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 LayersLayer 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