Critical Thinking and Scientific Method Concepts

Critical thinking

Analyzing and evaluating thinking to improve it. Involves questioning assumptions, forming clear questions, reasoning logically, testing ideas, being open to alternatives, and communicating clearly.

Scientific reasoning

Structured critical thinking—purposeful, theory-based, evidence-driven, and logically interpreted with measurable outcomes.

Inductive reasoning

A 'bottom-up' approach: general conclusions are drawn from specific observations. Probable but not guaranteed.

Example of inductive reasoning

Birds, rocks, and people thrown into the air fall. Conclusion: 'What goes up must come down.'

Deductive reasoning

A 'top-down' process: conclusions follow with certainty from general principles. If premises are true, the conclusion is guaranteed.

Example of deductive reasoning

All dogs have ears. Golden Retrievers are dogs. Therefore, Golden Retrievers have ears.

Inductive vs. deductive reasoning

Inductive: specific → general (probable). Deductive: general → specific (certain).

Falsifiability

A hypothesis is falsifiable if it can be proven false through testing. It's essential for scientific validity.

Science focus on falsifying hypotheses

It's more reliable to disprove an idea than to claim absolute proof. Disproving uses valid logic like contrapositive reasoning.

Valid argument forms

Direct reasoning, contrapositive, transitive, disjunctive.

Invalid argument forms

Converse fallacy, inverse fallacy, misuse of disjunction or transitivity.

Scientific method

A step-by-step process: Observation → Hypothesis → Experiment → Data Analysis → Conclusion → Peer Review.

Qualities of science

Empirical, objective, measurable, logical, and falsifiable.

Hypothesis

Testable idea.

Theory

Validated explanation with strong evidence.

Law

Theory consistently supported without falsification.

Iterative nature of science

Scientific knowledge evolves over time with new evidence, peer review, and repeated testing.

Experiments using controls and placebos

Control groups offer a baseline. Placebos mimic treatment to control psychological effects.

Independent variable

What is changed/tested.

Dependent variable

What is measured in response.

Evidence for continental drift

Jigsaw fit, geological and fossil matches, glacial scars, and coal in unlikely climates.

Problems in Wegener's theory

No mechanism, inaccurate speed estimates, implausible tidal force idea, and lack of support from scientists.

Harry Hess support for sea-floor spreading

Sonar revealed mid-ocean ridges (young crust) and trenches (old crust), supporting crust formation and subduction.

Geomagnetic striping support for Hess' hypothesis

Magnetic minerals aligned with Earth's polarity at formation, creating symmetrical stripes on both sides of ridges.

Radiometric dating

Young rocks were found near ridges; older rocks were farther away, matching magnetic striping patterns.

Pseudoscience

Imitates science but lacks key features like testability, objectivity, or evidence. E.g. astrology, flat Earth.

Information sources

Wikipedia: Accessible but editable. News: Current but can be biased. Books: Expert-written. Academic articles: Peer-reviewed and high-quality.

Types of academic articles

Empirical research: Original data. Review articles: Summarize other studies (includes meta-analysis/systematic reviews).

Population vs Sample

Population: Whole group of interest. Sample: Subset studied to represent population.

Sample representation

To generalize findings accurately and ensure valid conclusions.

Sample size factors

Larger samples increase reliability but cost and logistics limit size. Field standards vary.

Confounding variables

Hidden variables affecting both independent and dependent variables, potentially distorting results.

Types of bias in research

Selection bias: Non-random sample skews results. Attrition bias: Dropouts affect outcomes. Participation bias: Volunteers may not represent the population. Confirmation bias: Interpreting data to support prior beliefs. Funding bias: Sponsors may influence results. Publication bias: Only positive results get published.

Sampling protocols to avoid bias

Random sampling: Equal chance to be selected. Systematic sampling: Every nth individual. Convenience sampling: Easiest to access (less reliable). Stratified sampling: Ensures subgroups are proportionally represented.

Confirmation bias

Researchers or participants unintentionally influence data. Solution: blind or double-blind studies.

Placebo effect

Positive effect from an inert treatment due to expectations. Common in pain, fatigue, nausea outcomes.

Characteristics of a good scientific study

Clear hypothesis, controlled variables, unbiased methods, sufficient sample size, repeatable design, peer review.

Alfred Wegener's evidence for continental drift

Jigsaw fit of continents (e.g., South America & Africa), geological similarities across continents, fossil distributions (e.g., Mesosaurus, Glossopteris), paleobotanical fossils, paleoclimatic indicators like glacial deposits in now-tropical areas, coal beds in cold regions that suggest they were once tropical.

Problems in Wegener's theory

He lacked a mechanism for how continents moved, tidal forces he proposed were physically implausible, his data and calculations were not always accurate, the scientific community was skeptical due to lack of strong evidence.

Harry Hess's support for sea-floor spreading

Harry Hess supported sea-floor spreading by showing that new oceanic crust forms at mid-ocean ridges where magma rises and solidifies. He observed that sediments are thinner near these ridges, indicating younger crust there. He also proposed that old crust sinks at deep ocean trenches (subduction zones). This explained how the sea floor spreads and provided a mechanism for continental drift

Sonar

Used to map the ocean floor.

Mid-ocean ridges

Underwater mountain ranges formed by plate tectonics.

Abyssal plains

Flat areas of the ocean floor, usually found at great depths.

Trenches

Deep, narrow depressions in the ocean floor formed by subduction.

Crust formation

New crust forms at ridges and spreads outward.

Subduction zones

Areas where old crust is recycled at trenches.

Geomagnetic striping

Symmetrical magnetic stripes on both sides of mid-ocean ridges that support Hess' hypothesis.

Earthquake

A vibration of the Earth caused by the rapid release of energy, radiating from a focus as seismic waves.

Focus

The origin point underground of an earthquake.

Epicenter

The point on Earth's surface directly above the focus of an earthquake.

Tectonic plates

Large pieces of Earth's lithosphere that move and interact at plate boundaries.

Elastic rebound

The sudden release of stored energy when rocks on either side of a fault snap back after stress overcomes friction.

P waves (Primary waves)

Fastest body waves that move in a push-pull (compression) motion and travel through solids, liquids, and gases.

S waves (Secondary waves)

Slower than P waves, these waves move particles up and down and only travel through solids.

Surface waves

Waves that travel along Earth's surface, including Rayleigh waves and Love waves.

Love waves

Seismic waves that cause the most damage due to their side-to-side motion affecting building stability.

Seismometers

Instruments used to measure earthquakes, producing seismograms showing wave arrival times and amplitudes.

Epicenter location

Determined by measuring the time difference between P and S wave arrivals at three or more stations (triangulation).

Earth's layers

Core (inner solid & outer liquid), Mantle (upper fluid & lower solid), Crust (oceanic ~10 km & continental 30-50 km).

Plate boundaries

Three types: Converging (plates move together), Diverging (plates move apart), Transform (plates slide past).

Magnitude

The energy released during an earthquake (quantitative).

Intensity

The damage caused at specific locations during an earthquake (qualitative).

Modified Mercalli Intensity Scale

A qualitative scale based on observed damage, useful for mapping earthquake effects by location.

Richter scale

A logarithmic scale measuring magnitude using seismogram amplitude and distance from epicenter.

Richter-Gutenberg energy equation

𝐸 = 10^(11.8 + 1.5R), where R = Richter magnitude and E = energy released.

Moment Magnitude Scale (MW)

A modern scale for large earthquakes based on fault slip, fault size, and rock rigidity—more accurate than the Richter scale.

What two layers of the Earth are involved in plate tectonics, and how are each involved?

• Lithosphere: The rigid outer layer (crust + upper mantle); it breaks into tectonic plates.

• Asthenosphere: The softer, partially molten layer beneath the lithosphere; tectonic plates move over it.