book 42 – why does E=mc2? (and why should we care?)

It was so great to read a science book again!! Brian Cox is a beautiful writer, and since I don’t know what parts he actually wrote, I must conclude that Jeff Forshaw is a beautiful writer also. They are also both obviously passionate about the beauty and wonder of physics, and that makes this book a joy to read.

They first use some basic Pythagorean math to demonstrate how time dilation works under special relativity, and then use similar geometry to derive Einstein’s famous equation; E = mc2 (except for some bizarre and unexplained leap of logic requiring the reader to understand how the Pythagorean equation has positive and negative variants. I believe a very large amount of mathematics was skipped over for this part, and I had to just accept their conclusion and move on.)

In deriving this famous equation, we likewise are led to understand that it must be possible to convert energy to mass, and mass to energy. The most interesting side effect of this equality is that if it takes energy to cause something to happen, then the mass afterwards will be less than the mass before. For example, it takes energy to fuse two molecules together, which means they lose mass in the process. So two molecules of Hydrogen (H2) and two molecules of Oxygen (O2) are more massive than two molecules of water (2 x H2O) because energy is used to create the water which means mass is lost.

The final section of the book is a discussion around the formula representing the Standard Model, which describes how all particles of nature interact (excluding the influence of gravity). What was a revelation to me was how the Standard Model required something called “gauge symmetry” and how gauge symmetry, in turn, requires that all particles be massless. Fortunately, the recent discovery of the Higgs Boson at the CERN LHC collider may resolve this rather serious inconsistency. Exciting times for sure!

So, all in all, I found this an extremely enjoyable book, even though there are quite a few times that the authors make some pretty giant leaps based on unexplained or unrevealed assumptions. However, their passion and excitement for the science makes this book worth reading.

Rating: Buy it!

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