Why Does E=mc2?, Paperback book

Why Does E=mc2?: (and Why Should We Care?) [Paperback]

by Brian Cox and Jeff Forshaw

3.00 out of 5 (8 ratings)

The Perseus Books Group 
Publication Date:
04 March 2010 
Popular Science 


This is an engaging and accessible explanation of Einstein's equation that explores the principles of physics through everyday life. Professor Brian Cox and Professor Jeff Forshaw go on a journey to the frontier of 21st century science to consider the real meaning behind the iconic sequence of symbols that make up Einstein's most famous equation. Breaking down the symbols themselves, they pose a series of questions: What is energy? What is mass? What has the speed of light got to do with energy and mass? In answering these questions, they take us to the site of one of the largest scientific experiments ever conducted. Lying beneath the city of Geneva, straddling the Franco-Swiss boarder, is a 27 km particle accelerator, known as the Large Hadron Collider. Using this gigantic machine - which can recreate conditions in the early Universe fractions of a second after the Big Bang - Cox and Forshaw will describe the current theory behind the origin of mass. Alongside questions of energy and mass, they will consider the third, and perhaps, most intriguing element of the equation: 'c' - or the speed of light. Why is it that the speed of light is the exchange rate?Answering this question is at the heart of the investigation as the authors demonstrate how, in order to truly understand why E=mc2, we first must understand why we must move forward in time and not backwards and how objects in our 3-dimensional world actually move in 4-dimensional space-time. In other words, how the very fabric of our world is constructed. A collaboration between two of the youngest professors in the UK, "Why Does E=MC2?" promises to be one of the most exciting and accessible explanations of the theory of relativity in recent years.

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  • This was a great book for anyone that wants to understand physics just a little bit better. The author takes you through most of the detail of how Einstein came to the conclusion of E=mc^2 without having to walk through the âtough mathâ.Iâve read tons of books like this one but this is worth the read. I was most impressed with the fact that they really did walk you through the concepts without having math harder than the Pythagorean Theorem. If you understand that you can understand this book.The book had took you to the brink of the universe and brought you back to the inner workings of the atomic nucleus. I will be keeping this hard cover book on my bookshelf for years to come.

    5.00 out of 5


  • Cox and Forshaw have presented a streamlined, focused popular science book aimed at teaching relatively new science readers the basics and history of the famous equation in the title. While experienced physics readers will not likely learn new information, the book offers an approachable description of relativity, how we know it works, and why it is important in the modern world and beyond.While I personally didn't gain much new from this book (as an experienced non-professional physics reader), I believe new readers could be in for a treat. I'd certainly recommend starting a discovery of relativity with this book if the concept seems difficult. The authors take time to explain various concepts and make solid efforts to present reasonable analogies to aid in the explanation. Combined with a singularly-focused subject, the book is an excellent starting point for curious, intelligent readers wishing to know more details about E=mc2. Four stars.

    4.00 out of 5


  • This book is yet another popularized explanation of Einstein’s theory or (as the authors explain) theories of relativity. It is also one of the best available. Its special merit lies in the fact that it actually uses equations. The so-called “special” theory of relativity defines how observers moving at constant velocity relative to one another observe the same events. The theory begins with the assumption that the speed of light is a constant, no matter what the velocity of the light source. That assumption was originally derived from Maxwell’s equations of electricity and magnetism and subsequently verified experimentally by the famous Michelson-Morley experiment. From this assumption, the theory concludes that for different observers moving relative to one another, measuring rods shrink, clocks slow down, and the mass of all object increases as their velocity increases. Moreover, these conclusions can be derived with mathematics no more complicated than college algebra and the Pythagorean Theorem. Einstein was troubled by these conclusions. He wanted to know what laws of physics were truly invariant, no matter how different observers moved relative to one another. In fact, he thought the theory of invariance was a better name for his conclusions than the theory of relativity. To make sense of these calculations, which have been verified numerous times by experiment, we must assume that space and time are not separate entities, as we formerly thought, but are inextricably meshed together in a single entity now called space-time. The authors then demonstrate the consequences of the law of the conservation of momentum, expressed in space-time. Remarkably, by teasing the relativity equations regarding length, mass, and time in light of the conservation of momentum, the famous E=mc² pops out almost like magic! The conclusion that energy and mass are equivalent and related to one another in a very precise ratio is completely unexpected and profound. To the authors’ credit, they do not insulate the reader from the relatively simple math used to derive the theory. The reader’s appreciation of the profundity of the theory is greatly enhanced by following its mathematical derivation. When it comes to the general theory of relativity, which deals with systems accelerating relative to one another and explains the phenomenon of gravity as the localized curvature of Minkowski space-time, the math becomes much more difficult—it took Einstein ten years of intense effort to figure it out. I’ve seen the math in technical journals, and it is far too daunting for the average reader such as me. The authors mercifully omit that math, but point out that the theory ultimately was derived from the observation that objects fall at the same speed (unless differentially affected by air friction). The book also includes a chapter on the origin of mass, which takes us away from relativity theory into the realm of quantum mechanics. The math here is very difficult, but the authors simplify matters as much a possible by using Feynman diagrams. This is a well-written book for the curious layman with a mathematical bent who wants to explore modern physics.(JAB)

    4.00 out of 5


  • As a layman who is interested in Physics and finds some books too technical and many others lack of precision and depth, I found this book brilliant and very helpful. It is an easy-to-follow popular science book, yet more profound than that. <br/><br/>Most of all, it isn't a book that just throws out "facts", results and theories towards you. It gives the readers an opportunity to looke into minds of the great, to think like a physicist and to understand how theories of Relativity and some other scientific ideas came into being. <br/><br/>Finally, aided by this book, I came to understand Einstein's theories of Special Relativity in detail. It really has given me more insights into this subject than any other book I've read on the same topic. <br/><br/>The only thing that left me somehow unsatisfied, is its brevity on theories of General Relativity, of which, the book only explains its concept. Although the mathematics should be difficult, I'd really like to learn more, by following a similar way that this wondeful book has guided us through previously.

    4.00 out of 5


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