Name Period Partners The Earth s Shape Lab # Introduction: Pictures of the earth taken from space show that the earth appears to be perfectly round and smooth. However, to us, the earth appears to have a highly irregular surface. In addition, accurate measurements of the earth s shape show that the equatorial diameter is slightly different than the polar diameter. Objective: To understand the true roundness and smoothness of the earth Vocabulary: Relief Model Oblate spheroid Sphere Procedures: A. Roundness The ratio of the polar diameter to the equatorial diameter of a sphere is a measure of its roundness. We call this a roundness ratio. 1. Use the values given for the equatorial and polar diameters of the earth in the data chart on the report sheet to calculate the roundness-ratio of the earth. Record this value on the chart provided. 2. Measure the equatorial and polar diameters of the diagram in your lab. Record these measurements on the chart provided. 3. Calculate the roundness-ratio for the diagram using the data from Procedure 2. Record this value on the chart provided.
A. Roundness Report Sheet POLAR DIAMETER EQUATORIAL DIAMETER ROUNDNESS RATIO Earth 12,714 km 12,756 km Globe cm cm Diagram B. Smoothness A relief globe shows the relative height of its surface features such as mountains. It is a scale model of the earth. The following procedures will show you if these features are constructed to scale on the enclosed diagram. To do this you must use the following proportion: Actual height of the surface feature (in km) = To Scale Height of Everest (cm) (Solve for this)_ Earth diameter (in km) Relief globe diameter (in cm) When you substitute values into the equation, you will have one unknown. The To Scale Height of Everest. Use the actual height of Mt. Everest divided by the diameter of the earth which is given. Measure the diameter of the globe using your cm ruler. Note: The following chart information is to be recorded on the data chart under smoothness on your report sheet. 1. Measure the diameter of the Earth in cm using the diagram of the earth. 2. The actual height of Mt. Everest, the highest point in the world, is 8.8 km. 3. The average diameter of the earth is the average of the polar diameter (12,714) and the equatorial diameter (12,756 km). This value is 12735 km 4. Measure the equatorial diameter of the diagram globe in cm to the tenths place. 5. Using the values obtained in procedures 2 through 4 and the above equation, solve for the relief globe height of the surface feature (Mt. Everest) to correct scale for the globe. 6. Determine the percentage error between the height of Mt. Everest on the diagram and the height it should have been if drawn to the correct scale.
a. Smoothness Height of Mt. Everest on the diagram (measure) cm Actual height of Mr. Everest Average diameter of the earth Average diameter of diagram (measure) 8.8 km 12,734 km cm Correct scale height of Mt. Everest on globe diagram cm Percent Error (comparing the correct scale height to measured height of Mt. Everest) % Show all work for the calculations above. Actual height of the surface feature (in km) = To Scale Height of Everest (cm) (Solve for this)_ Earth diameter (in km) Relief globe diameter (in cm) 8.8 km = To Scale Height of Everest (cm) (Solve for this)_ 12,734 km Relief globe diameter (in cm) (8.8 x Diagram globe diameter (cm) = To Scale Height of Everest (cm) 12,734
The diagram below represents an average classroom globe. Mount Everest
Discussion questions: (ANSWER IN COMPLETE SENTENCES!!!!) 1. Using the roundness ratio you calculated, which is a more perfect sphere? The globe diagram or the earth? 2. How does the earth s polar diameter compare with its equatorial diameter? 3. Is the earth a perfect sphere? How does your data confirm your answer? 4. CHALLENGE: A 0.1cm deep scratch was made in the surface of a globe with a diameter of 40 cm. Calculate the actual depth of the surface feature (represented by the scratch) on the real earth. Use the information you gained from the previous calculations. (SHOW ALL WORK!!!) 5. In terms of roundness and smoothness, name an object which would be a good model of the earth. Explain your choice. Conclusion question : Describe how this lab helped you to understand that the earth is both round and smooth. Include specific information. Answer in complete sentences.