Ch 4.2-3 Earth’s Rotation & Revolution
pg 75-83
Rotation – The spinning of the Earth around its axis, an imaginary line running from North Pole
to South Pole.
 Axis is tilted 23 ½o in respect to its orbital plane
 24 hours - causes day and night
Revolution – the movement of the Earth in its orbit around the sun (365 ¼ days)
Effects of Revolution and Tilt
 Seasons (for mid latitudes)
 Changes in the length of days and nights
 Changes in which latitudes receive direct sun rays
Summer - June 21 – Summer Solstice: The Earth’s northern hemisphere is at maximum tilt
towards the sun.
Longest daylight period – because the sun’s path in
the sky is longer and higher than at any other time of
the year.
-Rays directly over the Tropic of Cancer - 23½oN.
-24 hours of daylight – North Pole – Arctic Circle
-24 hours of darkness – South Pole – Antarctic
Winter - December 21 – Winter Solstice: The Earth’s northern hemisphere is at maximum tilt
away from sun.
Shortest daylight period – because the sun’s path in
the sky is shorter and lower than at any other time of
the year.
-Rays directly over the Tropic of Capricorn - 23½oS.
-24 hours of darkness – North Pole – Arctic Circle
-24 hours of daylight – South Pole – Antarctic
Spring - March 21 – Vernal Equinox
Fall - September 22 – Autumnal Equinox
-Neither hemisphere tilts towards the sun
-Equal periods of day and night – 12 hours each
-Rays directly over the equator