2-DIMENSIONAL APPEARANCE OF A RELATIVISTIC CUBE

The two-dimensional or “photographic” appearance of a cube moving at relativistic speeds is investigated. It is shown that the appearance of the cube depends upon whether the camera is held fixed with the optic axis perpendicular to the direction of motion or panned to follow the cube as it moves. The Lorentz contraction, as it is usually defined, is not visible in either case. However, if the camera is rotated, the photographic appearance has some of the characteristics of a picture of a stationary rotated cube. The photographic appearance of a cube moving from left to right along the x axis at speed β= 0.9 has been investigated for two cases: (i) camera fixed so that the optic axis always makes an angle of 90° with the x axis and (ii) camera panned so that the optic axis always points toward the center of the cube. Consideration oT the slope of lines formed by the edges of the cube has shown that the two cases result in different photographic appearances. Furthermore, in one instance, the appearance is similar to that of a stationary, rotated cube. © 1979, American Association of Physics Teachers. All rights reserved.