SpaceTimeContinuumOfTheSpeicalTheoryOfRelativityConsideredAsAEuclideanContinuum 2006-04-01 20:32:34 2006-04-01 20:32:34 Topic Relativity: The Special and General Theory Changes for correction #46 ('SpaceTimeContinuumOfTheSpeicalTheoryOfRelativityConsideredAsAEuclideanContinuum'). % this is the default PlanetMath preamble. as your knowledge % of TeX increases, you will probably want to edit this, but % it should be fine as is for beginners. % almost certainly you want these \usepackage{amssymb} \usepackage{amsmath} \usepackage{amsfonts} % used for TeXing text within eps files %\usepackage{psfrag} % need this for including graphics (\includegraphics) %\usepackage{graphicx} % for neatly defining theorems and propositions %\usepackage{amsthm} % making logically defined graphics %\usepackage{xypic} % there are many more packages, add them here as you need them % define commands here \subsection{The Space-Time Continuum of the Speical Theory of Relativity Considered as a Euclidean Continuum} From \PMlinkname{Relativity: The Special and General Theory}{SpecialTheoryOfRelativity} by Albert Einstein We are now in a position to formulate more exactly the idea of Minkowski, which was only vaguely indicated in Section 17. In accordance with the special theory of relativity, certain co-ordinate systems are given preference for the description of the four-dimensional, space-time continuum. We called these ``Galileian co-ordinate systems." For these systems, the four co-ordinates $x, y, z, t$, which determine an event or---in other words, a point of the four-dimensional continuum---are defined physically in a simple manner, as set forth in detail in the first part of this book. For the transition from one Galileian system to another, which is moving uniformly with reference to the first, the equations of the Lorentz transformation are valid. These last form the basis for the derivation of deductions from the special theory of relativity, and in themselves they are nothing more than the expression of the universal validity of the law of transmission of light for all Galileian systems of reference. Minkowski found that the Lorentz transformations satisfy the following simple conditions. Let us consider two neighbouring events, the relative position of which in the four-dimensional continuum is given with respect to a Galileian reference-body $K$ by the space co-ordinate differences $dx, dy, dz$ and the time-difference $dt$. With reference to a second Galileian system we shall suppose that the corresponding differences for these two events are $dx', dy', dz', dt'$. Then these magnitudes always fulfil the condition\footnotemark. $$dx^2 + dy^2 + dz^2 - c^2dt^2 = dx' 2 + dy' 2 + dz' 2 - c^2dt'^2$$ The validity of the Lorentz transformation follows from this condition. We can express this as follows: The magnitude $$ds^2 = dx^2 + dy^2 + dz^2 - c^2dt^2$$ \noindent which belongs to two adjacent points of the four-dimensional space-time continuum, has the same value for all selected (Galileian) reference-bodies. If we replace $x, y, z$, $\sqrt{-I} \cdot ct$ , by $x_1, x_2, x_3, x_4$, we also obtaill the result that $$ds^2 = dx_1^2 + dx_2^2 + dx_3^2 + dx_4^2$$ \noindent is independent of the choice of the body of reference. We call the magnitude ds the ``distance'' apart of the two events or four-dimensional points. Thus, if we choose as time-variable the imaginary variable $\sqrt{-I} \cdot ct$ instead of the real quantity $t$, we can regard the space-time contintium---accordance with the special theory of relativity---as a ``Euclidean'' four-dimensional continuum, a result which follows from the considerations of the preceding section. \subsection{References} This article is derived from the Einstein Reference Archive (marxists.org) 1999, 2002. \PMlinkexternal{Einstein Reference Archive}{http://www.marxists.org/reference/archive/einstein/index.htm} which is under the FDL copyright. % Notes \footnotetext{Cf. Appendixes I and 2. The relations which are derived there for the co-ordlnates themselves are valid also for co-ordinate differences, and thus also for co-ordinate differentials (indefinitely small differences).}