Motions of the Earth

1
Motions of the Earth
2
Rotation and Tilt

• Rotation on its axis and tilt of 23.5 compared
  to our orbit are responsible for
• Day and Night (23h 56m 4s)
• Sun, planets, and moon rise and set daily
• Southern stars and constellations rise and set
  daily
• Circumpolar stars circle the celestial pole
  depending on ones latitude

3
Revolution

• Revolution around the sun is the basis for
• The year (365 ¼ days)
• Seasonal constellations being observed
• Length of daylight hours varying
• Sun, planets, and moon seem to move among the
  seemingly fixed stars
• Path of the sun is the ecliptic

4
Precession

• Precession of the Earth on its axis is
  responsible for
• Changing the star at the celestial pole
• Change has a 26,000 year period
• The position of the sun on the ecliptic changes
  its zodiac constellation
• Seasonal constellations will slowly change
• Orion will eventually be in a new season

5
Why watch the sky

• Observe seasons
• Record solstices and equinoxes
• Note star rising and setting for recording frosts
  etc.
• Constellation stories to record history, teach
  lessons and morals, entertainment, and explain
  nature
• Predict eclipses
• Tell time