Reviews

Why Does E=mc2?, by Brian Cox

bakudreamer's review against another edition

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1.0

An attempt to combinte pop science with chick lit. = to : (

rory_john14's review against another edition

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challenging funny informative medium-paced

3.0

hannahrus3's review against another edition

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4.0

People have this perception that you can either be good at the English-based subjects or the Maths-based subjects, but not both. To be a good physicist, you NEED both. Brian Cox is a good physicist.

thescrawford's review against another edition

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4.0

Having studied Advanced Higher Physics at school I knew a little about the topics in this book, but I would recommend this to anyone who hasn't had any previous knowledge of physics. I found this book very enjoyable as it explained complex theories without going overboard on maths and figures. Great read and well written however the only criticism I could have is the explanation of Minkowski Spacetime could have been clearer.

phileasfogg's review against another edition

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4.0

The authors of Why Does E=mc2? are physics professors at the University of Manchester. Brian Cox is well-known as the presenter of a series of popular TV documentaries on physics themes, and Jeff Forshaw was one of his physics lecturers. They're the same age but Jeff got a head start in physics by not being in a pop band for five years.

The first half of the book is about why E=mc2. The second half is about particle physics and the significance of the pending discovery (at the time of publication) of the Higgs boson.

The selling point of the book is that the authors think they can explain why E=mc2 such that anyone with even the most basic understanding of maths can follow the argument. I don't think they've succeeded, but it's a noble attempt and no real criticism to say they've failed to teach a significant amount of degree-level maths and physics in less than 150 pages. I doubt anyone has come closer. If you don't already have a thorough knowledge of physics, you'll certainly learn something.

I thought I had a pretty good handle on relativity theory before reading this -- the conclusions, that is, rather than the working out -- but among the first things I learned was that I didn't really know much about it.

Science fiction tends to focus on the time dilation aspect of relativity, which may be why I was so familiar with that. But there's a lot more to relativity than time dilation.

I'm not sure what was more surprising: that when you travel very very fast, the space in front of you shrinks; or that a spring weighs more when it's compressed than when it isn't. I always thought E=mc2 referred to the energy that would be liberated if e.g. particles were converted entirely into energy in a matter-antimatter annihilation; but it turns out that all stored energy adds to the mass of the matter in which it's stored. Just not very much, at the scales we're used to dealing with, which is why no-one ever noticed it before Einstein deduced it.

Our brains have evolved to navigate a world in which we interact mainly with comparatively slow, low-energy objects, and this has shaped the model of the world that we call 'common sense'. The discovery that the world sometimes behaves very unlike our 'common sense' model predicts, and the ability of many people to accept that discovery as fact, is surely one of the great achievements of human civilisation.

No doubt beings who spent all their time moving at more than 90 per cent of the speed of light would have 'common sense' models of the world that incorporate relativistic effects, and would be surprised when they deduced that slow things behave quite differently than they expected.

The book answered a question I've always had about the speed of light: is the speed of light the universe's speed limit because light is somehow 'special' enough that the laws of nature are defined around it? Or is it the speed limit for another reason, and light just happens to travel as fast as possible due to one of its quirks, like having momentum without mass? The answer is that the universe's speed limit would be the speed limit regardless of whether light or anything else happened to travel at it.

And it was good to finally read a thorough explanation of those Minkowski spacetime diagrams that tend to show up when people talk about relativity.

The stated aim of the book -- to explain how we know E=mc2 to people who know less about maths and physics than I do -- may be too ambitious for any book of this length. If you're capable of understanding Pythagoras's Theorem -- and you don't even have to know what that is when you start reading, only be capable of understanding it when it's explained -- the authors say they can explain all the steps that lead to E=mc2. They even explain what the little 2 means, just in case.

I didn't need the little 2 explained. But they lost me. If you google 'how can Pythagoras's Theorem have a minus sign?' you'll find a lot of people talking about page 77 of this book.

The edition I read has an appendix which explains the minus sign. The appendix did not seem to be pitched at the same level as the rest of the E=mc2 explanation and by the time I reached it I'd forgotten most of the context, so it didn't work for me. A footnote on page 77 pointing to the appendix would have helped a lot. It would be even better if the explanation could be incorporated into the main text.

NB: Speaking of little number 2s, throughout this review I used the HTML 'SUP' tag to make all my little number 2s little. But they aren't little, at least not in my browser. Grr.

huangv's review against another edition

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3.0



I wanted to learn about the Higgs particle. This was the perfect book for a non-physicist like me.

srreid's review against another edition

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4.0

My brain hurts, but it's a good hurt. Some of the maths bits are heavy going but the general language used around all that helps get the ideas across for those of us still not getting all the symbols.

cybergit's review against another edition

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5.0

Good overview of relativity with some great examples and thought provoking ideas. Read it at the same time as my brother in Australia (I live in the UK) which was a blast. We had some great discussions on the nature of time arising from the book.

mxd's review against another edition

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4.0

I found this book both frustrating and riveting. I'm abysmal at maths, so portions of the book that were heavy on the mechanics of the equations mentioned left me a little bored when I couldn't completely follow (not to mention depressed about not being good at adding). But then the non-math heavy parts were very engaging and it was hard to not get caught up in the enthusiasm of the authors. There were places I wished for more of an explanation and things I found would have been useful if they had been mentioned earlier, but overall I was very glad I stuck with the book. I got a sense of what went into that one small equation that says so much about the universe. It's pretty awe-inspiring.

Also, a million points to any book that makes you stick your hand in the air and smile as you imagine heaps of neutrinos passing through your thumb. Very cool.

kaalia's review against another edition

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5.0

Really good book. Authors tried to explain complex things in a very easy manner. Some places here require math knowledge, but the overall explanation is great and deep enough