Special relativity states that according to an observer at rest, a measuring stick on a moving platform will appear shorter. Would this observer still see the measuring stick as comprising of the same amount of atoms as the observer who is at rest with respect to the measuring stick? If this is the case, would the first observer actually measure the measuring stick as being more dense since it's length is contracted? I have a sense that this would violate conservation of mass and energy as this should still hold true regardless of the reference frame. I am no expert on relativity, so any insight as to where my logic is flawed would be greatly appreciated.