Why String Theory?

by Joseph Conlon

Physics World's 'Book of the Year' for 2016 An Entertaining and Enlightening Guide to the Who, What, and Why of String Theory, now also available in an updated reflowable electronic format compatible with mobile devices and e-readers. During the last 50 years, numerous physicists have tried to unravel the secrets of string theory. Yet why do these scientists work on a theory lacking experimental confirmation? Why String Theory? provides the answer, offering a highly readable and accessible panorama of the who, what, and why of this large aspect of modern theoretical physics. The author, a theoretical physics professor at the University of Oxford and a leading string theorist, explains what string theory is and where it originated. He describes how string theory fits into physics and why so many physicists and mathematicians find it appealing when working on topics from M-theory to monsters and from cosmology to superconductors.

Genres: Science, Physics, Nonfiction, Popular Science

260 pages, Paperback

Published January 5, 2016

About the author

Joseph Conlon is professor of theoretical physics at the University of Oxford and a teaching fellow of New College, where he has been since 2012. His scientific research ranges across string theory, particle physics, cosmology and astrophysics and his 75 scientific papers include foundational contributions to these subjects.

He was a three-times British junior chess champion; a precocious childhood led to him finishing his first mathematics degree at 18, done part-time along schoolwork.

Along with his physics research, he seeks to communicate the transcendently deep and beautiful ideas of physics in the language they deserve. He is the author of Why String Theory? (CRC, 2015), a defense of the broad and enduring intellectual value of string theory, and the upcoming Origins (Oneworld, 2024), a verse account of the early universe.

Photo credit Philippa Sims.

Reviews

[Brian Clegg · Rating 4 out of 5]

If, like me, you've tended to think of string theory as a way that applied mathematicians and theoretical physicists can have endless fun without ever contributing anything practical to our understanding of the universe, Joseph Conlon's is a useful book to remind us that string theory isn't quite so unlikely and useless as it can seem.

I must admit I've been strongly influenced by anti-string theory books such as Not Even Wrong and The Trouble with Physics. After reading Why String Theory? I have a more balanced view (if still being pretty doubtful of the theory's value). One thing that Conlon does, which I've never never seen elsewhere, is give a detailed description of it how the theory came into being, including the original, 26-dimensional approach that was an attempt to deal with the strong interaction. When this was trumped by quantum chromodynamics, it was almost as if the string theorists were so enamoured with their theory, which has some mathematically beautiful aspects, and a tendency to suddenly fit quite well with other mathematical constructs in physics, that they seem to have a spent a lot of time thinking 'Okay, what can we do with it?' And apart from the possibility of quantum gravity, it's remarkable in how many places it seems to have offered some use, despite its infamous lack of testable predictions to whittle down the vast numbers of potential solutions.

I won't say that this is an ideal popular science title. Like Not Even Wrong, it constantly throws out material that you just have to take the writer's word for being meaningful. It's not that there's heavy maths - there are pretty well no equations - but there's an awful lot you have to take on trust, or glaze slightly as meaningless (to the reader) terms are thrown at you. This isn't helped by a style that sometimes reminds me of a elderly schoolmaster (I was amazed that the author is considerably younger than me) with examples like referring to a person's bottom as a 'derrière' (something my grandma might have done) and throwing in 'crossing the Rubicon of physics' occurring within 2 lines of each other. I'm surprised their weren't Latin tags. Elsewhere we get 'I will, for now, let sobriety be the better part of speculation and be silent whereof I cannot speak...' Note that this is while calling pre-Big Bang ideas 'bad speculation' because they're not based on observation - unlike string theory?

There's also a touch of iffy history of science (we are told that Gell-Mann named the quark after a word in Finnegans Wake, for instance, where it was only the spelling that came from there), and the author rather sneakily compares string theory to astronomy as being 'pursued for the value of intrinsic understanding' rather than anything so grubby as commerce - but doesn't note that at least we know that what astronomers (as opposed to cosmologists) study exists. (Not to mention Conlon being unnecessarily sniffy about practical applications.)

However, I do still recommend this book for everyone who wants to get an up-to-date picture of the state of string theory with a lot of background, and is prepared to take the rather heavy approach, lacking much of an attempt to explain things in words most of us can understand. If, like me, you've tended to the anti-camp, this title (sadly, priced more like a textbook than a popular science title) is a very valuable antidote.

[Dedi Khana · Rating 5 out of 5]

This book is not for a laymen person book. Not even for college student with basic engineering and physic background. It required the reader to familiarize with the concept of general relativity, higher algebra, differential manifold, and so on. Its a good book though for anyone interest in superstring theory beyond the popular science jargon.

[Manuel Del Río Rodríguez · Rating 4 out of 5]

Enjoyability: ★★★★

This is a popular physics book, so, provided you are interested in string theory, it is a very enjoyable read. It is substantially more demanding than, say, The Elegant Universe, but still accessible to the interested lay reader, even if some parts are dense and you sometimes have to take the author’s word for his claims.

Enlightenment: ★★★★

Again, I am not a physicist, but I find no reason to doubt the claims in the book, and the author seems pretty humble and willing to recognize limitations and other points of view on the topic, which he illustrates, along with some self-deprecating humor. I already knew the basics of string theory, but this book expanded and clarified my understanding of the areas where it is now being applied, and what for.

Originality: ★★

I don’t think it is very original, but I think this label is mostly worthless except for scientific or literary texts that have massively changed their fields. Within the narrow range of “popularizations of string theory and the arguments in favor of it”, this is one of the books I know that shows greater scientific rigor and broad-mindedness, though at the cost of accessibility.

Cultural weight: ★★

Again, this label doesn’t really apply to this type of book. Why String Theory? was published about eleven years ago, so fairly recently, and I suspect it was meant to be a rebuttal of the rising trend since the noughties, seen in the media, the press, and in popular books by Smolin, Woit, and Hossenfelder, to disparage the field. I have no idea how successful it was at this.

*The Rise and Fall of Strings in the Popular Imagination*

If, in the mid-to-late nineties, you were a curious kid trying to get a popular explanation of cosmology and particle physics, you would likely have been shepherded towards, or simply found yourself stumbling upon, books like Hawking’s A Brief History of Time and Weinberg’s The First Three Minutes. In 1999, Brian Greene published The Elegant Universe. String theory was the hot new thing, at least for us pop-science readers, and promised to unify the four forces by incorporating gravity into the mix. Also, the metaphor of vibrating, resonating strings as the most elemental constituents of matter had a certain aesthetic appeal.

The 2000s, though, also brought to the fore an increasing degree of contestation and disagreement within the discipline, which also managed to percolate into popular science. That trend has continued to grow and spread with the passage of time, and with the apparent lack of progress in turning string theory into something that more conventionally fits the traditional view of a branch of science: that is, one with testable hypotheses that are falsifiable through experiments. As we are passing the meridian of the twenties, I’d say it has now become commonplace in the popular imagination to perceive string theory as at least a partial failure. Just to pick on one example from “the learned public,” Rationalists tend to treat the whole field with some contempt, as testified by podcasts and blog posts you can easily check up on.

The book we are reviewing today was published in 2016, and I guess was meant as a response to the common criticisms of string theory. I think it does a very good job at that, but I should disclaim that I have a favorable bias towards the area, so it is no surprise I found it convincing.

*Contents*

The book is pretty short — about 236 pages of actual text — and consists of fourteen chapters organized into four sections.

Section I, “Why?”, sets up familiar ground for those who have read popular books on modern physics. We get an overview of how we arrived at modern physics and of the “big lessons” that twentieth-century science has discovered about nature: that space and time form an inseparable whole; that spacetime is dynamical, as follows from Einstein’s theories of relativity; that quantum mechanics is the best theory we have for describing the world, with unimaginably precise experimental verification; that quantum mechanics and general relativity are inconsistent with each other; that nature exhibits many symmetries; that the universe began as a smooth, hot state very different from the present one; and that nature often unifies things that originally appeared separate.

Section II, “What?”, gives us a short history of string theory: its origins as an attempt to explain the interactions of the strong force, its repurposing as a quantum theory of gravity, its different “revolutions” and transformations, and how it has developed from the idea that particles are little vibrating strings into a broad framework connected with quantum field theory, extra dimensions, dualities, branes, and landscapes. It does so in quite accessible, not overly technical terms.

Section III, “What for?”, is the meatiest and most significant part of the book. Starting with a self-deprecating joke — a one-line chapter about the experimental evidence for string theory, included only to say that there is none as yet — the author presents different and quite appealing arguments for why string theory still proves its value for theoretical physics and other disciplines. We get a chapter showing its value to people working in quantum field theory, as the AdS/CFT correspondence discovered by Juan Maldacena makes calculations in some models much easier by using their dual, higher-dimensional gravity models. In mathematics, string theory has generated unexpected connections and insights, mostly involving topology and algebraic geometry, starting new areas such as mirror symmetry and making connections to number theory through monstrous moonshine. In cosmology and particle physics, the author’s particular area of expertise, it gives a natural home to ideas such as extra dimensions, moduli, axion-like particles, and possible mechanisms relevant to the early universe. Finally, in quantum gravity — its eventual home, rather than its original birthplace — it provides one of the few frameworks in which problems such as black-hole entropy and singularities can be addressed in a controlled way.

Section IV, “Who?”, starts with an exploration of the different types of physicists and their intellectual temperaments, and goes on to deal with some criticisms of string theory, which Conlon tries to refute. It then closes with some final arguments rounding out the reasons why string theory remains valuable in general, and why it is much better than its alternatives in quantum gravity in particular.

*Assessment*

Overall, I was pretty happy with the book and would endorse it enthusiastically. I found it reasonably easy to follow, although at times it becomes excessively technical for a completely lay audience. As I’ve mentioned from the beginning, I am not a physicist and stopped studying the subject in high school. I have read a lot of popular physics, though, some of it pretty dense, such as Schumm’s Deep Down Things, and I was still mostly capable of going along for the ride. The Elegant Universe was more accessible, though.

The author uses a lot of humor of a type that some reviewers I’ve consulted dislike and find pedantic and old-fashioned. Perhaps because I myself am pedantic and old-fashioned, I found it enjoyable. More importantly, I valued the modesty and informativeness of the book very highly. Conlon makes a compelling argument for the value of string theory and for the changes in focus it has undergone over time. He recognizes its limitations and can be quite critical of some of them, but ultimately makes a good case for string theory having survived as a field not because of hype or field capture, but because it continues to produce fruitful structures and deep connections between areas of physics and mathematics that would otherwise seem unrelated, and that can’t realistically have come out of the blue.

I leave the book with some surprises, mostly that the importance of string theory as a quantum theory of gravity is apparently now rather minor as an area of string-theory research, but also with slightly increased confidence in the field. I will have to test that confidence against more critical reads in the future, though. And if I could ask the author one question, I would ask whether, a decade after publication, the arguments in the book would need any tweaking.

[Richard Marney · Rating 4 out of 5]

Even I understood much of the book, and was able to explain parts afterwards to a physics professor without embarrassing myself. This is a testament to the clarity of the writing and the author’s knowledge of the topic.

[Reinosuke Kusano · Rating 4 out of 5]

"Why string theory?" is an interesting introduction into the history, motivation, and justification of one of the most prolific areas in theoretical physics. Conlon writes in a very approachable and understandable manner that highlights his love for the theory well, and successfully embeds the context of his work into the overall scientific landscape of the past and present.

However, while certainly not lacking in terms of content, this book makes me wonder slightly what demographic the author was actually writing for. Conlon makes a point towards the Introduction, saying that "the great structure of physics... is part of the inheritance of all interested minds". While completely true and valid, what I felt most from this book was that it is more or less impossible to write an introduction to string theory which satisfies "all interested minds"; the volume and difficulty of the content is far too heavy for an amateur physicist or someone casually interested in physics, neither is it rigorous or elucidating enough for a trained physicist. In fact, to the extent that I recall from the work, the sole equation given in the book is the five loop calculation in the super Yang-Mills theory, in relation to the AdS/CFT correspondence. While the lack of equations is to an extent understandable, it inevitably inhibits a more trained reader from truly understanding what makes string theory beautiful.

[Boštjan · Rating 5 out of 5]

I've always been fascinated by fundamental physics and string theory in particular. I've read about 10 books on the subject before dealing with this one.

The author has a good ability to explain the big lessons of modern physics and why our current theories, despite their incredible success, are incomplete. He's of the younger generation and his writing is compelling and interesting.

I also started understanding the gist of the AdS/CFT correspondence of Juan Maldacena. THat's why I love reading books like this in succession - each one, despite discussing the same topic, offers a new perspective for me and one of them "clicks" with me and then I get a deeper understanding of it!

Conlon’s writing is also witty and remarkably accessible. He uses brilliant analogies (comparing coupling constants to different types of human interactions) and a conversational tone that makes complex concepts digestible. He admits where analogies break down and where the math would say more, but he never lets the lack of equations hinder the flow of ideas.

It is a masterpiece of science communication. It doesn’t just explain what string theory is, it explains why it is a compelling, useful, and deeply fascinating human endeavor. It turned my skepticism into a genuine appreciation for the subject. Whether you're a student, a scientist in another field, or just a curious reader, this book is an essential and immensely rewarding read.

[To Chin · Rating 3 out of 5]

Focuses more on historical development.

[César Echevarría · Rating 5 out of 5]

Format audiobook

[Liam Connolly]

Answer: because

[Stephen Perrenod · Rating 4 out of 5]

It requires some familiarity with particle physics and/or physics more generally to appreciate this book. I have such familiarity, including some with string theory, but I felt at the end that he had not fully made the case. His coverage of the history and evolution of string and M-theory was excellent.

[RabidAnt · Rating 4 out of 5]

Good popular science. Some intriguing details. Enjoyable read. Highly recommend.

[phùng uyên · Rating 4 out of 5]

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