The problem of the three bodies can be considered as the unsolved enigma par excellence in physics. The problem has remained almost unsolved, in fact, for almost 350 years, despite the various theoretical attempts of physicists in the field of modern astrophysics: how can one calculate the reciprocal gravitational influence and evolution in the context of the laws of motion of a system consisting of three bodies in space?

Through the laws of motion provided by one of the greatest scientists of all time, Isaac Newton, it is still possible to evaluate the evolution of a two-body system, just as he demonstrated for the Earth orbiting the Sun; it would seem, however, impossible to calculate – except in exceptional cases – that of a three-body system: Newton wondered, in fact, what would have happened if the Moon had been added to the Earth-Sun system.

By inserting a third object in a system with two bodies, where each of them has its own specific dimension and distance from the central point taken into consideration, a sort of “gravitational struggle” between them would begin to develop, throwing chaos in the whole system, and overcoming the theories so far discovered. It is, therefore, complicated to apply a universal law for all cases of three-body systems.

Although it still does not seem to be completely solved, the problem of the three bodies has been addressed and untangled, in part, by a new research conducted by the astrophysicist Nicholas Stone, with his team and Professor Nathan Leigh, at the University of Jerusalem: after long analysis and tests, they proposed their research results, which have been published in Nature.

They discovered that, in a three-body system, one of the three, after a previous instability and struggle of their orbits, will be automatically expelled from the trio: the duo will thus begin to establish a binary relationship which, unlike the previous three-object system, will be stable. Even if this does not lead to a real solution to the problem, the concept is useful to evaluate certain statistical solutions in complicated processes between two bodies.

All this has been ascertained by applying the simple traditional mathematics used to predict the movement of the planets, using a methodology of probability hypothesis called “ergodicity”, since a statistical process is carried out on all the possible working points involved.

As Dr. Stone stated, “Take three black holes that are orbiting each other. Their orbits will necessarily become unstable and even after one of them is expelled, we are still very interested in the relationship between the surviving black holes”.

Even if the basic unknown has not been completely solved, this further study could be considered as the classic “step forward” towards the solution of a problem that Newton, back in 1687, had brought to the fore.