Mystery Class Update: March 14, 2003

Today's Report Includes:

• Is Everything Coming Together? Discussion of CQ #2
• Spring Begins Thursday--Happy Vernal Equinox!
• Tips for Success
• The Longitude Problem
• How Time and Longitude are Related
• Why Greenwich Mean Time is Important
• Let's Get Started! Now it's Your Turn
• This Week's Sunrise/Sunset Times
• Clues Calendar--Plan Ahead

Carol Berlin's Grade 3 class from Framingham, MA covered all the bases and predicted that "the lines representing the different mystery classes would be converging at about the 12 hour mark and MC# 7, which has been experiencing 24 hours of sunlight, will begin a rapid decline . . ."

Students from St. John Greek Orthodox Groups 1, 4, 9 and 10 also predicted that lines on the graph will "come together" around 12 hours because March 20 "is the Spring Equinox" when there is "basically the same amount of daylight all around the world."

And third graders Alex, Nicole, and Shoshana from Polly Jones' class in Canton, OH sent in their prediction that "we think most of the graphs will be at 12 hours, but we are not sure about MC# 7."

Nice job to all of you. Keep your eyes on your graphs because the Equinox is coming!

IMPORTANT: Be sure that you read and follow ALL the instructions in this report very carefully. The special Longitude Clues can help you estimate the APPROXIMATE Longitude for 9 of the 10 secret Mystery Classes. But remember, it's only an estimate, and you'll certainly need to use all the clues that you'll receive in the coming weeks too. (Why do the Longitude Clues help with only 9 of the 10 Mystery Classes? Keep reading to find out.)

In today's report, we'll also be giving you the latest sunrise and sunset times.

Everything you need to get started is available below.

• Since this Update is packed with information, we suggest you print this report and work from the printed copy. Then, BE SURE to read through all of the instructions carefully and completely, so your longitude estimates are as accurate as possible.

(PLEASE NOTE: For teachers with younger students (under grade 5), please don't be discouraged by this set of challenging clues--the clues will be easier after this, and we want you to know that at the end of the Mystery Class activity, we will group the answers by grade level, so the participants are grouped with others near their same grade level.)

NOW, let's get to our special Longitude Clues!

Well, get ready for some help, because here come the clues that we promised for the SPRING EQUINOX. These clues will help you estimate the approximate longitude for 9 of the 10 Mystery Classes. (Remember, they're estimates--they may not provide a location's exact longitude.)

Only on the Equinox (spring or fall) do these clues work. As your graph will show, on the Equinox everyone on earth has about the same amount of daylight. At all other times of year, either the Northern Hemisphere or Southern Hemisphere has more daylight. On the Equinox, neither of the poles of the Earth is tilted toward or away from the sun. Because of this fact, you will be able to estimate approximate LONGITUDE by knowing the time of sunrise at the Mystery Class on the Equinox when you are given that sunrise time in Greenwich Mean Time (GMT). Whew, sound confusing? Bear with us, because this is quite amazing!

360 degrees divided by 24 hours = 15 degrees per hour.

Using a division equation again, you can also figure out how many minutes it takes for the earth to spin 1 degree:

60 minutes divided by 15 degrees = 4 minutes per degree.

All Mystery Classes (except one) have revealed what time it will be using Greenwich Mean Time (GMT) when the sun rises at their Mystery site on March 20, 2003 (the Vernal Equinox.) By knowing this GMT sunrise time for a Mystery Class and also knowing the time the sun rises at Greenwich that day, you can figure out how long the earth spins between the time the sun rises at the Mystery Class location and the time it rises at Greenwich. Once you know this, you can estimate the approximate longitude of a Mystery Class location.

Instructions:

1. Print 10 copies of the GMT Worksheet below(one for each secret Mystery site) and follow the step-by-step instructions on the Worksheet to estimate the approximate longitude of each Mystery Class:

• Mystery Class GMT Worksheet

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 (two freebies!). Be sure to review the two examples below:

• GMT Worksheet Example One
• GMT Worksheet Example Two

(Note: Military time is usually expressed without any punctuation. We have used a ":" between the hours and minutes for clarity.)

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