However, concomitant with the growth of reason and the partial removal of the theological ban, there was developed a remarkable scientific movement, with a variety of discoveries and inventions. For more than a millennium the Greek developments in astronomy and physics had been accepted as final, but toward the close of the sixteenth and during the seventeenth century these _dicta_ were completely upset. The hypothesis of a solar system, which replaced the Ptolemaic interpretation, was published by Copernicus (1473-1543); Kepler (1571-1630) explained the motion of the planets by three simple laws; and, through the construction of a telescope, Galileo (1564-1642) revealed new celestial phenomena. Galileo also demonstrated that all bodies, allowing for the resistance of the air, fall at the same rate; by means of the barometer, Torricelli (1608-1647) and Boyle (1627-1691) proved the existing theories of a vacuum incorrect, and formulated important laws concerning the pressure of gases; and Guericke (1602-1686), inspired by their discoveries, succeeded in constructing an air-pump. Investigations of this kind paved the way for the formulation of the law of universal gravitation and the laws of motion by Sir Isaac Newton (1642-1727), which united the universe into a single comprehensive system and completed the foundations for modern mechanics. [Sidenote: Development of anatomy and physiology.] Likewise, about the same time, the other great development in science among the Greeks,--anatomy and physiology, was completely revolutionized. Through the discovery of valves in the veins by means of dissection and vivisection, the hypothesis of the double circulation of the blood by Harvey (1578-1657), and the microscopic demonstrations by Malpighi (1628-1694) of the existence of capillaries connecting the veins and the arteries, the old theory of the motion of the blood through suction, which had been promulgated by Galen, was completely shattered, and a great impetus was given to investigations in anatomy and physiology. In consequence of this scientific progress, the educational theorists began to introduce science and a knowledge of real things into the curriculum. It came to be widely felt that humanism gave a knowledge only of words, books, and opinions, and did not even at its best lead to a study of real things. Hence, new methods and new books were produced, to shorten and improve the study of the classical languages, and new content was imported into the courses of study. The movement also included an attempt at a formulation of scientific principles in education and an adaptation to the nature of the child. [Sidenote: Bacon rejected the deductive method of the day,] [Sidenote: but created a mechanical procedure.]