Unit 7 : Latitude : Longitude : Directions : Unit Questionnaire

Unit 1: How to Point to a Star
Unit 2: Where on Earth Are You?
Unit 3: Earth's Rotation and the Sun's Apparent Motion
Unit 4: Yearly Changes in the Sky
Unit 5: Seasons and Climate
Unit 6: Sundials
Unit 7: Navigation
Unit 8: Ancient Astronomy
Unit 9: Constellations

End of Unit 7 Assignment

This assignment consists of four parts. The first is a review with a couple of practice questions linked directly to their answers. The second is a short quiz that you take using Blackboard. It will be instantly scored for you by Blackboard; you only get once chance to take it, however, so be sure you are ready! The third part is an essay question. The question appears below; when you are ready to answer it, log on to Blackboard and submit your essay. Finally, for each unit, you should log on to Blackboard and contribute a question, an answer, or a comment to one of the posted topics. If you find the material in this unit challenging, you might want to start with the "discussion" part of the assignment in order to get some help with some of the ideas.

Brief summary of the unit

In this unit, we have related what you have learned about the location and motions of objects in the sky to the problem of navigating to a desired destination. A number of relatively easy methods will reveal your latitude, but longitude poses a harder problem. Historically important ways of determining both position and direction of motion from observations of the sky were discussed in this unit.

Practice Question One

Suppose you are able to observe the sky around local midnight. You observe that a star on Orion's belt is directly overhead, at your zenith. Your star catalog tells you that the declination of this star is about 0. You must be located _________________.

On another occasion, you observe that this same star has an altitude of 20 degrees. What have you packed for this trip: Swimsuit and sunscreen, slacks and a sweater, or layers and layers of woolly clothing? Explain!

Practice Question Two

You have an almanac that tells you that at 1AM UT there will be a conjunction of two moons of Jupiter. (A conjunction means that they will appear very close together in the sky.) You observe this event and according to your local solar time it occurs around 9PM. What is your longitude? Explain!

Practice Question Three

Navigators in the Pacific Ocean sometimes used a "star compass" to decide what direction to steer their boats. How does this work, and where does this work best?

Essay question

A. Describe two different ways to figure out your latitude by observing the sky. Your description needs to include what you would observe and also how that "observable" quantity is related to the latitude.

B. Describe how having an accurate watch should allow you to figure out your longitude with one observation of the sky. Include what you observe and how that is related to the longitude.

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