Moon clouds. The illuminated area of the visible sphere (degree of illumination) is given by formula_3, where formula_4 is the elongation (i.e., the angle between Moon, the observer (on Earth) and the Sun). The gravitational attraction that masses have for one another decreases inversely with the square of the distance of those masses from each other. As a result, the slightly greater attraction that the Moon has for the side of Earth closest to the Moon, as compared to the part of the Earth opposite the Moon, results in tidal forces. Tidal forces affect both the Earth's crust and oceans. The
Around the Moon to Earth. During the latter part of the voyage, it becomes apparent that the gravitational force of their earlier encounter with the asteroid has caused the projectile to deviate from its course. The projectile enters lunar orbit, rather than landing on the moon as originally planned. Barbicane, Ardan and Nicholl begin geographical observations with opera glasses. The projectile then dips over the northern hemisphere of the moon, into the darkness of its shadow. It is plunged into extreme cold, before emerging into the light and heat again. They then begin to approach the moon's southern hemisphere. From the safety of