Vee

If the time is orthogonal to the other three spacetime dimentions, we may have been able to travel independently along spatial dimension and time. As that is quite not possible. We can't make change in postion without advancing through time and also can't completly travel in time as there is no absolute rest possible. I think!

Light consists of quanta(small packets of energy). Then how do we explain doppler effect of light the same way we do for sound? What is the valid explanation of light doppler effect which is consistent with the photon picture?