Earth’s Shape and Size Unit 1. The Earth’s Shape Earth’s shape is nearly spherical (Oblate Spheroid) It is flattened at the poles and bulging at the equator.

Earth’s Shape and Size

Unit 1

The Earth’s Shape• Earth’s shape is nearly spherical (Oblate Spheroid)

• It is flattened at the poles and bulging at the equator

• This makes a person weigh slightly more at the poles than at the equator

• Earth’s surface is very smooth

• The height of Mt. Everest is only 7/10,000 of Earth’s diameter

Ancient Observations of Earth

• Shadow of Earth during an eclipse• Position of the stars as travelers

moved north or south• A ship’s mast disappeared last as it

sailed towards the horizon

• Aristotle, as early as the 3rd century BC concluded that the earth was a sphere.

Using the North Star

• The North Star (Polaris) appears to increase in altitude as you travel north

• It is always visible due north to an observer north of the equator– 900 for someone at the North Pole– 00 for someone at the Equator

• If the earth were flat, Polaris would appear the same to everyone.

Today….

• Photographs from space are the best way to see the shape of the earth

Other proof that the earth is round/spherical

Pre Lab Info

• Roundness Ratio– Tells us how close something is to a

perfect circle– A perfect circle would have a roundness

ration of 1 because the diameter would be the same in all directions

Pre Lab Info

• Scale Models are concrete representations of an object that is made in proportion to the object– They may be larger (ex. Model of an

atom)– They may be smaller (ex. Globe)

Finding the Proportions

• Think ratio: Part to whole = Part to whole

• Matchbox cars are made on a ratio of 1:59

• This means that the Matchbox car is 59 times smaller than the real car.

• Using the Matchbox car, figure out how big the real car is.

• 1/59 = 7.1/X

• X = 418.9 cm • How many meters

is this?• 4.189 m

7.1 cm