Quantum superposition   To do this we need to know some basic
facts about the waves: their amplitude (how big the wave is),
their speed (how fast the peak of the wave travels), their
wavelength (the distance between two peaks), and a period (the
time it takes for a single position to experience a peak, a
trough, and another a peak). There is also an important property
that relates the two waves to each other: phase, which measures
the time between peaks of the waves.  To create a superposition,
we perform an addition that takes into account all of these
factors. In some places the waves disappear if a peak from one
coincides with a trough of the other. At other locations, two
peaks or troughs will coincide to give a much larger wave. This
behavior is called interference and it can only occur when
adding through superposition is valid.  Sometimes, however, our
instruments can't perceive the patterns that are due to
superposition, or some of the wave properties change rapidly in
either time or space. In this ca