Living in a non-Newton universe

Isaac Newton’s theory of gravitation, a milestone of physics and science overall for centuries, is increasingly undergoing heretical attacks. Two new studies, by the physicists Pavel Kroupa and Manuel Metz from the University of Bonn in collaboration with Gerhard Hensler and Christian Theis from the Institute of Astronomy of the University of Vienna together with Helmut Jerjen from the Australian National University, Canberra, show results about so-called “satellite galaxies” at the periphery of the Milky Way which could rock the theoretical foundations of standard physics.

As modern cosmologists rely more and more on the ominous “dark matter” to explain otherwise inexplicable observations, much effort has gone into the detection of this mysterious substance in the last two decades. Yet, “no direct proof could be found that it actually exists”, Gerhard Hensler explains. Even if it does exist, dark matter would be unable to reconcile all the current discrepancies between actual measurements and predictions based on theoretical models. Their only problem is that they conflict with Newton’s theory of gravitation.

In these two new studies, scientists have examined the so-called “satellite galaxies”, a term used for dwarf galaxy companions of the Milky Way, some of which contain only a few thousand stars. Best cosmological models describe they exist presumably in hundreds around most of the major galaxies. Up to now, however, only 30 such satellites have been observed around the Milky Way, a discrepancy in numbers which is commonly attributed to the fact that the light emitted from the majority of satellite galaxies is so faint they remain invisible.

A detailed study of these stellar agglomerates has revealed some astonishing phenomena: “First of all”, Kroupa explains, “there is something unusual about their distribution. Satellites should be uniformly arranged around their mother galaxy, but this is not what we found”.

Physicists do believe this phenomenon can only be explained if the satellites originated a long time ago through collisions between younger galaxies. Or one must assume that some basic fundamental principles of physics have hitherto been incorrectly understood. “The only solution would be to reject Newton’s classical theory of gravitation”, says Pavel Kroupa. “We probably live in a non-Newton universe. If this is true, then our observations could be explained without dark matter”. Such approaches are finding support amongst other research teams in Europe, too.

It would not be the first time that Newton’s theory of gravitation had to be modified over the past hundred years. This became necessary in three special cases: when high velocities are involved (through the Special Theory of Relativity), in the proximity of large masses (through the theory of General Relativity), and on sub-atomic scales (through quantum mechanics).

Famous astrophysicist Bob Sanders from the University of Groningen declares: “The authors of this paper make a strong argument. Their result is entirely consistent with the expectations of modified Newtonian dynamics (MOND), but completely opposite to the predictions of the dark matter hypothesis. Rarely is an observational test so definite.”

This problem of the origin and nature of satellite galaxies and their implications for fundmental physics will be discussed by experts at a one-week long international conference to be held end of May in the Physics Centre of Bad Honnef near Bonn. Moreover, Gerhard Hensler who studies with his research group at the University of Vienna in a FWF-funded project the evolution of satellite galaxies by means of computer simulations must extend the parameter space of models according to these observational facts.


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