Anti-Matter Book

This post is a review of the book Antimatter: What it is and why is it important in Physics and Everyday life by Beatriz Gato-Rivera. I had been looking for a book on the topic for a while and I found it displayed at the workshop I am attending in Spain. Then I was able to access it online. Before I start the review, some photos I took of the village of Benasque.

A road in the village From across the river At the conference

This is a book with a fair amount of information. There are long sections on particle physics and on the nature of gravity. All good for general knowledge and required as necessary background for understanding antimatter. It was satisfying to extract answers to some of the questions about antimatter floating around in my mind.

1. What is antimatter? Matter is fundamentally made of particles. Particles have properties like mass, charge, etc. A particle and anti-particle have the same properties if the properties do not admit opposites (e.g. mass - negative mass does not make sense and does not seem to exist in the universe). Thus, a positron (the correct name for the antiparticle of the electron) has the same mass as an electron.

   
   

   On the other hand the two particles have opposite properties if the properties admit opposites (e.g. charge - the opposite of a positive charge is a negative charge). Thus, the positron has positive charge while the electron has a negative charge.

   
   

   It stands to reason to reason that if a particle has only properties that do not admit any opposites, then it is its own antiparticle. An example of such a particle is the photon.

   
   

2. Does antimatter need to exist? Yes, the existence of antimatter is an absolute necessity in our current understanding of physics. It arises from the marriage of quantum mechanics and special relativity, and without it, the mathematical foundations of the Standard Model of particle physics would collapse.

   
   

3. Does matter necessarily have to annihilate with antimatter? Yes, for the same reason that hydrogen and fluorine combine explosively - the rules of the reaction (various physics laws like the conservation of energy, charge, etc.) demand it.

   
   

4. Where can antimatter be found? The sources of antimatter are divided into primordial and secondary. The primordial source of antimatter is the Big Bang. It should have produced matter and anti-matter in equal quantities (so we should have antistars and antigalaxies - the book describes how to tell them apart from stars and galaxies). One of the great mysteries of the our universe is why we see so little antimatter in it. The book describes the various theories on the topic (check out the Sakharov conditions).

   
   

   Every source of antimatter other than the Big Bang is called secondary. This includes stars, cosmic ray showers, and accelerators (like the CERN antimatter factory).  In fact you have very likely held an antimatter source in your own hand: there is enough radioactive potassium in a banana to release 15 positrons in a day.

   
   

   The book describes satellite, space station and accelerator-based (don't miss Fig.2.11 showing a massive spectrometer being transported through the crowds in Leopoldshaven) searches for antimatter.

5. What is the brief history of antimatter discovery? The existence of antimatter was deduce as a consequence of the equation proposed by Dirac, which successfully combined quantum mechanics with special relativity. The first antiparticle to be discovered was the positron (Andersen found it and got the Nobel; the book describes how several groups almost found it before him).

   
   

6. What are some simple forms of antimatter? The positron is the simplest one. Some other elementary examples are the antiproton, the antimuon, the antihydrogen and the antideuteron. The book gives more examples.

The book ends with a chapter on technological applications as in medicine (e.g. PET) and the always tantalizing prospects of energy creation, given that annihilation is a thousand times more efficient than nuclear energy. There is an interesting appendix debunking several myths propagating in the field.

Summary

The author is a qualified physicist herself, has clearly gone to the primary literature, and interviewed a good number of practicing physicists. The writing is crisp and pointed, and expertly anticipates confusion. The book is well illustrated with more advanced concepts boxed away from the main text. A good introduction as well as a useful reference on the topic. Could be read as popular science.