Learning Goals:

To become familiar with the basics of the scientific method
To use the scientific method to explore a practical laboratory problem

Lab Background

All branches of scientific inquiry may be divided into two main groups: the empirical sciences and the non-empirical sciences. Biology, along with chemistry, physics, and their related disciplines, is an empirical science with the objectives to explore, explain, describe and predict the occurrences in the universe. For valid evidence, empirical science depends on events that can be observed either directly or by the use of instruments that extend the perception of the observer. The non-empirical sciences of logic and pure mathematics do not depend on this sort of evidence for proof of propositions. Biological knowledge is based on situations in which an individual made and recorded an observation.

Ultimately, then, scientists rely on sense organs, or "Doors of Perception", to use Aldous Huxley's phrase, to understand the world. However, technology has extended the perceptual limits and the sensitivity of man's sensory equipment. The microscope and telescope have greatly augmented the resolution of the vertebrate eye and ushered in great advances in many fields of science. Our eyes are not receptive to electromagnetic wavelengths above 760 nanometers (nm) such as infrared radiation, which the rattlesnake detects and uses to locate warm-blooded prey. Nor can we perceive wavelengths below 380 nm such as ultraviolet radiation, which the honeybee can see and use for orientation on cloudy days. Instruments can, however, detect and measure these wavelengths, thus extending our sensory range.

We lack sense organs to deal with certain basic aspects of reality. Magnetism was not part of the world that primitive man perceived, because he lacked sensory equipment to observe it. Only after the invention of instruments (e.g., compasses) that converted this non-sensible form of energy into one that humans could perceive could we obtain sufficient data to understand and use magnetism. It is interesting that certain creatures evidently possess sense organs that allow them to detect the earth's magnetic field. Pigeons seem to have a built-in compass that they can use for orientation on completely overcast days. There are doubtless other forms of energy of which we are unaware due to a lack of appropriate sensory equipment, and until devices are invented to transform these bits of reality into forms we can observe, they can never become a part of our world. From the outset, a scientist must recognize his or her complete dependence on sensory data.

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