Library · Public domain

Relativity: The Specialand General Theory

Über die spezielle und die allgemeine Relativitätstheorie (Gemeinverständlich)

Cover illustration of the book

Choose your version

The same text, told at every level, in every language and look shown here. Pick, then listen or download.

Listen and watch

The same player the product gives for your own book: the voice, the drawings as they are drawn, the text.

Einstein’s own account of relativity, written in 1916 for readers without higher mathematics: what space, time and motion mean once the speed of light is the same for everyone.

This is a sample: 4 of 29 sections. · Made in 170 min

From the lectures

Two positions of a rigid rod preserve the distance between its marks, supplying the physical rule that connects geometry’s predictions to measurement.
What Makes Geometry True

The Physical Bridge

Because the ideas of geometry grew out of real objects, and we are in the habit of seeing a line segment as two marks on a rigid body, such as a tape or a rod, and of judging three places to be in line when one eye can make them coincide. Here is the one idea everything rests on.

A cloud is located above a marked ground point by an imagined pole, then by three perpendicular distances from mutually perpendicular reference planes.
Saying Where Something Is

From landmarks to coordinates

Einstein then shows how this simple idea stretches without changing its nature. A cloud over the square has no landmark of its own, so imagine a pole erected on the square, tall enough to reach it; the measured length of the pole, with the place of its foot, says where the cloud is.

Matching clock ticks identify successive stone positions on the vertical carriage path and the curved ground path.
No Path in Itself

Pair Each Place With Time

What follows in practice is a second requirement. A path is not yet a motion; we must also say when the stone is at each point of it, and those times must be things that can be measured, not numbers assumed out of the air.

How it was made

Examples for: a curious adult with school physics; add one modern instance per idea, such as GPS satellite clocks

The source

The lectures retell the German text of Project Gutenberg #77850, the 1917 Vieweg edition. The author died in 1955; the work is in the public domain. The retelling, the drawings and the voice are made by AI and checked against the book by a second model; nothing was edited by hand. How AI is used.

The lectures are free to read, share and quote with a link to this page.

Your own hard book, the same way

Upload a textbook or any difficult book. The first five minutes are free.

Upload a book