  It has been known that dimensional constants such as $\hbar$, $c$, $G$, $e$,
and $k$ are merely human constructs whose values and units vary depending on
the chosen system of measurement. Therefore, the time variation of dimensional
constants lacks operational significance due to their dependence on them. It is
well-structured and represents a valid discussion. However, this fact only
becomes a meaningful debate within the context of a static or present universe.
As well-established theoretically and observationally, the current universe is
undergoing accelerated expansion, wherein dimensional quantities, like the
wavelength of light, also experience redshift phenomena elongating over cosmic
time. In other words, in an expanding universe, dimensional quantities of
physical parameters vary with cosmic time. From this perspective, there exists
the possibility that dimensional constants, such as the speed of light, could
vary with the expansion of the universe. In this review paper, we contemplate
under what circumstances the speed of light may change or remain constant over
cosmic time, and discuss the potential for distinguishing these cases
observationally.
