# Week 6 (Sep. 30 - Oct 4)

**Read:**

*From Astronomy to Cartography*(Chap. 9) and

*Climates and Continents*(Chap. 10).

**Quiz:**Monday. Covers Bede's

*The reckoning of time.*

**Homework exercises:**Latitudes (Ex. 9.1), Waldseemuller's worldview (Ex. 9.2). Due noon Saturday week 6.

**Laboratory exercises:**

*Latitude and longitude observations*(Ex. 9.3). For the

*latitude*exercise, you should find and measure the altitude of Polaris using your cross staff during any evening this week. Don't look up your latitude before going out to observe! After your observation, check your latitude. How far off is your measurement? If you were a sailor, how many (nautical) miles off would you be?

For the

*longitude*exercise, you should go out on a sunny day around noon, set up a small vertical stick (gnomon), and use a sheet of paper to measure the length of the shadow every five minutes between 12:15 and 1:15 pm. Draw a line from your gnomon to the end of the shadow for each measurement. Be sure to collect enough data both before -and- after local noon so that you can clearly identify the time of the shortest shadow. Make a data table that lists the time on your clock and the length of the shadow at that time. Then, for analysis, make a clearly labelled plot (using a graphing program such as Logger Pro) that shows your shadow length (vertical axis) versus the time of day (horizontal axis). Use a fitting function to pick out the time at which the shadow is shortest. At what (clock) time is local solar noon? Put all of this data and analysis in your lab notebook.

How, then, can you determine your

*longitude*based on your measurements of the time of local noon? To aid your thinking, you might consider that if the sun passes the prime meridian at noon in Greenwich, England, then a quarter of the way around the globe toward the Americas (90 degrees west in Longitude), the sun will pass the local meridian 6 hours later than it crossed the local meridian. If, then, one has (correctly) calibrated his watch to Greenwich time, then he can determine his longitude by measuring the time of local noon at his location on the earth.

Be sure to make a scan of your lab book that includes your data, sketches, and calculations of latitude and longitude. This is

**due noon Monday week 7.**

**From astronomy to cosmography (3 videos):**

**Climates and continents (no videos yet…):**