WHY DO WE HAVE SEASONS?

• Seasons are the result of the tilt of the Earth's axis.

• Earth’s axis is tilted 23.5°.• This tilting is why we have SEASONS

like fall, winter, spring, summer.• The number of daylight hours is greater

for the hemisphere, or half of Earth, that is tilted toward the Sun.

SOLSTICESSOLSTICES

• Solstices occur twice a year, when the tilt of the Earth's axis is oriented directly towards or away from the Sun, causing the Sun to appear to reach its northernmost and southernmost extremes.

• Winter solstice is the shortest day of the year. In the Northern Hemisphere. It occurs on December 21 and marks the beginning of winter.

• The Summer Solstice is the longest day of the year. It occurs on June 21 and marks the beginning of summer.

Tyrrhenian Sea and Solstice Sky Credit & Copyright: Danilo Pivato

SOLSTICE

• During the winter the Northern Hemisphere day lasts fewer than 12 hours and the Southern Hemisphere day lasts more than 12 hours.

• During the winter solstice, the North Pole has a 24-hour night and the South Pole has a 24-hour day.

• Sunlight strikes the earth most directly at the Tropic of Capricorn.

http://k12.ocs.ou.edu/teachers/reference/solstice.gif

EQUINOXES

• A day lasts 12 hours and a night lasts 12 hours at all latitudes.

• Equinox literally means "equal night".

• Sunlight strikes the earth most directly at the equator.

• This occurs twice a year.

http://k12.ocs.ou.edu/teachers/reference/equinox.gif

EQUINOX

• The vernal (spring) equinox occurs March 21.

• The autumnal (fall) equinox occurs September 21.

NEW MOON

•The moon is not visible from Earth. The moon is between the Sun and the Earth.

•The dark side is facing us.

•This phase lasts one night.

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WAXING CRESCENT

•Waxing means that the bright side is increasing. The right side is the bright side.

•Less than one half of the moon is illuminated.

•This phase includes any visible moon from a small sliver to almost half.

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FIRST QUARTER OR HALF MOON

•The entire right side of the moon is illuminated.

•The moon looks like a half circle.

•The illuminated side is increasing.

•This phase only lasts one night.

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WAXING GIBBOUS

•Gibbous means that more than one half is visible, but it is not quite full.

•This phase includes the night after the first quarter to the night before the full moon.

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FULL MOON

•The moon is full and bright. It looks like a large circle.

•The illuminated side is facing us.

•Only happens one night per lunation.

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WANING GIBBOUS

•The moon appears more than half but not quite full.

•Waning means that the illuminated side is decreasing.

•The left side is the bright side.

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LAST QUARTER OR HALF MOON

•Left Half of the moon is illuminated.

•The illuminated side is decreasing.

•This phase also only lasts for one night.

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WANING CRESCENT

•Less than one half of the moon is illuminated.

•The moon will continue to become smaller and smaller.

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THE TIDE CYCLE

• High tides occur on the side of the Earth closest to the moon due to the moon’s gravity pulling on the water

• High tides also occur on the side of the Earth farthest from the moon. The moon’s gravity pulls on the Earth more strongly than it pulls on the water leaving it behind

• In between the two high tides, low tides occur

SPRING TIDES

Sun’s gravity pulls on Earth’s waters

During a new moon – sun, moon and Earth are nearly in a line.

Gravity of sun and moon pull in same direction Combination of forces produce tide with greatest

difference between low and high tide Called a spring tide – occur twice a month during full and

new moons

NEAP TIDES

• During moon’s 1st and 3rd quarter, line between Earth and the sun is at right angles to line between Earth and moon.

• Sun’s pull is at right angles to moon’s pull.

• Produces a neap tide = least difference between high and low tide

• Occur twice a month

SPRING TIDES AND NEAP TIDES

TOTAL SOLAR ECLIPSES

TOTAL LUNAR ECLIPSES