The high density of gluon seen during the collision is often explained by contraction of the nucleus. Accordingly, this one would appear compressed along its direction of motion and as a result, the gluons inside the nucleus would appear to a stationary observer as a "gluonic wall" traveling near the speed of light. At very high energies, the density of the gluons in this wall would then increase greatly. However, this description is incorrect for two reasons: