Studying Earth - How it works

Introduction to the Earth Sciences

At the simplest level, the earth sciences can be divided into three broad areas: the geologic, hydrologic, and atmospheric sciences. These specialties fit neatly with three of the "spheres," or subsystems within the larger Earth system: geosphere, hydrosphere, and atmosphere. (See Earth Systems for more about the spheres.) The fourth of these subsystems is the biosphere, and this illustrates the difficulty of stating exactly what is and what is not a part of the earth sciences.

Usually the earth sciences are considered part of the physical sciences, as opposed to the biological sciences, such as biology, botany, and zoology. Yet the earth sciences clearly overlap with biological sciences in a variety of areas, such as oceanography and various studies of complex biological environments. There is even a new (and as yet not fully formalized) discipline called geophysiology, built on the premise that Earth has characteristics of a living organism.

OVERLAP WITH OTHER PHYSICAL SCIENCES.

The earth sciences also overlap with other physical sciences in several realms. There is geophysics, which addresses the planet's physical processes, including its magnetic and electric properties and the means by which energy is transmitted through its interior. There is also geochemistry, which is concerned with the chemical properties and processes of Earth. And there are numerous areas of confluence between the earth sciences and astronomy (among them, planetary geology), which fall under the heading of planetary science (sometimes called planetology or planetary studies).

These terms all refer to the same discipline, a branch of the earth sciences concerned with the study of other planetary bodies. This discipline, or set of disciplines, is concerned with the geologic, geophysical, and geochemical properties of other planets but also draws on aspects of astronomy, such as cosmology. Regardless of the name by which it is called, planetology is an example of the fact that the study of Earth is still very much an evolving set of disciplines. In many cases, the earth sciences are still in process of being defined.

Scientific Paradigms

This last point is an important one to consider because of what it implies about the nature of scientific study. In the past, scientists tended to think that they were in the business of discovering some sort of objective truth that was waiting for them to discover it; in reality, however, the quest of the scientific thinker is much less guided. The natural world does not in any way speak to the scientist, telling him or her how to categorize data. In fact, the divisions of scientific knowledge with which we are familiar have come about not because they necessarily reflect an underlying truth, but because they have proved useful in separating certain aspects of the physical world from certain others.

When science had its beginnings in ancient times, scientists were simply collecting observations (including a lot of incorrect ones) and sometimes forming theories of a sort, but they did not think in terms of developing models for viewing their objects of study. Today, however, scientific thinkers are acutely conscious of the model, or paradigm, that governs a particular discipline, school of thought, or theory.

A paradigm may be likened to a lens. The lens does not change the actual object that is viewed through it; it can alter only the way in which it is viewed. As thinkers within a particular discipline or theory begin to define the governing paradigm, they are much like an eye doctor testing various lenses on a patient. In such a situation, there is no one lens that is right for all circumstances. Rather, it is a question of finding the lens that best suits the patient's vision needs.

All sciences are gradually changing, evolving models that better suit the data under their consideration. Chemistry, for instance, was once primarily a matter simply of mixing chemicals and observing their external processes. In fact, the definition of chemistry has expanded greatly since about 1800, and today it is more like what people tend to think of as physics; that is, it is concerned with atomic and subatomic structures and types of behavior. The earth sciences are in an even more transitional state, and the problem of defining the disciplines it comprises is a still more fundamental one.

THE EVOLVING EARTH SCIENCES.

In the discussion that follows, we outline the broad parameters of the earth sciences, considering basic areas of study and specialties within them. This does not represent a definitive organizational scheme, nor does this brief review refer to every possible area of study in the wide-ranging earth sciences. To do so would require an entire book; rather, the purpose is to consider the most significant disciplines and subdisciplines.

To appreciate the way that these disciplines fit within the larger perspective, however, it is necessary to examine a few historical details. Most of these details concern the early history of the earth sciences, since much of the more modern history (for example, the development of plate tectonics theory during the 1960s) is treated in the relevant essays within this book. The purpose of this brief historical review, instead, is to impart an understanding about how the study of Earth emerged as a real science, as opposed to a merely descriptive undertaking concerned with recording observations. Important themes are the development of the scientific method as well as the search for proper ways of classifying the various studies under the heading of what became known as the earth sciences.