physics

• Thales (638-548 BC)

  • lives in Miletus
  • Earth is like a disk Floating on Water
  • concept of Floatiness
  • Precursor of Science - Started the Theories and formulation of Hypothesis
• Anaximander (610-545 BC)

  • Earth is a Cylinder and its Surface is Curved
  • Earth (Cylindrical) and Hollow at the center
  • Primary Element is Fire
  • Introduced the sundial
  • Hollow center
  • Earth is at the center
• Pythagoras (570-490)

  • He was the first one to originate a spherical earth
  • North and South Constellations; Sinking Ships; and Lunar Eclipse
• North and South Celestial Pole

  1. North Star is believed to be at a fixed position
  2. But when they travelled near the equator the North star appears to be closer
• Sinking Ships

  • If the Earth was flat, then a ship traveling away from an observer should become smaller and smaller
  • But when the ship became smaller, its hull disappeared first which means that the Earth is curved
• Partial Lunar Eclipse

  • Curved Shadow from a curved object
• Pythagorean Model

  • Geocentric Model
  • Earth is round
  • Heavenly Bodies move in circle
  • Earth is at Rest and at the Center, and everything rotates on it
  • "The Music of Spheres" - motion of planets were mathematically related to musical sounds and numbers
• Plato(428-348 BC)

  • Earth is form of a globe having its extremes in every direction equidistant from the center
  • He believed that the universe is perfect or ethereal and unchanging
  • He further described the stars embedded in the outer space as ETERNAL AND DIVINE
• Eudoxus of Cnidus (390-337 BCE)

  Homocentric Model

  • 1st model of the Geocentric Model
  • Celestial spheres share one common center (Earth)
  • 27 interconnected spheres
• Aristotle (384-322 BCE)

  • Earth is fixed as the center of the solar system that everything revolves around it
  • Proved that the earth is spherical
  • has 56 spheres around it (he added 3 sphere to jupiter and mars and added 4 to Sun, Moon, Venus and Mercury)
  • Prime movers - drives the motion of the planets
• Erastosthenes

  • gave most accurate sizes during their time
  • 40030 km - circumference of Earth
  • Using a stick
• Claudius Ptolemy (90-168 CE)

  • Earth Spherical Object
  • Planets moves with their independent motion which is Deferent and Epicycle
  • Deferent - Circular path in which planets moves
  • Epicycle - Circle where planets move in their own axis
  • Proposed the Equant - a point close to the orbit's center
• Geocentric Astronomers

  • Pythagoras
  • Plato
  • Eudoxus
  • Aristotle
  • Eratosthenes
  • Ptolemy
• Aristarchus' Model

  • Heliocentrism
  • 1st to place the sun at the center of the universe
  • Sun and stars are fixed
  • Earth is revolving around the sun in a circular orbit
• Nicolaus Copernicus (1473-1543)

  • proposed that the Earth revolved around the Sun.
  • corrected the geocentric theory and proposed the geocentric theory and proposed the Heliocentric theory
• Retrograde motion - in general, orbital, or rotational motion of an object in the direction opposite the rotation of its primary, that is the central object

  • direction from West to East
• Copernicus' Model

  • Celestial motions are uniforms, infinite and circular
  • Planets revolved around the sun
  • Earth motion explains the retrograde motion os other planets
  • Earth spins on a tilted axis, which accounts for the seasons
  • Distance from the Earth to sun is smaller than earth to stars
• Tycho Brahe

  • modified the geocentric model
  • designed and built huge instruments used to make precise measurements of the positions of the planets
  • discovered supernova in the constellation Cassiopeia
  • observations of planetary motions that are important to the development of Kepler's Laws and other models of solar system
• Tycho Brahe's Model

  • Geo-Heliocentric
  • the planets revolving around the earth, and the sun revolving around the earth
• Galileo Galilei

  • telescope
  • discovered sunspots and rough surface of the moon
  • 4 famous moons of Jupiter known as Galilean moons
  • Venus had phases like the moon
  • book "Sidereus Nuncius" (The Starry Messenger)
• Galileo Galilei's Corrections

  • Lunar Craters
  • Phases of Venus
  • Moons of Jupiter
  • Sunspots
  • Supernova
  • Identical Size of the Stars
• Johannes Kepler's 3 Laws of Planetary Motion

  1. The Orbit Ellipses
  2. Equal areas in equal time

  
• Kepler's 1st Law

  • It states that the orbits of the planets are ellipses, with the sun at one focus
  • Perihelion - point nearest to the sun
  • Aphelion - point farthest to the sun
• Kepler's 2nd Law

  • Planets travel faster during perihelion, travel slower during aphelion
• Kepler's 3rd Law

  • The cube of the radius of the orbit of a planet around the sun is proportional to the square of its period of revolution
  • The larger the planets orbit, the longer the revolution
  • The square of the revolution is directly proportional to the square of their average distances
• 1 Revolution of Planets

  • Mercury - 88 days
  • Venus - 225 days
  • Earth - 365 days
  • Mars - 687 days
  • Jupiter - 11.9 years
  • Saturn - 29.4 years
  • Halley's Comet - 76 years
• Astronomical Unit

  • is the average distance between Earth and the Sun. which is about 93 million miles or 150 million kilometers
  • measures the distance within our Solar System
• Heliocentric

  • Aristarchus
  • Copernicus
  • Galileo Galilei
  • Kepler