After the incredible response to two of our recent posts (Krauss on Intelligent Design, Religion (and String Theory); and From the Sublime to the Ridiculous), Sean, JoAnne, Clifford, Risa and I asked Lawrence Krauss if he would be interested in submitting a post summarizing his views on the issues raised regarding string theory, religion, and the popularization of science. Lawrence is an extremely well regarded member of the physics community, whose research, popular writings and remarkable efforts to defend science against pseudoscience and political distortion have earned the respect of all of us. We were therefore delighted when Lawrence agreed to make time to do this and we welcome him as Cosmic Variance's first guest blogger. We look forward to a high level of discussion regarding this post and, since it might need saying explicitly - keep it polite please folks! Here is Lawrence's post. __________________________ The contributors asked me to write and clarify some of my thoughts, especially since in one way or another I, and my writing, have been the subject of a few blog threads. I have already tried to respond; eventually hopefully clearly, within the threads to the concerns, but perhaps a single reasonably cogent monologue bringing some of these ideas together may be worthwhile. We will see: On popularizing: the most important thing to attempt to get at is the difference between what we know, and what we don't know; and how we can tell the difference. On String Theory: A mammoth and very deep and original enterprise which, to date, has not been particularly successful, in my opinion. While string theory has been a fruitful stimulation of new mathematical ideas, as a search for physical theory it hasn't been productive. This is not to say that it one day will not be so. It simply hasn't achieved the goals it originally had, and thus far has not been able to make contact in any useful way with either experiment or observation, nor has it yet explained any of the fundamental theoretical puzzles that drive particle physics. Is it interesting? Yes! Should theorists continue to investigate it? Yes! Might it be of vital importance if it leads anywhere? Yes. Is it worth talking about to the general public? I am not sure. As a study in the kinds of things that physicists sometimes like to think about, and why they think about them, yes; and that is what I have tried to talk about in my most recent book, and no doubt others have as well. As a demonstration of what is likely to be the underlying reality beneath what we observe in the world today, no; namely I personally do not think there is any compelling evidence that these ideas are going to be correct. Nor do I think it fair to place the large set of ideas that are currently being explored under the single banner of a "theory". What seems clear is that as these ideas are explored in greater depth, the mathematical complexities increase and the possible connections to the world we measure seem to have decreased. I don't know where things are headed, but frankly I see no reason for great optimism. And, as I try to emphasize to popular audiences, it is important to realize that most theoretical ideas, even great ones, are wrong. So in some sense it is important to keep that fact in the back of one's mind whenever any new ideas are being discussed. The good news is that ultimately science has been able to determine which ideas are wrong, and one hopes in the case of string theory this might be possible too, although, as Ed Witten himself has pointed out, it may turn out to be impossible for string theory to make any contact with the measurable world. It is also vitally important that those who are going to devote most of their productive years trying to work on an idea have faith that it is going to pan out. There is nothing wrong with that - it is required to keep up one's motivations - but it might not pan out. That is the way it goes in science. It was in this context that I think the example of the dual-string model and QCD, which so irked Clifford, is relevant. It is not to make fun of infinities; rather it (a) demonstrates some of the subtleties of mathematics, which lord knows is a difficult subject to try and popularize, and (b) it illustrates what I said in one of the blog comments, namely "My point was not to use infinities to argue against anything.. but to point out that canceling infinities, as the dual-string did, was not by itself a guarantee that it was right, but that a completely different theory ended up coming along and replaced it.. as could easily happen again... I didn't use it to argue that anything was flawed.. but merely that it is a mathematical problem that needs to be solved, but not every solution of it needs to correspond to reality." On String sensitivity: I understand that young people who currently work on string theory probably feel that they work under an undue burden, placed upon them by the original hype associated with the remarkable results in the mid 1980's, which has continued and sometimes escalated since. I also understand that they may be entranced with various aspects of the ideas that have been developed. That is fine. But it simply is not yet on a par--in almost any sense--with any of the other significant, successful, and well-defined theoretical and experimental developments in physics in the past century. That is neither a bad nor a good thing; it is a fact. And relating one's own excitement is fine, and good, but it should be tempered with a dose of realism, especially when discussing things to a popular audience, which cannot discern science from pseudoscience in general, much less the finer details of particle physics. It is bad for science to give the impression that we know more than we do. Moreover, I hope this explains some of the sensitivity of others who do not work on string theory - namely, there are truly great and wonderful developments in theoretical and experimental physics that have simply been far more important and successful at describing nature and which have, in addition, led to technological advances. There have also been concrete discoveries, like dark energy, that are astounding and about which we currently have no clear understanding, so that other areas where we may have little understanding, such as the inconsistencies between GR and quantum mechanics, while important, are perhaps not the most overpowering immediate concerns. On Extra Dimensions: I continue to remain neutral, if skeptical, here. While the notion of large undetectable extra dimensions is fascinating, and the fact that they can exist and have remained undetected is really fascinating, my own impressions, based on my understanding of particle physics data, is that they don't smell right as a solution of the hierarchy problem. The apparent unification of couplings, large top quark mass, etc, provide at least suggestive evidence to me that there really is a large scale involved in unification, and also that supersymmetry seems to be suggested at some level. The research I did for my new book also made me frankly more skeptical from a theoretical perspective as well; namely, if I think about what the ground state of M-theory might be, the likelihood of some single, relatively isolated, relatively flat brane on which we live existing embedded in a higher dimensional and large space, seems unlikely to me. But we shall see. On ID and Science: As many of you know who have followed any of my writing in this regard, the reason I took up this cause a bunch of years ago, and have spent many unfortunate hours defending science against attacks rather than doing what I prefer to do, which is getting people excited about science, is that I viewed the attack on evolution as an attack on science as a whole. The more I learned, the more I saw this as a campaign that was based on fear of the fact that God is not an explicit part of the scientific method. For some, this implies that science itself is immoral, and if you read much of the literature, in particular from the Discovery Institute, you will see this expressed explicitly. I also saw this campaign as not merely one by well-meaning but misinformed individuals, but rather by people who were very well schooled in public relations, who had a mission, and wanted to achieve it however possible. And since scientists, by nature, tend to be miserable at public relations, it seemed important to try and counter this in whatever ways possible. My own awareness for the necessity of being respectful of religious beliefs has increased tremendously during this process. It has also become more clear to me that scientists tend to, whether they want to or not, appear patronizing about this, and also tend to make the philosophical leap from the fact that science deals with natural causes and effects to the statement that there can be no purpose in the universe. Whatever one's personal perspective on this, and I see no evidence for purpose myself, this is a personal philosophical or religious notion, not a scientific one. In my piece in the NYT in May - the one that provoked the wrath of the Cardinal, Archbishop of Vienna - I used the example of Lemaitre and the Big Bang to point out that science functions independently of questions of purpose. Now, how does all of this relate to string theory and the source of all the concern in one of the blog posts and the resulting comments? Well; it is the point I mentioned at the end of one of them, when responding to Clifford. I paraphrase: "the context in which I referred to ID was actually to make a point that I am beginning to think is actually relevant... namely that when physicists refer to 'string theory' it is in the context of 'field theory'... namely as a technical replacement of one physical and mathematical framework for dealing with relativistic quantum mechanics with another.. but unfortunately in the context in which we complain about IDers saying Evolution is 'just a theory', the popular use of the term string theory is unfortunate.. because 'string theory' is not a theory in the context in which we claim evolution or general relativity is... i.e. something that has been tested time and again against experiment and observation.. calling it the string hypothesis would not be inappropriate in this sense.." Unfortunately, string theory and extra dimensions are often held up as examples of science being indistinguishable from religion. I have tried, even in my last NYT piece, to explain some of the differences, but in a statement I made elsewhere that got someone very upset, I do believe that saying, other than tongue-in-cheek, that the current ideas are so beautiful that they must be correct--without any recourse to empirical data, is almost indistinguishable from religion.