Branches of Science

Science describes an area of knowledge, typically about something in the physical world, that can be explained in terms of scientific observation or the scientific method. The scientific method is a discovery process that has evolved over several hundred years and can be summarized as follows:

a phenomenon in the physical world is observed
an explanation, or hypothesis, for the phenomenon is formed
the hypothesis is tested by means of objective, reproducible experiments

If the results of the experiments support the hypothesis, it becomes accepted as scientific theory. Later, if new information is found to contradict the hypothesis, it may be revised or abandoned in favor of a new hypothesis, which is then subjected to additional experiments.

The sciences that describe the physical universe are categorized in different ways. The largest distinction in science is whether a science is pure, or theoretical, or whether it is applied, or practical. Pure science explains a phenomenon, while applied science determines how a particular phenomenon may be put to use. In general, pure science is divided into the following categories:

Physical sciences, which deal with matter and energy and allow us to describe the material universe in terms of weight, mass, volume, and other standard, objective measures.
Earth sciences, which explain the phenomena of Earth, its atmosphere, and the solar system to which it belongs.
Life sciences, which describe living organisms, their internal processes, and their relationship to each other and the environment.

However, these three categories of pure science have areas of overlap, where one type of phenomenon may be associated with another. For example, light (studied in physics) is the energy source behind the (chemical) process of photosynthesis, or food production, in plants (studied in biology). For this reason, distinctions between pure sciences, and even between pure and applied sciences, can blur, and a new compound science can develop. An example of this is biochemistry, in which the chemical processes of living things (such as photosynthesis) are observed and explained.

Physical sciences	Life sciences	Earth sciences
Physics Kinetics Mechanics Electromagnetics Thermodynamics	Biology Botany Zoology	Geology Meteorology Astronomy
Chemistry Inorganic Chemistry Electrochemistry Analytical Chemistry
Examples of Overlapping Sciences
Physics + Chemistry = Physical Chemistry	Biology + Chemistry = Biochemistry Organic Chemistry	Geology + Chemistry = Geochemistry
Astronomy + Physics = Astrophysics	Biology + Geology = Paleontology	Geology + Astronomy = Astrogeology
	Biology + Astronomy + Physics = Astronautics