Please read the following articles, available in Library Reserves. The first one, by William J. Broad, is a science article from the New York Times that discusses some of the recent research into the strength of Earth's magnetic field and also briefly delves into the history of magnetic field measurements. Broad also touches on our Neat-o Interdisciplinary Idea that animals use the magnetic field to navigate. In fact, he references the study done by Kenneth Lohmann and colleagues using sea turtles that you will also read as part of this assignment. The brief article from The Economist is a synopsis of a study done by Sabine Begall and colleagues in which they used Google Earth to try to assess the extent to which cows line themselves up preferentially with magnetic north while they graze. I have also included a recent article regarding measurements of magnetic fields induced by the small tsunami generated by the mag 8.8 earthquake in Chile that happened in April 2010.
- Broad, W. J. (2004, July 13). Will Compasses Point South? New York Times, F.1.
- Lohmann, Kenneth; Cain, S. D.; Dodge, S. A.; & Lohmann, C. M. F. (2001). Regional magnetic fields as navigational markers for sea turtles. Science, 294(5541), pp. 364-366.
- Begall, Sabine (2008). Science and Technology: Animal attraction; Magnetism and behavior. The Economist, 388(8595).
- Manoj, Chandrasekharan and Stefan Maus (2011). Observation of Magnetic Fields Generated by Tsunamis. Eos, 92 pp. 13-14.
As you read, consider these questions
- What are some of the consequences of a deterioration of Earth's magnetic field for human activities?
- How has the path of evolution changed in response to field changes? (This is something I think about when I read about how animals interact with the magnetic field.) For example, turtles have been around since about the Devonian (around 400 million years ago). This is before the Atlantic Ocean even opened up, but since that time, how many times has the field reversed? (You can look this up!) How much do different migratory paths lengthen or shorten each year based on the movement of the plates? What does Lohmann speculate about how much a field reversal would impact his turtles?
- Do you understand how electromagnetic induction works? Does the Manoj and Maus article explain this property of tsunami waves or were they aiming at an audience who knows already? What are some of the practical uses of the kinds of measurements Manoj and Maus discuss?
Submitting your work
Once you have finished the readings, engage in a class discussion that will take place over the entire week devoted to Lesson 3. This discussion will require you to participate multiple times over that period. See the Overview page of this lesson for specific dates.
- Enter the Lesson 3 - Magnetic Field Discussion Forum in Canvas
- You will see postings already there, each containing one of the discussion questions above.
- Post a response to each question. If you feel that your response has already been "said" by another student, then post a response to someone else's remarks that expands on what has already been said, asks for clarification, asks a follow-up question, or furthers the discussion in some other meaningful way. By the end of the activity, I would like you to post at least one original thought/opinion/question and at least one thoughtful response to someone else's post.
- Don't feel like you have to give the most complete entire answer to each question as soon as you land on the discussion board. I want this to be an exchange of ideas, so it will work out better if everybody is able to contribute to the knowledge and ideas we are building as a class. Sometimes the best discussions are ones in which the first person only answers part of the question and thus leaves the door open for everyone else to participate.
You will be graded on the quality of your participation. See the grading rubric for specifics.