OK, we have briefly explored observation as a way to gain scientific information. Now it is time to explore the topic that most people think of when they think of science: Experiments.
What is an experiment? In spite of what your textbook may tell you, there is no official, scientific definition for the word “experiment”. If you pick up 100 different physics books and look for the definitions of energy, force, inertia, etc., you will find the same definition, usually word for word, in every one. You can do the same with 100 chemistry books, looking up the definitions of words such as element, covalent bond, and acid. All through science, you find very precise definitions for the words that play a role in the precision of science.
On the other hand, if you pick up 100 physics books, 100 chemistry books, 100 geology books, etc., and look through them all, very few if any will even have a definition for the word “experiment". If you dig through 100 books on the philosophy of science, you will find many different, conflicting definitions for the word. Some will say that an experiment must have variables and a control. Others will say that an experiment must test a hypothesis, which might not involve variables or a control. Others will say that an experiment can be used to demonstrate a known law or principle, while others will say that an experiment must be an attempt to answer a question. While the philosophers argue about it endlessly, working scientists don't worry about it.
Why the difference? When a physicist is performing an investigation, it is vitally important that the terms are precise, and that everyone use the same definitions. Words such as “force" and “pressure" have very precise, and very different definitions. If you use “force" when you really mean “pressure", every physicist in the room will scream at you. Confusing the two can be catastrophic.
On the other hand, you won't hear scientists arguing about the definition of an experiment, or arguing about whether something is an experiment or some other kind of investigation. As long as a scientific investigation is carried out properly for the subject you are investigating, no one in the scientific world cares whether you call it an experiment, investigation, testing a hunch, or something else. Unlike the terms “force" and “pressure", using “experiment" instead of “investigation” does not make any difference in the results or how they are interpreted or applied.
So, as we did with the word "science", we need to come up with a definition of "experiment" that we find acceptable for this course. Take a while to think about all of the different areas of science, from astronomy to archaeology, from physics to paleontology. How are their experiments different? More importantly, what do they all have in common? How would you define the word "experiment"?
After you think about it for a while, and BEFORE YOU GO ON TO THE NEXT PAGE, write your definition of an experiment in your journal. Again, don't worry about being "right" or "wrong", since there is no single, right answer that works for everyone.