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Mystery Class Update: March 19, 1999
Today's Report Includes:
- Celebrating Spring--Happy Vernal Equinox!
- The Longitude Problem
- How Time and Longitude are Related
- Why Greenwich Mean Time is Important
- Now It's Your Turn! Mystery Class GMT Worksheet
- This Week's Sunrise/Sunset Data
- Responses to Challenge Question #2
Celebrating Spring--Happy Vernal Equinox!
In celebration of this Saturday's Vernal Equinox, we have gathered a special set of longitude clues from the Mystery Classes 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, but first let's get right to our special clues!
**Since this week's Update is chockful of information, you definitely should print it out right away and work from the print out. BE SURE to read through the instructions carefully and completely.
(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
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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 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, 1999 (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 longitude of each Mystery Class location.
The worksheet below will walk you through the calculations, and we have provided two examples to guide you. So let's get started by giving you the GMT sunrise time for the Mystery classes first, and then trying out the 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
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Mrs. Berger's 5th Grade Class |
In celebration of this Saturday's Vernal Equinox, 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's today's data:
Journey North Mystery Class
Sunrise/Sunset Data
Data For: Monday, March 15, 1999
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Mystery Class |
Sunrise |
Sunset |
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# 1 |
06:30 |
18:31 |
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# 2 |
07:48 |
19:28 |
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# 3 |
06:44 |
19:05 |
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# 4 |
06:18 |
18:08 |
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# 5 |
06:56 |
21:05 |
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# 6 |
06:27 |
18:32 |
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# 7 |
05:59 |
17:56 |
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# 8 |
06:08 |
18:23 |
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# 9 |
06:47 |
18:34 |
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# 10 |
06:40 |
18:41 |
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:
"We think that the lines on the graph will all meet in the middle, at about 12 hours. We think that because although some are going up and some are going down, they all seem to be headed to the same spot." Lynn Connell's Humboldt Challenge Class (4th Grade) (lconnell@esu6.esu6.k12.ne.us)
"Our group thinks that on March 20, 1999 all of the mystery class graphs will reach the same photoperiod. We think that if they are not exactly equal they will all be close to 12 hours of sunlight. We think this because all of the graphs are heading towards 12 hours. Either decreasing or increasing. Also, that day is called Equinox, and so all of the classes should have almost equal hours of sun and night." Sincerely, Meghan m. Rachael, Emily. Canton, OH (pjones@ccd-school.org)
The Next Mystery Class Update Will be Posted on March 26, 1999.
Copyright 1999 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form
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