Mystery Class Update: March 14, 2003
Is Everything Coming Together? Discussion of CQ #2
Nice job to all of you. Keep your eyes on your graphs because the Equinox is coming! Spring Begins Thursday--Happy Vernal Equinox! In celebration of next Thursday's Vernal Equinox, we have gathered a special set of Longitude Clues from the 10 secret Mystery Sites, which will be provided below. 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. 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 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! 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 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! How Time and Longitude are Related In order to use the GMT/Longitude 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. 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. Let's Get Started! Now It's Your Turn Instructions: 2. In order to use the GMT Worksheet, you will also need to print out the: 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: 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 10, 2003
(Note: Military time is usually expressed without any punctuation. We have used a ":" between the hours and minutes for clarity.) Clues Calendar: Plan Ahead and Mark Your Calendars Here's the 2003 Mystery Class Schedule so you know what to expect from Journey North. Please be sure to plan ahead.
The Next Mystery Class Update Will Be Posted on March 21, 2003
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