Modified Newtonian Dynamics - Discussion and Criticisms

Discussion and Criticisms

An empirical criticism of MOND, released in August 2006, involves the Bullet cluster, a system of two colliding galaxy clusters. In most instances where phenomena associated with either MOND or dark matter are present, they appear to flow from physical locations with similar centers of gravity. But, the dark matter-like effects in this colliding galactic cluster system appears to emanate from different points in space than the center of mass of the visible matter in the system, which is unusually easy to discern due to the high-energy collisions of the gas in the vicinity of the colliding galactic clusters. MOND proponents admit that a purely baryonic MOND is not able to explain this observation. Therefore a “marriage” of MOND with ordinary hot neutrinos of 2eV has been proposed to save the hypothesis.

C. Sivram has noticed that the accelerations GM/r2 for the electron, the proton, the nucleus of an atom, the globular clusters, the spiral galaxies, the galactic clusters and the whole universe strikingly turn out to be equal to the critical acceleration a₀ of MOND. Hasmukh K. Tank has attempted to explain these recurrences as a consequence of a new law of equality of gravitational potential energy and energy of mass of reasonably independent systems of matter. In this paper, he has also shown that the carefully measured Sunward-accelerations of the Pioneer-10, Pioneer-11, Galileo and Ulyssus space-probes are quite close to the 'critical-acceleration' of MOND; and the 'cosmological-red-shift' when expressed as deceleration of cosmic photons, match strikingly with the 'critical-acceleration' of MOND. Tank has also proposed a wave theoretical explanation for the new law of equality of potential energy and energy of mass. It leads to a possibility that the law of conservation of energy is more fundamental than the strengths of fundamental forces; that is, the strength of a fundamental force gets decided in obedience to the law of conservation of energy.

Beside MOND, three other notable theories that try to explain the mystery of the rotational curves are Nonsymmetric Gravitational Theory proposed by John Moffat, Conformal gravity by Philip Mannheim, and Dynamic Newtonian Advanced gravity (DNAg)