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Effects, causes, and science adrift March 26, 2008

Posted by dorigo in Blogroll, physics, science.

Bee and Stefan at backreaction have just published a very nice post listing 10 (well, 11) fairly well-known physics effects, from the photoelectric effect to the MSW effect. The descriptions are concise and matter-of-fact, with good references for further reading. Definitely a pleasant grab-and-go read.

An “effect”, a reader has argued in the comments thread of the post, should be something experimentally observed, and then (or contextually) explained by a theory. Instead, there are things such as Hawking radiation -the thermal emission from black holes- which is dubbed “Hawking effect” despite having never been observed (a fact that is likely to continue in the future).

Rather than discussing the largely nominalistic issue of what is in earnest an “effect” (which we can do at Bee’s and Stefan’s blog), I would like to elaborate here on the observation that science has become increasingly bold in the XXth century. Perhaps the cause of this effect is our getting accustomed to the routine exploration of realms to which our senses have utterly no access: very few XXIst century men and women would be willing to negate the existence of atoms, although we have never seen one (waiving a few electronic microscope pictures which arguably do not show anything directly either). Can we do the same with cosmic strings ? Surely not, we need proof. But what is an acceptable proof, these days ? If we abandon some of the foundations of scientific investigation – reproducibility, falsifiability, direct testing – through confidence in our means, strength of our prejudices, and mastery in the practice of our science, aren’t we becoming sorcerers ?

Once the foundations are gone, Science is in danger. We are approaching the dangerous terrain where to progress one is required faith. Faith in a theory, faith in conjectures, faith in methodologies. I see this trend quite clearly in particle physics, my research field. On one side, we have started during the last twenty years to peruse multivariate methods such as Neural Networks, which indeed work wonders but contain a good measure of magic within; as an example, CDF and D0 both have evidence in their Run II datasets of single top production  -a process which the standard model predicts with great accuracy, and thus must exist- with neural networks playing a major role. On the other side, theorists get enamoured of concepts such as fine tuning, renormalizability, unitarity - things that strictly speaking are not physical but mathematical arguments – to justify assumptions and build or kill theories.  

I know I am being a bit provocative here. But I have a point: I do see a trend. Humanity faces big challenges in the future, challenges for its own existence. Is global warming a prejudice or a scientific fact ? If we cannot even all agree on something like that, we are bound to extinction. And maybe there is some logic in it.

UPDATE: I hate when this happens. After writing something that I think has some originality, or at least some personality, I stumble in another recent post discussing quite similar matters in more length, more depth, and in front of a larger audience. It happened before, and it is awkward: I have to swear I did not read the other piece first… In any case, Sean’s piece is worth a look (I learned about it in a post at NEW - so I have to thank Peter for keeping us all updated on most of what is worth being aware of from around the web).

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1. Bee - March 26, 2008

Hi Tommaso,

That is a very interesting posting! I think the question is tightly connected with the increasing specialization in our societies. The more pronounced this is, the more people HAVE TO rely on things others say, and export questions to experts. It is just simply not realistically possible to proof everything on your own. Even in our field, it is just not always possible to really check every detail of every work one builds up on, especially when it comes to theoreticians trying to explain data, the actual data analysis and presentation is often a grey area that only after some while clarifies – the way to do it is to find somebody who is familiar with running the simulations, i.e. a specialist who you rely on. You even see this trend in the blogosphere. I am sure you too have encountered people who judge arguments depending on who brought them up, or who seems to support one side or the other. Especially if prominent experts seem to hold a point of view, this suddenly makes the topic very interesting, or gives weight to an argument. From a scientific perspective this seems silly, but for people for whom the actual topic of discussion is too far of to be tangible the reliance on somebodies expert status becomes quite important (you see this very clearly in scientific journalism where they like to quote the ‘experts’)

Such, in the face of increasing specialization and fragmentation of knowledge areas, this trend isn’t surprising. E.g. the details of climate models etc aren’t trivial and I doubt many of the people who argue back and forth about it actually have looked into all the details. It eventually all comes down to the question of a) whether and how the scientific community is able to establish (and communicate) consensus (within the unavoidable uncertainty that should never be neglected, there are always people who disagree) and b) how this knowledge is incorporated into the society (and the political system). And yes, I too do think this is a big challenge.



PS: Thanks for the link.

2. Marco - March 26, 2008

Hi Tommaso… http://www.xkcd.com/401/

3. fefaith - March 27, 2008

This topic of certainty may be summarized with is called post modern era. Is a research based on cuantitave or qualitive reasoning. Over the centuries we have shifted from only a few having access to knowledge, as to knowledge being shared by a wider spectrum of professionals (refered to as experts) and not so widely known pensive minds. Science has always been related to matters that can be reproduced under same conditions for that knowledge to become verifiable and correct. Post Modernism is allowing the challenge of hypothesis and theories to be posted and analyzed in a virtual way not known by ancient scientist. Proofing by exclusion is no longer inconclusive but rather a step further in the direction of truth and reason.
Internet has the power of information dissemination to masses of pensive and analytical minds. Opinions and conclusions are no longer exclusive to the scientific community. It is in the best interest of mankind that relevant matters regarding life and death be handled by the scientific approach, but many other matters benefit with the diversity of opinions and facts inserted by the widely open discussions. Where does one sidebar a topic and assumes scientific research is a matter of individuality.

4. Lenny Sussunkind - March 27, 2008

“Once the foundations are gone, Science is in danger.”

Oh, come on. In danger of what? Anyway, there is nothing new here. People used to get all popperian about quarks, but nowadays nobody in his right mind thinks that there is anything wrong with that. When Inflation was first proposed, nobody had the faintest idea about how it could be “tested” — and now it goes from [observational] strength to strength. Nothing has changed. People see a mystery: what explains the behavior of hadrons? What was the early universe like? Then they put forward a speculative idea, usually without caring whether it can be tested yet. If it looks interesting people will work on it, if it looks boring it will die. Eventually data arrive and you can either kill it or justify further work on it. Similarly Sean Carroll thinks that the extremely non-generic state of the early universe needs to be understood, so he suggests an idea about that; maybe 30 years later somebody will come up with some way of testing it, maybe they won’t. *What is the alternative?*

No real scientist cares about that popperian crap, and the idea that there is some kind of crisis is just a fantasy propagated by journalistic hacks like John Horgan. If you want a more serious approach, I suggest that you read Susskind here:
I particularly appreciated “Throughout my long experience as a scientist I have heard un-falsifiability hurled at so many important ideas that I am inclined to think that no idea can have great merit unless it has drawn this criticism. ” Haha!

5. dorigo - March 27, 2008

Fefaith, I agree if you say science has evolved, I disagree if you claim it is a good thing. The problem is that scientists themselves do not agree any more. It took twenty years to agree on the reality of quanta in the early xxth century: 20 years back then are a small amount of time today if we consider the speed of scientific and technological advancement we have a century later and yet, we have been debating string theory for more time still, and we are on square one with respect to agreeing on the merits and demerits of that theory.


6. dorigo - March 27, 2008

Lenny, I may be old-fashioned, but I prefer to keep an idea in the drawer until it becomes testable rather than going hyper with it and monopolize my research field with something which is not yet science and may well never be. I am not saying we should keep ideas in the drawer, but that with string theory we have not been better off by drawing it out. Please see what I wrote in #5…

7. anomalous cowherd - March 27, 2008

Tommaso wrote:
“I am not saying we should keep ideas in the drawer, but that with string theory we have not been better off by drawing it out.”

I do not understand this point of view. Let’s look at what string theory has done:
[1] it predicts the existence of gravity (experimentally verified)
[2] it provides an ultraviolet complete, quantum mechanically consistent, theory of gravity.
[3] it predicts that the process of black hole formation and quantum evaporation is unitary [ie. preserves quantum mechanical coherence].
(not yet experimentally tested)
For reference, before string theory provided an existence proof for a theory of quantum gravity with this property, Hawking had argued that on general principles such a theory would be impossible [this is the substance of the famous bet with Preskill that Hawking finally conceded a couple of years ago].
[4] For all cases in which the string calculation can be done [which is
a large and growing class, including extremal Kerr black holes from recent work of Horowitz and Roberts], string theory provides a correct microscopic statistical mechanical calculation of the Bekenstein- Hawking thermodynamic entropy.
[5] For the cases in which the string calculation has been done, string theory provides a correct microscopic statistical mechanical calculation of the grey-body factors for black hole evaporation.
[6] For the cases in which the string calculation has been done, string theory provides a correct microscopic statistical mechanical calculation of the microcanonical fluctuations in black hole evaporation.
[7] it provides a solution space of ground states that is large
enough to provide an actual theory that incorporates Weinberg’s anthropic prediction of the cosmological constant. [I really don't like this solution of the cosmological constant problem, but it's the only proposal that I know of that's not obviously wrong so I may have to live with it].
[8] it provides a solution space of ground states that has a large subspace with (a) all moduli fixed (ie. no new long range forces), (b) gauge groups with matter bifundamentals, like the standard model, (c) chiral fermions, like the standard model. And this subspace is sufficiently large that it could plausibly include something as ugly as the standard model. We’ve just started exploring this subspace in the last 3-4 years; we’ll see what we find…
String theory has also led to new methods in relativistic quantum field theories: gauge-string dualities have:
[9] extensively generalized the strong-weak coupling dualities of the Seiberg-Witten type in field constructions. [eg. "brane-box" constructions, "geometric engineering" of field theories, etc. ].
[10] demonstrated holographic dualities (AdSCFT) allowing analysis of strongly coupled gauge field theories by weakly coupled gravity duals.
[11] these holographic dualities have allowed analysis of physical effects in gauge theories in regimes not accessible by any other method (eg. the strongly coupled relativistic fluid that hydrodynamic analysis of RHIC experiments reveals; eg. gravity duals of field theories arising in some condensed matter physics problems).

When you consider these beautiful results, do you really maintain that “we have not been better off by drawing it out”?

8. Jon Lester - March 27, 2008

Dear anomalous cowherd,

For completeness I would also appreciate to know the drawbacks of this approach. Just for comparison. Thanks.

Of course, anyone else that is aware is invited to point out them.


9. anomalous cowherd - March 27, 2008

Jon Lester Writes:
“For completeness I would also appreciate to know the drawbacks of this approach. Just for comparison. Thanks.”

I think that it is fair to say that at the present time string theory has had considerable success in helping us understand quantum gravity, but it has had little success in advancing our understanding of laboratory particle physics. This may come with time, as we begin to understand the “realistic” subspace of the solution space [ie. with all moduli fixed (no new long range forces), gauge groups with matter bifundamentals, and chiral fermions, like the standard model]. But this is a hard problem; string theory is hard to solve, and the solution space is really, really large. Actually a huge solution space is probably not just a problem for string theory, but will be a problem that ANY theory hoping to explain all of the fundamental interactions and elementary particles must solve. Mike Douglas estimates that there is a selection factor of over 10^(150) in getting all the weird fine-tunings and couplings of the standard model right [cosmological constant, hierarchy, strong CP phase, various tiny masses, CKM mixings, PMNS mixings, ...], so we need a solution space larger than that to have any shot at explaining nature. String theory is just the first theory to have to face up to this problem, but any potential alternative we may develop in the future will have to face the same challenges. I’m cautiously optimistic when it comes to probing the string theory solution space. The vacua tend to come [at least in the corner we've probed] in families related by the tuning of a “discreteuum” of quantized fluxes; and with a large number of independent fluxes, even tuning each them over a non-hierarchically large range can result in a huge family of vacua, but with some analytic control over the whole family. If we can get reasonable approaches to the taxonomy of the families, we may be able to make real progress in probing the space of realistic solutions of string theory. Time will tell…

Or as a longer shot, we might get lucky and find, for example, evidence for cosmological networks of fundamental- and D-strings in the stochastic gravity wave background [as advocated by Polchinski].
Again time will tell…

A final thought. String theory is an ambitous project and clearly is a long term endeavour. Like all scientific exploration, success is never guaranteed; but that doesn’t mean that we shouldn’t work hard trying.
At the same time we shouldn’t neglect other aspects of fundamental physics. In particular we have amazing new facilities coming online which will give us experimental/observational data which should revolutionize our field. The LHC turn on is later this summer, and PLANCK and GLAST get launched this year. I fully expect our field to be data driven for at least the next decade or two, and I for one can’t wait to be challenged by unexpected experimental results!

As Ben Lee wrote at the end of the physics reports on Gauge Theories that he wrote with Ernest Abers (quoting Voltaire):
“”tout cela est bien dit, mais maintenant il faut cultiver notre jardin”
I think that in modern american that means that it’s time to shut our traps and get back to work”

10. dorigo - March 27, 2008

Dear Anomalous,

I have to thank you for your insight in the matter. What I know about string theory is not much if I have to be honest: I was never able to read a string theory paper back to back without feeling I was fooling myself. So my opinion on it is of course less worthy than that of insiders as you (or at least you sound like one). For this reason, I read with interest your comments above.
On the other hand, I have to say that if the time scale of theories bringing fruit (like string theory finally getting proven by some experimental test) becomes longer than the average lifetime of a human being, then I have to say no thanks. I may be wrong by saying no thanks, but it reflects my personality and my human weakness: as a person who devolves his life to understanding reality, I feel cheated. I have to be given hope, so to speak, that I am not wasting my time in what I do and in what I try to understand. While string theory appears like a bet I will never cash.

Best of luck to string theorists. I am not saying they should disappear under the carpet. All I am saying is that I am not willing to lend my money to their cause. I might die before I can enjoy the dividends.


11. Peter Woit - March 29, 2008

About “anomalous cowherd’s” 11 arguments for string theory:

1. As Lisa Randall says, “Yeah, string theory predicts gravity: 10-dimensional gravity”

2. This is just not true. Until you actually know what string theory is non-perturbatively, you don’t know that you have a complete, consistent theory that gives 4d quantum gravity.

3-6. Maybe string theory is the current best way to study the quantum mechanical behavior of black holes, maybe not (LQG people disagree). Unfortunately I suspect it will be a very, very long time before any string theory predictions about this can be tested.

9-11. There’s no doubt that string theory provides an interesting way to study some strongly-coupled gauge theories via duality. No one is criticizing theorists for working on this.

Only 7 and 8 deal with the main feature that string theory has been sold as providing: a unified theory that gets us beyond the Standard Model. On this score, string theory has been an utter failure, and the “landscape” is the dead-end that this failure leads to. In 7., even “anomalous cowherd” seems to recognize that there’s something wrong with claiming an anthropic prediction of the CC as a positive argument for string theory. As for 8., I don’t see the point of bashing the Standard Model as “ugly” (I disagree strongly) and arguing that one should replace it with a stupendously complicated and ugly “string theory background”, which predicts absolutely nothing about anything. Both 7 and 8 are not arguments for string theory, but arguments against it. It is exactly this misguided attempt to sell the idea of a string theory anthropic multiverse as not a failure, but a new way of doing science that Tommaso and just about every other physicist recognizes as dangerous nonsense.

12. island - April 1, 2008

I know I am being a bit provocative here. But I have a point: I do see a trend. Humanity faces big challenges in the future, challenges for its own existence. Is global warming a prejudice or a scientific fact ? If we cannot even all agree on something like that, we are bound to extinction. And maybe there is some logic in it.

Or maybe your missing the most apparent point of the logic, which indicates that the conflict of opinion keeps either side from running away in either of TWO diametrically opposing directions of inevitable extinction:


This is highly typical anthropic ecobalance, which is ***self-regulated*** and you can learn all about it, right here:


See also: James Lovelock and Lynn Margulis on planetary homeostasis.

Believe me when I say we have a difficult time ahead of us, but if we are to be prepared for it we must first shed our fear of it. I stand here before you now truly unafraid! Why?! Because I believe something you do not? No! I stand here without fear because I remember. I remember that I am hear not because of the path that lay before me.. but because of the path that lies behind me! I remember that for one hundred years we have fought these machines! I remember that for one-hundred years they have sent their armies to destroy us and after a century of war I remember that which matters most! We are still here!!!

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