Transcript Models of the Earth

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. Model
makers in Science do not unearth some
Absolute Truth about Nature, but rather build
mathematical structures which reflects a
close example of Nature. This example is like
a geological map of some territory. A map
has a lot of useful information about the
territory, but the map is not the territory.
Models in Science
 Models in Science are not equal to, identical with, or a one-to-one
match with the aspects of the thing they describe.
 There is always 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.

Preference between competing models is 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.
Models of Earth
 Read the information below about the Hollow Model of Earth that has
been proposed in the past and write down evidence that may show that
it was a correct model and evidence that the model may be wrong.
Then in small groups talk about your answers and combine your
answers to make a really good answer.
 In 1692, 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.
 1. What evidence is there that this is a good model?
 2. What evidence is there that this is NOT a good
model?
Model of Earth – Single Sun Inside
 In 1846 the discovery of an extinct wooly mammoth frozen in ice in
Siberia was used by Marshall Gardner as evidence of a hollow earth.
Gardner subscribed to the single-sun-inside-the-earth theory and
suggested that the mammoth was so well-preserved because it had
died recently. Gardner 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.
 What evidence is there that this is a good
model?
 What evidence is there that this is NOT a good
model?
Model of Earth – Current Model
 What evidence is there that this is a good model?
 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 really 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
upper and lower mantle, moho, rocks, water,
and dirt, and atmosphere.
 Where is the densest layer? Where is the
least dense a layer?
Modern Layered Model of Earth
 Layered Model
Layered Model
Facts about the Layers
Layer
State of Matter
Composition
Density
Atmosphere
Gas
Gases
.0013 g/cm3
Crust
Solid
Rocks
3 g/cm3
Mantle
Solid with some
molten liquid
Rocks
4.5 g/cm3
Outer Core
Liquid
Metals (Iron &
Nickel)
10 g/cm3
Inner Core
Solid
Metals (Iron &
Nickel)
13 g/cm3
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
Good
Model?
Bad
Model?
Which item do you think makes the best model? Why?
 Earth as an Apple Video Clip