Sextant Readings at the Schooner Cays

Yesterday the Math Department took 24 students out to the Schooner Cays for an afternoon.  Due to the shifting sandbars in the vicinity, it is impossible to take a direct route, meaning the 5 mile trip becomes 8 miles.  You might ask yourself, what does riding in a motorboat out to a distant island have to do with mathematics?  The purpose of our trip was to expose students to the ancient maritime navigational aid of the sextant.  By using a combination of mirrors, angles, and eyepieces, sextant users  are able to take measurements of the sun at 3 very important times during the day; sunrise, noon, and sunset.

With the advent of standardized timing and time zones, plus technology such as GPS, the need to use a sextant has diminished considerably, but it can still be a valuable tool for any ocean-going vessel.  Despite being in the same time zone, Boston and Detroit do not have the same time of sunrise.  Despite having the same time of noon on a watch, the sun is not in the same position in the sky.  To compensate for this discrepancy, there is a term called the Local Apparent Noon.  This is a time of day where the sun is at it's peak in the sky.

The students began taking readings at or around 12:45 PM, after taking into account certain errors.  The dip error (eye height above the horizon) and the index error (when the calibration of the lenses is off) are important pieces of information that will allow you to have more precise readings.  We encouraged the students to take readings every minute.  At 1:04 PM questions came pouring in wondering why the numbers were going down.  Without having a true Celestial Navigation background, the concept of Local Apparent Noon had been glossed over and had to be experienced before it could be understood.

Continuing through the early afternoon, students took readings at intervals of either 30 seconds or a minute.  One group was so adventurous as to take a reading every 10 seconds.  Without every actually paying attention to the movements of the sun, students were amazed at how fast the Earth rotates and the difference each minute resulted in.  This appreciation of the world we live in and having it tangibly connect with mathematics is something that a traditional classroom cannot provide on a regular basis.