The visual appearance of rapidly moving objects

I would like to draw the attention of physicists to a recent paper by James Terrell in which he does away with an old prejudice held by practically all of us. We all believed that, according to special relativity, an object in motion appears to be contracted in the direction of motion by a factor ${\text{[1−(υ/c)]}}^{\text{1/2}}.$ A passenger in a fast space ship, looking out of the window, so it seemed to us, would see spherical objects contracted to ellipsoids. This is definitely not so according to Terrell’s considerations, which for the special case of a sphere were also carried out by R. Penrose. The reason is quite simple. When we see or photograph an object, we record light quanta emitted by the object when they arrive simultaneously at the retina or at the photographic film. This implies that these light quanta have not been emitted simultaneously by all points of the object. The points further away from the observer have emitted their part of the picture earlier than the closer points. Hence, if the object is in motion, the eye or the photograph gets a “distorted” picture of the object, since the object has been at different locations when different parts of it have emitted the light seen in the picture.

This article is only available in PDF format