Earth

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Earth
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Physical Characteristics of Earth

• Spherical shape
• -satellite photos
• -curved shadow on moon during a lunar eclipse.
• -approaching ships rise over the horizon

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Physical Characteristics of Earth

• 2. Rotation
• -Earth spins on its axis (an imaginary vertical
  line) causing night and day.
• -24 hours to rotate once on its axis
• -rotates 365 times in a year

Foucaults Pendulum shows the Earths rotation as
it swings
https//www.youtube.com/watch?vR3jr0DaV8N8
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Physical Characteristics of Earth

• 3. Magnetic Field
• -Movement of liquid iron inside Earth and its
  rotation create a magnetic field.
• -Helps protect Earth from harmful CMEs from the
  sun.

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Physical Characteristics of Earth

• 4. Revolution
• -Earths yearly orbit around the sun. (365 ¼
  days)
• -Path is elliptical in shape.

Farthest away from sun in July
Closest to sun in January
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What causes the seasons?

• ?

?
?
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What do you know about the Seasons?

• Summer
• NJ-warm, longer days, June-August
• Hawaii-80s, 12 hours of light
• Alaska- up to 24 hours of light
• Australia-Dec-Feb

• Winter
• NJ-cold, longer nights, Dec-Feb
• Hawaii- 70s, 12 hrs of light
• Alaska-up to 24 hours of darkness
• Australia-June-Sept.

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Distance from the sun does NOT cause our seasons.

• If it did, we would all feel winter in July and
  summer in January. Even Hawaii would have a cold
  winter!

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Physical Characteristics of Earth

• 5. A Tilted Axis
• 23.5 tilt
• -The Earth is always tilted the same direction
  during its yearly revolution around the sun.

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• Sunlight strikes the hemisphere tilted towards
  the sun more directly than the hemisphere tilted
  away.
• Summer occurs in the hemisphere tilted towards
  the sun. (direct light)

Sun
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Direct Light

• Areas receiving direct light from the Sun have a
  greater amount of sunlight, therefore higher
  temperatures.

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What season is it?
Northern Hemisphere-Winter Southern
Hemisphere-Summer
Sun
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So what causes the seasons?

• The Earths tilt causes the seasons!

http//lhsgems.org/Presentations/SSS203-820NSTA
20200920final.ppt362,35,Another Model for
Distance
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Solstice

• The day when the sun reaches its greatest
  distance north or south of the equator.
• Northern Hemisphere- (opposite of S. Hemi)
• Summer solstice June 21 or 22 (longest period of
  daylight of the year)
• Winter solstice December 21 or 22 (shortest
  period of daylight of the year)

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The suns path across the sky is higher in the
summer and lower in the winter
http//www.newscientist.com/blogs/shortsharpscienc
e/2011/10/about-time-beer-can-freezes-ti-1.html
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Equinox

• When the sun is directly above the Earths
  equator. Daylight hours are nearly equal all
  over Earth.
• Neither the N. or S. Hemisphere is tilted towards
  the sun.
• Spring equinox-March 20 or 21
• Fall equinox-September 22 or 23

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Seasons demos

• https//www.youtube.com/watch?vDD_8Jm5pTLk
• http//esminfo.prenhall.com/science/geoanimations/
  animations/01_EarthSun_E2.html

http//spiff.rit.edu/classes/phys301/lectures/gas_
planets/Seasons_Nav.swf
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Northern Hemisphere Solstice and Equinox positions
Seasons are opposite for the Southern Hemisphere
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Review Quiz
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Which diagram correctly shows Earths orbit
around the sun?
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• Identify for the N. Hemisphere
• Summer solstice
• Winter solstice
• Fall equinox
• Spring equinox

D
Spring
C
A
Winter
Summer
B
Fall
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How do we know the Earth is a sphere?

• -satellite photos
• -curved shadow on moon during a lunar eclipse.
• -approaching ships rise over the horizon

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What is an axis?

• The imaginary vertical line around which the
  Earth spins.

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What does A represent? What does B represent?

• A-Revolution B-Rotation

B
A
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How long does one complete rotation take on Earth?

• 24 hours

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How long does one complete revolution of Earth
take?

• 365 days (1 year)

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Why is a magnetic field important?

• It protects Earth from CMEs from the Sun

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How do we have a magnetic field?

• The motion of the liquid metal inside Earth and
  our daily rotation cause it.

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What causes the seasons?

• TILT! TILT! TILT!

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What season is it in the Southern Hemisphere?

• Summer-southern hemisphere is tilted towards the
  sun direct light summer!

Sun
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What type of light makes hotter temperatures?

• Direct!

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Where is the sun during the equinox?

• Directly over the equator.

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Whats the difference between northern and
southern hemispheres seasons?

• They are opposite!

Easter is celebrated in the fall (March or April)
Christmas (December) in Australia is warm!
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• http//www.teach-nology.com/worksheets/science/ear
  th/4/