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Time Zones. Astronomy Unit Ch. 4.2. Effect of Earth’s rotation. Created based on the rate at which the sun appears to move across the sky Sun rises in the east & sets in the west Earth takes 24 hours to rotate on its axis 24 time zones
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Time Zones Astronomy Unit Ch. 4.2
Effect of Earth’s rotation • Created based on the rate at which the sun appears to move across the sky • Sun rises in the east & sets in the west • Earth takes 24 hours to rotate on its axis 24 time zones • 360 in one circle, so each time zone is 15 apart • (360÷24hrs. = 15)
Dividing up Time Zones • Starting point is the Prime Meridian which runs through Greenwich, England • areas to the east (right) of the P.M. are ahead of Greenwich Mean Time (GMT or UTC) by one hour per time zone • areas to the west (left) of the P.M. are behind by one hour per time zone over
How many hours apart is point A and point B from each other? A B
Time Zones in the U.S. • The U.S. has 6 time zones: (from East to West) • Eastern Time behind UTC or GMT by 5 hours • Central Time (-6 hours) • Mountain Time (-7 hours) • Pacific Time (-8 hours) • Alaskan Time (-9 hours) • Hawaii-Aleutian Time (-10 hours)
The International Dateline • Separates two calendar days at 180˚ longitude (“on the other side” of the Prime Meridian) • Immediately to the left (west)is the eastern hemisphere which is always one day ahead of the western hemisphere to the right (east) • The line bends in order to include all of Pacific Island Nations