地球半径
Apart from the first observation of the Mercury transit, relatively little is known of Remus Quietanus, a privileged witness of the Copernican revolution. But he is not a passive observer. In his correspondence with Kepler, he took part in astronomical debate and asked questions that fitted exactly with the issues of his time: the calculation of longitudes, the nature of comets, the dimension of planets, their distances to the sun and especially the distance from the Earth to the Sun (Astronomical unit). On the last point, he had a better intuition than Kepler who gave an estimation of 3400 of Earth radius. Remus Quietanus proposed 14000. Not until 1685 did Christiaan Huygens suggest a more accurate estimation (around 23500 of Earth radius).