IV.

Branches of Science

Classifying sciences involves arbitrary decisions because the universe is not easily split into separate compartments. This article divides science into five major branches: mathematics, physical sciences, earth sciences, life sciences, and social sciences. A sixth branch, technology, draws on discoveries from all areas of science and puts them to practical use. Each of these branches itself consists of numerous subdivisions. Many of these subdivisions, such as astrophysics or biotechnology, combine overlapping disciplines, creating yet more areas of research. For additional information on individual sciences, refer to separate articles highlighted in the text.

A.

Mathematical Sciences

The mathematical sciences investigate the relationships between things that can be measured or quantified in either a real or abstract form. Pure mathematics differs from other sciences because it deals solely with logic, rather than with nature's underlying laws. However, because it can be used to solve so many scientific problems, mathematics is usually considered to be a science itself.

Central to mathematics is arithmetic, the use of numbers for calculation. In arithmetic, mathematicians combine specific numbers to produce a result. A separate branch of mathematics, called algebra, works in a similar way, but uses general expressions that apply to numbers as a whole. For example, if there are three separate items on a restaurant bill, simple arithmetic produces the total amount to be paid. But the total can also be calculated by using an algebraic formula. A powerful and flexible tool, algebra enables mathematicians to solve highly complex problems in every branch of science.

Geometry investigates objects and the spaces around them. In its simplest form, it deals with objects in two or three dimensions, such as lines, circles, cubes, and spheres. Geometry can be extended to cover abstractions, including objects in many dimensions. Although we cannot perceive these extra dimensions ourselves, the logic of geometry still holds.

In geometry, it is easy to work out the exact area of a rectangle or the gradient (slope) of a line, but there are some problems that geometry cannot solve by conventional means. For example, geometry cannot calculate the exact gradient at a point on a curve, or the area that the curve bounds. Scientists find that calculating quantities like this helps them understand physical events, such as the speed of a rocket at any particular moment during its acceleration.

To solve these problems, mathematicians use calculus, which deals with continuously changing quantities, such as the position of a point on a curve. Its simultaneous development in the 17th century by English mathematician and physicist Isaac Newton and German philosopher and mathematician Gottfried Willhelm Leibniz enabled the solution of many problems that had been insoluble by the methods of arithmetic, algebra, and geometry. Among the advances that calculus helped develop were the determination of Newton’s laws of motion and the theory of electromagnetism (see Magnetism).

B.

Physical Sciences

The physical sciences investigate the nature and behavior of matter and energy on a vast range of size and scale. In physics itself, scientists study the relationships between matter, energy, force, and time in an attempt to explain how these factors shape the physical behavior of the universe. Physics can be divided into many branches. Scientists study the motion of objects, a huge branch of physics known as mechanics that involves two overlapping sets of scientific laws. The laws of classical mechanics govern the behavior of objects in the macroscopic world, which includes everything from billiard balls to stars, while the laws of quantum mechanics govern the behavior of the particles that make up individual atoms (see Quantum Theory).

Other branches of physics focus on energy and its large-scale effects. Thermodynamics is the study of heat and the effects of converting heat into other kinds of energy. This branch of physics has a host of highly practical applications because heat is often used to power machines. Physicists also investigate electrical energy and energy that is carried in electromagnetic waves. These include radio waves, light rays, and X rays—forms of energy that are closely related and that all obey the same set of rules (see Electromagnetic Radiation).

Chemistry is the study of the composition of matter and the way different substances interact—subjects that involve physics on an atomic scale. In physical chemistry, chemists study the way physical laws govern chemical change, while in other branches of chemistry the focus is on particular chemicals themselves. For example, inorganic chemistry investigates substances found in the nonliving world and organic chemistry investigates carbon-based substances. Until the 19th century, these two areas of chemistry were thought to be separate and distinct, but today chemists routinely produce organic chemicals from inorganic raw materials. Organic chemists have learned how to synthesize many substances that are found in nature, together with hundreds of thousands that are not, such as plastics and pesticides. Many organic compounds, such as reserpine, a drug used to treat hypertension, cost less to produce by synthesizing from inorganic raw materials than to isolate from natural sources. Many synthetic medicinal compounds can be modified to make them more effective than their natural counterparts, with less harmful side effects.

The branch of chemistry known as biochemistry deals solely with substances found in living things. It investigates the chemical reactions that organisms use to obtain energy and the reactions they use to build themselves up. Increasingly, this field of chemistry has become concerned not simply with chemical reactions themselves but also with how the shape of molecules influences the way they work. The result is the new field of molecular biology—one of the fastest-growing sciences today.

Physical scientists also study matter elsewhere in the universe, including the planets and stars. Astronomy is the science of the heavens in general, while astrophysics is a branch of astronomy that investigates the physical and chemical nature of stars and other objects. Astronomy deals largely with the universe as it appears today, but a related science called cosmology looks back in time to answer the greatest scientific questions of all: how the universe began and how it came to be as it is today.

C.

Earth Sciences

The earth sciences examine the structure and composition of our planet, and the physical processes that have helped to shape it. Geology focuses on the structure of Earth, while geography is the study of everything on the planet's surface, including the physical changes that humans have brought about from, for example, farming, mining, or deforestation. Scientists in the field of geomorphology study Earth's present landforms, while mineralogists investigate the minerals in Earth's crust and the way they formed (see Mineralogy).

Water dominates Earth's surface, making it an important subject for scientific research. Oceanographers carry out research in the oceans (see Ocean and Oceanography), while scientists working in the field of hydrology investigate water resources on land, a subject of vital interest in areas prone to drought. Glaciologists study Earth's icecaps and mountain glaciers, and the effects that ice has when it forms, melts, or moves. In atmospheric science, meteorology deals with day-to-day changes in weather, but climatology investigates changes in weather patterns over the longer term (see Climate).

When living things die their remains are sometimes preserved, creating a rich store of scientific information. Paleontology is the study of plant and animal remains that have been preserved in sedimentary rock, often millions of years ago (see Fossil). Paleontologists study things long dead and their findings shed light on the history of evolution and on the origin and development of humans. A related science, called palynology, is the study of fossilized spores and pollen grains. Scientists study these tiny structures to learn the types of plants that grew in certain areas during Earth’s history, which also helps identify what Earth’s climates were like in the past.

D.

Life Sciences

The life sciences include all those areas of study that deal with living things. Biology is the general study of the origin, development, structure, function, evolution, and distribution of living things. Biology may be divided into botany, the study of plants; zoology, the study of animals; and microbiology, the study of the microscopic organisms, such as bacteria, viruses, and fungi. Many single-celled organisms play important roles in life processes and thus are important to more complex forms of life, including plants and animals.

Genetics is the branch of biology that studies the way in which characteristics are transmitted from an organism to its offspring. In the latter half of the 20th century, new advances made it easier to study and manipulate genes at the molecular level, enabling scientists to catalog all the genes found in each cell of the human body (see Human Genome Project). Exobiology, a new and still speculative field, is the study of possible extraterrestrial life. Although Earth remains the only place known to support life, many believe that it is only a matter of time before scientists discover life elsewhere in the universe.

While exobiology is one of the newest life sciences, anatomy is one of the oldest. It is the study of plant and animal structures, carried out by dissection or by using powerful imaging techniques (see Radiology). Gross anatomy deals with structures that are large enough to see, while microscopic anatomy deals with much smaller structures, down to the level of individual cells.

Physiology explores how living things work. Physiologists study processes such as cellular respiration and muscle contraction, as well as the systems that keep these processes under control. Their work helps to answer questions about one of the key characteristics of life—the fact that most living things maintain a steady internal state when the environment around them constantly changes.

Together, anatomy and physiology form two of the most important disciplines in medicine, the science of treating injury and human disease. General medical practitioners have to be familiar with human biology as a whole, but medical science also includes a host of clinical specialties. They include sciences such as cardiology, urology, and oncology, which investigate particular organs and disorders, and also pathology, the general study of disease and the changes that it causes in the human body.

As well as working with individual organisms, life scientists also investigate the way living things interact. The study of these interactions, known as ecology, has become a key area of study in the life sciences as scientists become increasingly concerned about the disrupting effects of human activities on the environment.

E.

Social Sciences

The social sciences explore human society past and present, and the way human beings behave. They include sociology, which investigates the way society is structured and how it functions, as well as psychology, which is the study of individual behavior and the mind. Social psychology draws on research in both these fields. It examines the way society influences people's behavior and attitudes.

Another social science, anthropology, looks at humans as a species and examines all the characteristics that make us what we are. These include not only how people relate to each other but also how they interact with the world around them, both now and in the past. As part of this work, anthropologists often carry out long-term studies of particular groups of people in different parts of the world. This kind of research helps to identify characteristics that all human beings share and those that are the products of local culture, learned and handed on from generation to generation.

The social sciences also include political science, law, and economics, which are products of human society. Although far removed from the world of the physical sciences, all these fields can be studied in a scientific way. Political science and law are uniquely human concepts, but economics has some surprisingly close parallels with ecology. This is because the laws that govern resource use, productivity, and efficiency do not operate only in the human world, with its stock markets and global corporations, but in the nonhuman world as well.

F.

Technology

In technology, scientific knowledge is put to practical ends. This knowledge comes chiefly from mathematics and the physical sciences, and it is used in designing machinery, materials, and industrial processes. In general, this work is known as engineering, a word dating back to the early days of the Industrial Revolution, when an 'engine' was any kind of machine.

Engineering has many branches, calling for a wide variety of different skills. For example, aeronautical engineers need expertise in the science of fluid flow, because airplanes fly through air, which is a fluid. Using wind tunnels and computer models, aeronautical engineers strive to minimize the air resistance generated by an airplane, while at the same time maintaining a sufficient amount of lift. Marine engineers also need detailed knowledge of how fluids behave, particularly when designing submarines that have to withstand extra stresses when they dive deep below the water’s surface. In civil engineering, stress calculations ensure that structures such as dams and office towers will not collapse, particularly if they are in earthquake zones. In computing, engineering takes two forms: hardware design and software design. Hardware design refers to the physical design of computer equipment (hardware). Software design is carried out by programmers who analyze complex operations, reducing them to a series of small steps written in a language recognized by computers.

In recent years, a completely new field of technology has developed from advances in the life sciences. Known as biotechnology, it involves such varied activities as genetic engineering, the manipulation of genetic material of cells or organisms, and cloning, the formation of genetically uniform cells, plants, or animals. Although still in its infancy, many scientists believe that biotechnology will play a major role in many fields, including food production, waste disposal, and medicine.