I.I Basic concepts of special relativity Figure 1.2 A jocular representation of a frame of reference in two spatial dimensions.Gnomes pervade all of space and time.Each gnome has a perfectly reliable clock. When an event occurs,the gnome nearest to the event communicates the time t and location (y)of the event to the observer. Inertial frames of reference An inertial frame of reference is a frame of reference in which Newton's first law of motion holds true. Any frame that moves with constant velocity relative to an inertial frame will also be an inertial frame.So,if you can identify or establish one inertial frame,then you can find an infinite number of such frames,each having a constant velocity relative to any of the others.Any frame that accelerates relative to an inertial frame cannot be an inertial frame.Since rotation involves changing velocity,any frame that rotates relative to an inertial frame is also disqualified from being inertial. One other concept is needed to complete the basic vocabulary of special relativity. This is the idea of an observer. Observers An observer is an individual dedicated to using a particular frame of reference for recording events. 131.1 Basic concepts of special relativity Figure 1.2 A jocular representation of a frame of reference in two spatial dimensions. Gnomes pervade all of space and time. Each gnome has a perfectly reliable clock. When an event occurs, the gnome nearest to the event communicates the time t and location (x, y) of the event to the observer. Inertial frames of reference An inertial frame of reference is a frame of reference in which Newton’s first law of motion holds true. Any frame that moves with constant velocity relative to an inertial frame will also be an inertial frame. So, if you can identify or establish one inertial frame, then you can find an infinite number of such frames, each having a constant velocity relative to any of the others. Any frame that accelerates relative to an inertial frame cannot be an inertial frame. Since rotation involves changing velocity, any frame that rotates relative to an inertial frame is also disqualified from being inertial. One other concept is needed to complete the basic vocabulary of special relativity. This is the idea of an observer. Observers An observer is an individual dedicated to using a particular frame of reference for recording events. 13