gravity and using only simple elementary-school arithmetic. Did McCutcheon himself ask amazon.com to delete the bad reviews? Did amazon.com delete the bad reviews since they feared that the book would not sell good enough?

I think it is most likely, that McCutcheon arranged for the 1-star reviews to be deleted (but of course, he had to ask amazon.com to do it). As an example of the contrary, Steven Weinberg’s excellent book “Dreams of a Final Theory” has received 9 reviews with a 4-star average (and this guy really knows what he is talking about) and Brian Greene’s famous books “The Elegant Universe” and “The Fabric of the Cosmos” received 425 and 117 reviews respectively, both with a 4.5-star average – and some of the reviews of these books are only 1-star reviews and have survived for much more than one week.

US Judge Rules Against Intelligent Design in Schools

The revenge of the monkeys… 

Today a federal judge ruled that a Pennsylvania school district cannot teach “intelligent design” (ID); the idea behind ID is that life is so complex, that it must have been created or “designed” by some kind of intelligent being. That being is usually assumed to be God.

Here is some more information from Reuters,

PHILADELPHIA (Reuters) – A judge on Tuesday barred the teaching of intelligent design as an alternative to evolution at a Pennsylvania school, saying in a scathing rebuke to the school board that it violated a constitutional ban on teaching religion in public schools. [...]

“Our conclusion today is that it is unconstitutional to teach intelligent design as an alternative to evolution in a public school classroom,” Jones wrote in a 139-page opinion in the case, brought against the Dover School District.

Jones condemned the “breathtaking inanity” of the policy of the board, all but one of whom have now been ousted by local voters. “Any asserted secular purposes by the Board are a sham and are merely secondary to a religious objective,” he said.

Jones said the students and teachers of Dover High School “deserved better than to be dragged into this legal maelstrom with its resulting utter waste of monetary and personal resources.”

The school district was sued by a group of 11 parents who claimed teaching intelligent design was unconstitutional and unscientific and had no place in high school biology class.

 

Most of the reactions to this ruling were not really unexpected. For example,

Christy Rehm, one of the plaintiffs, said she was “ecstatic” about the judge’s ruling. “This is a victory for education, a victory for science and a victory for science education,” she told Reuters.

One of the proponents of ID, Casy Lusin of the notorious Discovery Institute surely did not agree:

But Casey Luskin of the Discovery Institute, a Seattle-based think-tank that champions intelligent design theory, criticized the ruling.

“The judge thinks intelligent design is a supernatural explanation, but it clearly is not. So the entire decision is predicated on a false perception of intelligent design,” Luskin said in a telephone interview.

What about president Bush who earlier actually promoted teaching Intelligent Design in schools? Well,

Asked about the ruling, White House spokesman Scott McClellan said the president has said he believed such decisions should be made by local school districts.

“The president has also said that he believes students ought to be exposed to different theories and ideas so that they can fully understand what the debate is about,” he said.

 

The White House still seems to think, that there really is something to debate about. Like if the next decision about the future of the US troops in Iraq should be determined by either political discussions or astrology?

More related articles can be found at google news.

Note: Heavy construction, hardhat required!

After discussions with Paul Cook I decided to move my blog, Thoughts on science and life from Blogger.com to WordPress instead (one reason being the ease of use of LaTeX commands). So currently, I’m moving some old post to this “new” blog…

Weinberg Wandering in the Landscape

(This article was originally posted on blogger.com on Nov 4, 2005)

Today, Steven Weinberg posted an article at the arXiv entitled ”Living in the Multiverse” (which is based on a talk he gave at a symposium in September at Cambridge on the topic “Expectations of a Final Theory”).

Weinberg is by any standard an exceptional physicist. He has made numerous contributions to particle physics and also cosmology. One of his controversial – but in many ways also successful – predictions was the prediction in 1987 of the size of the cosmological constant assuming that galaxies should have formed. If the cosmological constant is too large, galaxies and stars cannot have formed since then space would expand and dilute too quickly, before any kind of galaxy can be created by the gravitational pull. On the other hand, if the cosmological constant is too negative, the Universe would simply collapse – that is, approach the Big Crunch too early. Later experiments showed that Weinberg’s rough estimate was correct. Weinberg’s calculation of the cosmological constant is a typical application of the “Anthropic Principle”: the constants of nature (and everything else, I guess) should be such that galaxies and eventually life could form.

As a side remark, we could ask the following question: What did we actually learn from Weinberg’s successful calculation of the cosmological constant? Basically only that nature is the way it is, since it is the way it is. I would have found it much more interesting if Weinberg’s estimate was completely off from what later experiments confirmed. Then we would have known, that our understanding of galaxy formation – and maybe even particle physics – was fundamentally flawed.

In the talk mentioned above, Weinberg presents some novel ideas to support the anthropic principle. Weinberg argues that revolutions in physics not only answer questions in new ways (as for example by principles of symmetry as in the general theory of relativity or in quantum mechanics), but they even change our view of which questions are important and well-defined and which are not (as for example the one in quantum mechanics as: “what path did the electron follow?”).

Weinberg argues that the anthropic principle and the “landscape” of string theory seem to be implying something along these lines. As an example, he says:

The larger the number of possible values of physical parameters provided by the string landscape, the more string theory legitimates anthropic reasoning as a new basis for physical theories: Any scientist who study nature must live in  a part of the landscape where physical parameters take values suitable for the appearance of life and its evolution into scientists.

The last statement is kind of trivial. The first one does not seem to be substantiated in any way: that the number of solutions is large (~10^500) does not imply, that there is no scientific principles which determine the “correct” solutions (and here I don’t count the anthropic principle as scientific). I find his comment about the hierarchy problem even more problematic:

If the electroweak symmetry breaking scale is anthropically fixed, then we can give up the decades long search for a natural solution of the hierarchy problem. This is a very attractive prospect, because none of the “natural” solutions that have been proposed, such as technicolor or low energy supersymmetry, were ever free of difficulties.

How can we ever know, that this scale is “anthropically” fixed? By realizing, that we could not solve the hierarchy problem in 30 years? In 120 years? Sorry, but to me, this kind of reasoning sounds much like “Intelligent Design”. Just because there is something – like the immune system, blood clotting or the relative masses of ‘fundamental’ particles – which we have not fully understood yet, does not imply that we should resort to aliens, a God (which I don’t think Weinberg would) or our own existence as beings for an “explanation”.

In conclusion, Weinberg seems to be suggesting that asking for an explanation of the values of the free parameters of the Standard Model is equally meaningless as asking how to describe the path followed by an elementary particle.

While writing this comment I realized that Lubos Motl and also Peter Woit already posted some comments to Weinberg’s paper. I tend to agree with their conclusions, but for different reasons…

String Theory = Intelligent Design? (Part II)

(This article was originally posted on blogger.com on Nov 4, 2005)

Of course I have to respond to Peter’s criticism – which is more than welcome – of the merits of string theory, which I listed below.

At the moment we actually have two separate theories; the Standard Model of particle physics and the general theory of relativity. String theory aims at finding a theory, which combines the two, i.e. is a theory of quantum gravity, and which in a certain sense is more “fundamental” and maybe “simpler” than the former two theories taken together. The point is not just that you would “like to” have a theory, which combines the two (and surely, this was not the historical reason for studying string theory, but that is rather irrelevant). There are some obvious reason for why we should try to find a theory of quantum gravity; I’ll just list some of them: 1) because of singularity theorems (originally formulated by Hawking and Penrose). It follows from general relativity, that singularities in space-time are unavoidable, so general relativity actually predicts its own breakdown in the sense, that the theory does not apply to the singularities themselves; 2) because we should be able to understand the initial conditions in cosmology: cosmology is incomplete if its beginning cannot be described in physical terms; 3) because of the evolution of black holes: black holes radiate with a temperature proportional to Planck’s constant (the Hawking temperature). To understand the final evaporation, a full theory of quantum gravity is needed; (in this respect, black holes are important testing grounds for a quantum theory of gravity); 4) because we would like to have unification of all interactions: all non-gravitational interactions have so far been successfully accommodated into the quantum field theory framework (i.e. in the Standard Model); 5) because of the inconsistency of an exact semi-classical theory: all attempts to construct a fundamental theory where a classical gravitational field is coupled to quantum fields have failed up to now – –and there is an obvious reason for this; if matter is quantum-mechanical, then the energy-momentum tensor in Einstein’’s equation is not a c-number, but an operator and should presumably be replaced by its expectation value. Then we end in turmoil, since the metric depends nonlinearly on the state of the matter system 6) because of the avoidance of divergences: String theory (and to a certain extend also loop quantum gravity) provides indications for a discrete structure at smaller scales, and therefore the emergence of a natural cutoff at small distances.

Peter is of course correct in saying, that what I said below (the list of credits of string theory) has been said many times before. That, however, does not make it less true -or more correct for that matter. Science should not be like politics, philosophy (or intelligent design), where you can discuss the pros and cons without ever reaching a “final” conclusion. So, I’ll defend some (for now, only a few) of the comments I made below.

My statement about the “reproduction” of the Standard Model in string theory was clearly not precise enough.

The Standard Model in itself contains a lot of unexplained assumptions; a gauge group (SU(3) x SU(2) x U(1)), some 21 free parameters, the number (three) of fermion generations, the 3+1 dimensions of space-time, chiral fermions in certain representations; gauge bosons, such as the gluons, the W^(+-) and the photon. The masses of these particles have not been computed in string theory (which was also secretly implied in what I was saying since I did not claim, that we understand how supersymmetry should be broken). What we can get is the gauge group and chiral fermions. Let’’s see how this could work: the gluons, for example, are described by a four-dimensional SU(3) Yang-Mills theory -– and this theory is closely related to the U(3) Yang-Mills theory which arises at low energies on the world-volume of three coincident D3-branes. This is because the U(3) gauge theory of nine (3 times 3) interacting gauge fields on three coincident D-branes contains a decoupled U(1) theory – the remaining eight interacting gauge fields define the SU(3) gauge theory (since, locally, U(3) = SU(3) x U(1)). Likewise, the SU(2) x U(1) electroweak Yang-Mills theory can be realized by including two additional coincident D3-branes; these two D-branes should obviously not coincide with the three color D-branes, since otherwise we would get a U(5) Yang-Mills theory. Furthermore, at low energies the gauge group is SU(3) x U(1) and this symmetry breaking is triggered when certain charged scalar fields, the Higgs fields, acquire expectation values. But in order to use string theory to describe the full Standard Model, we must study the matter particles and the charges they carry. Roughly, the fermions are represented as strings ending on the D-brane configurations that carry the gauge bosons. A central property of the Standard Model is that the spectrum of fermions is chiral (i.e. the left- and right-handed particle states do not have the same charges). How can we get chiral fermions?

First of all, in the Standard Model, the electroweak interactions SU(2) x U(1) acts chirally, so the fermions remain massless until the Standard Model gauge group is broken down to SU(3) x U(1), after which the masses are determined by the Higgs sector mentioned above. In the string theory picture, quarks, for example, are simply open strings that have one endpoint on one of the three coincident D-branes mentioned above (so that the color charges are determined by which D-branes the open strings end on) -– and the anti-quarks are simply oppositely oriented open strings. Now, where should the other endpoints of the open strings lie?

For illustrational purposes, I’ll just mention the left-handed quarks. The quark states fall into representations of SU(2) (weak symmetry) and are characterized by their isospin. The state with isospin I=1/2 is an up-quark and the one with I=-1/2 is a down-quark. The D-brane picture is very simple: a u-quark is an open string that begin on one of the two coincident D3-branes mentioned above (which we can call the weak-branes), and end on one of the three coincident D3-branes (or color-branes).

However, with a group of three coincident (color) D3-branes and a parallel group of two coincident (weak) D3-branes as above, our construction is doomed to fail: the spectrum is not chiral since the spectrum contains left-handed and right-handed quarks with the same charges (this can also be seen by noticing, that a string stretching from a color-brane to a weak-brane is massive). So the color D3-branes should actually intersect with the other two coincident weak D3-branes (I will not go into detail with this).

This was just included to give an illustration of how the Standard Model can be incorporated in string theory – but the embedding of the Standard Model in string theory is obviously not unique. There are other ways to obtain a string theory model of the Standard Model; one, for example, includes intersecting D6-branes wrapped on a six-torus T^6 in the Type IIA theory. But of course we should note, that these models are not fully realistic – the breaking of the electroweak symmetry needs to be worked out, the mass parameters and other couplings should also be calculated etc, and we cannot have six extra non-compact dimensions as above, since these other dimensions would be visible.

What about the free parameters of the Standard Models?

In string theory, on the other hand, there are no adjustable dimensionless parameters; the parameters of the Standard Model should come out as vacuum expectation values of certain scalar fields. These values are determined by the correct vacuum – which we don’t know how to find yet (and I don’t think the anthropic principle will help much).

The discussion about the number of dimensions “‘predicted”’ by string theory is rather old, and often also a bit off-mark, I think. Some argue, that string theory started by predicting 26 dimensions (the bosonic string), then ten dimensions (the superstring) and then eleven dimensions (via M-theory). I don’’t think anybody thought of the 26-dimensional theory as a “realistic”’ one, since it does not include space-time fermions. In superstring theory, ten dimensions are required by a vanishing total central charge, which is a mathematical constraint. There are no obvious reasons for why the result should be exactly ten dimensions – in principle, it could have been five or seven. In the Standard Model, the 3+1 dimensions is something, which is an input, and the theory could have been mathematically consistent in, for example, 7+1 dimensions. In M-theory, we have not ten, but eleven dimensions, which can seem strange; however, if we think of M-theory as the strong coupling limit of the Type IIA theory, then the original ten dimensions were just a result of a calculation done in a perturbative superstring theory, so roughly, the string coupling interpolates between a ten-dimensional and an eleven-dimensional theory (that the question about the number of space-time dimensions is subtle, is also something we learn from the AdS/CFT correspondence).

But, sure, string theory (or whatever it is going to be called) is not in any way a final theory and much work has to be done…

Note: More comments relating to Peter’s critique will be posted later

The $100 Laptop

(This article was originally posted on blogger.com on Nov 21, 2005)

On January 2005, the MIT Media Lab officially launched a research initiative (headed by Nicholas Negroponte, chairman and founder of MIT’s Media Labs) to develop the $100 laptop – a technology that could revolutionize how the world’s children are educated. For this purpose, a non-profit association, called One Laptop per Child (OLPC), was created by Negroponte.

The laptop basically looks like a mutated version of ordinary machines, and uses an LCD display. Some of its current specifications are: 500 Mhz processor, 1GB flash-based memory, 1 Megapixel LCD screen. The laptop will be WiFi-enabled and have USB ports.

It has a removable keyboard and has an actual crank (!) to turn so it can be powered anywhere (see the RHS of the picture above; [Image courtesy of MIT Media Lab]). This lends credence to the “laptops around the world” ideal. It’s a brilliant idea for children in the developing countries, where there are not too many powerlines avaliable, but also for poor children in the Western world, such as in Massachusetts, USA .

However, one should take notice, that (according to the develolpers at the Media Lab):

… the $100 laptops—not yet in production—will not be available for sale. The laptops will only be distributed to schools directly through large government initiatives.

But surely, this will be good for competition not only in the educational market for computers. When the $100 laptop is released, most likely a powerful laptop (like an Apple iBook) could end up costing maybe $150. News about the $100 laptop can be found at Google News. A FAQ-list  about the $100 laptop is here. More pictures of the $100 laptop can be found at the following page.

Such IT leapfrogging may not do much to help the very poorest of the poor, but for people in China, India, throughout Latin America and the more successful states in Africa, it can be incredibly valuable. Life-changing, for some and – perhaps – even world changing.

String Theory = Intelligent Design?

(This article was originally posted on blogger.com on Oct 27, 2005)

Don’t get me wrong. I don’t think – as Peter Woit seems to be doing – that the scientific status of string theory is in any way comparable to that of the crazy set of ideas called “Intelligent Design”. Basically, Intelligent Design (ID) purports to ‘explain’ the complicated structures seen in life – as the DNA, the structure of a human eye, blood clotting, the immune system etc. by introducing a ‘designer’ (God, aliens, or whatever) clever enough to yield the blueprint of life in all its forms. But in reality, ID does not explain anything at all.

Commenting on Lawrence Krauss’ new book on extra dimensions, Peter Woit says:

The behavior of string theorists that Krauss identifies as most like religion is the argument that “the theory is so beautiful it must be true.” I actually don’t hear many string theorists making this argument these days. If the theory actually were beautiful in the sense of providing some impressive new understanding of physics in terms of some simple, compelling mathematical or physical idea, that actually would be a good reason for believing in it, although not a completely conclusive one. All attempts so far to connect the theory to real physics lead to hideously complicated and ugly constructions.

and,

Some string theorists such as Susskind, argue that one should believe in string theory anyway, and it is this argument which seems to me to be more like religion than science. It’s my impression that Susskind and others are believing something for sociological and psychological reasons, something for which they have no rational, scientific argument. This behavior is not distinguishable from that of many of the intelligent designers, and if it becomes more widespread it ultimately threatens to do real damage to the public perception of science in general and theoretical physics in particular.

Peter’s main argument for comparing string theory with ID is, that

[...] if after a lot of work, there still is no indication that an idea can produce predictions, the continued pursuit of it at some point stops becoming science and starts becoming something more like religion. Susskind and other anthropic landscapeologists have already gone past this point: they have no plausible idea about how to ever get real predictions out of their framework. String theorists who argue that the theory is still too poorly understood, that more work is needed to understand whether there is some way around the radical non-predictivity implied by the landscape, are nominally still doing science.

There are some obvious reasons for which ID is not in any way a scientific theory:

it can in principle not be falsified

it violates Occam’s razor

it is rumored to be supported by a (completely flawed) understanding of the chance of a biological structure like an eye to appear as a result of evolution (typically estimated to be 1 in 10^{150} or less – even though such a ‘calculation’ does not make any sense)

it makes no real predictions for any biological systems

it is like saying, that science should stop trying to find explanations for things, since supporters of ID argue, that everything which as of yet is not explained by evolution must by explained by an ‘intelligent designer’

In comparison, string theory is completely different; some of the reasons are, I think, that in string theory:

the appearance of gravity is inevitable

all interactions are unified

there are no adjustable dimensionless parameters

gauge invariance, supersymmetry and higher dimensions comes out in a very natural way (and moreover, the number of dimensions is not something which is assumed, but something which is determined by mathematics)

the extra dimensions can be ‘large’ (like in the Randall-Sundrum models) and the existence of those dimensions can be tested, for example at the LHC

the Standard Model can be reproduced in a very simple way (for example by intersections of D6-branes wrapping a T^6, or by D3-branes placed at an orbifold singularity – though symmetry breaking remains to be worked out)

the ‘hierarchy problem’ can be solved by the existence of extra large dimensions (Randall-Sundrum)

the entropy of certain classes of black holes can be accounted for (for example in terms of coincident D1- and D5-branes,  a la Strominger-Vafa), which no other theory of quantum gravity has been able to do so far

AdS/CFT can be related to well-established physical theories like QCD (even though the relation is not completely understood yet)

the ‘holographic principle’ can naturally be realized, for example in AdS/CFT, which in turn also implies an ‘IR/UV connection’ (two principles, which seem to be pivotal in the search for a quantum theory of gravity)

So, when I say, that string theory is intelligent design, I mean, that string theory is the result of years of clever research in trying to find the most fundamental theory of physics and actually – in contrast to ID – is trying to solve a problem, namely that of finding a quantum theory of gravity. In opposition to Lubos Motl, I would call string theory “the Apple of quantum gravity” and not the Microsoft of quantum gravity (but only in the sense, that string theory has proven to be extremely fruitful, both for physics and mathematics, and is built on a tower of innovative new ideas, much like Apple is – and not measured by how popular Microsoft vs. Apple is, where Lubos’ analogy of course is completely correct