## Vorwort von Lewis C. Epstein zur Englischen Ausgabe

Who contributes the most to progress: The mountain man who ﬁnds the ﬁrst pass at 10,000 feet through a high range, or the railroad engineer who later ﬁnds a low pass at 7,000 feet which will be used by trains, motor vehicles, pipelines, electric lines and optical cables?

In the realm of physics, all the credit, the Nobel Price, goes to the "mountain man". In physics, the "railroad engineer's" reward is best some money from writing and selling "low pass maps", which are books that make good understanding accessible to those who for various reasons cannot go up to 10,000 feet.

I am a "railroad engineer". I found a low pass through the theoretical physics mountains into Einstein land. The pass is mapped in a picture and a story book called Relativity Visualized. Here David Eckstein has taken my picture story and transliterated it into kosher physics. The story pivots on an intuitive idea I called: the speed of time.

From where came this "speed of time" story? Like many post 1960 physics ideas, it just came out of the smoke, which opens the band pass ﬁlter of the mind. Through the open ﬁlter comes lots of noise, a few distant memories and unusual convolutions of thought.

Recall childhood. I remember how slow time crawled when I was kept in detention, after school going home time, because of bad spelling or bad gooﬁng. And I remember how fast time ﬂew on the special occasion of riding up front on a steam locomotive's footplate. The Ancients too felt earthly time ran slow and fast. Slow in summer; each daylight hour became longer. Fast in winter; each daylight hour become shorter. Even in the lower spheres of heaven, the planets pace through the zodiac was not only variable, but occasionally back stepping.

Galileo put his ﬁrst thermometer into chile pepper and demonstrated that part of what had been called heat was subjective, not objective. And he suspected time might also be, in part, subjective. So he tried hard to express the falling body law in terms of objective geometry, on distance from the top. Only reluctantly did he permit time to enter the falling body law. After all, how could time, a thing without material existence, have a linear control of a material object's speed? Time was not part of the tangible world. The Good Book relates how God created the world: 1) In the beginning God created the heaven and the earth, 2), 3), 4), 5), 6), 7) And on the seventh day he took a rest. On which day did God create time? Answer: The Ancients did not think time had objective existence, so it need not to be created. Time came out of men's head.

But once permitted into physics, time soon established itself as the immutable universal independant variable which drives all physical processes. The current of time, unalterable, untouchable by any force, any motion, any environment, anything whatsoever, ruled the dynamic world for the three centuries after Galileo.

No sooner had this immaculate conception of time set hard in human intuition than along came Einstein's wild idea: different, equally valid times can simultaneously coexist in the same space. The universal independent variable view of time was only three centuries old when Einstein arrived. Three centuries is brief when you realize the ancient view of time had sufﬁced for six hundred centuries.

If different times can coexist, then something like the child's view of time, something akin to the ancient view, is reopened. Different times can run at different speeds relative to each other. And so the words "speed of time" are reinﬂated with life. What follows in this work is David Eckstein's perspective on the new life and its immediate consequences.

San Francisco, California, Summer of 2008                                               Lewis Carrol Epstein