To calculate the relativistic volume of a moving aluminum cube, one must apply the concept of length contraction. As the cube moves at 0.90c, its length in the direction of motion contracts while its width and height remain unchanged. The volume can be determined using the formula for volume, adjusting for the contracted length. The rest density of aluminum is 2.7x10^3 kg/m^3, but the primary focus is on the volume change due to relativistic effects. Understanding this principle is essential for solving problems involving objects moving at significant fractions of the speed of light.