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Popular Science books, E= mc^2

When I was at school I used to read lots of popular science books, especially things by John GribbonPaul Davies and others on cosmology, relativity, quantum physics, and particle physics. I even toyed with doing something as esoteric as astrophysics at University, and thought that life as a particle physicist might be the job for me. I didn’t read Carl Sagan, which is odd considering the press he is getting at the moment as something of an inspiration for many scientists of my sort of generation, Brian Cox (who I share the distinction of being a Royal Society University Research Fellow with) in particular.

How I ended up as an optical physicist is perhaps a different story but I think in part it stems from the fact that while all these esoteric subjects areas are great, they are what is presented as (in this case) physics to the outside world and little else seems to matter. Also as a school kid I started to read New Scientist, and these topic areas were always prominent (and they still are). What most of us researchers do, however, falls into different areas: optics, materials, condensed matter, biophysics, statistical physics, atomic and molecular etc etc. I think these are just as exciting (and actually often far more so) as looking for Higgs Boson, but the public seem to want the esoteric, or at least the media find it easier to sell (it probably more complex than that, but that is a different discussion). So after a while I got saturated with these ideas. By the time I got to University (doing vanilla physics, and later Laser Physics and Optoelectronics) I was full of knowledge about quantum mechanics, particle physics etc and raring to go. I studied a reasonable amount of quantum at University but dropped the particle stuff after second year, so I never took an honours course in particle physics, and focussed on shiny optics instead. Perhaps calculating probability density functions, when it got down to the actual maths, didn’t seem so exciting after all. However all this background information now poses me with a problem. Do I dare to read popular physics books at all?

Here’s the problem: in order to explain anything that goes beyond material that I have covered, and covered well in my degrees and subsequent career, then a book needs a good few chapters to get everyone up to speed. We need to learn about relativity at length and its consequences, or we have to learn the basics of quantum mechanics and Einstein must be heard to utter that ‘God doesn’t play dice’ and Bohr must comment on ‘how if quantum mechanics doesn’t shock you then you haven’t understood it’. This plays out in nearly any popular physics book you care to mention. And so I get bored…I know I should revel in a new explanation of such material, and that it will give me news ways to think about it, but I get bored (this happened even with ‘A Brief History of Time’). And this is a shame, because by the time we get to half way we move away from my comfort zone. As an ‘expert’ reader maybe I should just read half the book?

This then brings me to ‘Why does E=mc^2’ by the aforementioned Brian Cox and Jeff Forshaw. This is an interesting question, and the answer (if you don’t mind a spoiler) is that it is a consequence of space-time and falls naturally from this model of the Universe. But I guess I knew that too. So what did I learn from this book? Well, I learnt about the ‘master equation’… For me the most interesting part of the book was the discussion of the standard model and the interactions between particles. This isn’t something that I can ever remember looking at in detail before, or at least not for a long time. The key thing was that particle interactions can be described in a nice equation (and fair play to the authors for putting something this complex in such a book), which Cox and Forshaw do a decent job at explaining. The equation, which they call the ‘master’ equation (but perhaps more precisely is a Lagrangian for the system):

The 'master' equation for the standard model

For anyone with a bit more knowledge this is a somewhat simplified version (a scarier version is here), but this gives us the essence. The top line tells us about the different particles and force mediators (the photon mediates (‘carries’) the electromagnetic force, for example), giving us kinetic energies and interactions. The second line tells us about quarks and leptons (such as electrons) and their energies and interactions. The third and fourth lines tell us about particle masses and couplings (including the Higgs).

And so there we sort of have everything…except maybe gravity. Right at this moment the LHC is trying to pin down the Higgs Boson, and with that the standard model would pretty much be complete, as it is the only predicted particle that we haven’t found yet. If we don’t find it, then we’re going to need a new theory.

At the end of the book I feel I have learned a lot, and perhaps more about the hunt for the Higgs than any of the many expositions on it that have been put forward in the popular and technical press over the past few years. So it was worthwhile in the end. I’m just not sure that was the point of the book. My bottom line: for a non-expert it’s a really good read but may be demanding at times. For a part way expert, like me, you’ll likely get something out of it, for a proper standard model geek, I’m not so sure. Maybe I just need to start to learn that I can just jump to the middle of a book and still get something from it. Oh, and maybe I should write a popular book about optics…if I could find the time.

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