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The Minkowski diagram, also known as a spacetime diagram, was developed in 1908 by Hermann Minkowski and provides an illustration of the properties of space and time in the special theory of relativity. It allows a quantitative understanding of the corresponding phenomena like time dilation and length contraction without mathematical equations. The term Minkowski diagram is used in both a generic and particular sense. In general, a Minkowski diagram is a graphic depiction of a portion of Minkowski space, often where space has been curtailed to a single dimension. These two-dimensional diagrams portray worldlines as curves in a plane that correspond to motion along the spatial axis. The vertical axis is usually temporal, and the units of measurement are taken such that the light cone at an event consists of the lines of slope plus or minus one through that event.〔Mermin (1968) Chapter 17〕 A particular Minkowski diagram illustrates the result of a Lorentz transformation. The horizontal corresponds to the usual notion of ''simultaneous events'', for a stationary observer at the origin. The Lorentz transformation relates two inertial frames of reference, where an observer makes a change of velocity at the event . The new time axis of the observer forms an angle α with the previous time axis, with α < π/4. After the Lorentz transformation the new simultaneous events lie on a line inclined by α to the previous line of simultaneity. Whatever the magnitude of ''α'', the line forms the universal〔See Vladimir Karapetoff〕 bisector. == Basics == For simplification in Minkowski diagrams, usually only events in a universe of one space dimension and one time dimension are considered. Unlike common distance-time diagrams, the distance will be displayed on the horizontal axis and the time on the vertical axis. In this manner the events happening in the one dimension of space can be transferred easily to a horizontal line in the diagram. Objects plotted on the diagram can be thought of as moving from bottom to top as time passes. In this way each object, like an observer or a vehicle, follows in the diagram a certain curve which is called its world line. Each point in the diagram represents a certain position in space and time. Such a position is called an event whether or not anything happens at that position. The space and time units of measurement on the axes may, for example, be taken as one of the following pairs: * units of 30 centimetres length and nanoseconds, or * astronomical units and intervals of 8 minutes and 20 seconds (500 seconds), or * light years and years. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Minkowski diagram」の詳細全文を読む スポンサード リンク
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