Transcript Time Zones and the International Date Line

What time is it?
 Given no modern conveniences.
 You will be dropped off someplace in the
world.
 You will have a 2-way radio and 48 hours
to radio me and tell me the correct time
at your position, accurate to within 5
minutes.
 Then I’ll pick up up and give you…
$1,000,000!!!
What time will you pick to call
me?
How will you know when it is
that time?
Hint:
NOON
Another hint...
Day 1
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Find a straight stick
Put it in the ground before the sun comes up
As sun rises it will make a shadow of the stick
What do you do with the shadow?
 Place a little stick at the end of the shadow
 Continue placing sticks at the end of the shadow
periodically throughout the day
Day 1 cont...
 Are all the little sticks the same distance
from the tall stick?
 Which little stick will you want to use the
next day?
 Which sticks marks noon?
 How do you know which stick marks
noon?
Day 2
 When do you call me to come get you on
this day?
Clocks
Big city clocks had to be adjusted daily
Highly inaccurate: too fast or too slow
Every city had it own noon
Whose noon is first? Mesa or Yuma
Was every city having it’s own noon a problem
in horse and buggy days?
 Every city having it’s own noon became a
problem when what was invented?
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Railroads
Why designate time zones?
 Railroads were so reliable that people
wanted schedules
 In order to make schedules there
needed to be a system of designated
time, so that every cities noon wasn’t
different
International Meridian
Conference
 1884
 27 nations
 Established Royal Observatory at
Greenwich as the Prime Meridian
 72% of ships already used Royal Obs
 Greenwich Mean Time (GMT)
Time Zones
 Earth is a sphere
(360º)
 Rotates at the
rate of 15º per
hour
 Takes 24 hours to
complete 1
rotation
Time Zones
 24 different time zones across the globe
 6 times zones in United States
Daylight Savings Time
 Do Arizonan’s observe DST?
NO
Differences between time zones?
 What is the time in California?
 What is the time in Dallas, TX?
What is the first thing said in
every episode of Star Trek?
 “Captain’s log, star
date…”
 Why?
Who was Ferdinand Magellan?
What was Magellan’s route?
What solves the problem of
losing a day when traveling west?
International
Date Line
International Date Line
 Marks the place
where each day
officially begins
 New day sweeps
westward
 Earth turning
eastward
Cross the line heading west? Add a
day
 Cross the line heading east? Subtract a day
Practice…
 How many time zones between San
Francisco and Tokyo?
 When you fly to Japan, how will you
adjust you watch calendar?
More practice…
 Crossing the International Date Line
going west what do you do?
 Crossing the International Date Line
going east what do you do?