As early as 1687, Isaac Newton published the law of gravitation named after him. This law includes the so-called ‘universal gravitational constant’, also named after him. With the help of this law, it was possible, amongst other things, to calculate the orbital paths of the planets in our solar system with such precision that perturbations in the orbit of Uranus were detected. These perturbations led to the prediction of the existence of another planet. In 1883, the new planet Neptune was indeed discovered at the predicted position, with a deviation of barely 1 degree.In recent decades, many new measurement results with ever-decreasing errors have been published. Unfortunately, the results often differed by more than the sum of their uncertainties. The results often do not merely represent a fixed value, but also time-varying components. Of particular interest are, for example, short-term variations, as their exact date is helpful in the search for their cause. Even more interesting, however, are periodic variations, as knowledge of the period length greatly narrows the search for the cause. One such variation with a period length of 5.9 years is well established. Based on the ‘Alternative Reflections on Gravitation’ (ARG), the search quickly leads to the suspected polluter: Jupiter, the largest planet in the solar system. Perhaps this planet is involved also in a non-gravitational effect, the Solar Cycle with a period of about 11 years.