What Causes Seasons?mrlafrancaearthscience.weebly.com/uploads/2/3/1/8/23188960/lesso… · •The...
Transcript of What Causes Seasons?mrlafrancaearthscience.weebly.com/uploads/2/3/1/8/23188960/lesso… · •The...
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Aim: What causes Seasons?
Do Now: What is the difference between
revolution and rotation?
Notepack 28
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Earth’s rotation • The Earth rotates on its axis
(imaginary vertical line around which Earth spins) every 23 hours & 56 minutes. (counter clockwise)
• One day on Earth refers to the length in time that it takes for one rotation of the Earth.
• Daytime on Earth is when one side of the Earth faces the sun.
• Nighttime on Earth is when the side of Earth we are on faces away from the sun.
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A Day on other Planets
• On Jupiter, a day
takes only 9 hours
and 50 minutes.
• On Venus, a day
last 243 Earth
days.
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Earth’s revolution
• It takes the Earth 365
days (or rotations) to
travel or revolve
around the Sun once.
• One complete
revolution is called a
year.
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A Year on other Planets
• On Mercury, one
revolution takes
only 88 days.
• On Neptune a
revolution takes
almost 165 Earth
years.
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Earth’s orbit • The Earth’s orbit around the Sun in not a perfect
circle.
• The Earth’s orbit has an elliptical shape (oval).
• Because the Sun is closer to one side of the ellipse, the Earth’s distant from the Sun changes as it goes around the Sun.
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•Perihelion- When Earth is closest to the sun
•Aphelion – When Earth is furthest from the
sun
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Why do we have seasons?
• Seasons are not caused by how close the Earth is to the sun.
• In fact, the Earth is closest to the sun around January 3 and farthest away from the sun around July 4.
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Why do we have seasons? (cont) • 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, and summer.
• The number of daylight hours is greater for the hemisphere, or half of Earth, that is tilted toward the Sun.
• The more daylight hours , the more time the ground has to be warmed up by the Sun.
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ANGLE OF INSOLATION • The angle at which the sunlight hits the Earth is
called the Angle of insolation.
• The higher the angle the more heat that
location receives.
• The more heat the ground gets, the warmer the
air will be.
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Why do we have Seasons? (cont) • Because the Earth’s tilt always points towards
Polaris and the Earth revolves around the
Sun, The Northern and Southern
Hemispheres receive different amount of light
throughout the year.
• When the North pole points towards the Sun,
it is Summer in the Northern Hemisphere and
Winter in the Southern Hemisphere..
• When the North pole points away from the
Sun, it is Summer in the Southern Hemisphere
and Winter in the Northern Hemisphere.
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N
S
N
S
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Why do we have seasons? (cont)
• Summer is warmer than winter (in each
hemisphere) because the Sun's rays hit the
Earth at a more direct angle during summer than
during winter
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Why do we have seasons? (cont)
• Also the days are much longer than the
nights during the summer.
• During the winter, the Sun's rays hit the
Earth at an extreme angle, and the days are
very short.
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Seasons…in a nut shell
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The Movement of the Sun across the
sky during the change of seasons.
• Because the amount of sunlight areas
receive between Summer and Winter
changes, the Sun appears to travel north
and south throughout the year.
• This is an apparent movement – The Sun
isn’t moving but it is the revolution of the
Earth and its tilt that actually cause this
affect.
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The Movement of the Sun across the
sky during the change of seasons.
• In the Northern Hemisphere, the Sun
travels furthest north during the Summer
months.(June)
• In the Northern Hemisphere, the Sun
travels furthest South during the Winter
months. (December)
• In the Southern Hemisphere it is opposite
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Solstice
• Solstices occur twice a year, when the tilt
of the Earth's axis is oriented either
directly towards or away from the Sun,
causing the Sun to appear to reach its
northernmost and southernmost extremes.
• The days of Solstice has either
– The longest day of the year – about 16 hours
– Or the shortest day of the year – about 8
hours
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Winter Solstice
• Winter solstice is the shortest day of the
year. In the Northern Hemisphere. It
occurs on December 21 and marks the
beginning of winter.
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Winter Solstice • 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. 23 ½ degrees South Latitude.
•
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Summer Solstice
• 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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Summer Solstice • During the summer
solstice, the North Pole has a 24-hour Day and the South Pole has a 24-hour night.
• Sunlight strikes the Earth most directly at the Tropic of Cancer. 23 ½ degrees North Latitude.
•
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Shadows during the Solstice • During the Winter Solstice, shadows are at
their longest.
• During the Summer Solstice, shadows are at
their shortest.
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Equinoxes • An Equinox is when the northern and
southern hemispheres experience 12
hours of day and 12 hours of night.
• Equinox literally means "equal night".
• Sunlight strikes the earth most directly at
the equator.
• This occurs twice a year:
– The vernal (spring) equinox occurs
March 21.
– The autumnal (fall) equinox occurs
September 21.
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http://www.nmm.ac.uk/uploads/gif/seasons-full.gif
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