Science is a search for order in our surroundings. People have concepts, or
mental images, about material objects and intangible events in their surroundings. Concepts are used for thinking and communicating. Concepts
are based on properties, or attributes that describe a thing or event.
Every property implies a referent that describes the property. Referents
are not always explicit, and most communications require assumptions.Measurement is a process that uses a well-defined and agreed upon
referent to describe a standard unit. The unit is compared to the property
being defined by an operation that determines the value of the unit by
counting. Measurements are always reported with a number, or value, and
a name for the unit.
The two major systems of standard units are the English system and
the metric system. The English system uses standard units that were originally
based on human body parts, and the metric system uses standard
units based on referents found in nature. The metric system also uses a
system of prefixes to express larger or smaller amounts of units. The metric
standard units for length, mass, and time are the meter, kilogram, and
second.
Measurement information used to describe something is called data. One way to extract meanings and generalizations from data is to use
a ratio, a simplified relationship between two numbers. Density is a ratio
of mass to volume, or p = m/V.Symbols are used to represent quantities, or measured properties.
Symbols are used in equations, which are shorthand statements that describe
a relationship where the quantities (both number values and units)
are identical on both sides of the equal sign. Equations are used to (1) describe
a property, (2) define a concept, or (3) describe how quantities
change together.
Quantities that can have different values at different times are called
variables. Variables that increase or decrease together in the same ratio are
said to be in direct proportion. If one variable increases while the other decreases
in the same ratio, the variables are in inverse proportion. Proportionality
statements are not necessarily equations. A proportionality constant can be used to make such a statement into an equation. Proportionality
constants might have numerical value only, without units, or
they might have both value and units.
Modern science began about three hundred years ago during the
time of Galileo and Newton. Since that time, scientific investigation has
been used to provide experimental evidence about nature. The investigations
provide accurate, specific, and reliable data that are used to develop
and test explanations. A hypothesis is a tentative explanation that is accepted
or rejected from experimental data. An accepted hypothesis may
result in a scientific law, an explanation concerned with important phenomena.
Laws are sometimes identified with the name of a scientist and
can be expressed verbally, with an equation, or with a graph.
A model is used to help understand something that cannot be observed
directly, explaining the unknown in terms of things already understood.
Physical models, mental models, and equations are all
examples of models that explain how nature behaves. A theory is a broad,
detailed explanation that guides development and interpretations of experiments
in a field of study.
Science and nonscience can be distinguished by the kinds of laws and
rules that are constructed to unify the body of knowledge. Science involves
the continuous testing of rules and principles by the collection of new facts. If the rules are not testable, or if no rules are used, it is not science. Pseudoscience uses scientific appearances to mislead.
