In our modern society, we are constantly reminded of the benefits derived from science. But what exactly is the nature of scientific inquiry? Science is a process of investigation that leads to the production of knowledge, based on making careful observations and on creating explanations that make sense of those observations. Developing an understanding of how science is performed and how scientists work is an important theme you will encounter throughout this book. You will explore the difficulties in gathering data and some of the ingenious methods that have been developed to overcome these difficulties. You will also see many examples of how hypotheses are formulated and tested, as well as learn about the evolution and development of some major scientific theories.

All science is based on the assumption that the natural world behaves in a consistent and predictable manner that is comprehensible through careful, systematic study. The overall goal of science is to discover the underlying patterns in nature and then to use that knowledge to make predictions about what should or should not be expected, given certain facts or circumstances. For example, by understanding the circumstances and processes that produce certain cloud types, meteorologists are often able to predict the approximate time and place of the cloud formation and the intensity of the associated weather.

The development of new scientific knowledge involves some basic logical processes that are universally accepted. To determine what is occurring in the natural world, scientists collect data through observation and measurement ▼. The data collected often help answer well-defined questions about the natural world. Because some error is inevitable, the accuracy of a particular measurement or observation is always open to question. Nevertheless, these data are essential to science and serve as a springboard for the development of scientific hypotheses and theories.

Once facts have been gathered and principles have been formulated to describe a natural phenomenon, investigators try to explain how or why things happen in the manner observed. They often do this by constructing a tentative (or untested) explanation, which is called a scientific hypothesis. It is best if an investigator can formulate more than one hypothesis to explain a given set of observations. If an individual scientist is unable to devise multiple hypotheses, others in the scientific community will almost always develop alternative explanations. A spirited debate frequently ensues. As a result, extensive research is conducted by proponents of opposing hypotheses, and the results are made available to the wider scientific community in scientific journals.

Before a hypothesis can become an accepted part of scientific knowledge, it must repeatedly pass objective testing and analysis. If a hypothesis cannot be tested, it is not scientifically useful, no matter how interesting it might seem. The verification process requires that predictions be made based on the hypothesis being considered and that the predictions be tested by being compared against objective observations of nature. Put another way, hypotheses must fit observations other than those used to formulate them in the first place. Hypotheses that fail rigorous testing are ultimately discarded. The history of science is littered with discarded hypotheses. One of the best-known discarded hypothesis is the Earth-centered model of the universe—a proposal that was supported by the apparent daily motion of the Sun, Moon, and stars around Earth.

Theory

When a hypothesis has survived extensive scrutiny and when competing hypotheses have been eliminated, it may be elevated to the status of a scientific theory. In everyday language, we might say, “That’s only a theory.” However, a scientific theory is a well-tested and widely accepted view that the scientific community agrees best explains certain observable facts.

Some scientific theories that are extensively documented and extremely well supported are comprehensive in scope and may incorporate several well-tested hypotheses. For example, the theory of plate tectonics provides the framework for understanding the origin of mountains, earthquakes, and volcanic activity. In addition, plate tectonics explains the evolution of the continents and the ocean basins through time.

Scientific Methods

The process just described, in which researchers gather facts through observations and formulate scientific hypotheses and theories, is called the scientific method. Contrary to popular belief, the scientific method is not a standard “recipe” that scientists apply in a routine manner to unravel the secrets of our natural world. Rather, it is an endeavor that involves creativity and insight.

There is no fixed path for scientists to follow that leads unerringly to scientific knowledge. However, many scientific investigations involve the steps outlined in the figure below ▼. In addition, some scientific discoveries result from purely theoretical ideas that stand up to extensive examination. Some researchers use high-speed computers to create models that simulate what is happening in the “real” world. These models are useful when dealing with natural processes that occur on very long time scales or take place in extreme or inaccessible locations. Still, other scientific advancements are made when a totally unexpected event occurs during an experiment.

Scientific knowledge is acquired through several avenues, so it might be best to describe the nature of scientific inquiry as the methods of science rather than as the scientific method. In addition, it should always be remembered that even the most compelling scientific theories are still simplified explanations of the natural world.

Bear in mind that our knowledge of Earth is changing daily, as thousands of scientists worldwide make satellite observations, analyze drill cores from the seafloor, measure earthquakes, develop computer models to predict climate, examine the genetic codes of organisms, and discover new facts about our planet’s long history. This new knowledge often updates hypotheses and theories. Expect to see many new discoveries and changes in scientific thinking in your lifetime.

• Scientists make careful observations, construct tentative explanations for those observations (hypotheses), and then test those hypotheses with field investigations, laboratory work, and/or computer modeling.

• In science, a theory is a well-tested and widely accepted explanation that the scientific community agrees best fits certain observable facts.

• As failed hypotheses are discarded, scientific knowledge moves closer to a correct understanding, but we can never be fully confident that we know all the answers. Scientists must always be open to new information that forces change in our model of the world.

• hypothesis: A tentative explanation that is tested to determine whether it is valid.

• scientific methods: The processes by which researchers raise questions, gather data, and formulate and test scientific hypotheses.

• theory: A well-tested and widely accepted scientific view that explains certain observable facts.