In which the travellers pass an uneventful first night in their projectile, contemplating the sensations of motion and the mysteries of inertia as the moon gradually looms above them; a lively discussion then unfolds as Barbicane patiently elucidates, through algebraic reasoning, the complex calculations required to determine the initial speed necessary to reach the moon, much to Michel Ardan’s simultaneous admiration and bewilderment. The conversation culminates in the startling realisation that the velocity achieved may fall short of the crucial threshold, provoking anxious concern for the journey ahead.