  Among the symmetries in physics, the rotation symmetry is most familiar to
us. It is known that the spherical harmonics serve useful purposes when the
world is rotated. Squeeze transformations are also becoming more prominent in
physics, particularly in optical sciences and in high-energy physics. As can be
seen from Dirac's light-cone coordinate system, Lorentz boosts are squeeze
transformations. Thus the squeeze transformation is one of the fundamental
transformations in Einstein's Lorentz-covariant world. It is possible to define
a complete set of orthonormal functions defined for one Lorentz frame. It is
shown that the same set can be used for other Lorentz frames. Transformation
properties are discussed. Physical applications are discussed in both optics
and high-energy physics. It is shown that the Lorentz harmonics provide the
mathematical basis for squeezed states of light. It is shown also that the same
set of harmonics can be used for understanding Lorentz-boosted hadrons in
high-energy physics. It is thus possible to transmit physics from one branch of
physics to the other branch using the mathematical basis common to them.
