Phys Sci WW3

Greek Evidence of a Spherical Earth

Ships Over The Horizon, The Shape of Earth's Shadow on the Moon, Difference in the Night Sky by Location, Eratosthenes' Measurement of Earth's Circumference

The Shape of Earth's Shadow on the Moon

The earth's shadow on the moon is always circular, supporting the concept that Earth is a sphere.

Eratosthenes' Measurement of Earth's Circumference

He measured the sun's angle at two locations to estimate Earth's size using geometry.

Anaximander’s Concept of Aperion

Described Earth as a free-floating cylinder and introduced the concept of infinite or boundless (Aperion) in the universe.

Pythagoras' View on the Cosmos

Believed numbers and geometric relationships governed the cosmos and one of the first who proposed that Earth is spherical.

Plato's Circular Motion Concept

Believed all celestial motions were perfectly circular and encouraged models that matched observations.

Eudoxus' Concentric Spheres Model

Proposed 27 concentric spheres carrying celestial bodies, one of the first mechanical models.

Aristotle's Prime Mover

Adopted Eudoxus' model and proposed the Prime Mover to explain the motion of celestial bodies.

Aristarchus' Heliocentric Model

Famous for propose a heliocentric model with the sun at the center of the universe.

Ptolemaic Model's Epicycles

Introduced the concept of epicycles to explain the retrograde motion of planets within a geocentric framework.

Copernican Revolution

Revived the heliocentric model, explaining retrograde motion more simply by placing the sun at the center.

Tycho Brahe's Hybrid Model

Tycho Brahe's model kept Earth stationary at the center but had other planets orbit the sun.

Galileo's Telescope Improvements

Galileo improved telescope designs, increasing magnification and image quality, leading to significant astronomical discoveries.

Discovery of Lunar Craters

Galileo observed that the moon was not smooth but covered with craters, challenging the belief in perfect celestial bodies.

Phases of Venus

Galileo found that Venus went through phases, providing evidence for the heliocentric model.

Moons of Jupiter

He discovered four moons orbiting Jupiter, showing Earth was not the only center of motion.

Sunspots

Galileo observed spots on the sun that changed, challenging the notion of celestial perfection.

Supernova Observation

He observed a bright new star, providing evidence that celestial bodies can change.

Apparent Size of Stars

Galileo noted stars as distinct points of light at varying distances, challenging the fixed celestial sphere concept.

Tycho Brahe's Systematic Observations

Known for precise astronomical observations and advanced instruments for measuring planetary positions.

Johannes Kepler's Laws

Law of Ellipses, Law of Equal Areas, Law of Harmonies

Law of Ellipses

Planets move in elliptical orbits around the sun. This law challenged the belief in perfect circular orbits, explained the planetary motion more accurately, eliminating the need for epicycles

Law of Equal Area

Planets move faster when closer to the sun (perihelion) and vice versa (aphelion). This law proved that planetary speeds change, explained seasonal changes, refuted Aristotle's idea of uniformity

Law of Harmonies

The square of a planet's orbital period is proportional to the cube of its average distance from the Sun. This law allowed astronomers to predict planetary positions, provided a mathematical relationship between a planet's distance from the Sun and the time it takes to complete 1 orbit, provided a foundation for newton's laws of gravitation

Aristotelian Motion

Introduced Natural and Violent motion

Natural Motion

Objects tend to return to its natural state based on its composition

Violent Motion

A cause if necessary for an object to move

Galilean Motion

Used Falling Object Experiment and Inclined Plane Experiment

Falling Object Experiment

With no air resistance, all objects fall at the same rate

Inclined Plane Experiment

Objects in motion accelerate uniformly and they stay in motion unless acted upon by an external force

Law of Inertia

Object will keep moving unless acted upon by a force

Law of Acceleration

An object is directly proportional to the force applied and inversely proportional to its mass

Law of Action

Every action there is an equal opposite reaction

Acceleration

Change in velocity over time

Velocity

Objects seed up, slow down, and change directions

Kinematics

Branch of physics that studies the possible motion of a body or system of bodies

Why Kinematics?

Newton’s laws explain why motion happens, equations describe how objects move when forces act on them, allows us the predict the velocity and displacement without explicitly calculating force