## C1 Epstein’s Myth

In 1981 Lewis C. Epstein published the book [15] “Relativity Visualized”. In this book Epstein introduces a truly new and easily interpreted depiction of relativity theory. It is often referenced, but rarely really taken seriously. Most text books continue to exclusively use Minkowski diagrams to depict relativistic phenomena from the point of view of two coordinate systems in relative motion to each other.

Hermann Minkowski began his famous 1908 speech to the 80th Meeting of German Natural Scientists and Physicians with the following words:

“The views of space and time, which I wish to lay before you, have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth, space by itself and time by itself are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality. ... “ [10-152]

Minkowski continued in this lecture to develop a consistently four-dimensional viewpoint of physical events, by combining the three space coordinates and time into a four-dimensional vector. In so doing he provided the STR in a geometrical manner a much more descriptive depiction - at least for mathematicians. Einstein joked at first that he no longer understood the STR, since the mathematicians took it up; however later it was clear to him that the new perspective provided a great step forward.

This is precisely the starting point of Epstein’s “myth”, on which he develops his representation. He says: It only seems to us that we live in a three-dimensional world, in which we make our small trips as a function of linear time. We actually all live in four-dimensional space-time. Our perception stems from the fact that we always move with the speed of light in this four-dimensional space-time - and that the direction in which **we** move, we call **time**, and the three others, which are perpendicular to it, we call **space**! That we cannot perceive spatially the direction in which we are moving with the speed of light, as we do the others, is quite understandably due to Lorentz contraction. Epstein explains it this way:

"To understand the Special Theory of Relativity at the gut level, a good myth must be invented, and here it is.

Why can't you travel faster than light?Thereason you can't go faster than the speed of light is that you can't go slower. There is only one speed. Everything, including you, is always moving at the speed of light.How can you be moving if you are at rest in a chair? You are moving through time." [15-78f]

Thus the whole phenomena of the STR result from the fact that we are not all moving in the same direction of four-dimensional space-time! We want to show this graphically and we will see that Epstein diagrams (as they must be called) not only show the phenomena qualitatively correctly, but that all three basic phenomena can be quantitatively correctly read from these diagrams. For many problems one needs only a sheet of graph paper, a compass and a ruler; one draws the suitable Epstein diagram and immediately the solution can be read to two or three decimal places!