Time Zones

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Time Zones

• Does anybody really know what time it is?

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What is Time?

• An interval in which an event occurs
• Our senses cannot feel it
• How do we measure time?

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Measuring Time

• One Year
• One day
• One Hour
• One Minute

One revolution around the sun
One rotation around the axis
24 in one day
60 in one hour
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What Happens in Time

• 1 second - average heart beat
• 2 minutes - hold your breath
• 3 days - live without water
• 2 weeks - hair grows out
• 75 years - average human life span

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One Year

• Earth makes one complete revolution around the
  sun
• 365 1/4 days
• 52 weeks
• Extra day every 4 years - February 29th
• Measured with a calendar

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One Day

• One complete rotation of the earth on its axis
• 24 hours - measured with a clock or watch
• Divided into two 12 hour periods
• Am - ante meridiam - before the meridiam
• Pm - post meridiam - after the meridiam
• Measured with a calendar

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Time Zones

• Earth is divided into 24 time zones
• Each time zone is one hour later - earlier
• Distance from one time zone to the next is 15
  seconds longitude
• US has four time zones

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Add one hour
Subtract one hour
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The Prime Meridian

• Line of zero longitude
• Travels through Greenwich England
• GMT - Greenwich Mean Time
• UT Universal Time
• 180 degrees opposite of the International Dateline

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Prime Meridian
International Dateline
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More Information

• Time and Date
• World time zones
• Earth and Moon Viewer
• Map showing day and night

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