This post is a review of the book The Science of Spin by Roland Ennos. The book is about the role played by physical rotation in the universe and in our lives. This is a favorite topic of mine - I am fascinated by things that rotate.
The Galaxies: The book discusses the effect of rotation on the shapes of the galaxies (spiral galaxies have more and elliptical galaxies have less rotation).
The Solar System: The book begins with explaining the role of rotation behind the fact that all the planets go around the sun in the same direction and in the same plane, and the same for the moons of any planet. It discusses how the Sun's rotation is slowing down due to the angular momentum carried away by the radiation it emits.
The Earth: There is a very engaging discussion of the tides, which are caused by the Earth's rotation with respect to the moon and the sun. The movement of water causes friction relative to the Earth's rotation, leading to the length of days increasing by a couple of milliseconds per century. This effect, in reverse, can be seen on the moon, because it is tidally locked, and always shows the same side to the earth.
There are also illuminating explanations of how the earth is stabilized by rotation about its own axis and about the moon; how the planet's rotation-induced magnetic field protects it from radiation from space; and how planetary rotation creates days and nights, seasons, wind patterns.
Technology: This part of the book covers many of the technological applications of rotation over the course of history: drills, spindles, the wheel, rollers, the Archimedes' screw, windmills, spinning jennies, flywheel, paddle wheels, propellers, turbines, etc. Automation and flying are covered quite extensively.
The Human body: Balance, gait, force transmission (throwing, hitting, etc.) by human beings are addressed here. There is a long chapter on the role of body part rotation in sports. The author's expertise as a biomechanics person seems most directly relevant here.
Evaluation
The book is well written, with no equations but a good many diagrams. The technical material is well explained.
One of the themes of the book is a sustained complaint against physicists who have 'delayed' the progress in the understanding of rotational science by an 'over-dependence' generally on mathematical analysis and specifically on equations. The author supports this allegation e.g. by quoting several instances of claims by scientists who ended up being wrong about rotational systems.
But of course this is the usual course of science. Scientists often come to wrong conclusions - but science eventually self-corrects. The story becomes a bit clearer when the author reveals that he found physics so mathematical he switched to zoology at university; so there's nothing wrong (and in fact everything right) with the math - it just so happens that our scientist author is not mathematically inclined (there are many).
This perhaps explains why some of the more fundamental advances in our knowledge of rotational science not mentioned or emphasized in the book, e.g.:
i) the spin-statistics theorem which relates the spin of particles to their statistics
ii) the Stern-Gerlach experiment, which discovered quantum spin
ii) the existence of bosons and fermions, and perhaps anyons
iii) how the Pauli exclusion principle determines the stability and structure of matter
iv) how Regge showed angular momentum can be considered to be complex (rather than real) with benefits to particle scattering analysis
v) Light can carry more angular momentum than (polarization-related) spin.
...
Appreciating these advances might require a bit more sophisticated mathematics than described in the book. Still, it's quite readable.
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