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Mystery Class Update: March 17, 2000

Today's Report Includes:

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

We'll also be giving you the latest sunrise and sunset times from Mrs. Berger's class, and some 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 guess each Mystery Class location by the April 28 deadline. Here are some important Mystery Class dates for the coming weeks:

  • March 17: Longitude Clues given

  • March 24, 31; April 7, 14, 21: New clues from the Mystery Sites given each week

  • April 28: Deadline for guesses

  • May 5: Mystery Sites Revealed!

  • May 12: Meet the Mystery Sites

Equinox Clues Rule!

** Since this week's Update is packed with information, you definitely should print this report right away and work from the print out. Then, BE SURE to read through the instructions carefully and completely so your guesses 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 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.

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
To use GMT clues to help you find the longitude of a Mystery Class, you must first understand a little 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 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 location of your Mystery Classrooms. Each Mystery class has revealed what time it was in Greenwich Mean Time(GMT) when the sun rose at the Mystery Class on March 20, 2000 (the Vernal Equinox.) By knowing this GMT sunrise time for a Mystery Class and also knowing the time the sun rose at Greenwich that day, you can figure out how long the earth spun between the time the sun rose at the Mystery Class location and the time it rose 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. The GMT Worksheet will first link you to the GMT sunrise times for the Mystery classes, and then link you to two examples.

Now It's Your Turn!!
The following document will walk you through this activity. Print it and go. Good Luck!

This Week's Sunrise/Sunset Times

Mrs. Berger's 5th Grade Class

Mrs. Berger and her students from East Hills School in New York had no "problem" gathering this week's sunrise and sunset data for you.

Remember, this information was recorded on Monday, the same day you collected your sunrise/sunset data. Here are this week's data:

Journey North Mystery Class

Sunrise/Sunset Data

Data For: Monday, March 13, 2000


































Counting the Days until Spring? Responses to CQ #2
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 "hit the mark" and "lined up" on your responses, and here are just a few examples:

"Our class decided that the lines will keep going straight. They will all meet on March 20, 2000 at approximately 12 hours. March 20th is the Spring Equinox which means there will be approximately 12 hours of daylight and 12 hours of night." Bath Local Schools,in Lima, OH (SCHMIDD@BATH.NOACSC.ORG)

"Dear Sun Watchers, The lines will intersect on March 20 as they keep going in the direction they are headed. Eventually, we think it will look like an X because some are losing sunlight and some are gaining sunlight. " Nick, Grade 5, Mrs. Howley's Class, Pemetic School in Southwest Harbor, ME (

The Next Mystery Class Update Will be Posted: March 24, 2000

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