Basic assumptions that modern science makes about the universe: 

Centuries of experience allow us to assume some fundamental properties about the universe. Firstly, the universe (=nature) is real. For science, the world that our senses identify is the only real one. We no longer debate whether it is ideals that are real and what we see and experience mere shadows of this reality, or whether this world is but illusion or some dreamer's cosmic dream. Plato's allegory of the cave, or the notion that the world in which we live is but "dream time" have been relegated (along with other myths and speculations) to the philosophical realm, and excluded from the scientific one. 

Secondly, the universe is consistent. The universe behaves the same way, any time, any place, for any one. There are no special cases, no exceptions, no miracles, no special people to intervene with magic, wizardry or special knowledge. Science is not the domain of a special priesthood or mystical initiations. Our experiences today are the same as Newton's and Einstein's experiences. They are repeatable. 

Thirdly, the universe is reasonable. This word has two meanings, and both apply here. The first is that the universe behaves in a logical, orderly fashion. The second, is that the human mind is capable of reasoning it out. The world is neither too mysterious, nor are we too stupid to understand it. 

The domain of science 

The domain of science is limited to the real, the natural, the sensory. Science deals with all the objects and phenomena that are accessible to our senses and to the various instruments that expand these senses. Because these phenomena are universal, they are accessible to anyone. And because the universe is consistent, they are accessible over time and space, they are repeatable. While speculation about astrology, dowsing, Nostradamus, people being abducted by aliens in UFOs, or the Bermuda Triangle might be fun, they are not within the domain of science.  

The method of modern science 

How do scientists arrive at those systematic descriptions and explanations, and how do these become incorporated into the accepted mainstream of science? Usually, the sequence of steps associated with scientific methodology is listed as follows:  

1. collecting data (=making observations); 2. formulating a hypothesis (often defined as an educated guess); 3. testing the hypothesis (doing experiments); 4. elevating it to a theory (less iffy than a hypothesis) 5. testing the theory (doing more experiments) which eventually, when proven, 6. the theory becomes a law; and 7. this law allows predictions which lead to new observations, etc. 

This is a wonderful algorithm but, the most polite thing that can be said for this model is that any resemblance to how scientists really do science is purely coincidental. It just is NOT done that way. 

They do NOT begin with observations as the above litany would suggest, Even the simplest object in the world, the simplest event, is so complex, so multifaceted, that is is impossible to know how, or what part to observe or describe unless it is within a context. Nor do scientists do science as a matter of course, like a mechanic would maintain an aircraft to keep it flying. They become engaged in the process of doing science when they perceive that there is a reason.  

  • Commonly, they begin when confronted by a problem with the existing explanations and descriptions; when they perceive that the current explanations which make up science are either wrong, inadequate or incomplete. It is at that point that they focus their attention on the perceived problem. and it is that problem that provides the context, a direction, a focus for the observations. After all, if it ain't broke, why fix it?
  • Once a scientist perceives that there is a problem, it is important to see if the problem is valid. This often involves a search through the literature. Such a search will indicate if the problem has surfaced before, and if so, if it has already been solved.
  • Assuming that the problem has not already been solved, the next step may be to gather additional information that bears on this issue. Some sciences are more descriptive and this may involve more in the way of observations; others are more experimental and may rely more on testing or experiment; and even then, the experiment may be a thought experiment.
  • The underlying purpose of science is to explain how nature operates, to describe the patterns we perceive in it. The critical and often difficult next step therefore is formulating that explanation. This inductive process is poorly understood, but it is the essential, creative, change-producing process of science. This explanation may be a hypothesis, (a working explanation, NOT a guess), a theory (a large scale explanation), or a law (a limited quantitative relationship). It may or may not be verified with additional data or experiments.
  • Once the scientist is satisfied with the explanation he has created, it is imperative that he publish it in a reputable journal recognized by his profession. 
  • After publication, it is up to the researcher's colleagues to determine whether the proposed descriptions and explanations are better (more inclusive, exact or simpler) than the existing, accepted ones. Only if and when consensus is reached by the profession, does the work become accepted into the corpus (body) of science. Otherwise, the idea may be rejected, languish or even be forgotten. Thus, it is sobering to realize that libraries which are the repository of everything that has been published contain not only all what is new and better, but also much of the old, trivial, speculative and wrong.
Depending on the particular discipline, certain aspects of science, especially the descriptive or experimental portions may receive greater or lesser emphasis. But the three basic steps of perception of a problem, creation of an explanation and publication are steps that are common to all the sciences. The processes of peer review and consensus before acceptance as part of science are also requisites.