If I were in the middle of a speeding train carriage, while the flashlight to train the forward direction and the opposite direction, speed instruments must be measured the same projection speed, that is 300,000 kilometers per second.
If I stand in the middle of a speeding train carriage and turn on the flashlight in the direction of the train's advance and the opposite direction at the same time, the speed measuring instrument must measure the same projection speed, that is 300000 kilometers per second.<br>