Customer Reviews

Why Does E=mc2?: (And Why Should We Care?)

5 star:		(30)
4 star:		(13)
3 star:		(7)
2 star:		(5)
1 star:		(5)

 

 

Cox and Forshaw have presented a streamlined, focused popular science book aimed at teaching relatively new physics 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 a reasonably experienced non-professional physics reader), I believe newer 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 points, and offer solid presentations and 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.

It's a great feeling to come back tired from work and pick up such a book. After all, like most people I rarely have time to ponder seriously about the universe and the meaning of time and space.I am a high school French teacher so my training in science is rather limited. But after a few hours spent thinking about time,space, distance, energy and matter with Cox and Forshaw,I felt enlightened and rejuvenated! It really read like a thriller, whenever I put the book down I could not stop thinking about it and at dinner I could not shut up about it. The more my friends asked me questions about what I read the more I felt like going back and re-reading until I could explain it in my own words. Now that I am done with it, it's haunting me, driving home or playing with my cat; it keeps me thinking...

I read Professors Cox & Forshaw's new book on Einstein's E = mc2 in one day: I couldn't put it down. I have tried for years to get a handle on the equation and how to think about spacetime, have read many books for the lay public (I am a psychiatry professor, so I am a layman when it comes to physics) -- and this new book is the only one that I could grasp and that really made sense. It's a great tribute to the authors and a great service to the public.
Michael H Stone, MD

The authors do a good job of describing the role on invariants in physics, and for that I am grateful.

However the way the choose to simplify the math and science created more confusion for me than light.

Their decision to not state the underlying formulas directly but instead to explain them in words required the authors to spread the formulas out over page after page making them unnecessarily difficult to follow. You cannot go back and review an equation because you can't find in buried in the text.

Page 22 is a good example of unnecessary explanation. It requires the entire page to laboriously explain that x, y,and z are variables. (Do the authors really believe someone would buy a book with the title E=mc^2 if they did not understand the concept of a variable??)

Minor point are belabored while major shifts are completely unexplained. For example, on page 80, the authors explain invariants in terms of the radius of a circle, all points on the circumference are equal (invariant) distance from the center. They explain that when this model is applied to space-time, it violates Cause and Effect. The explanation is enlightening; so far, so good. To fix the problem with cause and effect, the authors take a next step that is bizarre and unexplained. They change the Pythagorean formula to create a hyperbola and never explain how this new model of S/T maintains the invariance that was so obvious in the last model (the circle). Several commentators have noted this particular problem with book.

Another example from page 131-3 is even more bizarre. After demonstrating that (gamma)MC (the scaling factor of S/T time) is conserved, they then state the (gamma)MC^2 is also conserved (Ok, I will take your word on that ...). Then they make an unexplained substitution saying that (gamma)MC^2 = mc^2 + 1/2mv^2. I don't claim to know much math, but how something multiplied by gamma could ever equal that same something plus kinetic energy should be explained in more detail. No help here. Instead, the authors immediately say "We have discovered that there is a thing that is conserved that is equal to something (mc^2) plus the kinetic energy." WHAT?? Discovered?

Another obvious problem with the book is the graphics. They are terrible. The graphs have no legends, no sub text explaining their meaning and are only referred in the text several pages after they first presented. Nuts.

Bottom line: the authors needed an editor and the courage to display the mathematics more plainly rather than spreading them out over pages of text creating lots of unnecessary confusion. The subject is good and I like what they are trying to say, but this book needs a 2.0 version.

My husband is a math guy and has read books about relativity for fun. I'm not so keen on math myself, but have a master's degree in organic chemistry (I can do math, sure, I just don't do it for fun). I bought this book so that we would have something to read together - I keep buying him books as gifts, and they often collect dust.

It turned out to be a great idea. We have often forgone watching TV in order to read more about E = mc2. We read, stop, discuss, and try to wrap our brains around the ideas. I think I have come to understand more of the underlying ideas briefly presented in my physics classes, and in an environment of no stress and no time limit! I am not in a position to critique the physics itself, but I have found no errors or issues that suggest a problem.

However, as much as the author's try to make the subject accessible, I am fairly certain my non-math and science family members would have been lost after the first few chapters. Without some experience in thinking in equations, it's just hard to wrap your brain around the ideas.

I would highly recommend this book to anyone with at least a basic math or science background who is interested in understanding something fundamental that hardly ever gets explained outside of an upper level physics course, or someone without a math or science background who is interested in really stretching their brain.

For someone who never found the light clocks and shrinking meter sticks of the standard attempts to explain relativity without math very comprehensible, this book does a better job of presenting more intuitive models for nonintuitive concepts. You have to accept that Einstein's theories, which flow naturally out of the existence of a universal speed limit, have been experimentally validated: the muon that should decay in 2.2 milliseconds actually does take 29 times more seconds to "die" when it is accelerated to almost the universal speed limit. In other words, from the standpoint of an observer at rest with respect to the muon, the muon lives longer as it gets closer to the speed limit. The authors tell you to imagine a spacetime world where speed and time, added together, are conserved. So as you use up more of your velocity vector, you use up less time, so your time slows down from the standpoint of an observer. A photon, which is going at the universal speed limit, apparently does not age. While the layperson can "get" this concept, since it is not that dissimilar to Newtonian concepts, when you sit back and think about it, it unfortunately still makes no sense, and your rational brain keeps saying, "there must be some other explanation for this." The authors say that from the standpoint of the muon, which still thinks it is living 2.2 milliseconds, the space that it's traversing must shrink. At other points they tell us the muon itself is shrinking at high speeds. Are both of these true? Is the natural consequence of this that all photons are everywhere at once -- is all of space just a point to a photon? If photons have no mass then why do massive objects, like black holes, have an effect on them? The authors wait until the last few pages to disclose that the standard model, which the book is based on, only works as is in a world where nothing has mass, and that to connect the model to the real world, scientists must find a Higgs boson particle that mediates the relationship between the field that supposedly exists all around us and everything that is in it. Without that field and the Higgs boson, there is no explanation within the current model for mass. In other words, our entire understanding of the world of quantum mechanics and relativity may soon turn out to be based on mistaken assumptions. The definitive book for the layperson on this subject has yet to be written, but in the meantime, this is a good place to start.

Francis Ford Coppola has said that happiness consists on learning new things every day. People like Brian Cox and Jeff Forshaw help us to become happier. Scientists like these who devote part of their precious time to divulge scientific ideas are the real missionaries of the XXIst century helping to extend the gospel of science, which, contrary to other gospels, it is non dogmatic and subjected to possible disproval by experiment , a feature of science introduced by Muslim scientists (!) according to the book (page 40).
The book is not only, as it title suggests, an explanation of the famous Einstein formula but a very up-to-date and understandable review of XXth century physics, including cosmology, special and general relativity and the Standard Model with its awe inspiring master equation.
The book uses, sometimes, very simple mathematics, which the authors suggest the math averse reader to skip, if necessary, but with important results. For instance, making use of the very famous, old and simple Pythagorean theorem Cox and Forshaw prove that the half life of muons accelerated to 99.94% of the speed of light is extended, due to relativistic effects, 29 times, a fact that is verified experimentally.
There are also several examples of theoretical predictions confirmed experimentally which is one of the beauties of physics. Fred Hoyle's prediction of an energy level of the carbon nucleus which makes it crucially possible the synthesis of heavier elements in the stars, gravitational waves (whose existence has been indirectly confirmed studying a double pulsar) , the masses of the W and Z bosons (confirmed at CERN), the existence of the positron posited by Dirac or Chandrasehar's limit for the mass of white dwarves.
The story unfolds from Faraday's experiments and Maxwell's equations which lead to the constancy of the speed of light which, in turn, lead to the Special Theory of Relativity, to Minkowski's space time, the conservation of the energy-momentum vector and the famous E=mc2 formula (which is an approximation, by the way). The final chapters are devoted to General Relativity (and its clear effects on the GPS system), the Standard Model (with a good introduction to gauge symmetry) and the Higgs boson, the last particle, among the fundamental particles of the model, to be found experimentally (in the Large Hadron Collider hopefully when they get it working) .
There are also some curiosities such as that if the Earth was flat we would see a laser fired horizontally bending to its surface. To sum up: a very entertaining book that I hope will make you happier. It made me.

Here are my 4 thoughts on the book:

1. Let me be honest, there are parts of the book that are challenging As is often the case with such books that claim to simplify and easily explain difficult scientific or mathematical concepts, there is still a substantial gap between what may be considered the lay person and someone who understands such concepts. So don't be fooled. Parts will need work, which means more than one reading and some time to sit down and actively think about what you have just read.

2. The effort to understand will be worth it. This book comes at Albert Einstein's famous equation from a different angle than most. It places the equation within a framework of understanding the physical world and how it integrates special relativity. That is the real strength of the book, it helps to explain as a whole.

3. It leaves the reader with a clear understanding of just how physicists look at the world and how they start to understand it through their theories and how they build those theories. At that level, as well as explaining the special theory of relativity it works at helping to demystify scientific work.

4. It leaves me in awe at just what Albert Einstein achieved in changing our understanding and view of the universe. It is an invaluable aid in helping to understand Einstein's legacy.

Recommendation - A good book to buy if you want to understand Einstein's work, rather than just know about the man.

Every few years I read a book on physics written for the lay person. Most of them are pretty good, but make the mistake of covering too much ground i.e. relativity, quantum mechanics and string theory. This book focuses on relativity and the most famous equation in scientific history E = mc2. As the title suggests, the book does an admirable job in making the theory accessible and also delivers on the promise of explaining why we should care. It is the only book of its type to take the mystery out of why the speed of light should be related to energy or mass. I am not giving much away by revealing that the speed of light is somewhat of a red herring. "C", it is explained, is the cosmic speed limit. It also happens to be the speed of light because it can be derived that it is the speed of a massless particle. The writing is witty and engaging. The small amount of math presented does not go beyond basic high school trigonometry.

E = mc2

The energy contained in anything is equal to its mass multiplied by the speed of light.

As the title of this book suggests this book seeks to answer the twin questions of why nature should work this way and why we should care that nature works this way.

Like all basic questions the ones posed in this book actually turn out to be quite instructive about why nature works the way it does.

Though admittedly we still have much more learning to do about whys and wherefores of this process this book was great in making the connection that there is a correlation between the mass of a thing and the potential energy it contains.

Burn a log and it weighs less. Start a uranium reaction and mass itself is extinguished in the process producing energy that travels at the speed of light.

Why the energy produced from such a reaction should travel at the speed of light tells us much about what Oxford's John Barrow would term the impossibilities of science...inherent limits to nature and how it operates that give us useful guides to understanding it better.

And understanding nature, as both Einstein and Spinoza would have us believe is understanding God, "the old one," himself...reason as good as any why we should care.

This book is highly recommended.