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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: explaining 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). And more subtle things like why H2O molecules exist in gas, liquid, and solid forms, and why all three co-exist at water's triple point rather than forming a uniformly soft paste. All of this is possible because physics is a "Natural Science" - a continuing process in which hypotheses that survived 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, geology, etc. And following from these understandings, it enables whole fields of practical application called engineering: mechanical, electrical, civil, aeronautical, etc.
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Historically physics formed the core of "Natural Philosophy", which 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.
Cognitive Structure of Physics
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