Seasons, eclipses, and tides
Key Concepts
•What are solar and lunar
eclipses?
•What causes the tides?
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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.
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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.
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During the winter the
Northern Hemisphere day lasts
fewer than 12 hours and the
Southern Hemisphere day
lasts more than 12 hours.
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During the winter solstice, the
North Pole has a 24-hour night
and the South Pole has a 24hour day.
Sunlight strikes the earth most
directly at the Tropic of
Capricorn.
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http://k12.ocs.ou.edu/teac
hers/reference/solstice.gif
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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/re
ference/equinox.gif
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The vernal (spring)
equinox occurs March
21.
The autumnal (fall)
equinox occurs
September 21.
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Occurs when:
moon’s shadow hits Earth or
Earth’s shadow hits moon
When an object in space comes between the sun
and a third object it casts shadow on that object
= eclipse
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New moon – moon is between sun and Earth
Most months the moon is a little above or
below sun in the sky.
Solar eclipse occurs when the moon passes
directly between the Earth and sun, blocking
light from the sun
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Not safe to look at the
sun during a partial
eclipse because an
extremely bright part of
the sun remains visible
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During the full moon when the Earth is
directly between the sun and moon
Moon is in Earth’s shadow
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Earth’s shadow has an umbra and penumbra
When moon is in Earth’s umbra – you see a
total lunar eclipse
Can see total lunar eclipse from anywhere on
Earth
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Most lunar eclipses, Earth, the moon and the
sun are not quite in line = partial lunar eclipse
Brainpop: Eclipses
Youtube: Eclipse
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Rise and fall of ocean water
that occurs every 12.5 hours
Water rises for 6 hours and
then falls for 6 hours
Caused by differences in how
much the moon’s gravity pulls
on different parts of Earth
Bay of Fundy Tides Video
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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
Study Jams video
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Pick up from here after moon phases
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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
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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