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

4.03  ·  Rating details ·  7,952 ratings  ·  461 reviews
The most accessible, entertaining, and enlightening explanation of the best-known physics equation in the world, as rendered by two of today’s leading scientists.

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 equatio
Hardcover, 249 pages
Published July 1st 2009 by Da Capo Press (first published 2009)
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Denise Nader I wouldn't say "easily", but nonetheless, the effort was satisfying. Although no background in STEM is necessary, I would say that having read other s…moreI wouldn't say "easily", but nonetheless, the effort was satisfying. Although no background in STEM is necessary, I would say that having read other scientific divulgation books is. At least, having read about relativity, cosmology, astronomy and similar subjects, because this book is very specific and assumes you are familiar with certain theories.(less)

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Courtney Johnston
I loved this book, and it wasn't just that cheeky Brian Cox going on all the time about being covered in tweed and chalkdust (somebody please hand me a fan).

'Why does E=mc2' is my fifth book from the Royal Society science book shortlist. If Marcus Chown is magical cellulite cream, this is physics bootcamp - no corners cut, no let's-take-it-easy-today-shall-we. Cox and Forshaw don't just want to explain this equation - they want you to understand it, to understand its power (predictive and descri
Aug 02, 2017 rated it really liked it
Shelves: physics
Cox and Forshaw pack Einstein’s theories of relativity and much more into 250 pages. They state upfront that their book is intended to be challenging. And it is, despite simplistic analogies and explanations tucked in between some pretty dense material. Their underlying premise is “From the simplest of ideas”. Einstein noticed that Maxwell had shown that the speed of light was a constant and from this he constructed the Special Theory of Relativity. Then Einstein thought about the fact that all ...more
I was expecting, from the first few paragraphs of the book, that I was going to breeze right through this. It didn't really happen that way. I had to take college physics, which included the basics of relativity and quantum theories, so I probably have a bit more knowledge than the average non-physicist. All the same, there were areas of this book that just did not seem to click at all, even after reading paragraphs over and over again. Usually the parts that didn't click were the "easy" example ...more
Feb 25, 2018 rated it it was amazing  ·  review of another edition
I would love to say that I understood every word and every example of this book, but unfortunately there were many times I felt like the concepts were far too complicated for me. I'm not an unintelligent person but my math and physics knowledge is rather old and rusty.
I'll give it another 2 or 3 read through before making any firm judgements on the books.

I feel I have learned something from this book...I just don't know what it is I've learned..
Jun 22, 2012 rated it did not like it
Absolutely senseless. If he ever gets close to talking about the matter at hand, another long passage about a motorcyclist will pop up to "explain things"

Look. The reason you use so many horrible analogies is because you are a horrible explainer! Convey it the first time, don't waddle about.
Feb 24, 2010 rated it really liked it
On a good day, high school physics class used to leave me feeling kind of (for lack of a better word) high. This book brought back that old, familiar feeling, but in an even better way. In the end, I walked away with a much clearer understanding of Einstein's theories of special and general relativity than I ever achieved slogging through high school physics. (I think our teacher must have been unable to articulate and synthesize the underlying questions that the equations sought to answer.) The ...more
Have you watched Wonders Of The Universe with Brian Cox? You should. And afterwards, when you’ll read this book, his voice and passion will accompany you all along.

For me it wasn’t a breakthrough experience, but if one’s not familiar with the theory of relativity and physics concepts of space and time, it will be a more than pleasant reading, for it is written in a very accessible language, with day to day examples and a bit of humor on occasion.

And you can even accompany your reading wit
Jan 13, 2010 rated it liked it
Shelves: science
I’ve got rather mixed feelings about this one. I think writing a simple account of very difficult material is hard to achieve and so every such effort should be praised wherever it is found – but there is a fine line between simple and patronising and I’m not sure this one respects that line all of the time.

It is clear these guys know their stuff, but I found it hard to concentrate on parts of this book as they would go into a longish chat about how hard the maths is and so how they have made t
Bob Nichols
Feb 29, 2012 rated it it was ok
For those trying to nudge themselves into Einstein's world a little more, this book's title has great appeal. At some very general level, the equivalence of energy and mass can be understood, but the role of light ("c") and light squared remains a challenge.

The authors do a good job of describing how mass converts to energy (heat/photons/light carry away mass; when wood burns, energy is released and mass is reduced). In the reverse, energy adds to mass. When energy (heat) is added to mass, mass
Dec 26, 2011 rated it it was amazing
Superb review of latest in particle physics and spacetime. Cox explains things as clearly as possible, but I believe I will need to reread this before I could begin to explain any of it to anyone else. Check out Cox's (who's a prof at Manchester U and a scientist at CERN, working on the Large Hadron Collider) wonderful videos on YouTube.
Dec 07, 2014 rated it really liked it
Shelves: science-physics

Who was this Adventure in Space-Time Written For?

The challenge of writing any popular science book is that the audience has different levels of knowledge. The author needs to choose the appropriate level of knowledge to aim the writing at. It follows that the reader’s appreciation of the book depends on what they know. To understand my perspective, you should know my background:

A long time ago I completed first year university science before switching into computers. I have since read a number o
Actual Rating: 3.5 Stars.

The writing of science books is a difficult task. On one hand, you have a ready market of science nerds that will instantly pick up your book (an easy sale), but they want hard facts, maths and challenging concepts. On the other hand you have a large mass market audience wanting desperately to learn more about science but if you dive in with the hard facts, maths and challenging concepts you are (possibly) going to lose some of them along the way and turn them off scienc
2020 TBR Challenge: Read a book you don't remember why you added or bought

I really enjoy Brian Cox, I watched his series Wonders of Life ages ago, and I've always liked seeing him on various panel shows etc. He is incredibly intelligent (to state the obvious), but gets across ideas in an accessible and easily understood way, and has a great sense of humour to boot.

This all extends to Why Does E=mc²? - I still don't think I fully grasp any of the concepts explored in it, I have never had a brain
May 10, 2019 rated it it was amazing
Shelves: science
Omg I had no idea how shallow my understanding of relativity was!! Eye opening & exciting read. A bit difficult to follow at times and I still have a few technical questions that I'll need to look-up myself, but I still learned a lot!
While the progress we've made is astounding, I can't help but feel a bit of despair at the thought of how this progress was achieved sometimes (see the Minkowski spacetime "why not try Pythagora's theorem with a minus sign???") and all the "forced" assumptions we'v
Carlos Martinez
Jun 17, 2019 rated it really liked it
Shelves: science
An entertaining and not-entirely-impossible guide to Einstein's physics. I enjoyed reading it, but it'll take me at least one more go to master the main concepts.
David Readmont-Walker
Plan on going back to this, and crunching the numbers.
Bruno Espadana
Aug 15, 2019 rated it really liked it
Einstein’s theory of special relativity for dummies. Which, in this case, is probably most of us.
It will be hard for someone to come up with a simpler way to explain Einstein’s work - if you’re well versed on maths or physics, you will probably find this annoying or maybe too dumbed down. But this isn’t for you - it’s for all people that are curious about Einstein and our universe, can follow a logical discussion, but are not technical enough to follow a more detailed explanation. Not that this
(I never say this, but thank goodness I read this book in Hungarian. It was difficult enough without having to try and decipher what are the Hungarian equivalents of all the terms.)

I have been meaning to read this book every since it came out in Hungarian, but now it seemed like just the light summer read I needed… which, of course, it isn’t, but I’m fairly certain that I’d find some parts of it very complicated even in winter, so what the hell. My main motivation to read this book was Brian Cox
Jan 08, 2014 rated it it was ok
Well, thank the gods that's over! I bought this as further reading on an iTunes U course I'm doing, thinking that it would offer further insight. The first half of the book is so patronising that I could barely bring myself to claw through it (but unfortunately I have a Magnus Magnusson approach to reading). This merely added to the annoying impression that the authors are explaining all the n a s t y, d i f f i c u l t s c i e n c e y - w i e n c e y v e r y s l o w l y t o y o u. B e c a u s e ...more
Jun 29, 2012 rated it it was ok
Why is E=mc^2? It was an enormous ask, and Cox and Forshaw were never going to deliver.
It is easy reading, but unless you understand maths you won't get it at all.
When I read on page 77 "although we did not prove (the maths)" I began to feel cheated, and then they tried to explain in several thousand words space-time vectors, which could have been done in two lines of maths, then I thought to myself it would have been much easier if they had used the maths throughout, and dispensed with all thos
JJ Coetzer
Mar 28, 2013 rated it really liked it
this is a great read, very interesting, but it is not a book I would suggest to anyone who does not have a understanding of astrophysics, the book does start of easy to understand, but it does get complicated
Oct 29, 2017 rated it really liked it  ·  review of another edition
"In following the book up to this point, you may well be juggling a lot of mental balls as you read this sentence". Cox and Forshaw say this at some point halfway through the book, but it might as well be applied to my feelings when finishing it. I don't really know how to criticize, comment or even rate it (for the most of the reading I was pretty sure I would leave no rating at all). I started in August, read a couple of chapters and loved it; never had I understood relativity and physics so w ...more
Aug 07, 2019 rated it really liked it
So, first of all, this is a lovely little introduction to relativity, both special and general, produced with just the right amount of math to make all the concepts clear without too many confounding and always unhelpful analogies (though at times it did feel a bit patronizing – they spend quite a while explaining, for example, the concept of a variable that, if you don’t already have in your toolbox, pretty likely means you will not be able to follow any of the math anyway).

Now, how this was su
Oct 10, 2020 rated it really liked it  ·  review of another edition
I really enjoyed this book. I probably understood only 5% of it, and even that only just, but it still offers a fabulous window into the world of theoretical physics. Despite my limited understanding I love the fact that there are people out there who do actually understand this stuff, and try to shine a light (at a fixed, universally constant speed) into the darkness of our ignorance. My only criticism, and hence only 4 stars, is the authors' repeated assertion that this was accessible and 'eas ...more
Rachel Welton
Nov 18, 2017 rated it really liked it
There are some books that are enhanced by metamorphosis into audiobook, and others that need to remain firmly in the realm of the written word. Jeff Forshaw manfully reads out the equations but I couldn't manage to conjure them up in my mind's eye.
The numerous analogies were enlightening, and I certainly feel I have learned things that I didn't know before, however often there was a big, unexplained leap from analogy to completion, possibly at the speed of light, or failing that at the square r
Nov 08, 2017 rated it really liked it  ·  review of another edition
Shelves: non-fiction
Fantastic book if you're interested in physics or just want to know the actual science behind the worlds most famous equation. They authors do a fantastic job explaining everything, building on what's come before, so that buy the time to get the the complicated theoretical stuff you're not completely lost.
Naveen Gwalia
Jul 13, 2019 rated it it was ok
Shelves: audio-book
I listened to the audio book,dont you do that.even if the author says otherwise,this book is to be read because it involves lots of math.there was no surprise elements in this book which is the main spur for me to put one more star.maybe since i have already read some bestseller books of this genre i didnt find one.i wont recommend you to read this book if you have limited time.
Jun 12, 2020 rated it it was amazing
Shelves: favorites, science
It's incredible how just a bit of knowledge can make everything else shine brighter. Suddenly everything else I've read makes so much more sense. Couldn't stop connecting things while reading this and I love that this was such a quick and enjoyable yet very eye opening read.
Jul 27, 2020 rated it it was amazing  ·  review of another edition
Brilliant introduction to relativity and the famous E=mc2 equation. The math part requires at least one level of algebra/physics post high school. Other keywords that might be useful before reading: neutron, quark or qubit.
Jan 19, 2020 rated it really liked it
Great read however I would say you need to have a basic understanding of physics before reading
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Science and Inquiry: September 2013 - Why Does E=MC2? 4 92 Sep 23, 2013 05:12AM  

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Not to be confused with actor [Author: Brian Cox].

Brian Edward Cox, OBE (born 3 March 1968) is a British particle physicist, a Royal Society University Research Fellow, PPARC Advanced Fellow and Professor at the University of Manchester. He is a member of the High Energy Physics group at the University of Manchester, and works on the ATLAS experiment at the Large Hadron Collider (LHC) at CERN, nea

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