Notes Shape of Earth.notebook
November 05, 2015
Causes of the Earth’s Shape
inward
• Gravity: Pushing _____________ equally in all directions
Oct 29­1:41 PM
Causes of the Earth’s Shape
Oct 29­1:41 PM
Causes of the Earth’s Shape
Outward
• Centrifugal Force: ________________ acting force caused
expand
• Actually causes Earth to ___________________
spinning
by the __________________ of Earth on its axis.
• The ________________ the speed, the
greater
expanding
greater
________________ the _________________ force
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Oct 29­1:41 PM
Causes of the Earth’s Shape
Causes of the Earth’s Shape
Does the Earth rotate at the same rate of speed at every location ?
greater
• Therefore, the __________________ expanding force
equator
is at the __________________
flatten
• This causes the Earth to ______________ slightly at
poles
bulge
the __________________ and _________________
equator
at the ___________________
Oct 29­1:41 PM
Oct 29­1:41 PM
1
Notes Shape of Earth.notebook
November 05, 2015
Causes of the Earth’s Shape
• Because of this, the shape of the Earth is called an
OBLATE SPHEROID
____________________________________________
( a flattened sphere)
Your drawing here:
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Oct 29­2:19 PM
Observable Evidence of Earth’s Curved Surface
Lunar
1. _______________ Eclipse
curved
moon
• Shows a ________________ shadow on the _________
as it enters and exits Earth’s shadow
Please add to
your notes:
http://www.youtube.com/watch?v=L1qCcgp8Sg4&feature=related
Equatorial Diameter > Polar Diameter
(about 40 km greater)
http://www.youtube.com/watch?v=2dSdRJ7dXjo&feature=related
http://www.mathsisfun.com/equal­less­greater.html
Oct 29­2:23 PM
Observable Evidence of Earth’s Curved Surface
disappear
horizon
2. Ships ___________________ over the __________________
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Observable Evidence of Earth’s Curved Surface
Pictures
3. ______________________ from space
in __________ directions
all
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Oct 29­1:41 PM
2
Notes Shape of Earth.notebook
November 05, 2015
Determining Earth’s Circumference
Okay … it‛s round, but how round (how big)?
• Eratosthenes’ Method
• Ancient Greek mathematician (~200 BC) http://www.wimp.com/greekscientist/
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Determining Earth’s Circumference
• Eratosthenes’ Method
no
• Well at Syene had _____ shadow at noon on a given day of the year.
• A stick in the ground at Alexandria cast a shadow with
Oct 29­1:41 PM
In order for Eratosthenes to do his math, he needed
know:
1. The date and time the sun would be
directly above one of the two locations.
2. The distance between the two locations.
3. The angle formed between the two
locations from the center of the Earth.
7.2
an angle of _____ degrees at that ________ same time.
exact
distance
• Knew the ___________ between both locations.
Add these notes on a separate
piece of paper and keep them
with this note-taking guide.
Oct 29­1:41 PM
Oct 29­1:41 PM
In order for Eratosthenes to due his math, he
needed know:
In order for Eratosthenes to due his math, he
needed know:
1. The date and time the sun would be
directly above one of the two locations.
2. The distance between the two locations.
Summer Solstice (longest day of
the year) on June 21st....sun
directly above Syene (@ 23.50
North Latitude)
Don't mark your
drawing until later.....
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Camel caravans travelled
100 stadia per day
and it took 50 days
to make the journey.
5000 stadia
(500 miles)
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3
Notes Shape of Earth.notebook
November 05, 2015
In order for Eratosthenes to due his math, he
needed know:
In order for Eratosthenes to due his math, he
needed know:
3. The angle formed between the two
locations from the center of the Earth.
3. The angle formed between the two
locations from the center of the Earth.
7.20
This could be observed
(and measured) at noon
on June 21st.
7.20
According to
the rule of alternate
interior angles
Oct 29­1:41 PM
Place this information on the
diagram in your notetaking guide:
500 miles
7.20
7.20
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Determining Earth’s Circumference
• Eratosthenes’ Method
• Used rule of alternate interior angles along with
Part/Whole proportion to make his calculation
7.20
Oct 29­1:41 PM
Oct 29­1:41 PM
Determining Earth’s Circumference
Determining Earth’s Circumference
• Eratosthenes’ Method
• Eratosthenes’ Method
• Used rule of alternate interior angles along with
Part/Whole proportion to make his calculation
• Used rule of alternate interior angles along with
Part/Whole proportion to make his calculation
cross multiply
Part
Whole
=
7.2 0 = 500 miles
3600
C
Oct 29­1:41 PM
7.2 0 = 500 miles
3600
C
7.20 (C) = 3600 (500 miles)
Oct 29­1:41 PM
4
Notes Shape of Earth.notebook
Determining Earth’s Circumference
November 05, 2015
Determining Earth’s Circumference
• Eratosthenes’ Method
• Eratosthenes’ Method
• Used rule of alternate interior angles along with
Part/Whole proportion to make his calculation
• Used rule of alternate interior angles along with
Part/Whole proportion to make his calculation
7.20 (C) = 3600 (500 miles)
7.20
0
7.2
Oct 29­1:41 PM
Determining Earth’s Circumference
7.20 (C) = 3600 (500 miles)
7.20
7.20
C = 360 (500 miles) = 180,000 miles
7.2
7.2
Oct 29­1:41 PM
Determining Earth’s Circumference
• Eratosthenes’ Method
• Eratosthenes’ Method
• Used rule of alternate interior angles along with
Part/Whole proportion to make his calculation
• Used rule of alternate interior angles along with
Part/Whole proportion to make his calculation
C = 360 (500 miles) = 180,000 miles
7.2
7.2
C = 25,000 miles
Oct 29­1:41 PM
C = 360 (500 miles) = 180,000 miles
7.2
7.2
C = 25,000 miles
Actual circumference = ~24,900 miles !
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