The Physics
Opus in profectus

About The Physics Hypertextbook

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La dernière chose qu'on trouve en faisant un ouvrage est de savoir celle qu'il faut mettre la première.

The last thing one knows when writing a book is what to put first.

Blaise Pascal, 1662

The Physics Hypertextbook is a reaction to three problems with textbooks in the US at the turn of the Twenty-first Century — lack of writer's voice, layouts that reduce readability, and outdated economics.

Too many textbooks are written by corporations, not authors. This is especially true of the textbooks for secondary schools. They sound like they were written by no one. The Physics Hypertextbook is written by me and should have a recognizable voice to it. Whether or not it's a good voice is, of course, open to debate.

The Physics Hypertextbook is presented as a work in progress. Some parts of this book are essentially finished. Some parts are comically underdone (containing only placeholder text). I work on this project in my spare time. I never add anything to it out of obligation. I only work on it when I feel like it. I hope that results in better writing, but I expect that I will never finish this project.

Too many textbooks are layout disasters with special sections not part of any topic and images with no relation to the main text floating in little boxes off to the side. This crazy quilt style decreases readability. Every page of the Physics Hypertextbook is designed to be read from top to bottom. When an image appears, the text around it is discussing it. You read the text, read the image, and read some more text. Images are a part of the stories being told.

Although every page is meant to be read from top to bottom. The whole of this book will probably never be read from start to finish by anyone — including me. It's not a scroll. The Physics Hypertextbook is like a book in that you can flip to any page at any time. It's a random access repository of information. In this respect, a hypertextbook is no different than a conventional book.

We don't buy physical media much any more. I haven't listened to a CD, cassette tape, or phonograph record in years. I took all the music I collected and converted it to digital data in the early 2000s. If I want to listen to new music, I stream it. If I want to own new music, I download it. I stopped renting DVDs and videocassettes a little later. The only time I ever put a newspaper in my hands is when I visit my parents.

We're living in the future. Every form of media has been affected by the stupendous growth of the internet — except textbooks. They are the last holdout of the old media economy. Why are schools still buying textbooks? Why do professors still make their students buy textbooks? It's time for textbooks to die so they can be reborn. It's time for the textbook companies to die too. They need us more than we need them.

The Physics Hypertextbook exists! Read it if you want to learn more about physics. Read it if you need to learn more about physics to achieve some other end. Read it if you are curious about physics or enjoy science in general. It's an interesting diversion and you just might learn something in the process. Certainly no harm can come from any of these objectives.


Dimidium facti qui coepit habet; sapere aude; incipe!

He who has begun has half done. Dare to be wise; begin!

Horace, ca. 20 BCE

The Physics Hypertextbook is organized like many printed physics textbooks. The whole of physics is divided into five major books. Each book is divided into chapters and sections.

  1. Mechanics (8 chapters, 60 sections)
  2. Thermal physics (4 chapters, 18 sections)
  3. Waves and optics (4 chapters, 23 sections)
  4. Electricity and magnetism (8 chapters, 31 sections)
  5. Modern physics (5 chapters, 25 sections)

Supplementary sections on units and mathematics as well as reference material are gathered into a sixth book.

  1. Foundations (5 chapters, 23 sections)

Each section is divided into five pages (except the sections that contain only reference material).

Special colors are used whenever a word or phrase is explained for the first time on a page. (I'd say "defined", but that's not quite the right word.) Primary concepts are highlighted in bright red, secondary concepts in dark red, and important persons in blue. (Blue because they are links to the Wikipedia page for that person.)

If there's one thing America needs, it's more lawyers.

Lionel Hutz, 1993

The Physics Hypertextbook was not designed to satisfy the requirements of any syllabus nor was it designed to integrate into any specific curriculum. Reading it will not build character nor will it provide moral guidance. The author makes no claims of accuracy, efficacy, or user-friendliness. It is expected that someone will read it and be offended, but it is strongly hoped that someone will read it and be educated, entertained, or enlightened.

The Physics Hypertextbook is the intellectual property of Glenn Elert who is solely responsible for its content. No person or organization besides the author played any part in its creation (except where explicitly stated). You can view, copy, and reproduce any part of this work for non-commercial purposes as described in the fair use clause of United States Copyright Law. Reproduction of any part of this work in any form for commercial purposes is strictly forbidden.