Download Careful measurements reveal that the earth has a slight difference in

Careful measurements reveal that
the earth has a slight difference
in its dimensions
EUREKA!!!
EARTH’S SHAPE?
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• The shape of the earth is
technically called an
OBLATE SPHEROID:
•Slightly flattened at the
poles and bulging in the
middle(equator)
EXAGGERATED PICTURE!
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BUT….. IT
LOOKS
PERFECTLY
ROUND TO
US!
OBLATE SPHEROID
check this out!!!
IT’S DRILL
TIME!!!!!
Equatorial
Circumference
Polar
Diameter
Polar
Circumference
Equatorial diameter
Actual Numbers
• Polar diameter
= 12,714km
(7882mi)
• Equatorial
diameter
= 12,757km
(7909mi)
• Polar
Circumference
= 40,006km
(24,804mi)
• Equatorial
Circumference
= 40,076km
(24,847mi)
MODEL
• A MODEL is a
way of
representing the
properties of
some object
– (Drawing,
diagram, graph,
chart, photo,
table)
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Evidence for the
Earth’s Shape:
• 1. Altitude of Polaris
• 2. Gravity Measurements
• 3. “Sinking” ships
• 4. Lunar Eclipses
*
POLARIS= NORTH STAR
NORTH POLE
Geographic Poles
SOUTH POLE
Earth’s AXIS of
Rotation
WHAT ABOUT THE SOUTH
POLE?
• At the present time, Polaris is the pole
star in the northern direction. Sigma
Octantis is the closest star to the south
celestial pole, but it is too faint to serve
as a useful pole star. The Southern
Cross constellation functions as an
approximate southern pole
constellation. Some people travel to the
equator in order to be able to see both
Polaris and the Southern cross.
Pointer Stars!
POLARIS
Polaris is found
in the little
dipper!!
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Detailed Evidence for the
Earth’s Shape
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1.
Altitude of Polaris:
The altitude is the ANGLE above the
horizon
Polaris is directly over the North Pole
(Fixed Star)
 Your LATITUDE (degrees North or
South of equator) equals ALTITUDE of
POLARIS!
90O
30O
0O
Person standing at 30ON
POLARIS
90O
45O
0O
2.
Gravity Measurements
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 Gravity is a force affected by mass
and Distance from center of earth

As the distance from center of earth
increases, your weight decreases
(equator)
WEIGH
MORE
WEIGH
LESS
X
Center of
earth!
3.

Sinking ships:
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As ships sail toward the horizon,
they appear to “sink” over the
horizon Curved Earth
4.
Polaris:
COPY
 As you head NORTH towards the
North Pole, Polaris appears higher
and higher in the sky
That’s
far out!!!
300 light years from Earth, or about 3000 trillion
km = 3,000,000,000,000,000 km = 1860 trillion
miles = 1,860,000,000,000,000 miles
POLARIS---Stays still COPY
Earth's AXIS makes one
complete wobble every
26,000 years!
What star is next?
During the past 5000 years the axis
has pointed at the star Thuban (Alpha
Draconis)
In the year 7500 the North Star will be
Alpha Cephei
In the year 15,000 it will be the star
Vega.
 About 9000 years after that, Polaris
will again become the North Star.
5.
Lunar Eclipse:
COPY

During eclipse, shadow of earth that
is cast on moon is in the shape of arc
MOON
Earth’s
shadow
Blood red total
Eclipse
Lunar Eclipses
THINK GRAVITY!
(Affected by distance!)
WEIGH
SLIGHTLY
MORE!
WEIGH
SLIGHTLY
LESS
CLOSER!
FARTHER!
CENTER OF EARTH!