Yukawa also worked on the theory of K-capture, in which a low energy electron is absorbed in the nucleus. In 1955, Yukawa, and ten other leading scientists and intellectuals, joined to sign the Russell-Einstein Manifesto calling for nuclear disarmament. On September 8, 1981, Hideki Yukawa died in his house in Sakyo-ku, Kyoto from pneumonia and heart failure. I feel as though Hideki Yukawa studied a very complicated matter, theoretical physics. The reason why I say this is because theoretical physics is basically a branch of physics that employs mathematical models and abstractions of physics to rationalize. That was hard for me to understand, but to put it in more simple terms, it’s basically using mathematics to describe a certain aspect in nature. Theoretical physics all began about 2.300 years ago, under the Pre-Socratic Philosophy, and was continued by Plato and Aristotle, whose view held sway for the millennium. During the Middle Ages and Renaissance, the concept of experimental science, the counterpointto theory, began with scholars such as Ibn al-Haytham and Francis Bacon. The great push toward the modern concept of explanation started with Galileo, one of the few physicists who was both a consummate theoretician and a great experimentalist. By Newton's era, people had already used algebra and geometry to build marvelous works of architecture, including the great cathedrals of Europe. But algebra and geometry only describe things that are sitting still. In order to describe things that are moving or changing in some way, Newton invented calculus. Newton's new calculus, combined with his "Laws of Motion", made a mathematical model for the force of gravity that not only described the observed motions of planets and stars in the night sky, but also of swinging weights and flying cannonballs in England. Today's theoretical physicists are often working on the boundaries of known mathematics, sometimes inventing new mathematics as they need it, like Newton did with calculus. Today the functions of theory and observation are divided into two distinct communities in physics. Both experiments and theories are much more complex than back in Newton's time. Theorists are exploring areas of Nature in mathematics that technology so far does not allow us to observe in experiments. Many of the theoretical physicists who are alive today may not live to see how the real Nature compares with her mathematical description in their work. Today's theorists have to learn to live with ambiguity and uncertainty in their mission to describe Nature using math. Other than theoretical physics, Hideki Yukawa was also interested in something called