Time Zones
description
Transcript of Time Zones
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Time Zones
Aim: How are time zones created?
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Objectives
• Understand the relationship between longitude, rotation and time.
• Calculate local time when given GMT
• Calculate longitude when given GMT
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• http://www.youtube.com/watch?v=hSGeSRdztzM&feature=related
• http://video.google.com/videoplay?docid=-5041127474937930014#
• http://www.time.gov/
• http://www.usflashmap.com/products/time_zone_map/actionscript-time-zone-map.htm
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1. How are time zones created?
• And also in here
• Earth is divided into 24 time zones based on longitude.
• Each zone is about 15o of longitude = 1 hour
• The Earth rotates 150/hour
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http://www.timezonecheck.com/
The time zones are not perfect.
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Ex 1: 6 am in Denver = ________ in San Francisco?
• As you travel WEST, time goes ______________ (subtract)
• As you travel EAST, time goes _____________ (add)
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Ex 2: 4 pm at A = __________ at B?
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Ex 3: If you could instantly travel 45o west from NYC, what would be the time difference?
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2. What is solar noon?
• 12:00 pm is known as solar noon or local solar noon, or the time of day when the sun reaches its highest point in the sky.
• Locations with the same longitude have the same solar noon, because the sun hits its highest point in the sky all along that line of longitude at the same moment.
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3. What is Greenwich Mean Time (GMT)?
• The prime meridian passes through Greenwich, England.
• Your longitude can be calculated by comparing local time with GMT.
• Your longitude = difference from GMT x 15o/hour
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Ex. 4: What time is it in Greenwich, England (at 0° longitude), when it is noon in Massena, New York?
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Example 5: Your local solar noon occurs at 8 AM Greenwich time. What is your longitude?
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Example 6: Your longitude is 150oW and the time is 6:40 AM. What time is it in London, England?
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4. What happens when we cross the International Date Line?
September 1, 2010 September 2, 2010
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5. Time Math
• Example: (hh:mm:ss)
Remember: You must “borrow” or take 60 minutes or 60 seconds
11: 15 : 32-07: 23 : 04 3: 52 : 28