Models of the Earth

1. Models of the Earth

2. Models in Science • Making models of things in Science can be thought of as the "Art" of constructing models which approximate the Real World.

3. 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 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.

4. Models of Earth • 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?

5. 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?

6. Stories

7. 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 

8. 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.

9. Raised relief globe Flat surface globe Globe Models of Earth When would these models be appropriately used? When would it not be appropriate to use each?

10. Raised Relief Globe • Look close-up photograph of the raised relief globe below.

11. 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!

12. Maps as models • Anything wrong with map models?

13. 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).

14. True Shape of Earth • Oblate Spheroid

15. 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, athenosphere, 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?

16. Modern Layered Model of Earth • Layered Model

17. Layered Model

18. Earth’s Layers • Slide Show

19. Facts about the Layers Fact Chart Densities of Layers

20. M & M Model of Earth • Is an Peanut M & M a good or bad model of the Earth. • Should we observe and M & M and find out? • Activity Link

21. Best Model? • Make chart like the one below and complete it. When you are finished write your response to the question below. Which item do you think makes the best model? Why?

22. Model of Earth Video • Earth as an Apple Video Clip

23. 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. • 1. Errors (1-10) • 2. Range of Application (1-10) • 3. Simplicity (1-10)

24. Clay Earth Model Follow up • What did you learn from making the model that you didn’t expect?

25. Clay Earth Model Follow up • What is the density of each layer? • Crust = • Mantle = • Outer Core = • Inner Core =

26. 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.