Unit 6 : Equatorial Sundials : Variations : Horizontal and Vertical Sundials : Tech Notes : Unit Questionniare

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 6 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 would like to introduce a new topic instead of contributing to an existing thread, please send your topic idea to your instructor. 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, you learned about different kinds of sundials, and you were encouraged to relate this to the apparent daily and annual motions of the Sun. Some sundials are constructed so that they are aligned with Earth's axis in some way; this usually makes the computation of where to put the hour lines simple. Others are constructed to be conveniently part of a wall, vertical, or a table, horizontal. For these, somewhat more complicated calculations or constructions are needeed.

Practice Question One

1. An equatorial sundial (like this one) has its axis parallel to the Earth's axis, and its dial face or ring parallel to the Earth's equator. On such a dial, the hour lines are how far apart?

If this equatorial dial has small holes at each hour marker right along the equatorial line, on what date will the sunlight pass through those holes and reach the axis right at the center?

Practice Question Two

2. A horizontal dial located at __________________ will have hour lines exactly 15 degrees apart; a vertical dial located at __________________ will have hour lines exactly 15 degrees apart. A horizontal dial won't work at all at _________________ and a vertical dial won't work at all at ________________.

Essay question

Explain to someone who doesn't know any astronomy:

(a) Why does a horizontal sundial that is built to work in Los Angeles generally not work in Minneapolis, and vice versa?

(b) What kind of dial can easily be made adjustable to work at any latitude, and what adjustment does it need?

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