Like other educated men of his day (and those of the 1200s through the 1500s), he believed that the earth was the center of the universe and in astrology, that is, that the position of the stars and planets influenced man and other earthly things. For instance, the position of the stars at a person's birth determined his character. The angle and therefore potency of the sun's rays influenced climate, temperament, and changes of mortal life such as disease and revolutions. There was a propitious time to have a marriage, go on a journey, make war, and take herbal medicine or be bled by leeches, the latter of which was accompanied by religious ceremony. Cure was by God, with medical practitioners only relieving suffering. Pressure and binding were applied to bleeding. Arrow and sword wounds to the skin or to any protruding intestine were washed with warm water and sewn up with needle and silk thread. Ribs were spread apart by a wedge to remove arrow heads. Fractured bones were splinted or encased in plaster. Dislocations were remedied. Hernias were trussed. Bladder stones blocking urination were pushed back into the bladder or removed through an artificial opening in the bladder. Bacon studied the planetary motions and astronomical tables to forecast future events. He did calculations on days in a month and days in a year which later contributed to the legal definition of a leap year. He knew about magnetic poles attracting if different and repelling if the same and the relation of magnets' poles to those of the heavens and earth. He calculated the circumference of the world and the latitude and longitude of terrestrial positions, which was the beginning of the study of geography. He foresaw sailing around the world and pointed the way to the Copernican astronomy, which was founded on the concept of the earth and planets revolving around the sun. His contribution to the development of science was abstracting the method of experiment from the concrete problem to see its bearing and importance as a universal method of research. He advocated changing education to include studies of the natural world using observation, exact measurement, and experiments.