Hi I cant see the error in this can someone please explain where I went wrong? A man is in a space ship travelling at a constant velocity He makes 2 identical tubes of length L with a mirror at one end, tube a and tube b He has a single light bulb. Next to the bulb is a detector. He carefully measures that the bulb and the detector are equidistant from the mirrors. He places the non mirrored ends of the tubes at the globe, with the tubes perpendicular to each other see the figure The detector detects if 2 flashes of light arrive at the detector at the same time. The bulb flashed for a brief instant and the detector detects if the flash arrives from each tube at the same time. The analysis for tube “a” is T = ((L – vt)/c) + ((L + vt)/c) (L – vt)/c = is the time taken for the light to leave the light source and travel to the mirror. (L + vt)/c = the time to do the return trip. T = the time taken for the round trip The analysis for tube “b” is T = 2L/square root(c^2 - v^2) But 2d/square root(c^2 - v^2) does not equal ((L – vt)/c) + ((L + vt)/c) There are 4 identical space ships, travelling at the same velocity, wrt and external observer, east, north south and west. They all conduct exactly the same experiment, simultaneously and the observer in each space ship all get the same result.