Intellectual Revolutions That Defined Society

Major historical shifts in thought, knowledge, and worldview that challenged traditional, religious, and myth-based explanations in favor of rational, empirical methods.
Replaced answers provided by religious authorities with scientific enquiry.
Encompasses three primary revolutions: Copernican (Astronomy & Physics), Darwinian (Biology & Evolution), and Freudian (Psychology & Human Mind).

Geocentric Model: Proposed by Claudius Ptolemy ( $100\text{--}170\,\text{CE}$ ) in Almagest, asserting that Earth is the stationary center of the universe; dominated astronomical thought for over $1{,}400$ years.
Heliocentric Model: Introduced by Nicolaus Copernicus ( $1473\text{--}1543$ ) in On the Revolutions of Celestial Spheres ( $1543$ ), positioning the Sun at the center of the Solar System and explaining planetary retrograde motion.
Galileo Galilei ( $1564\text{--}1642$ ): Known as the "Father of Modern Science"; improved the telescope to observe Jupiter's moons, sunspots, and phases of Venus in support of heliocentrism.
Johannes Kepler ( $1571\text{--}1630$ ): Formulated the Three Laws of Planetary Motion:
- First Law: Planets move in elliptical orbits with the Sun at one focus.
- Second Law: A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
- Third Law: The square of a planet's orbital period ( $T^2$ ) is proportional to the cube of the semi-major axis of its orbit ( $R^3$ ), maintaining a constant ratio ( $\frac{R^3}{T^2}$ ).

Charles Darwin ( $1809\text{--}1882$ ): Published On the Origin of Species ( $1859$ ), establishing that life evolves over time through natural selection.
Evolution vs. Creationism: Shifted scientific paradigm from creationism (belief that God created fixed, unique species) to evolutionary theory (gradual adaptation and change over time).
Evidence for Evolution:
- Homologous Structures: Anatomically similar structures shared across species due to common ancestry (e.g., forelimbs in humans, cats, birds, and whales).
- Analogous Structures: Structures with similar functions but different evolutionary origins (e.g., wings in bats vs. birds).
- Embryology: Vertebrate embryos share homologous features during development, such as tails and limb buds.
- Molecular Evidence: Similarities in genetic code ( $\text{DNA}$ ) and protein amino acid sequences among related species.
Adaptations & Fitness: Adaptations like camouflage and mimicry enhance survival; fitness measures trait effectiveness.

Sigmund Freud ( $1856\text{--}1939$ ): Austrian neurologist and founder of psychoanalysis who demonstrated that human behavior is driven by the unconscious mind and early childhood experiences.
Psychoanalytic Methods: Developed therapeutic techniques including free association, dream analysis, and interpretation of slips of the tongue ("Freudian slips").
Tripartite Model of Personality:
- Id: Present from birth; operates on the pleasure principle seeking immediate gratification of instincts and desires.
- Ego: Develops in early childhood; operates on the reality principle as a rational mediator between the Id and Superego.
- Superego: Develops around age $5\text{--}6$ ; incorporates internalized moral values, operating via the conscience (punishes with guilt) and ego ideal (rewards with pride).