Scholars Online Astronomy - Chapter 9: The Earth as a Planet
Reading: Astronomy, Chapter 9: The Living Earth
Study Notes: notes on your assigned reading from the text
- 9.1 Energy from the sun drives thermal currents in the atmosphere and oceans; pressure from tidal warping due to the moon's gravitational pull, and pressure on the Earth's core, drive thermal currents in the magma and core of the Earth's interior. The composition of the atmosphere determines how the planet receives and retains energy radiated from the sun.
- 9.2 Earthquakes generate S waves and P waves, which together give us clues to the earth's internal structure. The theory of plate tectonics can be used to account for the formation of multiple and dissimilar characteristics. Note the struggle the theory went through for acceptance: without direct evidence, it was very difficult for its proponents to convince their colleagues that it was a viable theory. Ultimately, satellite measurements provided data supporting the movement of the plates. Note how the no-oceans view of the earth's surface compares to Venus and Mars!
- 9.3 Plate movmements and pressure at plate edges generate earthquakes and volcanic activity.
- 9.4 In addition to its other physical characteristics, the earth has a very strong magnetic field which interacts with the "solar wind", the flow of materials from the sun (gas, ionized particles), effectively protecting life on earth from dangerous particles. Fluctuations in the solar wind can change the shape of the magnetic field.
- 9.5-6 Both the atmosphere and the oceans undergo circulation, so their study is more complicated by their rapid rate of change.
- 9.7 Human populations use resources and produce wastes in sufficient quantities to affect the natural balances in the atmosphere, oceans, and land surfaces.
Also note life forms create changes in the earth's surface (and not just human life: consider the erosion capabilities of plants and the ability of beavers to completely change their environments in very short time periods!)
Key Formulae to Know
Read the following weblecture before chat: The Earth
- Planetarium Program:
If you can, use your planetarium to view Earth from Space. In Sky Safari, chose on of the planets and then the "orbit" option, then maneuvre to see Earth, select it and fly to it with "Orbit". In Starry Night, use the Explorations option to choose Earth.
Once you have located Earth in your screen, use the planetarium conrols to explore the surface, and note how sunlight affects the poles at this time of year. (If you are doing this exercise around Thanksgiving, the northern hemisphere is approaching midwinter, so the north pole will be in darkness, and the south pole -- Antarctica -- will be in sunlight, regardless of the time of day.)
- Optional Website Viewing the earth as one of several planets with similar characteristics offers us a new perspective. The Univeristy of Washington's astronomy department offers courses on planetary atmospheres, planetary surfaces, and the origin of the solar system. Take a look at the topics discussed for these courses.
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Go over the list of Key Words and Key Ideas at the end of the chapter. If you don't remember the definition of the key word, review its use (the page number on which it is explained is given).
- Read through the Review Questions and be prepared to discuss them in class. If any of them confuses you, ask about it!
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- Required: Complete the Mastery exercise with a passing score of 85% or better.
- Go to the Moodle and take the quiz for this chat session to see how much you already know about astronomy!
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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