I have heard that if one is hypothetically placed in a box completely solid, whith a shield that leaves everything that would have entered a normal box, like light, or neutrinos, out of it. If you sent that in a certain speed, with nothing affecting it, just traversing through space, the person inside it could not in any way find out where he is, or what speed he is going in. Or something similiarly, i don't explain it that good. Anyway, my question is, that you COULD find out what your speed is, if you originally know what for example what frquenzies glowing hydrogen gas sent out. Then you measure the frequenzie of it in all directions. Let's say (i don't know anything about it, just as an example) normal hydrogen gas sent out light in frequenzies of 5, then the doppler effect would have made the frequenzy higher the way the box is moving. if the box is moving half the speed of light, the frequenzy would be doubled, since the light waves are compressed. on the opposite side the light frequenzy would be halfed. so theoretically wouldn't they say something about what speed, or at least what direction they are moving in? Or have i misunderstood the doppler effect?