Eminent theoretical physicist Lisa Randall regards her new book "Knocking on Heaven's Door" as a "prequel" to her earlier "Warped Passages". But it is much more than that, as a clearly written statement by a distinguished scientist explaining how science works to an interested, if substantially scientific illiterate, public. While there are other books, such as those written by her high school and college classmate, physicist Brian Greene, which emphasize the state-of-the-art thinking in theoretical physics, Randall's is one that still deserves a wide readership, especially for its emphasis on how scientists conduct their scientific research, and in noting how the public often misinterprets it. These aspects of science, and the public's understanding of it, are the most important reasons why "Knocking of Heaven's Door" is an important contribution to popular scientific literature.
The notion of scaling - or rather, scale - is one of the most important concepts which Randall returns to again and again in "Knocking on Heaven's Door". She argues persuasively that, on a macroscopic scale, Newton's laws of motion are still relevant in explaining the motions of large objects such as planets and moons in the Solar System; it is only at atomic and subatomic scales that quantum mechanics does a much better job in explaining motions of subatomic particles. In other words, in plain English, Newtonian classical mechanics has become merely a subset of modern theoretical physics. A similar analogy exists for biology, with regards to the Darwin/Wallace Theory of Evolution via Natural Selection, now subsumed within the Modern Synthesis Theory of Evolution; the latter also incorporates population genetics and some aspects of both developmental biology and paleobiology (As an aside, I also recommend her reminder that evolution denialism isn't a problem only for religious conservatives, by recounting at the end of Chapter Three, an airplane conversation she had with a Hollywood actor trained in molecular biology, an Obama supporter, who rejects the biological evolution of humans since it is contrary to his religious views.).
Probabilistic thought is something which Randall also stresses throughout much of "Knocking on Heaven's Door". While she does not explain probability theory at any great length, she does explain via probability, why science is by very nature, a very tentative process in which there are no clearly defined answers that can be answered in the affirmative or negative with utmost certainty. This very underlying theme is one which underscores her conversations with noted Hollywood screenwriters and New York City dance choreographers that she cites as notable examples of misconceptions about the nature of science widely shared by the public. A firm understanding of probability theory is required for determining risk, which is discussed at length late in "Knocking on Heaven's Door" (Chapter Eleven). In a similar vein, I found equally rewarding her discussion of uncertainty as it pertains to both risk and experimental design (Chapter Twelve).
Most readers will appreciate her extensive discussion on the building and ongoing operation of the Large Hadron Collider at CERN's Swiss research facility. She eloquently ties that into current theoretical models in particle physics and cosmology, as well as to the two overarching themes of scale and probability that the reader encounters repeatedly throughout "Knocking on Heaven's Door". However, as compelling as that discussion is, the reader shouldn't forget that hers is a book which conveys to the general public, the very nature of science as seen through the eyes of this distinguished physicist.