Science is a way of thinking much more than a body of knowledge.
—Carl Sagan, Broca's Brain
[Science is] the observation, identification, description, experimental investigation, and theoretical explanation of phenomena.
—American Heritage Dictionary of the English Language
These two complementary definitions eloquently summarize both the nature of science and the activities in which scientists engage. Science is a systematic method of learning about the universe that relies on logic and revolves around the notion of cause and effect. Scientists begin with the important presumption that the universe operates according to certain laws that can, at least in principle, be understood. Scientists attempt to describe these natural laws and ultimately may use them to make useful predictions and to devise technological applications that make our lives easier.
The great success of science stems from its reliance on observations to document phenomena and its use of logical reasoning to explain what is observed and why. One of the key elements in this process is the understanding that new observations might cast a different light upon previous descriptions (theories) of how nature works. Thus, scientific descriptions of natural phenomena are continually evolving, with each revision bringing a clearer and broader understanding of the principles at work.
From determining the function of a mysterious protein inside a human fat cell to charting the stars that make up the galaxies, scientists engage in a diverse array of activities to answer a wide range of questions. However, the same basic principles of science underlie each type of investigation, and can be applied to almost any question one could pose about the natural world. Although there are certainly exceptions, most types of scientific research can be distilled down to a simple series of steps. These steps are often referred to as "the scientific method."