Basic Principles and Processes · 4 min read
The Nature of Science
What Science Is
Science is a systematic way of building knowledge about the natural world through testable explanations and predictions. It is both a body of knowledge (facts, laws, theories) and a process (inquiry) for generating, testing, and refining that knowledge. Scientific explanations must rely only on natural causes and must be checkable against evidence that others can observe.
Science is limited to questions that can be investigated empirically. Questions of morality, aesthetics, or the supernatural cannot be tested with natural evidence, so they fall outside science, even though science can inform decisions about them.
Core Characteristics
Observation vs. Inference
An observation is information gathered directly through the senses or instruments ("the solution turned blue"; "the mass is 12.4 g"). An inference is an interpretation or conclusion drawn from observations and prior knowledge ("a chemical reaction occurred"). Observations can be qualitative (descriptive: color, odor, texture) or quantitative (numerical, with units).
| Statement | Type | Why |
|---|---|---|
| The leaves are yellow and brown. | Qualitative observation | Directly seen, no number |
| The plant grew 4.2 cm in a week. | Quantitative observation | Measured value with units |
| The plant is not getting enough water. | Inference | Explanation drawn from observations |
| Fossil shells occur on this mountaintop. | Observation | Directly seen |
| This area was once under the sea. | Inference | Interpretation of the fossils |
Hypotheses, Theories, and Laws
Hypothesis: a tentative, testable explanation or prediction for a specific set of observations. Scientific theory: a well-substantiated explanation of some aspect of nature, supported by a large body of evidence from many independent lines of inquiry, that explains why or how something happens (cell theory, atomic theory, plate tectonics, the theory of evolution by natural selection). Scientific law: a concise statement, often mathematical, that describes what happens under given conditions without explaining why (Newton's law of universal gravitation, the law of conservation of mass, Boyle's law).
| Term | What it does | Example |
|---|---|---|
| Hypothesis | Proposes a testable explanation | Fertilizer X increases bean growth |
| Law | Describes a regular pattern | Mass is conserved in reactions |
| Theory | Explains a broad set of facts | Atoms combine in fixed ratios |
| Fact | Repeatedly confirmed observation | Water boils at 100 °C at 1 atm |
Hypotheses, laws, and theories work together. Boyle's law states that the pressure of a fixed amount of gas at constant temperature varies inversely with its volume; the kinetic molecular theory explains why, describing gas particles in constant random motion colliding with container walls more often when the volume is smaller.
How Scientific Knowledge Grows
Knowledge is cumulative: new work builds on earlier discoveries. Most change is gradual refinement, but occasionally a major shift in thinking replaces an established framework (for example, the move from an Earth-centered to a Sun-centered model of the solar system, or from fixed continents to plate tectonics). Such shifts happen only when new evidence accumulates that the old framework cannot explain.
Science vs. Pseudoscience
Pseudoscience uses scientific-sounding language without scientific practice. Warning signs include claims that cannot be tested or falsified, reliance on testimonials or anecdotes, no peer review, refusal to revise in light of contrary evidence, and appeals to authority instead of data. Astrology and claims of perpetual-motion machines are classic examples.
- Science never "proves" a hypothesis absolutely; evidence supports or fails to support it.
- A single well-designed contrary result can falsify a hypothesis; no number of confirming results can prove it.
- Reproducibility by independent researchers is the standard for accepting a result.
- Scientific explanations must invoke natural, not supernatural, causes.
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