Motion Mountain

Inspiring physics textbook

This is not your father’s physics textbook. It is the self-published 1,500-page (!!), still-unfinished physics textbook written and designed by your polymath genius uncle who dwells on a mountain with the spirits of departed philosophers (whom he quotes, in German). It’s what a physics textbook would be like if a poet wrote it and made no mistakes. The book is massively visual. There is minimal math. It’s a textbook with soul.

The guiding metaphor of Motion Moutain, and thus its name, is to frame physics as varieties of motion and change. When it gets to quantum mechanics it considers this in almost Taoist terms, as the “smallest change.”

This textbook is a work of art. Unlike standard texts, it is an enthusiastically personal masterpiece, yet still has exercise problems for students to practice. It sprawls across topics you won’t find in any other physics textbook: semantics, lying, color theory, the physics of pleasure. In many ways it reminds me of Godel, Escher, Bach in its witty brilliance, stupendous range, and self-designed idiosyncrasies. Motion Moutain is an amazing portrait of the physical world as flux. It has the power to equip you with the intellectual tools to work with, and love, this flux. Studying it is an adventure in understanding.

Best of all, it is a free PDF book. A PDF means that it is hyperlinked to footnotes and intensely cross-referenced. And it is easily searchable. Every student — anywhere — can download a copy.

-- KK 01/4/08


Why do change and motion exist?
How does a rainbow form?
What is the most fantastic voyage possible?
Is 'empty space' really empty?
How can one levitate things?
At what distance between two points does it become
impossible to find room for a third one in between?
What does 'quantum' mean?
Which problems in physics are unsolved?

Astonishingly, it is actually impossible to distinguish an original picture of nature from its mirror image if it does not contain any human traces. In other words, everyday nature is somehow left-right symmetric. This observation is so common that all candidate exceptions, from the jaw movement of ruminating cows to the helical growth of plants, such as hops, or the spiral direction of snail shells, have been extensively studied. Can you name a few more? The left-right symmetry of nature appears because everyday nature is described by gravitation and, as we will see, by electromagnetism. Both interactions share an important property: substituting all coordinates in their equations by the negative of their values leaves the equations unchanged. This means that for any solution of these equations, i.e., for any naturally occurring system, a mirror image is a possibility that can also occur naturally. Everyday nature thus cannot distinguish between right and left. Indeed, there are right and left handers, people with their heart on the left and others with their heart on the right side, etc.

Do all objects on Earth fall with the same acceleration of 9.8 m/s2, assuming that air resistance can be neglected? No; every housekeeper knows that. You can check this by yourself. A broom angled at around 35 degrees hits the floor before a stone, as the sounds of impact confirm. Are you able to explain why?

Sexual Preferences in Physics
Fluctuating entities can be seen to answer an old and not-so-serious question. When we discussed the definition of nature as made of tiny balls moving in a vacuum, we described this as a typically male idea. This implies that the female part is missing. Which part would that be? From the present point of view, the female part of physics might be the quantum description of the vacuum. The unravelling of the structure of the vacuum, as an extended container of localized balls, could be seen as the female half of physics. If women had developed physics, the order of its discoveries would surely have been different. Instead of studying matter, as men did, women might have studied the vacuum first.

When do clocks exist?
In general relativity, we found out that purely gravitational clocks do not exist, because there is no unit of time that can be formed using the constants c and G. Clocks, like any measurement standard, need matter and non-gravitational interactions to work. This is the domain of quantum theory. Let us see what the situation is in this case.... In short, quantum theory shows that exact clocks do not exist in nature. Quantum theory states that any clock can only be approximate. Obviously, this result is of importance for high precision clocks. The quantum of action implies that a precise clock motor has a position indeterminacy. The clock precision is thus limited.Worse, like any quantum system, the motor has a small, but finite probability to stop or to run backwards for a while. You can check this prediction yourself. Just have a look at a clock when its battery is almost empty, or when the weight driving the pendulum has almost reached the bottom position. It will start doing funny things, like going backwards a bit or jumping back and forward.When the clock works normally, this behavior is strongly suppressed; however, it is still possible, though with low probability. This is true even for a sundial.

(This post was originally part of Cool Tool's Five Good eBooks. — editors)

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