A sphere with radius R 1 is chosen as the object to be hidden. The cloaking region is to be contained within the annulus R 1 < r < R 2. A simple transformation that achieves the desired result can be found by taking all fields in the region r < R 2 and compressing them into the region R 1 < r < R 2. The coordinate transformations do not alter Maxwell's equations. Only the values of ε ′ and μ ′ change over time.