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1.2: What Is Science?

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  • Ouch!

    This young man is getting a flu vaccine. You probably know that getting a vaccine can hurt, but it's usually worth it. A vaccine contains dead or altered forms of "germs" that normally cause a disease, such as flu or measles. The germs in vaccines have been inactivated or weakened so they can no longer cause illness, but they are still "noticed" by the immune system. They stimulate the immune system to produce chemicals that can kill the actual germs if they enter the body, thus preventing future disease. How was such an ingenious way to prevent disease discovered? The short answer is more than two centuries of science.

    Figure \(\PageIndex{1}\): U.S. Navy photo by Photographer's Mate Airman Philip A. McDaniel. Image used with permission (Public Domain; US Navy).

    Science as Process

    You may think of science as a large and detailed body of knowledge, but science is actually more of a process than a set of facts. The real focus of science is the accumulation and revision of scientific knowledge. Science is a special way of gaining knowledge that relies on evidence and logic. Evidence is used to continuously test ideas. Through time, with repeated evidence gathering and testing, scientific knowledge advances.

    We've been accumulating knowledge of vaccines for more than two centuries. The discovery of the first vaccine, as well as the process of vaccination, dates back to 1796. An English doctor named Edward Jenner observed that people who became infected with cowpox did not get sick from smallpox, a similar but much more virulent disease (Figure \(\PageIndex{2}\)). Jenner decided to transmit cowpox to a young boy to see if it would protect him from smallpox. He gave the boy cowpox by scratching liquid from cowpox sores into the boy's skin. Then, six weeks later, he scratched liquid from smallpox sores into the boy's skin. As Jenner predicted, the boy did not get sick from smallpox. Jenner had discovered the first vaccine, although additional testing was needed to show that it really was effective.

    Figure \(\PageIndex{2}\): A young child in Bangladesh is covered with skin lesions from smallpox. Until it was eradicated, this highly contagious infection caused many deaths, and those that survived were often severely scarred for life. Image used with permission (Public Domain; Centers for Disease Control and Prevention's Public Health Image Library).

    Almost a century passed before the next vaccine was discovered, a vaccine for cholera in 1879. Around the same time, French chemist Louis Pasteur found convincing evidence that many human diseases are caused by germs. This earned Pasteur the title of "father of germ theory." Since Pasteur's time, vaccines have been discovered for scores of additional diseases caused by "germs," and scientists are currently researching vaccines for many others.

    Benefits of Science

    Medical advances such as the discovery of vaccines are one of the most important benefits of science, but science and scientific knowledge are also crucial for most other human endeavors. Science is needed to design safe cars, predict storms, control global warming, develop new technologies of many kinds, help couples have children, and put a man on the moon! Clearly, the diversity of applications of scientific knowledge is vast!

    Chapter Overview: The Nature and Process of Science

    In the rest of the chapter, you'll learn much more about science, including how scientists think and how they advance scientific knowledge. Specifically, you'll learn that:

    • Science is a distinctive way of gaining knowledge about the natural world that is based on evidence and logic. Scientists assume that nature can be understood with systematic study; that scientific ideas are open to revision, although sound scientific ideas can withstand repeated testing; and that science is limited in the types of questions it can answer.
    • A scientific theory is at the pinnacle of explanations in science. A theory is a broad explanation for many phenomena that is widely accepted because it is supported by a great deal of evidence. An example of a theory in human biology is the germ theory of disease. It took more than two centuries of research to provide enough evidence that microorganisms ("germs") cause disease for this explanation to become widely accepted and attain the status of a theory.
    • The process of science is epitomized by scientific investigation. This is a procedure for gathering evidence to test a hypothesis. A scientific investigation typically involves steps such as asking a question based on observations and formulating a hypothesis as a testable answer to the question. It also generally involves collecting data as evidence for or against the hypothesis, drawing conclusions, and communicating results. In reality, the process of science is not simple and straightforward. The process actually tends to be nonlinear, iterative, creative, and unpredictable. "Doing" science can be very exciting!
    • Scientific experiments are a special type of scientific investigation, in which variables are manipulated by the researcher to test expected outcomes. Experiments are performed under controlled conditions to mitigate the effects of other variables on the outcome variable. Experiments provide the best evidence that one variable causes another variable in scientific research. An example of an experiment in human biology is the astounding public health experiment to test Salk's polio vaccine that was undertaken in 1953. Some 600,000 children received a vaccine injection; another 600,000 received a placebo injection of useless salt water. The vaccine group had a significant drop in polio cases relative to the placebo group, providing support for the hypothesis that the vaccine prevented the disease.
    • Many questions in human biology are not amenable to experimental research. Consider the question, "Does smoking cause lung cancer?" It would not be ethical to deliberately experiment with human subjects by exposing them to harmful tobacco smoke in order to see whether they develop lung cancer. For questions like this, observational studies are done to look for correlations between variables. For example, Doll and Hill gathered information on past smoking habits from a large sample of lung cancer patients and another large sample of controls without lung cancer. Smoking and lung cancer were found to be correlated. Correlation does not imply causation, but it can be a big hint!
    • Research involving human subjects presents special challenges to scientists. Until the 1970s, there were few ethical guidelines for researchers to follow when studying human subjects. A shamefully unethical syphilis study called the Tuskegee study changed all that. The Tuskegee study was conducted on African-American men in Alabama from 1932 to 1972. this study was done to see the progression of syphilis; In this study, the control group with the disease was not treated for syphilis. When details of the study were leaked to the media, the public was outraged and the U.S. Congress got involved. In 1974, Congress passed important legislation to protect human subjects in scientific research projects. Chief among the protections was the necessity of informed consent.


    • Science is more of a process than a set of facts. The focus of science is the accumulation and revision of scientific knowledge through repeated evidence gathering and testing.
    • Medical advances such as the development of vaccines are one of the most important benefits of science, but science and scientific knowledge are also crucial for most other human endeavors.


    1. Explain why science is more accurately considered a process than a body of knowledge.
    2. State three specific examples of human endeavors that are based on scientific knowledge.
    3. Jenner used a young boy as a research subject in his smallpox vaccine research. Today, scientists must follow strict guidelines when using human subjects in their research. What unique concerns do you think might arise when human beings are used as research subjects?
    4. What gave Jenner the idea to develop a vaccine for smallpox?
    5. Why do you think almost a century passed between the development of the first vaccine (for smallpox) and the development of the next vaccine (for cholera)?
    6. How does science influence your daily life?

    Explore More

    Watch this eye-opening TED talk to learn why truly innovative science demands a leap into the unknown. The inspiring speaker explains how improv theater helped him find joy instead of fear in the unknown and how to use creativity in the scientific process.

    Check out this video to learn more about the Smallpox vaccine: