  His scientific career was varied and complex, if never quite associated with glowing triumph. Some historians consider his greatest accomplishment in this sphere to be his contribution to the revival of ancient atomism but this represents only one end of his anti-Aristotelian physics, and a small, albeit core element of his scientific interests. His other accomplishments in physics includes a study of bodies in free fall (closely modeled on Galileo's work), a mature enunciation of the principle of inertia, and an early and reasonably accurate interpretation of the Pascalian barometry experiments of the late 1640s. Gassendi also ventured into experimental science: he attempted to measure the speed of sound by cannon fire, arranged to have weights dropped from the mast of a moving ship to enact Galileo's thought experiment (and so dispel doubts about the motion of the Earth), and conducted numerous chemical trials involving, among other things, the dissolution of salts and formation of crystals (which he took to bolster his molecular theory of matter).  These are only some of his better-known exploits. In addition, he offered a wide variety of speculations on the earth sciences based partly on geological fieldwork and biological and physiological observations—and as shaped by his atomist hypothesis. Finally, Gassendi devoted much of his time to astronomical pursuits. He made regular observations of the skies for decades, producing confirmatory evidence for Kepler's views, observing sunspots, the anses of Saturn, and the passage of Mercury before the Sun (1631), and successfully predicting an eclipse in 1654. Moreover, he commissioned the first map of the moon, defended the Copernican view as plausible save for its conflicts with Church teachings, and offered many disparaging words on what he considered the scurrilous and empirically intolerable practice of astrology.