LESSON 2

• Motion is a change in position with respect to a reference point and time.
• Reference points are very important in describing the motion of objects.
• Aristotle’s View of Motion

  • Motion did not only refer to locomotion or a change in position
  • He classified motion as: Terrestrial ( or sub lunar) and Celestial
• Terrestrial Motion-The movement of objects on earth
• According to Aristotle, Earth is the center of the universe and everything on earth was made up of only four elements:

  ·        Earth (center)

  ·        Water

  ·        Fire

  ·        Air
• Each element had a natural place.

  When an element was removed from its natural place, it would return to its natural place following a straight line (rectilinear) motion.
• Celestial Motion-Aristotle described celestial motion as the motion of celestial bodies which only possessed the tendency for uniform circular motion.
• Hipparchus of Nicaea (190 BCE-120 BCE) was able to determine correctly the circumference of Earth.
• hipparchus- He was once considered as the greatest observational astronomer because he was able to explain the precession of equinoxes.
• Precession of Equinoxes refers to the movement of the Earth relative to its orbital plane.
• Copernicus's View of Motion

  -Studied the motion of Earth.

  -He had two descriptions of Earth’s motion based on his observations (rotation and revolution) which are classified as either diurnal (daily) motion or annual (yearly) motion.
• Diurnal Motion refers to the rotation of earth about its axis from west to east.
• Diurnal Motion

  -As the Earth rotates, some of its parts are exposed to the sun’s rays while other parts are not.

  -This results in the occurrence of day and night.
• Annual Motion refers to the movement of earth in reference to the sun.

  There are two types of annual motion: Earth’s revolution and tiltration.
• Annual Motion-Earth revolves around the sun from west to east.
• Annual Motion-This takes around 365 ¼ days (365 days and 6 hours) to be completed and is the reference for the number of days in a standard year.
• Annual Motion-The occurrence of seasons: (spring, summer, autumn, and winter) is a consequence of both earth’s revolution and tilted axis.