variations du mouvement

Why does a stone thrown into the air keep going, even after it has left the thrower's hand? Why does it slow down before speeding up again? Could it be thrown in a void without end? Is there a rest at the peak of its flight? Interpreting this movement has aroused impassioned debate since antiquity; the controversy was still ongoing at the time when the Jewish philosopher Ab? al-Barak't (d. 1152), physician to the Caliph of Baghdad, provided a new approach to it. This book takes the reader through a labyrinth of texts dealing with notions of space, emptiness, time, infinity, and continuity; it sheds light on mediaeval Arabic contributions to physics. The author also explores the barriers that have hitherto obstructed complete understanding of the subject. The history of science, which sometimes fixates on the study of continuities finds it hard to get to grips with disruptive theories if they do not seem to follow the larger trajectory of history.