Referring to fig 2 Points A,B,E and F are all within a shipping container (Container 1) and the points are at rest wrt the shipping container. There is a laser at A that fires a thin beam of photons (say a single photon) to point B where there is a very thin detector. There is an observer at point E and a red light at point F. If the photons are not hitting the detector then the red light at F turns on. Still referring to fig 2 there is a second shipping container identical to the container 1, call this container Container 2. Again points A hat, B hat, E hat and F hat are all within the second shipping container and are at rest wrt that shipping container. Again there is a laser at A hat that fires an extremely thin beam of photons, a single photon stream, to point B hat where there is a very thin detector. There is an observer at point E hat and a red light at point F hat. If the photons from A hat are not hitting the detector at B hat then the red light at F hat turns on. The observer at E can see the light in Container 2 and visa versa. Initially the 2 sea containers are at rest wrt each other and the lasers are aligned so that the photons in each container strike point B and B hat respectively. Container 1 is then accelerated up to a constant velocity D. At all times the observer in container 1 can see the light in container 2 and visa versa Referring to fig 3 This is a magnified view of container 1 which is now moving at a constant velocity. As can be seen the photons in container 1 will take a finite time to travel from point A to the opposite side of the container. In that time the as container 1 is moving at some velocity D the container would have moved to a new position in space by the time the photons strike the opposite side of the container. Therefore the photons will NOT strike point B but will instead strike some other point to the left or right of B. Ill assume they strike a point to the left of B, point G. As the photons are not striking point B the light at F will turn on and the observers at points E and E hat will see that light. The observer at E will know he is moving as the light has come on. The observer at E hat will know the observer at E is moving wrt E hat as E hat will see the light. As the light at F hat has not turned on the observer at E hat and E will know he (the observer at E hat) is not moving. Anyone disagree ? Referring to fig 4 The observer at E in container 1 now knows he is moving he doesn’t know his velocity or direction. I now want to propose a method of determining direction and relative velocity In fig 4 I have a third container that is identical to the other two containers (container 3). This container is set up identical to the other 2 containers. Whilst container 3 is at rest wrt containers 1 and 2 the laser in container 3 is adjusted so the photons move from point A in container 3 and strike point B in container 3. Which is the same as described above. Again in container 3, there is a laser at point A that fires a thin beam of photons or say a single photon stream at point B in container 3. There is an observer at point E and a light at point F in container 3. Fig 4 is identical in every way to figs 2 and fig 3. The only difference is that the apparatus in fig 4 can be rotated in the direction of the circular arrow in fig 4. Assume the light at point F in container 3 has come on so the observer in container 3 knows he is moving but doesn’t know the direction or velocity. Suppose the direction of movement is in the direction of the arrow shown at point V in container 3. By rotating the apparatus and measuring the length of deflection of the photons from point B, when this length is at its greatest, the observer in container 3 can determine the direction of travel. By measuring the length of deflection the observer in container 3 can determine his relative velocity but not his absolute velocity. The observer in container 3 will know his velocity relative to the velocity of the container where the light has NOT come on. If relative velocity is known time dilation is known and length contraction is known relative to the container where the light has NOT come on. Anyone disagree ? .