Latitude, Longitude and Time Zones

[Music] one way of locating something in a city a building for instance is to do it in terms of two streets that cross saying that the First National Bank is at the corner of Lincoln and Oakton locates it a similar method is used to locate places anywhere on Earth this system combines parallels of itude with meridians of longitude before we study this system let's review some geography let's look down on the Earth from above the North Pole our Earth is a nearly perfect sphere we can draw circles on it the largest that can be drawn is called a great circle like any other Circle it is measured in degrees in a quarter of a circle there are 90° in half a circle 180° and in a full circle 360° the Earth rotates on an axis whose ends are marked by the North Pole and the South Pole the equator is a great circle halfway between the poles it is the starting place for the measurement of latitude we call it latitude zero all places on the equator are at Latitude zero all places on this circle which is north of the equator and parallel to it are at 10° north latitude to see what this means we'll cut away the Earth along a great circle that passes through the poles the angle between the Equator and the circle marked 10° measures 10° 20° north of the equator we can draw another Circle all places on this circle are at 20° north latitude we can draw circles every 10° north of the equation until at the North Pole we reach 90° north latitude we can mark off circles in the same way south of the Equator we call all these circles parallels of latitude about half of the United States lies between the 30th and 40th parallels of north latitude parallels can also be marked for single degrees of latitude the distance between any two parallels of latitude is the same around the earth one degree of latitude is about 70 M wide using only degrees we can locate a place within 70 Mi of its actual position to give the location of places more exactly we divide the degree into 60 Parts each called a minute a minute of latitude is about 1 and 1 16 miles wide to locate a place even more exactly we divide one minute of latitude into 60 Parts each called a second 1 second of latitude measures about 100 ft in width so if we know the degrees minutes and seconds of latitude of a place or object like this highway bridge then we know within 100 ft how far north or south of the Equator it is but for its East West position we need another set of lines we saw that the equator is a great circle midway between the poles each half of a great circle that passes through the poles is called a Meridian the Meridian that passes through grenwich England is the starting place for our measurement of longitude we call it the prime meran all places on this Meridian are at longitude zero all places along this Meridian 15° west of the Prime Meridian are at 15° west longitude to see what this means we'll cut away the Earth along the Equator the angle between the Prime Meridian and the Meridian marked 15° measures 15 de another 15° west of the Prime Meridian we can draw another Meridian all places along this Meridian are at 30° west longitude we can draw meridians every 15° west of the Prime Meridian until we reach 180° halfway around the earth from the Prime Meridian in the same way we draw meridians of longitude east of the Prime Meridian to the 180th Meridian if we look at a section of the full Earth between two meridians we see the distance is widest at the equator and narrowest at the poles one degree of longitude at the equator is about 70 Mi wide halfway to the poles a degree of longitude is only about 50 m wide we also divide degrees of longitude into minutes and seconds by using both meridians of longitude and parallels of latitude we can give the nearly exact location of this highway bridge or any other place on Earth on a map we often find lines of latitude and longitude drawn in on this kind of map a Mercator Projection meridians are not shown meeting at the poles as they really do suppose we wanted to give the location of Denver Colorado Denver is nearest to the 40th parallel north of the equator it is west of the Prime Meridian on the 105th Meridian Denver is located at Latitude 40° North longitude 105° West let's locate Sydney Australia it is south of the Equator on the 34th parallel and east of the Prime Meridian on the 151st Meridian its location is latitude 34° South longitude 151° East so we've seen how we use use latitude and longitude to give locations of places anywhere on Earth we also use longitude to help us set up time zones we measure Time by The Turning of the Earth on its AIS the Earth rotates once every 24 hours and 24 hours is the length of our day because the Earth turns we know that at any moment while it is night at some places on Earth at other places the sun is rising or high overhead the time of day everywhere on Earth is in general determined by the Sun as the Earth rotates all parts of it turn through a full circle of 360° every 24 hours this means that in 1 hour the Earth turns through 124th of a circle or through 15° per hour knowing this we can see how the Earth is divided into 24 time zones each 15° wide the starting place for the system of time zones is the meridian that passes through grenwich England the prime meridian longitude zero it is the center of a time zone that is 15° wide when the sun has reached its highest point over the prime meridian that is when it is noon suntime there the time is considered to be noon across the full Zone the time in this zone is usually called Greenwich time the 15th Meridian west longitude is the center of the first Zone to the west of Greenwich time when it is noon Greenwich time it is 11:00 a.m. in this Zone time in the second Zone West of Greenwich The Zone including the 30th Meridian is 10:00 a.m. and so every 15° of west longitude Standard time is earlier by 1 hour time is later in the zones east of Greenwich when it is noon Greenwich time in the first Zone East of grenic the time is exactly 100 p.m. 1 hour later than Greenwich time and every 15° of east longitude time is later by 1 hour and so the rotating Earth has been divided into 24 time zones one for each of the 24 hours of the day while the time zones were planned to follow meridians parts of the boundaries of many have been changed for convenience we can see some of these changes by looking at the time zones of the United States each Zone has been given a name the Eastern parts of the United States are in the Eastern Standard time zone when it is noon Greenwich time it is 7 a.m. eastern standard time at the same moment it is 6:00 a.m. Central Standard Time 5:00 a.m. Mountain Standard Time 4:00 a.m. Pacific Standard Time 3:00 a.m. Yukon Standard Time and 2 a.m. in this Zone which has two names in Alaska it is called Alaska Standard time but in Hawaii the same zone is called Hawaiian Standard Time in the Far Western Parts of Alaska including the uan islands it is 1:00 a.m. gnome Standard Time 11 hours earlier than grenwich time located in the region of the Pacific Ocean is a line generally following the 180th Meridian it has been agreed that each new calendar day begins along this line This is the International Date Line it is one day later on the west side of the line than it is on the east side so if it is Monday on the east side of the line then it is Tuesday on the west Travelers who cross the date line from west to east repeat a day Travelers who cross the line from east to west lose a day so with parallels of latitude and meridians of longitude we can give the location of places anywhere on the earth and from the meridians of longitude we we have the basis for a worldwide system of time zones [Music]