  It is surprising that we hardly know only 5% of the universe. Rest of the
universe is made up of 70% of dark-energy and 25% of dark-matter. Dark-energy
is responsible for acceleration of the expanding universe; whereas dark-matter
is said to be necessary as extra-mass of bizarre-properties to explain the
anomalous rotational-velocity of galaxy. Though the existence of dark-energy
has gradually been accepted in scientific community, but the candidates for
dark-matter have not been found as yet and are too crazy to be accepted. Thus,
it is obvious to look for an alternative theory in place of dark-matter.
Israel-scientist M. Milgrom has suggested a 'Modified Newtonian Dynamics
(MOND)' which appears to be highly successful for explaining the anomalous
rotational-velocity. But unfortunately MOND lacks theoretical support. The
MOND, in-fact, is (empirical) modification of Newtonian-Dynamics through
modification in the kinematical acceleration term 'a' (which is normally taken
as $a=\frac{v^{2}}{r}$) as effective kinematic acceleration $a_{effective} = a
\mu (\frac{a}{a_{0}})$, wherein the $\mu$-function is 1 for usual-values of
accelerations but equals to $\frac{a}{a_{0}} (\ll 1)$ if the acceleration 'a'
is extremely-low lower than a critical value $a_0 (10^{-10} m/s^{2})$. In the
present paper, a novel variant of MOND is proposed with theoretical backing;
wherein with the consideration of universe's acceleration $a_{d}$ due to
dark-energy, a new type of $\mu$-function on theoretical-basis emerges out
leading to $a_{effective} = a(1 - K \frac{a_{0}}{a})$. The proposed
theoretical-MOND model too is able to fairly explain qualitatively the
more-or-less 'flat' velocity-curve of galaxy-rotation, and is also able to
predict a dip (minimum) on the curve.
