1. Aim: How do we use time zones to determine longitude?

2. Do Now:
When the clock strikes midnight on New Years Eve in New York, what time will it be in Los Angeles, California? How do you know? 9pm

3. Time Zones
Time Zones: There are 24 time zones in the world to represent 24 hours in the day. A. 360o in a circle/ 24 hours in a day=15o/hr *This is why each time zone is 15o longitude in width.

4. Finding Longitude Using Time Zones
Chronometer- a device that tells the time at the Prime Meridian (Greenwich Mean Time).
If you know the time at the Prime Meridian and your time, you can determine your longitude.
PM ?
What is your Longitude
12pm
____30oW__

5. West Side or East Side
C. If your time is earlier than prime meridian time, you’re in the west. If your time is later than prime meridian time, you’re in the east. PM WEST EAST 10am 12pm 2pm

6. Steps to determine your longitude
Count how many hours it is from your time to the Prime Meridian time
Multiply how many hours you calculated from step 1 by the number 15 (15o/hr)
If your time is earlier than P.M. time that you are in the west, if it is later than P.M. time than you are in the east.

7. Lets Practice Time Zones