This Week's Book Review - The Science of Spin

[Seawriter]

Looking for a good read? Here is a recommendation. I have an unusual approach to reviewing books. I review books I feel merit a review. Each review is an opportunity to recommend a book. If I do not think a book is worth reading, I find another book to review. You do not have to agree with everything every author has written (I do not), but the fiction I review is entertaining (and often thought-provoking) and the non-fiction contain ideas worth reading.

Book Review

Putting a Spin on Things

Reviewed by Mark Lardas
August 27, 2023

“The Science of Spin: How Rotational Forces Affect Everything from Your Body to Jet Engines to the Weather,” by Roland Ennos, Scribner, 2023, 288 pages, $28.00 (hardcover) $14.99 (ebook), $14.88 (audiobook)

Spin: it is not just for politicians anymore. It dominates all aspects of our lives.

“The Science of Spin: How Rotational Forces Affect Everything from Your Body to Jet Engines to the Weather,” by Roland Ennos makes this clear. He shows how rotation affects everything, from the way you move to the existence of the Universe.

Ennos starts with a prologue exploring the difficulties created by spin, including our difficulty in understanding it. He then splits the book into three main parts: how spin affects our world and the universe, how technology uses it, and how it affects the human body. He then wraps things up by putting spin into perspective, its impact and how to teach and explore spin.

In the first section he shows the role rotation plays in our physical world, including its creation. When God created the heavens and the Earth, he used spin to do so. Spin effects continued after the creation of our Solar System. Ennos provides chapters showing how it affects the Earth’s magnetic field, the weather, tides, and virtually every aspect of the world we live in.

He goes on to explore spin in technology. He starts with the humble whorl, a weighted stone used to make thread, one of our earliest tools. He explores the role rotation plays in increasingly sophisticated technology, right down to today’s turbine engines. The wheel, watermills, lathes, pumps, all get a look. It is a fast trip from the Stone Age to the Space Age.

Next, Ennos looks at the role rotation plays in our bodies. Rotation rules how humans move. He starts by showing how simply standing relies on bodily rotation. He then goes on to explore the role it plays in walking, running, throwing, and hitting. It turns out all of these are the functions of surprisingly complicated combinations of rotation.

The best part? Ennos explains everything without using mathematics. The book has no equations. He avoids them believing they do little to explain what happens, even to the mathematically capable. He even argues mathematics hindered our understanding of rotation. Scientists got lost in a welter of equations, sometimes missing obvious explanations. Instead Ennos relies on physical explanations for the phenomena created by spin.

“The Science of Spin” is a delightful book, equally entertaining and enlightening. Read it and you will come away with a better understanding of our world and how it works.

Mark Lardas, an engineer, freelance writer, historian, and model-maker, lives in League City. His website is marklardas.com.

[johnwalker]

@Seawriter

He even argues mathematics hindered our understanding of rotation. Scientists got lost in a welter of equations, sometimes missing obvious explanations.

Well, maybe, but there are aspects of spin which have defied understanding by philosophers and physicists from antiquity to the present day.

Imagine you are in a room which is totally isolated from the outside world: you can’t see outside and no influence (noise, vibration, etc.) can enter. There is no experiment you can do which will tell you whether you are stationary with respect to other objects or in uniform (non-accelerated) motion and, if so, with what direction and speed. This is the principle, first described by Galileo in 1632 in the Dialogue Concerning the Two Chief World Systems, and called “Galilean relativity”. Einstein extended the principle in 1905 to correctly describe velocities which are a substantial fraction of the speed of light.

Now, inside the same isolated room, start a gyroscope spinning. If it’s well balanced and has minimal friction, its spin axis will remain pointing in the direction you started spinning it, and if the room is rotated around any axis, the gyroscope will remain pointing in its original direction, showing the rotation. And this works just as well in space as on the Earth—it has nothing to do with the sense of “up” that gravity provides for us.

Why is this? How does the gyroscope “know” to maintain its position with respect to the “distant stars”. Didn’t we reject the idea of the distant stars affecting us on Earth when the astrologers changed the the sign on the door to “astronomer” and got all scientific?

Basically, nobody knows—it’s just how the universe is—get used to it. If you ask a physicist, especially one dabbling in general relativity, they’ll usually send you to Mach’s principle which, when you boil it down and filter out all of the equations, says that the distant stars (or, nowadays, galaxies and clusters of galaxies) do tell the gyroscope which way to point, through the origin of inertia caused by the mass and distribution of bodies in the universe, by means of a phenomenon like the Lense–Thirring effect.

And, if that isn’t weird enough, lurking within quantum mechanics is spin 1/2, which describes every particle from which your body, the Earth, and the distant stars are made.

[Seawriter]

He acknowledges that. He raises some of the paradoxes you talk about in your comment, and hints at some of the others.

I don’t think your inference that a gyroscope is influenced by distant stars is quite fair. Rather a gyroscope maintains its initial rotation axis regardless of the orientation of the room it is in. It is equally meaningful to say the distance stars maintain their position relative to the gyroscope and the gyroscope is affecting the position of the stars rather than the stars affecting the orientation of the gyroscope.