Revolution and Rotation• Revolution – object’s path as it orbits another body in space

– Earth’s revolution is 365 1/4 days (leap year)

• Rotation – spin of an object in space– Earth spins about its axis (imaginary line through center of Earth from pole to

pole)

– Earth’s rotation is 23 hours and 56 minutes• Day – time required for Earth to rotate once on its axis

Earth’s Position and the Sun• Earth is positioned so half of the planet is lit (pointing towards the Sun) and

half is dark (pointing away from the Sun)

• The Sun’s rays – hit the Earth more directly at the equator, that is why it is hotter

– are dispersed at the poles, that is why it is colder

• The Seasons– 23.5° tilt causes the seasons

– Has nothing to do with how close to the sun we are

– The North Hemisphere points away from the Sun in the winter

– Equinox – Sun directly above the equator

– Solstice – Sun farthest North or South of the equator

Season’s Yearly Cycle• March Equinox (March 21st)

– Vernal Equinox – spring begins in northern hemisphere

– Daylight hours equal night hours

• June Solstice (June 22)– Summer Solstice – summer begins in northern hemisphere

– North pole pointed towards Sun

– More daylight hours in northern hemisphere

• September Equinox (September 23)– Autumnal Equinox – fall (autumn) begins in northern hemisphere

– Neither Northern or Southern hemisphere are pointed towards the Sun

• December Solstice (December 22)– Winter Solstice – winter begins in northern hemisphere

– North pole pointed away from Sun

– Fewer daylight hours in northern hemisphere

•http://www.enchantedlearning.com/egifs/Earthseasons.GIF

Moon Phases• Moon has revolution around Earth which equals 27.3 days

• Moon rotates on its axis at the same rate (about 27 days)

• Phases of Moon – different appearances of moon due to its changing position– Waxing – sunlit part of the moon gets larger

– Waning – sunlit part of the moon gets smaller

– Gibbous - almost fully lit

– Cresent – cresent, sliver shaped

•http://www.utahskies.org/image_library/shallowsky/planets/earth/moon/Moon_phases.jpg

•http://en.wikipedia.org/wiki/Lunar_phase

Eclipses• Eclipse – shadow of celestial body falls on another

body

• Lunar Eclipse – Earth comes between Sun and Moon

– Shadow of Earth falls on Moon

– Moon appears red because of Earth’s atmosphere reflecting the sunlight

• Solar Eclipse– Moon comes between Earth and Sun

– Shadow of moon falls on Earth

•http://www.theastronomer.org/images/lunar_eclipse_960927.jpg

•http://www.bbc.co.uk/science/space/myspace/images/rick_bentley_eclipselarge.jpg

Moon and Tides• Earth and Moon pull together due to gravity (force of attraction between two

objects)• Tides – daily movements of ocean water that change the level of ocean’s

surface• On the side of Earth that faces the Moon, the ocean water bulges due to

gravitational pull (same on opposite side of Earth due to the fact that Earth spins)

• 2 high tides and 2 low tides a day• Sun helps a little too• Tidal Range – difference between levels of ocean water at high and low tide

– Spring tides – tides with the greatest tidal range– Neap tides – tides with the smallest tidal range

•http://www.thehopewellrocks.ca/images/tidechart3.jpg