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.
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:
Equinox Clues--Tips for Success
(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.)
The Longitude Problem
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
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
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:
The Next Mystery Class Update Will be Posted on March 23, 2001
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