Three Major Discoveries of Natural Science in the 19th Century

The three major achievements formed by natural sciences in the 19th century: the cell theory, the law of conservation and transformation of energy and the theory of evolution. In the 19th century, some major fields of natural science have successively entered from the empirical field into the theoretical field. Although a series of important discoveries have taken place in the fields of astronomy, geology, physics, chemistry and biology, the “three major discoveries” were the most representative achievements among them.

The cell theory is a theory about the composition of living organisms. In 1838, German biologist Schleiden (1804–1881) published the article Contributions to Our Knowledge of Phytogenesis, which put forth that the plants were composed up of cells. In 1839, German biologist Schwann (1810–1882) published Microscopical Researches Into the Accordance in the Structure and Growth of Animals and Plants, which clearly pointed out that animals, like plants, were also composed of cells. The cell theory has revealed the structural uniformity of plants and animals, proved the uniformity of the entire biological world in terms of structure and its common origin in terms of evolution. The establishment of the cell theory has shown the character of universal interconnection of the material world.

In the 1840s, Mayer, Joule, von Helmholtz and others have discovered the law of conservation and transformation of energy through their respective ways. This law shows that, under certain conditions, various forms of energy in nature can transform into each other in fixed relations and that energy will neither increase nor disappear in the process of transformation. Therefore, all motion in nature resolves itself to a process of constant transformation from one form to another and the total energy before and after such transformations remains the same. This furnished the consistent materialist notion with a natural science basis.

In 1859, English biologist Darwin’s book On the Origin of Species by Means of Natural Selection was published. In this book, he systematically put forth the theory of biological evolution based on natural selection and, using a large number of facts, he proved that any species in the biological world has its history of generation, development and passing away, which is the result of natural selection and long-term evolution of biological species, thus revealing the laws of development of organisms from simple to complex and from the lower to the higher. The theory of evolution showed that everything has its process of change and development and that the world is a complex of processes.

Together with other achievements of natural sciences such as the Kant-Laplace nebular hypothesis in the field of astronomy, the theory of electromagnetic transformation in the field of physics, the atomistics and the periodic law of elements in the field of chemistry, the “three major discoveries” revealed the historical development and the universal interconnection of nature from different aspects; they revealed the diversity of the forms of motion of matter in nature as well as their interconnection and transformation into each other, vividly and profoundly displayed the objective dialectics of nature and furnished the dialectical materialist world outlook with a natural science basis.