Virginia Tech > College of Science > Physics Dept > Tatsu Takeuchi > Special Relativity > Lecture Notes > Section 1
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1. Frames of Reference

In order to describe the motion of moving bodies, we need to state where the object is at any given time. But to state where an object is, we need to measure its position relative to something else, right? So we need a reference point from which to define the position of objects. Once we have chosen such a point, which is called the origin, we can specify the position of the object by saying, for instance, that the object is distance x to the east, distance y to the north, and distance z up from the origin. We also need a clock so that we can specify at what time t the object was at the given position.

When we have the origin and the directions in which to measure the distance from the origin set up, and a clock to measure the time, we say that we have a frame of reference or simply a frame.

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