100 Years of Relativity Space-Time Structure: Einstein and Beyond ...

PREFACEThe goal of this volume is to describe how our understanding of space-timestructure has evolved since Einstein’s path-breaking 1905 paper on specialrelativity and how it might further evolve in the next century.Preoccupation with notions of Space (the Heavens) and Time (theBeginning, the Change and the End) can be traced back to at least 2500years ago. Early thinkers from Lao Tsu in China and Gautama Buddhain India to Aristotle in Greece discussed these issues at length. Over centuries,the essence of Aristotle’s commentaries crystallized in the Westernconsciousness, providing us with mental images that we commonly use.We think of space as a three-dimensional continuum which envelops us.We think of time as flowing serenely, all by itself, unaffected by forces inthe physical universe. Together, they provide a stage on which the drama ofinteractions unfolds. The actors are everything else — stars and planets, radiationand matter, you and me. In Newton’s hands, these ideas evolved andacquired a mathematically precise form. In his masterpiece, the Principia,Newton spelled out properties of space and the absolute nature of time. ThePrincipia proved to be an intellectual tour de force that advanced Sciencein an unprecedented fashion. Because of its magnificent success, the notionsof space and time which lie at its foundations were soon taken to be obviousand self-evident. They constituted the pillars on which physics rested forover two centuries.It was young Einstein who overturned those notions in his paper onspecial relativity, published on 26th September 1905 in Annalen der Physik(Leipzig). Lorentz and Poincaré had discovered many of the essential mathematicalunderpinnings of that theory. However, it was Einstein, and Einsteinalone, who discovered the key physical fact — the Newtonian notionof absolute simultaneity is physically incorrect. Lorentz transformationsof time intervals and spatial lengths are not just convenient mathematicalways of reconciling experimental findings. They are physical facts. Newton’sassertion that the time interval between events is absolute and observerindependentfails in the real world. The Galilean formula for transformationof spatial distances between two events is physically incorrect. What seemedobvious and self-evident for over two centuries is neither. Thus, the modelv