  This paper revisits previous papers related to the theory of relativity.
Afterwards, a reconsideration of the hypothesis of ether-dragging is discussed.
The ether is compatible with the theory of relativity and historical
experiments; this paper explains the Michelson-Morley experiment using the
ether-dragging hypothesis without the orthodox interpretation that the speed c
is a fixed constant in terms of any system of inertial coordinates.
