Movie 6 (1:24)

Script : We now look at moving objects. A tram moving close to the speed of light displays many effects, becoming distorted, and changing colour and brightness. Its shadow also falls at an unusual angle.

The effects of distortion,the Doppler effect and intensity can be separately treated, so for the moment we "enhance" our image, correcting it so only distortion appears. This correction occurs within the large rectangle. The tram appears to have been shortened, sheared (with the two ends no longer perpendicular to the sides), and slightly bent.

To explain the shear, we again move to the schematic world. As the tram moves close to the speed of light, it is shortened by the Lorentz contraction. As the back side of the tram is further from us than the front side, the light takes longer to reach us. Thus the light we see at any one time must have left the front and back surfaces of the tram at different times. As the tram is moving at a speed comparable to that of light, this time delay also means that we see the front surface of the bus later and further along the track than the back surface, thus we see a shear. This effect is known as the Terrell rotation, as the degree of contraction and shear combine to the exact proportions that a rotation would produce. However, this effect is dependent on the object appearing small and distant. If we are too close to the object it's different parts will appear rotated by different amounts, sometimes resulting in extreme distortion.