A modification of the Newtonian dynamics as a possible alternative to the hidden mass hypothesis.

The author considers the possibility that there is not, in fact, much hidden mass in galaxies and galaxy systems. If a certain modified version of the Newtonian dynamics is used to describe the motion of bodies in a gravitational field (of a galaxy, say), the observational results are reproduced with no need to assume hidden mass in appreciable quantities. Various characteristics of galaxies result with no further assumptions. The basis of the modification is the assumption that in the limit of small acceleration a very low a₀, the acceleration of a particle at distance r from a mass M satisfies approximately a²/a₀ ≈ MGr^-2, where a₀ is a constant of the dimensions of an acceleration.