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Models of the Earth
Models in Science
 Making models of things in Science can be
thought of as the "Art" of constructing models
which approximate the Real World.
Models in Science
 Models in Science are typically not equal to, identical with, or a one-
to-one match with the aspects of the thing they describe.
 Models of Science usually have some limited range over which a
model is a useful predictor of the real thing.
 Models of Science are not unique. There may be two or more models
which describe the same thing equally well.

Models are judged by:
a. Size of the error. The smaller the size of the error between actual
measurements and predictions, the more accurate the model.
b. Range of Application. The larger the range over which a model
faithfully reflects the real thing, the more universal the model.
c. Simplicity. How simple the model is to use and understand
determines how it will be used.
Proposed Models of Earth
 In 1692, Edmund Halley proposed that the Earth was hollow and within
it was a second sphere. To account for all the variations in the
magnetic field, Halley finally proposed that the Earth was composed of
some four spheres, each nestled inside another. Halley also suggested
that the interior of the Earth was populated with life and lit by a
luminous atmosphere. He thought the aurora borealis, or northern
lights, was caused by the escape of this gas through a thin crust at the
poles.
 1. What evidence is there that this is a good model?
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Halley was fascinated by the earth's magnetic field.
The Earth’s magnetic field varied some so there must be several spheres
with several magnetic fields.
 2. What evidence is there that this is NOT a good
model?
Edmund Halley
 Edmond Halley, Edmond also
spelled Edmund (born Nov. 8,
1656, Haggerston, Shoreditch, near
London—died Jan. 14, 1742, Greenwich,
near London), English astronomer and
mathematician who was the first to calculate
the orbit of a comet later named after him
(Halley’s Comet). He is also noted for his role
in the publication of Isaac
Newton’s Philosophiae Naturalis Principia
Mathematica
Model of Earth – Single Sun Inside
 In 1846 the discovery of an extinct wooly mammoth frozen in ice in
Siberia was used as evidence of a hollow earth and single-suninside-the-earth theory. It suggested that the mammoth was so wellpreserved because it had died recently. Supporters thought that
mammoths and other extinct creatures wandered freely in the interior of
the earth. This one had wandered outside by using the hole at the
North Pole, then was frozen and carried to Siberia on an ice flow. Some
supporters include Leonhard Euler, a Swiss mathematician, cottish
mathematician Sir John Leslie and American ex-Army officer John
Symmes.
 What evidence is there that this
is a good model?
It can’t be argued that the Earth is indeed very Hot inside.
 What evidence is there that this is
NOT a good
model?
- United States Navy Admiral Richard Byrd flew across the North Pole in 1926 and the South Pole in 1929
without seeing any holes leading to inner-earth.
Hollow Earth with Life Inside
 That same decade (1840’s) a new theory about the hollow-earth
appeared. It was the brainchild of Cyrus Read Teed. Teed proposed
that the Earth was a hollow sphere and that people lived on the inside
of it. In the center of the sphere was the sun, which was half dark and
half light. As the sun turned it gave the appearance of a sunset and
sunrise. Teed changed his name to Koresh and founded what might
today be called a cult. After buying a 300 acre tract in Florida, Koresh
declared himself the messiah of a new religion. He died in 1908 without
proving his ideas.
Model of Earth – Current Model
 What evidence is there that this is a good model?
 See http://www.mnh.si.edu/earth/text/index.html
 What evidence is there that this is NOT a good model
Flat Earth - Round Earth
 A carpenter building a house uses the model that
the Earth is flat except for local irregularities, which
are usually flattened out before building. A carpenter
makes no practical errors in the accuracy of his
measurements in assuming that the Earth is flat.
 An airline pilot, uses a model that the Earth is
perfectly spherical, like a ball, this is useful for
navigating over long distances. The path that uses
the least fuel, the shortest path, is the arc of a great
circle on a sphere, and not a straight line on a map.
 Which model you use depends upon the amount of
accuracy needed in your measurement.
Globe Models of Earth
Raised relief globe
Flat surface globe
When would these models be appropriately used? When would it not be
appropriate to use each?
Raised Relief Globe
 Look close-up photograph of the raised relief
globe below.
Raised Relief Globe Problems

Possible model problems: When you look closely at the raised relief globe,
you see an attempt to demonstrate differences in elevation. Mountains are
shown as being raised well above the Earth's surface. While it is true that
mountains are higher than the average surface of the Earth, the scale does
not match the globe. At the scale of a globe, the entire surface would
appear flat. At this scale, when compared with the enormous size of the entire
earth, even Mt. Everest would appear flat!
Maps as models
 Anything wrong with map models?
Map Problems
 The main problem with maps is that they
distort things.
 Remember, the Earth is sort of round. When
you flatten the Earth out on a map it distorts
things making them distorted (especially at
the poles).
True Shape of Earth
 Oblate Spheroid
Inside Model of the Earth
 The study of Earthquake or Seismic (shock)
waves has led scientist’s to believe that the
Earth is made of four main layers; the inner
core, outer core, mantle and crust.
 Other less significant layers may include; the
lithosphere, asthenosphere, rocks, water, and
dirt, and atmosphere.
 The MOHO is not really a layer but is a
boundary between the crust and mantle.
 Where is the most dense layer? Where is the
least dense a layer?
Modern Layered Model of Earth
 Layered Model
Layered Model
Earth’s Layers
 Slide Show
Facts about the Layers
Fact Chart
Densities of Layers
Best Model?
 Make chart like the one below and complete it. When you are finished
write your response to the question below.
Item:
Apple
Egg
Peach
M&M
Orange
Picture:
Good
Model?
Bad
Model?
Which item do you think makes the best model? Why?
 Model of Earth Video
Clay Earth Model Follow up
 Judge your model by giving your self a 1-10
score for each of the following original model
judgment criteria. 1 is the lowest. 10 is the
highest.
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1. Errors (1-10)
2. Range of Application (1-10)
3. Simplicity (1-10)
Clay Earth Model Follow up
 What did you learn from making the model
that you didn’t expect?
Clay Earth Model Follow up
 What is the density of each layer?
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Crust =
Mantle =
Outer Core =
Inner Core =
What did you learn from making
the model that you didn’t expect?
 How can the inner core be the most dense
(13.0 g cm3) and have the smallest volume?
Explain.