Earth

1
Earths Shape and Size

• Unit 1

2
The Earths Shape

• Earths 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

3

• Earths surface is very smooth
• The height of Mt. Everest is only 7/10,000 of
  Earths diameter

4
Ancient Observations of Earth

• Shadow of Earth during an eclipse
• Position of the stars as travelers moved north or
  south
• A ships mast disappeared last as it sailed
  towards the horizon
• Aristotle, as early as the 3rd century BC
  concluded that the earth was a sphere.

5
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.

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7
Today.

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

8
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

9
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)

10
Finding the Proportions

• Think ratio Part to whole Part to whole
• Matchbox cars are made on a ratio of 159
• 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.

11

• 1/59 7.1/X
• X 418.9 cm
• How many meters is this?
• 4.189 m

7.1 cm