  We investigate the effects of the repeated application of Lorentz-boosts to
the four momentum of a photon in the transverse direction and observe that this
can take us to a reference frame in which the direction of the photon's
momentum is apparently reversed. We further extend this to an infinite
succession of infinitesimal transverse Lorentz-boosts and show it amounts to a
rotation of the photon's momentum, while the transformation is not a simple
rotation but a Lorentz transformation. These possibly surprising results can be
understood in light of the Wigner rotation: the combination of Lorentz-boosts
along different directions amounts to a Lorentz-boost combined with a rotation.
The presented exercises are some more illustrations of the counterintuitive
behavior of Lorentz-boost combinations.
