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h3. Introduction to Physics

Open most introductory physics textbooks and you will read that physics is the study of matter and light, and their interactions.  Indeed, physics offers understanding of the natural world that is awe-inspiring in its scope and precision:  explainingIt explains the properties of atoms, how the moon, stars, and galaxies move, and how gravitation generated their obvious lumpiness,  starting with a big bang uniform except for tiny quantum fluctuations of extra density (mandated by the uncertainty principle).   Physics allows you to notice significant things about the natural world and to explain them. The way, likefor whyexample, H{~}2{~}O molecules exist in gas, liquid, and solid forms, and why these forms of matter are so fundamental that water co-exists in all three forms at water's triple point, rather than simple turning into a soft paste. 

This understanding and insight is possible because physics is a _science_ \- a continuing process in which hypotheses that survivedsurvive every well-done experimental test of their predictions against the natural world are deemed to be "Laws of Nature" (sometimes called "theories" even though this word does not generally carry the requirement of experimental test).   In fact, physics underlies all other physical sciences: chemistry, biology, and even more specialized sciences like materials science, environmental science, earth science, and geology, etc.  AndFollowing following from these understandings, it enables whole the existence of entire fields of practical application called _engineering_ : mechanical, electrical, civil, aeronautical, etc.

h3. Physics as a way of thought

Historically, physics formed the core of the discipline called "Natural Philosophy",. whichThis correctly emphasizes that physics is much more than a collection of facts, physical laws, and formulae - it is a powerful way of thinking about, and making sense of, the physical universe that we inhabit.  In order to understand the world-view provided by physics, and especially to apply its understanding and methodology to other areas, you must not only know the facts and some formulas, but you must also _think like a physicist. _ This involves organizing this knowledge so that it can be applied (transferred) to new situations, and being able to reach reliable conclusions about these situations.

h3. Cognitive Structure of Physics

*Facts* - definitions, properties like the density of iron or air, or the value of the g,Gravitational unitConstant of*g* distance

*Procedures* - e.g. how to define a system, or to draw a force diagram, or find the moment of inertia of an object about a given axis

*Concepts*   \-\- e.g. Newton's Third Law

*Concept clusters* -e.g. That Physicalphysical interactions result in forces on objects,

*Representations* - How to think about models, (e.g. equations, graphs, pictures, words)

*Models* - theoretical idealizations of the world, (e.g. Circular Motion, Energy, Momentum)

*Hypotheses* - are consistently and logically developed guesses about how nature works

*Laws of Nature* - hypotheses with no experimental exceptions in their domaindomains of validity

*Experiments* - careful observationobservations of constructed situations that have the ability to falsify Laws

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