physci first quiz

• THALES (628 — 548 BC)


  believed that earth was a disk floating on water. was a cosmologist, he studied sun, moon, stars and other heavenly bodies.
• ANAXIMANDER (610 — 545 BC)


  both thales and him were from miletus. for him, the earth is a cylinder and its surface is curved.
• ANAXIMANDER (610 — 545 BC)


  he made the sundial (oldest known instrument which tells time).
• PYTHAGORAS (570 — 490 BC)

  • He was the first one to originate a spherical earth using observations such as North and South Constellations, Sinking Ship, and Lunar Eclipse
  • He was the first one to say that the earth is round.
• PYTHA EVIDENCE: North Celestial Pole (NCP) and South Celestial Pole (SCP) Constellations


  North Star was believed to be in a fixed position in the sky. However, when the Greeks traveled to places nearer the equator, like Egypt, they noticed that the North Star was close to the horizon.

  • If the Earth is flat, the Polaris (North Star) must have had a fixed position.
• PHYTHA EVIDENCE: Sinking Ships


  If the Earth was flat, a ship would become smaller until it disappeared. However, the Greeks observed that the ship became smaller, and then its hull disappeared first before the sail as if it had been enveloped by the water until it completely disappeared.
• PHYTHA EVIDENCE: Shadow Formed during Partial Lunar Eclipse


  They saw that during a partial lunar eclipse that the shadow is curved.
• PYTHAGOREAN MODEL


  Made by pythagoras. Earth is round → Heavenly bodies move in a circular motion. Earth is at rest at the center, and everything rotates around it.
• • “The Music of Spheres” — motion of planets was mathematically related to musical sounds and numbers as they were moving rhythmically and uniformly
• pythagora

  • First ever to discuss the Geocentric Theory
• plato


  he was pythagora's student.

  • He quoted that earth is a form of a globe having its extremes (sides) in every direction equidistant (equally far) from the center.
  • Believed that the universe is perfect or ethereal and unchanging

  He further described the stars as ‘eternal and divine’
• PLATO’S “SAVING THE APPEARANCE”

  • Their observation that Mars suddenly reversed its rotation from E → W to W → E raised the question, “What uniform and ordered circular motion must be assumed for each of the planets to account for their apparently irregular annual paths?”
• EUDOXUS OF CNIDUS

  • A student of Plato
  • Attempted to answer Platos’ question by making the first model of the Geocentric Theory
  • According to him, there are 27 interconnected geocentric spheres
• HOMOCENTRIC MODEL

  • Celestial spheres share one common center— earth
  • First model of Geocentric Model
• ARISTOTLE (384 - 322 BCE)

  • believed that the earth is fixed at the center of the solar system and that everything revolves around it
  • Supported the claim of Eudoxus of Cnidus
• ARISTOTLE’S MODEL

  • Proved that the earth is spherical 
  • Believed that all stars have fixed points which rotate on a single celestial sphere
  • It has 56 spheres
  • Prime mover — drives the motion of the planets
  • Prime mover was an attempt to answer Plato’s question, but was not sufficient enough
• In conjunction with Eudoxus' model, aristotle added 3 spheres to Jupiter and Mars: Sun, Moon, Venus, and Mercury
• ERATOSTHENES (384 - 322 BCE)

  • Ancient scholars tried to provide proof of a spherical Earth and its circumference through calculations
  • It was he who gave the most accurate size during their time [7.2°/360°=800/x=40,000 km]
• CLAUDIUS PTOLEMY (90 - 168 BCE)

  • Earth is a spherical object
  • The stars are fixed bodies attached to a solid spherical exterior part of the universe
  • Planets move independently of the fixed stars, and that sometimes, the planet seems to reverse in motion
• PTOLEMY’S MODEL

  • Shows the deferent (orbit; circular path in which planets moves) and an epicycle (own path where planets move independently)

  Proposed the equant (a point close to the orbit)
• ARISTARCHUS OF SAMOS (310 - 230 BCE)

  • He stated that the sun and stars are fixed.
• ARISTARCHUS’S MODEL

  • First to place the Sun at the center of the universe
  • The Sun and the stars are fixed
  • The Earth revolves around the Sun in a circular manner
• NICOLAUS COPERNICUS (1473 - 1543)

  • He corrected the geocentric theory and proposed the Heliocentric Theory with the following objectives:
  • Earth is considered the only one of the planets that move around the sun
  • Earth rotates on its axis daily and revolves around the sun once a year
  • Earth experiences an annual tilting of its axis 
  • The tilt of light causes variations in the seasons
  • The retrograde motion of the planets is explained by earth’s motion
  • The distance from earth to the sun is small compared to earth’s distance from the stars
  • The universe is large
• RETROGRADE MOTION

  • It is explained by Copernicus that in astronomy in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is the central object
  • Seemingly backward or opposite direction of spin of the planets because the earth itself is moving, the earth is not fixed hence all planets are spinning around the sun in their own orbit 
  • The motion of heavenly bodies is from west to east
• COPERNICUS’ MODEL

  • Celestial motion is uniform, infinite, and circular
  • Planets revolve around the sun
  • Earth’s motion explains the retrograde motion of the other planets
  • Earth’s spins on a tilted axis, which accounts for the seasons
• TYCHO BRAHE (1546 - 1601)

  • The following are his important contributions to modern astronomy:
  • He modified the geocentric model to the universe
  • He designed and built huge instruments used to make precise measurements of the positions of the planets
  • He discovered a supernova in the constellation Cassiopeia in 1572
  • He made observations of planetary motions that are important to the development of Kepler’s Laws and other models of the solar system
• GEO-HELIOCENTRIC 

  • Tychonic model
  • His model of the universe was both helio, and geocentric, with the planets revolving around the sun, and the sun revolving around the earth
  • In his studies of the heavens, he witnessed and record two supernovae, which opposed Ptolemy’s idea that stars were unchanging
  • Earth is center; sun revolves around the earth while planets revolve around the sun
• GALILEO GALILEI (1564 - 1642)

  • Invented telescope
  • Using his telescope, the following is what he observed:
  • He discovered sunspots, the rough surface of the moon, and supernovas
  • He discovered the 4 famous moons of Jupiter known as Galilean moons
  • He discovered that Venus has phases like the moon
  • Church got mad, excommunicated him, but this decision was taken back and he was recognized after his death
• JOHANNES KEPLER (1571 - 1630)

  • Thanks to enormous and meticulous data collected by his mentor Tycho Brahe, Johannes Kepler was able to summarize the collected data and propose the three laws of planetary motion in the early 1600s.
  • His detailed records in solving the mysteries of the challenging planet “Mars” were the tools Kepler needed
• KEPLER’S 3 LAWS OF PLANETARY MOTION

  • The orbits are ellipses
  • equal areas in equal time 
  • T = time to complete orbit
• FIRST LAW: ELLIPSES

  • 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 from the sun
• SECOND LAW: EQUAL AREAS

  • Planets travel faster during perihelion (due to the gravitational pull of the sun, covering greater area at a faster time) and travel slower during aphelion
• THIRD LAW: HARMONIES

  • The larger the planet’s orbit, the longer the revolution 
  • The square of the revolutions of the planet are directly proportional to the cubes of their average distances
  • An Astronomical Unit (AU) is the average distance between Earth and the Sun, which is about 93 million miles or 150 million kilometers
  • Astronomical Units are usually used to measure distances within our Solar System