Book Review - ‘The Particle at the End of The Universe’

by Grace King 

If we were to describe an object’s mass as equivalent or proportional to the force required to move said object, it is easy to see how this may apply on earth. 

Imagine a scenario in which there are two objects - with object A having a greater mass than object B. If we were to apply the same force to both objects, parallel to the ground, we would expect to see a lower acceleration or velocity in object A than object B. Or we may see Object A come to a stop sooner than Object B. We can easily attribute this to the effects of gravity and the subsequent effects of friction acting between the object and the ground. However if we were to repeat the experiment in space or in some other hypothetical vacuum, in which there is no gravitational influence or resistance of any kind, and if we were to replace our two objects with a proton (Object A) and an electron (Object B), according to Newton’s second law: Force = Mass x Acceleration or F=MA, the lighter particle (the electron) would still have a greater acceleration than the heavier object (the proton). Why is this? What is it that could be causing the proton to travel more slowly? The answer is the Higgs Field.

Published in 2012, Sean Carroll’s book ‘The particle at the end of the universe’ details the various complexities of the particle physics surrounding the Higgs field and the Higgs Boson. This book was published in the same year that the Higgs boson was discovered at CERN in the Large Hadron Collider or LHC. In order to understand the magnitude of this discovery, Carroll first describes the very basics of particle physics and the Standard Model. 

Essentially all particles are categorised as ‘Fermions’ or ‘Bosons’, fermions are particles that take up space and bosons are particles that are able to pile on top of each other. Fermions are the particles that make up all matter including you and me. The next thing to understand is that the world is made up of fields - the gravitational field and the electromagnetic field are commonly known examples of this - and all particles are simply vibrations within a field. Certain bosons are known as force carriers and are responsible for forces being able to act on fermions. Within the gravitational field there exist bosons called ‘gravitons’ which are the particles responsible for the effect of gravity - particles exchange gravitons and therefore an object can feel the force of gravity. The equivalent in the electromagnetic field is the boson known as a ‘photon’.

So what is the Higgs field? The Standard Model predicted another field that exists throughout space responsible for giving particles their mass. This is known as the Higgs Field, and its associated boson is known as the Higgs Boson. So how does this field give a particle mass? A massless particle such as a photon doesn’t interact with the Higgs Field at all, in the same way as a neutrally charged particle doesn’t interact with the electromagnetic field, and it therefore travels straight through at the speed of light. Another particle, however, such as a proton, does interact with the Higgs field and is slowed down by it, therefore it requires more force to move through the field at the same velocity as a particle that interacts less strongly with the field such as an electron. 

Carroll takes us on a journey throughout this book, from the very first papers written that predicted a Higgs Boson to the very discovery of this particle at CERN almost half a century later (although the story is not written chronologically). Carroll also discusses surrounding topics such as politics within the scientific community and tantalising tales of dissolving gold nobel prize medals in acid in order to hide them from Nazis, only to extract the gold and recast the medals later on. Contrastingly a large proportion of the book details complicated concepts such as symmetries and how they spontaneously break due to the Higgs Boson, as well as nearly all the known fundamental particles including every kind of quark, lepton and its antimatter pair. 

Carroll even introduces us to the typical daily life of both theoretical and experimentalist physicists and all the goings on at CERN since the construction of the LHC. Carroll’s often satirical and casual style of writing makes difficult topics such as, in depth statistical analysis of data and ‘bump hunting’,when looking at graphs, much easier to absorb and also induces a great amount of respect for the data analysts that worked tirelessly to sort through the incomprehensible amounts of data produced by the LHC during the hunt for the Higgs Boson.

Overall, Carroll has an immense impact on one's understanding of the world around them, explaining, for example, how a particle with a greater mass will take up less space than a particle with a lighter mass. It was interesting, when reading this book, when I came across a section discussing the locality of the universe and related concepts that we now know to be incorrect as a result of the 2022 Nobel Prize on quantum entanglement. So readers should feel encouraged to explore the up to date information of leading scientists.