physical science-astronomy

• Astronomy


  • The science of the universe outside of our planet
  • The branch of physical science dealing with heavenly bodies
• Astronomy has resulted in many practical inventions, ideas, including calendars, navigational techniques, laws of motion, engineering of products and an increased understanding of energy and weather
• Astronomical phenomena known to astronomers before the advent of telescopes

  • Rising and setting of the Sun in the east and the west, respectively
  • Phases of the Moon
  • Eclipses
  • Daily and annual motion of the stars
  • Planets

  
• Gnomon


  A primitive version of sundial
• Babylonian and Egyptian civilizations used a gnomon


  1. Systematically observing the motion of the sun

  2. Looking at the shadows that the gnomon casts

  3. Observing the sun rises in the eastern part of the sky, reaches its highest point in midday, and sets in the western part of the sky

  
• Greek astronomers recorded that the points where the sun rises and sets on the horizon varies over a year and these variations happen periodically

  
• Greek astronomers observed that these variations are related to weather and so concluded that seasonal changes in climate happen during a course of one year
• Phases of the Moon

  • New Moon
  • First quarter
  • Waxing Crescent
  • Waxing Gibbous
  • Third, or last quarter
  • Waning Gibbous
  • Full Moon
  • Waning Crescent

  
• Moon


  • A relatively small object that is orbiting around a planet
  • Half of the moon is always lit by sunlight and the other half is in shadow
  • It takes 27 days, 7 hours, and 43 minutes for our Moon to complete one full orbit around Earth
  • It takes our Moon about 29.5 days to complete one cycle of phases (from full Moon to full Moon)

  
• Types of eclipses


  • Lunar eclipse
  • Solar eclipse

  
• Lunar eclipse


  Occurs when moon moves into the shadow of the Earth causing the moon to be darkened

  
• Solar eclipse


  Occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks the light from the Sun

  
• Diurnal motion


  The apparent movement of stars and other celestial bodies around Earth caused by Earth's rotation from west to east

  
• Annual motion


  • The apparent yearly movement of the sun across a background of stars
  • The ecliptic is the projected pathway of the sun with regards to the stars
  • As the sun appears through the ecliptic, the zodiac which consists of 12 ancient constellations appears

  
• Annual motion explains the existence of 4 seasons: winter, spring, summer and fall, and why we experience solstices and equinoxes
• Precession


  • The change in the orientation of the rotational axis of the rotating Earth
  • Discovered by Hipparchus of Nicaea (Turkey)

  
• The gravitational force of the sun and the moon on Earth causes the cyclic precession or "wobbling" of the Earth's axis of rotation
• At present, Earth's North Pole points to Polaris, but it will eventually point to another star, Vega, because of precession

  
• Planets


  • Mercury
  • Venus
  • Mars
  • Jupiter
  • Saturn
• Mercury


  The smallest planet in our solar system, a little bigger than Earth's Moon, the closest planet to the Sun, but not the hottest
• Venus


  The second planet from the Sun, a rocky planet with a mass and size narrowly second in the Solar System to Earth, and with an atmosphere, which is the thickest of all four rocky planets of the Solar System
• Mars


  The reddish planet, the only other known body whose surface conditions seemed suitable for life of some kind, with Martian days and nights about the same lengths as ours and its seasons about 6 months long and at least as pronounced as ours
• Jupiter


  A huge planet, shrouded in thick clouds that its surface cannot be seen, with a volume about 1,300 times that of earth, but its mass only 300 times as great, consisting primarily of hydrogen and helium, the two lightest elements, with an average diameter about 11 times greater than the earth's
• Saturn


  Characterised by its famous rings, much like Jupiter, with the rings - two bright ones and a fainter inner one - surrounding the planet in the plane of its equator, appearing to be composed of many small bodies, which revolve around Saturn like miniature satellites