  If the recent observations suggesting a time variation of the fine structure
constant are correct, they imply the existence of an ultra light scalar
particle. This particle inevitably couples to nucleons through the
\alpha-dependence of their masses and thus mediates an isotope-dependent
long-range force. The strength of the coupling is within a couple of orders of
magnitude from the existing experimental bounds for such forces. The new force
can be potentially measured in the precision experimental tests of the
equivalence principle. Due to an interesting coincidence of the required
time-scales, the scalar filed in question can at the same time play the role of
a quintessence field.
