Thus the time passed in never-ending conversations all about the moon. The projectile, its situation, its direction, incidents which might happen, the precautions necessitated by their fall on to the moon, were inexhaustible matters of conjecture. As they were breakfasting, a question of Michel's, relating to the projectile, provoked rather a curious answer from Barbicane, which is worth repeating. Michel, supposing it to be roughly stopped, while still under its formidable initial speed, wished to know what the consequences of the stoppage would have been. It is known now that heat is only a modification of motion.
Heat is but the motion of atoms, a simple oscillation of the particles of a body.
It is transformed into heat, and the brake becomes hot. To prevent their heating, because this heat would be generated by the motion which is thus lost by transformation. Simply because my motion is changed into heat. And this theory allows us to infer that the heat of the solar disc is fed by a hail of meteors falling incessantly on its surface. If there are inhabitants, they must breathe.