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Mystery Class Update: March 16, 2001

Today's Report Includes:

Spring Begins Tuesday--Happy Vernal Equinox!
In celebration of next Tuesday's Vernal Equinox, we have gathered a special set of longitude clues from the 10 secret Mystery Sites, which are given below!

IMPORTANT: Be sure that you read and follow the instructions in this report very carefully. The special longitude clues can help you estimate the approximate longitude of each 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. Good luck!

In today's report, we'll also be giving you the latest sunrise and sunset times, a new Teacher Tip, and some of your responses to last week's challenge question too.

Clues Calendar
We'll be sending new clues every week for the next five weeks, to help you try to determine each secret Mystery Class location by the April 27 deadline. Here are some important Mystery Class dates for the coming weeks:
  • March 16: Longitude Clues given

  • March 23, 30, April 6, 13 & 20: New clues from the Mystery Sites given each week

  • April 27: Deadline for Answers

  • May 4: Mystery Sites Revealed!

  • May 11: Meet the Mystery Sites

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

  • Printing Tip: The information below will print properly if you set the font of your e-mail software to a "fixed width" font (such as Courier, New Courier, Monaco, or any other fixed width font).

(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 contest, 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!

The Longitude Problem

The changing photoperiods that you've tracked have provided some clues about the LATITUDE of the Mystery Classes. But that photoperiod information doesn't help you much when you try to determine the LONGITUDE of the Mystery Classes.

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 of the Mystery Classes. (Remember, they're estimates--they may not provide a location's exact longitude.)

Only on the Equinox (spring or fall) does this clue work. As your graph shows, 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 time in Greenwich Mean Time (GMT). Whew, sound confusing? Bear with us, because this is quite amazing!

How Time and Longitude are Related
In order to use the GMT clues to help you ESTIMATE the approximate longitude of a Mystery Class, you must first understand a little background about the relationship between time and longitude. Think about this: In order for sunrise to occur everyplace on earth each day, the earth must spin 360 degrees every 24 hours. If you hold your globe with the North Pole on top, you can see that the vertical longitude lines (called "meridians") add up to 360 degrees. Using the following equation, you can figure out how many degrees the earth turns in each hour:

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.

Why Greenwich Mean Time is Important
Greenwich Mean Time (GMT) is an international time-keeping standard, based on the local time at the 0 longitude point in Greenwich, England. Using GMT, you have an important clue to the approximate longitude location of your Mystery Classrooms.

Each Mystery class has revealed what time it will be using Greenwich Mean Time (GMT) when the sun rises at their Mystery site on March 20, 2001 (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 each Mystery Class location.

The GMT Worksheet below will walk you through the calculations. We also provide you with two examples where we show you how to calculate the approximate longitude for two of this year's Mystery sites.

Now It's Your Turn!
So let's get started by having you go to the GMT Worksheet. This will give you the GMT Sunrise time for the 10 Mystery classes first, and then walk you through two examples. Print it and go. Good Luck!

This Week's Sunrise/Sunset Times
Remember, the secret Mystery sites recorded their times last Monday, the same day you collected your own local sunrise/sunset data.

Journey North Mystery Class

Sunrise/Sunset Data

Data For: Monday, March 12, 2001


































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

Teacher Tip: Rappin' and Rhyming With Longitude

"That big tall dude called Longitude
Had an attitude about Latitude..."

So starts the "rap" that Florida Teacher Alison Bailey composed to "to help my third graders understand longitude and latitude while they're doing Mystery Class." Take a look:

Spring Fever Anyone? Discussion of Challenge Question #3
Thanks to all of the classes who answered this Challenge Question. We can tell that you are watching your graphs very carefully! Many of you really "lined things up" in your responses, and here are just a few examples:

"We think that all the lines of the graph will come together at the 12 hour line. The first day of spring is March 20th - the equinox. On that day there will be equal day and equal night. Someone in our class said that it looks like Mystery Class 5 is racing to catch up to everyone else." Miss Donohue's class, Marlboro Middle School, NJ

"Because each location is like 12:00, 12:01, 12:02, 12:03, 12:04, they might get closer and closer." Jonah from Miss Bailey's 3rd Grade Class, Citrus Elementary School in Vero Beach, FL

"My partner and I think that the lines on the graph will meet. Afterward I think they will criss-cross and separate. The lower hemisphere is almost to their winter months while the upper hemisphere is going into our summer months." Alex G. & Phillip S. from St. John's Greek Orthodox in Tampa, FL

"We think that all the lines of our graph will be close to 12 hours of daylight on March 20 because it is the Vernal Equinox or first day of spring . This means equal day and night." Mrs. Raftery's Sixth Grade, Richmond, MA.

The Next Mystery Class Update Will be Posted on March 23, 2001

Copyright 2001 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form

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