Careful measurements reveal that the has a slight difference in its dimensions

EUREKA!!! COPY EARTH’S SHAPE? •The shape of the earth is technically called an OBLATE SPHEROID: •Slightly flattened at the poles and bulging in the middle(equator) EXAGGERATED PICTURE! COPY BUT….. IT LOOKS PERFECTLY ROUND TO US! OBLATE SPHEROID check this out!!! IT’S DRILL TIME!!!!! Polar Equatorial Circumference Circumference

Polar Equatorial diameter Diameter Actual Numbers • Polar diameter • Equatorial diameter = 12,714km = 12,757km (7882mi) (7909mi)

• Polar • Equatorial Circumference Circumference = 40,076km = 40,006km (24,847mi) (24,804mi) MODEL COPY

•A MODEL is a way of representing the properties of some object – (Drawing, diagram, graph, chart, photo, table) Evidence for the Earth’s Shape: • 1. Altitude of

• 2. Gravity Measurements

• 3. “Sinking” ships • 4. Lunar Eclipses * POLARIS= NORTH

NORTH POLE Earth’s AXIS of Rotation

Geographic Poles

SOUTH POLE WHAT ABOUT THE SOUTH POLE? • At the present time, Polaris is the in the northern direction. Sigma Octantis is the closest star to the south , but it is too faint to serve as a useful pole star. The Southern Cross 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 !

POLARIS

Polaris is found in the little dipper!!

COPY

COPY Detailed Evidence for the Earth’s Shape COPY 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 COPY

 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: COPY

 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 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 7500 the North Star will be Alpha Cephei In the year 15,000 it will be the star .  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 WEIGH SLIGHTLY SLIGHTLY MORE! LESS CLOSER! FARTHER!

CENTER OF EARTH!