Aim: How do we find Aim: How do we find longitude?longitude?

Topic: Unit 1Topic: Unit 1

Main Idea: Time zonesMain Idea: Time zones

1) How fast does the earth spin?1) How fast does the earth spin?

The earth does one The earth does one 360 degree spin 360 degree spin every 24 hours so:every 24 hours so:

360 degrees/ 24 360 degrees/ 24 hours=hours=

15 degrees/hour15 degrees/hour

2) What are time zones?2) What are time zones?

They are sections of the world 15 degrees They are sections of the world 15 degrees of longitude apart with one hour of longitude apart with one hour difference.difference.

3) What is Greenwich Mean Time?3) What is Greenwich Mean Time?

This is the time on This is the time on the prime meridian the prime meridian where all of the where all of the world sets its timeworld sets its time

4) If you are west of the Prime 4) If you are west of the Prime Meridian your time is ____________, but Meridian your time is ____________, but if you are east then your time is if you are east then your time is ______________ because______________________ because________

______________________________________________________________

___________________________.___________________________.

5) How do we find longitude using 5) How do we find longitude using difference in time?difference in time?

Step 1: Find the Step 1: Find the difference in time in difference in time in hourshours

Step 2: Multiply by 15Step 2: Multiply by 15 Step 3: Local time is Step 3: Local time is

earlier=Westearlier=West

Local time is later=EastLocal time is later=East

SummarySummary

GMT Local Time Longitude12:00 P.M. 3:00 P.M.12:00 P.M. 6:00 A.M.12:00 P.M. 9:00 P.M.

3:00 P.M. 45oW

3:00 P.M. 105oW

3:00 P.M. 90oW12:00 A.M. 6:00 A.M.

4:00 A.M. 150oE