Scientific Revolution and Key Figures

Overview

This lecture covers key contributors to the Scientific Revolution, focusing on Copernicus, Darwin, and Freud, and explains paradigm shifts in scientific thought and their impacts on society.

Intellectual Revolution & Scientific Revolution

The intellectual revolution marked a shift from traditional beliefs to modern scientific thinking.
It involved discarding old ideas and embracing new scientific paradigms.
Major paradigm shifts challenged long-held views about the universe and nature.

Copernican Revolution & Modern Astronomy

Copernicus challenged the geocentric (Earth-centered) model, proposing a heliocentric (Sun-centered) system.
The geocentric model claimed the Earth was the center, stars were immutable, planets moved in circles, and Earth was flat and stationary.
Copernicus' heliocentric model argued Earth rotates on its axis and revolves around the Sun.
His ideas faced resistance, especially from the Church, but inspired the birth of modern astronomy.
By Nicolaus Copernicus
Ptolemy believed that the Earth is at the center of the universe (Geocentrism). The sun, the moon, and other planets revolve around the Earth. The movement of the sun explained why we have days and nights.
Ptolemy’s geocentric model held sway for 1400 years.
Geocentrism was later refuted by Copernicus when he introduced Heliocentrism.
He positioned that the Sun is the center of the Solar System
This gave birth to modern astronomy.
The era that was known as Scientific Revolution.
Copernicus was declared a heretic, an enemy of the church, for his contradicting beliefs about the earth and the universe.
He acknowledged the fact that the position and motion of planets and other objects in space could be estimated through systematic data gathering and interpretation.

Geocentric Assumptions

The Earth is the center of all motion
- Everything revolves and moves towards the Earth. 
- Like the rain, snow, and meteors.
Stars are immutable. 
- There is no death of stars.
Planets move in circular orbits, not elliptical orbits.
The Earth is flat. 
- Because the horizon is flat. If the Earth were round, then the heavenly bodies would fall off. There is still no concept of gravity.
The Earth does not move. 
- The Sun moves because that is how they see it. We do not feel the movement of the Earth; therefore, we assume that we are still.

Other Key Astronomers & Discoveries

Galileo 
- Supported heliocentrism by discovering Jupiter’s moons ( 19 satellites, 4 owned and discovered by him) and observing sunspots, showing celestial bodies did not revolve around Earth.
- Galileo’s study of Venus’ phases contradicted geocentrism, supporting the heliocentric model. Crescent's biggest size. The size of Venus is bigger when it is closer to the Earth, and smaller in its full phase because it is at its opposite side of the orbit. It would have the same size if it were revolving around the Earth, just like the Moon. 
- Rejects that the Earth is the center of all motion.

Tycho Brahe 
- developed a hybrid solar system model that was intermediate between the Ptolemaic and Copernican models. 
- Brahe’s ideas about his data were not always correct, but the quality of the observations themselves was central to the development of modern astronomy. 
- Made precise astronomical observations, including recording a supernova, the explosion of a star, which disproved the idea that stars are immutable.

Johannes Kepler 
- formulated three laws of planetary motion:
- Law of Ellipses- each planet moves in an elliptical orbit with its star (Sun) at one focus. 
- Law of Equal Areas- an orbiting object will take the same amount of time to travel between points A & B as it takes to travel between points C & D. A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time. 
- Law of Harmony - The square of a planet’s orbital time is proportional to its average distance from the star (Sun) cubed. 
- Proves that the orbit was elliptical instead of circular.
Isaac Newton 
- Formulated the Universal Law of Gravitation & Laws of Motion:
- Law of Inertia - an object persists in its state of rest or uniform motion in a straight path unless an external force acts upon the object. 
- Law of Acceleration - an object accelerates relative to the force applied and in the direction of the force. The greater the force applied, the greater the distance travelled, and the higher speed achieved. 
- Law of Interaction- for every action, there’s an equal and opposite reaction. 
- Why we run towards the earth is due to gravity.

Albert Einstein
- The Theory of Relativity showed that motion is relative and explained why the Sun appears to move around the Earth from our perspective.
- Energy = mc^2 
- Other striking consequences are associated with the dependence of space and time on velocity; at speeds near that of light, space itself becomes contracted in the direction of motion, and the passage of time slows. 
- Motion is relative, not absolute. Explain why the Sun is moving around us.

Key Terms & Definitions

Geocentrism — The belief that the Earth is the center of the universe.
Heliocentrism — The Sun-centered model of the solar system.
Paradigm Shift — A major change in basic scientific concepts.
Supernova — An exploding star, disproving the idea that stars are unchangeable.
Ellipse — An oval shape; describes the true path of planetary orbits.