Knocking on Heaven's Door: How Physics and Scientific Thinking Illuminate the Universe and the Modern World [Versión Kindle]

The last few years have seen a proliferation of popular physics books aimed at explaining the mysteries of modern physics to the layman. This is a worthy endeavor and Lisa Randall is one of its leading expositors. This book is really two books in one. The first part is a clear and spirited discussion of particle physics and cosmology. The second part is an equally clear meditation on the nature of the scientific method and the value of science and reason.

Randall especially shines in explaining the real everyday science (as opposed to just the philosophy) behind frontier research in physics. Thus, she spends a sizable amount of time explaining some of the less emphasized practical aspects of the science like errors and uncertainty in measurements, risk factors, "effective theories" (theories applicable at particular scales) and statistics. She provides a readable treatment of the Standard Model of particle physics and emphasizes why finding the Higgs boson is so important. In addition she has what I think is one of the clearest accounts of the structure and function of the LHC in Geneva. In the part about cosmology, she discusses in detail the riddle of dark matter and dark energy and what the latest telescopes and satellites might tell us about the birth and structure of the universe.

The second half of the book presents a robust defense of science and reason as well as some thoughts on the connections between beauty, creativity and science. Randall understands that while mathematical beauty may be a guiding principle for theoretical physics, ultimately beauty is subjective and the only true test of a theory is a clear connection to experiment. Earlier in the book she traces the development of modern science from the seventeenth century, especially emphasizing Galileo's life and his pioneering work in exploring nature through indirect measurements which ever since have been at the heart of scientific investigation. She also touches on the science-religion debate but does not explore it in great detail; she concludes this section by admitting that if you are a religious scientist, you have to at least accept a disconnect in your mind between the very different worlds of science and faith.

In general the book is very well written and Randall's passion for science shines through. The reason I gave it three and a half stars is that it says very little that's new. Randall's discussions of particle physics, cosmology, the LHC and the value of scientific thinking have been explored in great detail by other writers and scientists. In the past few years, Brian Greene, Stephen Hawking, Richard Panek, Ian Sample and John Barrow to name but a few authors have repeatedly treated us to treatments of the Big Bang, particle accelerators, neutrino astronomy, quantum theory, string theory and multiple universes. Is there really a need for yet another book on these topics for the layman, no matter how skillfully written? Plus, while Randall's explanations are reasonably clear, some of these other authors write much more clearly and present cleverer analogies to illustrate the concepts. In my opinion, Randall's book is emblematic of the state of the popular physics literature which seems to have reached a point of diminishing returns; it's become really hard to write a truly new book on the topic without recycling known facts and anecdotes or pitching highly speculative ideas.

On the other hand, there have been a few popular physics books published during the same period that have actually tried to present novel and original work. Examples of genuinely interesting and new thinking would include critiques of string theory by Lee Smolin and Peter Woit, Robert Laughlin's "A Different Universe", David Deutsch's "The Beginning of Infinity" and (while not entirely about physics), Stuart Kauffman's "Reinventing the Sacred". While these books are not all as clearly written as books by Randall, Greene or Hawking, they present fresh perspectives and novel thought-provoking ideas and not just accounts of known science. In my opinion, while books like Randall's do a good job of introducing audiences to contemporary physics concepts, these other authors have done a much better job of disseminating original, groundbreaking material. They deserve to be more widely read and emulated.

Several string theorists such as Brian Greene or Leonard Susskind and cosmologists such as Alexander Vilenkin have written popular books about physics but as far as I know, Lisa Randall is the only popular writer among the "high-energy phenomenologists", i.e. the theoretical particle physicists who think about Nature from the viewpoint of phenomena that have been observed or that may be observed in a foreseeable future (mostly at the particle accelerators).

And we, the readers, have been especially fortunate because the book about physics from the viewpoint of phenomenologists wasn't written by a random phenomenologist but by one of the most prominent ones. In fact, Randall was identified as the most referred to particle physicist - among both women and men, just to be sure - in a recent 5-year period. She remains extremely active and influential.

Knocking on Heaven's Door has two basic goals. One of them is to introduce the reader to the cutting-edge research in particle physics which is dominated by the LHC experiment. Collisions of protons inside the 27-kilometer ring on the Swiss-French border have interrupted decades of theoretical dominance and relative experimental impotence (even though the book describes some smaller colliders or LHC predecessors, too). Randall who constantly interacts with the experimenters offers us an exciting story of the LHC collider from its conception to the first femtobarn of collisions.

We learn how it was built, what it is composed of, how it accelerates the particles nearly to the speed of light, how it observes the products of every collision (in the detectors such as CMS and ATLAS) and identifies the particles that are born in the collisions, and how the resulting huge amounts of data are being processed by computers and statistical techniques to learn something new. However, we also learn many things about the human factor: who are the people who work there, how they interact with each other, how they assure their colleagues that they're right, what they like to cook, how the Americans differ from the Europeans, and so on. I am not aware of a competing book written in plain English that could give you the feeling of being an LHC insider. And the book covers not only the colliders but also experiments trying to detect dark matter on Earth and many others.

But the book has another, grander goal which is nothing less than to clarify how scientists actually think. Philosophers would call these issues "gnoseology" or "epistemology" but the content of their thoughts would be less tangible. Instead, Randall talks about the actual strategies and issues that are important and misconceptions that the laymen often believe. One of the key methods to organize our knowledge is the concept of scale: different basic objects and "effective theories" describing their mutual interactions are being used for different sizes or, equivalently, different energies per particle. For a particle phenomenologist, and not only for her, the laws of physics resemble a giant onion. The laws relevant for longer scales may in principle be derived from those at shorter scales. But the former are independent of many details of the latter and it is often useful to think about them independently.

These initial chapters about scale are no random musings. They're the essential skeleton on which particle physics (phenomenology but not just phenomenology) organizes the insights from the experiments such as the LHC. A related question is what it means for our knowledge to expand. The book does a very good job in explaining that the theories we typically use are approximate and aware of their own limitations; on the other hand, it means that when new phenomena and better theories are found, the older theories are not completely eliminated.

Randall's book also talks about non-physicists (in many cases, famous people from all walks of life whom Randall has met or whom she knows very well), their way of looking at the physical phenomena, and what a physicist finds funny about this looking. One example is the relationship between science and religion: Randall, who is obviously an atheist, doesn't stay on the surface. She is not satisfied with claiming that "religious people are silly" which is what many other books do (with a great commercial success) but she also tries to find the core differences. One of the major lessons is that scientists are able to live and work with ignorance or uncertainty about a particular issue; in fact, they view it as a part of their knowledge (especially if they know rather accurately where their knowledge ends). This point is often misunderstood by other self-described atheists whose thinking is actually religious and dogmatic in character.

For another example, a chapter is dedicated to the LHC doomsday scenarios which assume (or attempt to "prove") that the collider will create a black hole or another lethal object that will devour our blue planet. The book explains several different levels of evidence we have to be sure that such a catastrophe won't happen.

I forgot to say that the book also covers theoretical models (which are the focus of her first book, Warped Passages) that are being tested by the LHC, including the models with supersymmetry and especially extra dimensions for which Randall (and Sundrum) became particularly famous. The Higgs boson gets its well-deserved chapter as well. Randall compares the phenomenological, bottom-up approach to physics with the top-down approach favored by string theorists.

To summarize, it is a book about some very exciting and specific experimental developments that are underway combined with all the infrastructure one needs to place these experiments into their proper place and to interpret them correctly. Highly recommended to everyone who doesn't want to lose touch with particle physics and any cutting-edge science as of 2011. Randall is a multi-dimensional personality and so is her book: but I am confident that most readers may find a lower-dimensional projection of the book that will enrich the way how they look at the world.

I am a working physicist, 30 years past my Ph. D., and I picked up this book thinking it would be interesting to learn about progress in particle physics and cosmology. I was very disappointed. The meat of the book is Chapters 16 and 17, where Prof. Randall finally gets to describing the theory behind the Higgs boson and other anticipated discoveries from the LHC. These are so poorly written it seems like her editor just figured, "no one will understand this, so why bother trying to make it readable." The sentence structure is convoluted to the point that, even with multiple readings, it's impossible to tell the point she's trying to make. She throws around terms like "weak charge" without ever bothering to explain whether this quantity is a weak version of the electric charge or an analogy of electric charge that conveys the weak force. She frequently makes reference to the Planck length, without ever saying what it is, where it comes from, or how to translate between distance and energy, which she uses interchangeably.

This weakness is illustrated by her explanation of the possible applicability of extra dimensions to explain the 16 orders-of-magnitude difference between gravity and the weak force, one of the few contributions she takes personal credit for. You could just say, "the forces are of different strengths" and leave it at that. Randall says, in essence, "Imagine gravity is 10^16 times stronger on another brane in another dimension, but that dimension is coupled to our world by an arbitrary coupling constant of 10^-16." This adds nothing of intellectual value to the field, but the buzzwords have been used, so it's time to schedule a book tour and let the accolades roll in.

Now, of course, there may be some actual content to her brane theory, but, my point is, you won't find it in the book, which is, therefore, a waste of time.

The balance of the book is devoted to a description of the design of the LHC (which, as near as I can tell, is nothing more than a yet-bigger and more expensive synchrotron, an accelerator that hasn't had its fundamental design changed in 60 years) and a travelogue of her VIP tours of various physics sites and parties. I learned a lot more from "The 4 percent universe: dark matter, dark energy, and the race to discover the rest of reality" by Richard Panek. He focuses only on cosmology, but does a reasonable job making his material clear.

Skip it.