Although our analysis of patterns of scientific publication is useful, it turns out that the heat of the string theory controversy does not reveal itself in mainstream scientific journals. Rather, it is predominantly through publicly accessible websites and popular publications that the debate over string theory becomes evident. As such, we will now examine the web presence and popular media presence of the string theory debate. In order to understand how the string theory debate manifests itself on the internet, we will once again use a network mapping approach. First, the Issuecrawler web tool was used to map hyperlinks between websites relevant to the debate. To analyze string theory blogs, the Resseau-Lu software package was used once again, this time in conjunction with Google blog search. To analyze popular publications, we take a more conventional approach, examining a selection of important books and articles.
Above is an Issuecrawler map of websites relevant to the string theory controversy. The map was generated from an initial seed of six websites, mostly blogs and research institutions. Then, the issuecrawler tool searched through hyperlinks on each of these websites, keeping the URL of any site that was referenced by at least two of the seed sites. This process was iterated 3 times, and the results of the final iteration are shown in the map. Nodes represent specific websites, and arrows imply a hyperlink exists from the starting node to the terminal node. Nodes are color coded by domain extension, as summarized in the legend to the right. Finally, the lower portion of the legend displays statistics for the nodes in the graph. Clicking on a node will display the site URL, the number of links found to that site, and the sites in the map which link to it.
While not exremely useful in judging the intensity of the string theory debate, the Issuecrawler map does reveal the different interest groups to which string theory is relevant. On the left hand side of the map we see a cluster of websites belonging to the American Physical Society (APS). Each site is the homepage for a journal or magazine published by the APS. That this cluster appears on the map is expected, as we know from our analysis of networks within the scientific community that new developments in string theory research are often published in these journals. Towards the bottom right corner of the map, we see a cluster of websites belonging to different particle accelerator institutions, such as CERN, DESY, SLAC, and FermiLab. The presence of these sites highlights the expectation of string theorists that their work is useful in predicting the results of accelerator experiments. Additionally, it also reflects the hope of many in the string theory community that experimental evidence for or against the theory will be found. Lastly, in the upper right corner of the map we see a cluster of nodes belonging to space research institutions, such as NASA and the ESA. The presence of this cluster shows that string theorists are quick to apply their theory to the structure of the universe. Issues such as the string theory vacuum problem, the anthropic principle, and black hole thermodynamics - which we encountered previously - confirm this tendency. Thus, we are led to conclude that string theorists expect to find in cosmology possible confirmation of their theory, and that critics of string theory see in cosmological evidence a possible falsification of that theory.
Lastly, there are some nodes on the map which, while not part of any of the clusters mentioned above, are interesting in their own right. First, we see that the website of the Perimeter Institute appears at the bottom of the map. This suggests their importance as one of the pre-eminent groups researching other theories of quantum gravity as an alternative to string theory. Finally, on a more mundane note, we see in the upper left corner of the map nodes representing Flickr, Amtrak, and the New Jersey Transit system. These nodes can be interpreted as artifacts from conference websites, which offer transportation directions and photos of previous events.
Above we have a map of string theory blogs and certain keywords relevant to the controversy. The map was generated using the Resseau-Lu software package. The program used Google to find blogs matching the keywords, and retained the top 50 most relevant results. The blogs are shown as blue circles on the graph, and the keywords as green squares. An edge between a blog and a keyword indicates that that word appears prominently in the blog. Below is a map of the co-occurence of common themes among the blogs retrieved. In this map, green squares signify each blog, and blue circles are identified with common words occuring in the blogs. A connection between a blog and a word naturally signifies that the word is used commonly throughout the blog.
Examining the blogs that appear in the map, we see that they fall into three distinct categories. First, we have general physics news updates, such as Universe Today, the CERN Document Server, and the Physical Review D string theory updates (PRD: String Theory on the map). Second, we have blogs critical of string theory. These range from the openminded Backreaction to Peter Woit's vocal Not Even Wrong, and even the fringe Aether Wave Theory. Lastly, there are the blogs supporting string theory, such as Luboš Motl's The Reference Frame and Shores of the Dirac Sea.
What all of these blogs have in common is that, in addition to whatever stance they take with regards to string theory, they report recent developments in all fields of physics. Most even do so fairly impartially. With regards to string theory however, tone varies widely between the different blogs. The general blogs in the first category tend to be impartial, reporting developments as they come, but not promoting any given interpretation of them. On the critical side, we see a range of styles. Backreaction is rather tame as far as rhetoric is concerned, but still emphasizes the need to consider alternative viewpoints to string theory. Peter Woit's blog, on the other hand, is very harsh in its criticism of string theory. For example, on May 1st 2009 Woit wrote: "It has become increasingly clear to me in recent years that there is a large cohort of people who have so much invested in string theory that they will never, ever give up on the idea of string theory unification, no matter how clear it becomes that the game is crooked and not legitimate science." We see this same dichotomy of rhetorical style on the supportive side. Shores of the Dirac Sea shows its support for string theory only insofar as it is a blog by a string theorist. On the other hand, Luboš Motl's rhetoric is just as heated as Peter Woit's. For example, on August 19th 2006 he states that the claim that string theory makes no predictions is an "extraordinarily dumb wide-spread myth."
In addition to blogs, there have been over the years many attempts by physicists to present a side of the string theory debate to the public. These have mostly taken the form of magazine articles and books. The most significant of these popularizations expressing support for string theory is Brian Greene's The Elegant Universe, published in 1999. It gives a plain-language summary of what string theory was and how it developed. It is not designed to defend string theory against criticism, but rather to kindle in the reader interest in and support for string theory research. On the critical side, the two most significant books are Peter Woit's Not Even Wrong and Lee Smolin's The Trouble with Physics, both published in 2006. These two books attempt to convince the lay reader that string theory should be regarded as a guess rather than a full fledged theory of physics. Both books object to the fact that string theory is not supported by experimental evidence, and both are strongly critical of the notion that string theory is the "only game in town" when it comes to quantum gravity research. Nevertheless, these two books each have a slightly different audience. While Smolin's book is targeted to the same group as that of Greene's book, Peter Woit targets a slightly more sophisticated audience that already possesses some knowledge of physics.
Thus, the preceding analyses makes evident the nature of the debate surrounding string theory. The partisans in the debate are trained physicists, though they choose not to conduct the debate in scientific journals. Rather, they choose to debate each other through public channels. Arguments for or against string theory are not made towards the physicists themselves, but towards the largely nonscientific public. In this way the string theory controversy directly illustrates the role of opinion in scientific decision making. It is not in peer-reviewed journals that the string theory controversy will be settled, but in the realm of public opinion. Thus, we see in the dichotomy between the coolness of string theory journal articles and the heat of the public debate strong evidence for the view that changes in the dominant scientific paradigm are most strongly influenced by non-scientific factors.