Mystery Class GMT Worksheet Estimating Approximate Longitude using GMT Sunrise Times on the Spring Equinox Instructions: 1. Print 10 copies of this GMT Worksheet (one for each secret Mystery site) and use the step-by-step instructions to estimate the approximate longitude of each Mystery Class. 2. In order to use the GMT Worksheet, you will also need to print out the: Equinox Sunrise Table 3. To help get you started, we've already calculated the approximate longitude for two of this year's Mystery Class sites, using the GMT Worksheet. Be sure to review the two examples below: GMT Worksheet Example One GMT Worksheet Example Two Worksheet Step # 1 Fill in the GMT sunrise time and date for the Mystery Class. This is the time it is in Greenwich, England when the sun rises at the Mystery Location. Put in Box A. BOX A Step # 2 Fill in the time that the sun rises in Greenwich, England on March 20, the spring Equinox. This year that sunrise time is 06:03 A.M. Put in Box B. BOX B 06:03 A.M. (3/20) Step # 3 Figure out how many hours and minutes there are between the time in Box A and the time in Box B. Put answer in Box C. This is the difference in time between sunrise at Greenwich and sunrise at the Mystery Location. (CAUTION!!! This may not be a simple subtraction or addition equation. Remember that hours and minutes are not in decimal form. Be sure to think about your answer!) Put in Box C. BOX C _______hours______minutes Step # 4 For the next step you'll need to convert hours to minutes. Multiply each hour in Box C by 60, add the remaining minutes from Box C. Put the answer in Box D. BOX D ________minutes Step # 5 Almost done! You now know how many minutes the earth spins between the time the sun rises at the Mystery Class location and the time it rises at Greenwich. Since the earth spins 1 degree longitude every 4 minutes, you must next divide by 4 to get the number of approximate longitude degrees away from Greenwich. Divide the number of minutes given in Box D by 4. Put the answer in Box E. BOX E ________degrees Step # 6 Eastern or Western Hemisphere? To determine the site's longitude you need to know if it is in the Eastern or Western Hemisphere (i.e East or West of Greenwich, which is 0 degrees). If the sunrise in Box A is later than the sunrise in Box B, the Mystery Class is west of Greenwich (Western Hemisphere). If the sunrise in Box A is earlier than the sunrise in Box B, the Mystery Class is east of Greenwich (Eastern Hemisphere). BOX F East or West? Back to Today's Report Copyright 2001 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form