PhySci

• Gaia is the personified name of Earth in Greek mythology. Gaia is the ancestor of all life on Earth and the mother of all goddess.
• During the early period, people have thought a lot of things about the earth and what lies beyond its boundaries.
• Most of the primitive ideas about the earth and other planetary objects originated from the famous Greek philosophers like Aristotle, Ptolemy, and Galileo.
• These people have asked a lot of questions about the earth and the universe that they tried to answer using their logical way of thinking.
• Some of the ideas were proven to be true and still being considered until today, but most were replaced with the new theories and laws that were developed after the advent of the telescope that allowed astronomists to explore the universe with a larger sight.
• In this chapter, the common question about the earth and the solar system shall be discussed.
• Starting from the shape of the earth up to the models of the universe.
• Students are expected to have the better understanding of the evolution of ideas and theories about the earth and the universe in entirety.
• Essential Questions


  • What is the earliest Greek notion on three types of terrestrial motion?
  • What are diurnal motion, annual motion, and precession?
  • How do the Greeks know that Earth is spherical?
  • How Plato's idea on "saving the appearances" constrained Greek models of the universe?
  • What are the similarities and differences in the universe models by Eudoxus, Aristotle, Aristarchus, Ptolemy, and Copernicus?
• Review


  • All things on Earth is made up of matter that occupies volume and space. This matter can be convertible into different forms such as solid, liquid, and gas. These serve as the common components of the earth.
  • In this unit, it is important to recall that the earth is part of a bigger system of planets that revolve around the sun. This system of the planet is called the solar system.
  • Sun is the center of the solar system. It provides primary energy to the earth that is essential for sustaining life forms.
  • Several Greek philosophers have tried to study matter and life forms. They also tried to study planetary objects and explained the different astronomical phenomena.
• Ancient Greeks had several beliefs about matter and motion. They are the ones who started the curiosity in studying different objects in the universe. Several hypotheses and theories were formed.
• Matter


  Any substance that has specific mass and consumes space by having its own volume
• Motion


  The change in the position of matter over a certain period of time
• Empedocles's theory


  • All things are made up of four elements: fire, air, water, and earth
  • The combination and ratio of the four elements dictate the properties of the matter
• Atomos


  Small pieces of matter that are indivisible, eternal, and indestructible (according to Democritus)
• Democritus's theory of atomos was rejected by Aristotle and Plato, who supported the idea of Empedocles.
• John Dalton's Atomic Theory


  • All matter is composed of atoms
  • All atoms of an element are entirely identical; atoms from other elements are different by having different properties
  • Chemical reactions happen due to the interactions of atoms through combination. Atoms are indestructible and unchangeable
  • Elements react to form compounds in defined ratios
• Natural motion


  Motion in which the object moves upward and downward due to the weight of the matter (according to Aristotle)
• Violent motion


  Motion which is a product of pushing or pulling caused by humans (according to Aristotle)
• Aristotle believed and taught that heavier things fell faster than lighter things.
• Natural motion


  Motion that moves upward and downward due to the weight of the matter
• Violent motion


  A product of pushing or pulling caused by humans, can be voluntary or involuntary
• Aristotle


  • Introduced the concept of motion during the Greek era
  • Believed there are two forms of motion: natural and violent
• Galileo


  • First person to lay down laws of motion for objects with masses
• Newton


  • Developed three laws of motion based on Galileo's work
• Diurnal motion


  Apparent movement of stars and other celestial bodies around the Earth, caused by Earth's rotation
• Annual motion


  Apparent yearly movement of the sun across a background of stars, caused by Earth's revolution around the sun
• Precession


  Conical motion of Earth's axis as it spins, caused by gravity continuously changing the orientation of the rotational axis
• Key points


  • Empedocles introduced theory of 4 elements (fire, air, water, earth)
  • Democritus proposed presence of small indivisible atoms
  • John Dalton developed first atomic theory
  • Aristotle introduced natural and violent motion
  • Galileo laid down laws of motion
  • Newton developed 3 laws of motion
  • Diurnal, annual, and precession are forms of non-terrestrial motion
• Motion of an object within the earth is not called non-terrestrial motion
• The ecliptic is the projected pathway of the sun with regards to the stars
• An object at rest is not in its natural form of motion
• Newton's second law of motion states that the force is equal to change in momentum per time interval, not that action and reaction forces are equal
• Involuntary motion refers to motion not caused by the will or capacity of humans, not their ability to move
• Flat Earth model


  An old belief that the earth is plane or discoidal form
• Many old cultures believe that the earth is flat
• The idea of round and spherical Earth was only proposed in the 6th century BC
• Flat Earth model according to the Egyptians and Mesopotamian


  • The world is a disk in the ocean
• Flat Earth model according to the Hebrews


  • The earth is like a disc floating on the water where an arched bowl separates the earth from the heavens. The sky is a solid dome with the sun, Moon, and other planetary objects embedded in it.
• Pythagoras


  Introduced the idea of the round model of the earth's shape in the 6th century BC