# Breakfast with Einstein

Orzel is a physicist who authored several popularizing books already. How to teach quantum mechanics to your dog is probably the best known because it was a bestseller. In this book, Orzel does something similar and explains all the quantum effects that we are constantly (and probably unknowingly) experience as one gets out of bed and have breakfast at sunrise.

For example the sun is a gigantic nuclear reactor essential for our existence. What is happening in the sun? Why it exists the way it does? And more generally how to explain the whole existence of the universe? These are the first topics to be explained. It is all a matter of particles being attracted, and repulsed as they are subject to several forces. This causes the collapsing of stars, evolving into a white dwarf, a neutron star, or a black hole depending on its total mass. It is all an interplay of gravity, electromagnetism, and strong and weak nuclear interaction. This introduces some model of atoms consisting of a kernel and electrons, forming a system that is kept in a stable state by all these forces. In fact the growing insight into the structure and the physics that take place at an atomic scale is used to lead us throughout the historical evolution sketched in this book.

The next trigger is the observation that heated material shows a red glow (like in the toaster). This is a reason to discuss light, wavelength and photons. It was Einstein's suggestion in his analysis of the photoelectric effect that light might be a particle. Recall that it was this, and not relativity theory, that eventually resulted in his Nobel Prize. So now that we got Einstein involved, we have a complete explanation of the title of the book. The alarm clock is triggering reflections on time keeping, which in modern times depends on the oscillations of a cesium atom. This requires a more detailed analysis of the atomic structure and the physics that happen there.

The Internet is the next trigger. This chapter is an exploration of glass fibers and deals again with the interaction of light and atoms. We are introduced to the physics of lasers. The smell of a cup of coffee is a reason to explain why and how we can smell something. This is related to how atoms bond and form molecules. The planetary model of an atom with kernel and electrons needs to be replaced by atoms that are sharing electrons. The Schrödinger equation characterizes the probability distribution of the position of the electron and we are confronted with the Heisenberg uncertainty principle. Next is the question why solid objects are solid. Why do they not collapse like stars do and cause a nuclear explosion? To answer this, one needs to look at the global behaviour of many atoms. And of course this can be applied to how we experience a loaf of bread as well as to how we can explain some astrophysical phenomena.

Computer chips, require semiconductors and diodes. These are explained starting from a single molecule with a discrete energy spectrum emitting particular wavelengths of light, but many molecules together emit a certain continuous frequency band. In this context Orzel explains a surprising fact about some parrot feathers that seem to be blue, while consisting of filaments of keratin which is actually grey and slightly translucent. It is all a matter of matching wavelengths. Ordinary magnets are even more mysterious to explain. It depends on the spin of the electrons and how they are paired in different states of excitation, taking into account Pauli's exclusion principle and how they interact when in bulk.

A smoke detector depends on light being reflected by tiny smoke particles. More advanced ones can detect particles that do not reflect light well and these use a small ionization chamber and detect disturbances. The latter depends on alpha particles generated during the decay of an artificial radioactive element. Radioactivity and quantum tunnelling are explained and these effects are also important for X-ray radiography and other medical applications. The final application explains entanglement, the EPR (Einstein-Podolsky-Rosen) paradox and sketches the related Bell theorem and the Aspect experiment. It explains how this can break down our whole encryption system when quantum computing becomes a common reality.

Orzel uses physics, not mathematics in his explanations of the quantum effects. These are mostly related to the structure of the atom and the interaction of electrons in molecules. All the atomic models are explained with the increasing complexity that grew as physicists got more and more insight. Historical context is given of all the physical models proposed and the related experiments but also about the application that is being considered like time keeping, the Internet, the use of the magnetic compass by sailors, etc. It is interesting to note that in this context some puzzling observations could only be explained by breaking with traditional views. The new model that was proposed depended partly on intuition and it was often only later confirmed by mathematical computations and experiments. Original ideas are what makes the quantum leap advances in science just like an original angle of approach from a different area can solve a long standing problem in mathematics. It is also noteworthy that in the course of history, several breakthroughs were proposed by scientists who spent some time away from their usual research environment. Newton is a well known example who proposed calculus when he returned from his stay in the countryside during the plague, and Orzel gives other examples.

Orzel often refers to some scientist "who did the mathematics" and could confirm what he or somebody else had proposed, or, that in a more complicated situation of more than just one atom "the mathematics become much more involved". Thus it is clear that Orzel suggests that there is mathematics underlying all these models, but he does not go anywhere into the mathematics itself. So it may be a bit disappointing that with Einstein in the title, there is not more mathematics. Even relativity theory is absent. It is not relevant at this level of detail anyway. Neither is Orzel visiting the zoo of subatomic particles that have been proposed more recently. He is not even hinting at the Theory of Everything, a theory where theoretical physicists are nowadays wandering is an almost purely mathematical maze. Some have criticized this modern evolution as pure mathematical speculation which is not even scientific because it is not verifiable by experiment any more.

Thus if you expect to find mathematics in this book you may be disappointed, but you will find a readable introduction of the quantum physics that are connected to atomic models and you will know that you walk on solid ground since it is all supported by mathematics as well as by experimental verification. There are some effective illustrations and exceptionally a formula, but most of the book is just text. Since there is a lot of material presented, even in a popular science book, (and perhaps especially in such a book), one might have expected a subject index which would facilitate to look up something from a previous chapter that you need to recall later. Orzel gives cross references in the text, but sometimes a reader will like to recall some concept, and then it is difficult to find it in previous chapters.

**Submitted by Adhemar Bultheel |

**25 / Nov / 2019