W2

• Phases of the moon

  • New moon
  • Waxing crescent
  • First quarter
  • Waxing gibbous
  • Full moon
  • Waning gibbous
  • Third quarter
  • Waning crescent
• Sundial


  Primitive version of a sundial used by Babylonian and Egyptian civilizations to observe the motion of the sun
• Gnomon


  Part of a sundial that casts a shadow to observe the motion of the sun
• Babylonian and Egyptian civilizations used a primitive version of a sundial, called gnomon, in systematically observing the motion of the sun. By looking at the shadows that the gnomon casts, they were able to observe that 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.
• The point where the Sun rises and sets in the horizon varies in a year
• Moon


  A relatively small object that is orbiting around a planet
• Just like the Earth, half of the moon is always lit by sunlight and the other half is in shadow.
• It takes our moon about 29.5 days to complete one cycle of phases (from full Moon to full Moon).
• Lunar eclipse


  The lining up of the earth, moon, and sun produces a lunar eclipse when the moon passes into the shadow of the earth.
• Solar eclipse


  A solar eclipse occurs when the moon's shadow falls on the earth. Because of the large size of the sun, rays of sunlight taper to provide an umbra and a surrounding penumbra.
• Diurnal motion


  The apparent daily revolution of the celestial sphere around the celestial poles as a direct effect of the Earth's rotation on its axis.
• The apparent motion of celestial bodies viewed from Earth is east to west.
• Annual motion


  The apparent yearly movement of the stars as observed from Earth as a direct effect of the Earth's revolution around the sun.
• Precession of the equinoxes

  The apparent motion of the equinoxes along the ecliptic as Earth 'wobbles,' and this motion happens about every 26 000 years. At present, Earth's North Pole points to Polaris. However, it will eventually point to another star, Vega, because of precession.
• As the sun revolves around the ecliptic, it intersects the celestial equator twice during a year at two points. These points are called the equinoxes: vernal and autumnal. During an equinox, the length of daytime is almost equal to the length of nighttime.
• Planets discovered before the invention of telescope

  • Mercury
  • Venus
  • Mars
  • Jupiter
  • Saturn
• Statements to complete


  • Sun
  • Horizon
  • Moon
  • Eclipse
  • Solar
  • Stars
  • Venus
  • Mars
  • Jupiter
  • Saturn
• Tycho Brahe


  A Danish astronomer and nobleman who made accurate observations of the movement of celestial bodies. He was able to invent different astronomical instruments, with the help of his assistants, and made an extensive study of the solar system.
• Johannes Kepler


  An assistant of Tycho Brahe. Kepler postulated that there must be a force from the Sun that moves the planets. He was able to conclude that this force would explain the orbit of Mars and the Earth, including all the other planets, moved fastest when it is nearest from the Sun and moved slowest when it is farthest from the Sun. After Brahe died, all his writings and instruments were passed to Kepler. From Brahe's data, Kepler was able to formulate his laws of planetary motion: the law of ellipses, the law of equal areas, and the law of harmonies.
• Kepler's Law of Ellipses

  Describes that the actual path followed by the planets was elliptical, not circular, with the Sun at one focus of the ellipse.
• Kepler's Law of Equal Areas


  States that when an imaginary line is drawn from the center of the Sun to the center of a planet, the line will sweep out an equal area of space in equal time intervals.
• Kepler's Law of Harmonies

  States that the ratio of the squares of the periods of two planets is equal to the ratio of the cubes of the average distances of these two planets from the Sun.