Earth’s Dimensions

Vocabulary

• ________- a perfectly round circle • ________- a round circle that is not perfectly

round it is flat on top and bulging on the sides • ____________- North star• ____________- refers to an object’s angle in the

sky • ____________- as a sphere is rotated the angle

of a fixed point from the observer is the same is the degrees of the observers position of the point in the sphere.

Earth’s Shape

• The Earth’s shape seems to be a perfect sphere according to the naked eye – Therefore, the BEST

MODEL for the earth is a perfectly round ball.

• HOWEVER, the earth’s shape is actually an OBLATE SPHEROID– That means it is flattened a

little on top and bulging on the sides

The proofs that the Earth is an oblate spheroid.

• There are three proofs that the Earth is an oblate spheroid – Polaris – geometry pf

a sphere – Photography– Law of gravitational

pull.

Polaris tells us the truth

• If you would put a straight pole from the South pole through the center of the Earth and out the north pole you would eventually hit Polaris – Polaris is the North

star and is always over the North pole.

Proof #1 Continued

• Some points of information – When observing an object in space or in the

sky the angle the object is in above the horizon is called the altitude

– When locating a point on the map • ____________ - is the position of a points North

and south of the equator • _____________- is the position of the points West

and east of the North and South pole

Geometry of a Sphere

• This is a rule that states as a sphere is rotating the place where the fixed point hits the sphere will make and angle measurement with the same Exact measurements will be the same as the measurements of the points position

The proof is here……….

• Now that we know the following facts – Polaris is a fixed point – Latitude is the

measurements North and South of the equator

– The Earth revolves

Therefore …………….

• If the Earth is a perfect sphere then the angle that Polaris hits the Earth would be exactly the same measurement as the latitude that it hits

• However, with precise instruments scientists prove that the angle measurements are not exactly the same

Proof #2 –Pictures say a thousand words

• With the technology that we have today and our ability to travel in space we can take incredible picture of earth.

• The pictures show that the earth is slightly flat on top by the poles and fatter by the equator m

Proof #3- Laws of Gravitation

• _______- is the force of attraction between any two objects

• Since the earth has such a great mass smaller objects with less mass gets pulled towards the earth.

Laws of gravitation

• The law of gravitation states that the amount of force is proportioned (equally given to amount of distance there is between the two object – In other words if you have two objects that

have the same mass on opposite sides of the earth they both should weight the same because it has the same gravitational pull.

Here is the Proof • Therefore according to the rule

of gravitation If the earth is a perfect sphere that means that objects on the pole should weight the same as the same objects on the equator.

• However, scientist have crazy precise instruments and they discovered objects on the poles are very slightly heavier than objects on the equator

• Therefore it must be that the poles are slightly closer to the center of the earth than the equator– OBLATE SPHEROID

Earth’s sphere