The forwards and backwards movement of a rotating cylinder experiment

This paper is a shortened version of one more detailed and thus easier to read, which is also online on Hal : Langevin's twin paradox and the forwards and backwards movement of a rotating cylinder experiment.-Fd II − EA4281 − 6, avenue Jean Jaurès − 63500 Chamalières – France PACS 01.70.+w – Philosophy of Science PACS 03. 30.+p − Special relativity Abstract –Langevin's twin experiment does not lead to a contradiction within the frame of special relativity. Though, such is not the case of one of is variants, the forwards and backwards movement, relative to a Galilean space, of a thin elastic spinning cylinder. The crucial difference is that the space between the 'motionless' part and the one 'making the journey' is always bridged by some continuous portion of the cylinder. The study of the cylinder's behaviour and of its changes of shape shows that the experiment can be run with zero intrinsic twist and with intrinsic angular speeds of sections remaining constantly equal to the same value ω. Then, if we calculate the numbers m and n of turns around the axis that two particular points M and N make, we prove n−m is both a zero and a non-zero integer