The phenomenon of tides and tidal currents had been well studied in the Middle Ages and a number of treatises had been written on the subject. But the credit for treating the subject in a logical manner goes to Alberuni. He realized that tides are produced by the attractive power of the Sun and the moon. He emphatically says that the gravitational pull of the moon is far greater than that of the Sun as the former is closer to the earth. However, the part played by the Sun in producing this phenomenon is also significant. Thus, Alberuni's hypothesis was embryonic of the Newtonian law of gravitation.

Alberuni specifically points out that the motions of the Sun and the moon produce motions in the water.⁶³ He also points out that the Sun, when positioned closer to the earth, i.e., when it is on the perigee, exerts a...