Observation of Length by a Single Observer, Roy Weinstein, Am. J. Phys. 28(7), October 1960
One problem arising in teaching special relativity is the confusion in many texts of the thought experiments, used in developing the theory, with other simple laboratory observations. As an example we consider here the observation of length. The existence of the Lorantz-Fitzgeneral contraction as led educators to conclude that one sees a contraction of a rapidly moving body. However, the act of seeing involves a single observer, while the observation of the Lorentz-Fitzgerald contraction involves at least two observers. It has shown here that the length seen by a single observer is not the usual contraction, and indeed, under circumstances, one sees a body considerable lenghtened rather than contracted.