In this chapter, we obtain a modified form of the Foldy–Wouthuysen and Cini–Toushek transformations by using a noncommutative spacetime geometry, starting from the Klein–Gordon equation. Also, we obtain a shift in the energy levels due to noncommutativity and from these result a limit for the Lorentz factor in the ultra-relativistic case has been derived in conformity with observations. This is to be expected because the usual Lorentz transformation works in smooth Minkowski space but if this space is noncommutative, slight deviations show up. This leads to a limit on velocities of particles. All this leads to the ZPE as we saw in Chapter 1 as also is an observable footprint.