A Globe, Latitudes and Longitudes Chapter Notes | Footprints Class 6: Book Solutions, Notes & Worksheets PDF Download

The Globe

We know that the Earth is shaped like a sphere, but it's slightly flattened at the poles and bulges at the Equator due to the centrifugal force from its rotation. This shape is called a geoid. In our studies, we use a spherical model called a globe to represent the Earth. The globe is always mounted on a stand with its axis tilted.

The Earth's Axis

The Earth's axis is an imaginary line passing through its center around which it rotates. It's tilted at an angle of about 23.5 degrees. 

• This tilt is the angle between the Earth's axis and a line drawn perpendicular to its orbital plane—the path it takes around the Sun. 
• The North Pole is at the north end of the axis, and the South Pole is at the south end.
• To locate places on Earth, geographers use two sets of imaginary lines drawn on globes or maps: latitudes and longitudes. 
• These lines are not physically on the Earth's surface but help us study locations and navigate the globe.

Latitudes

• The Equator splits the Earth into two equal halves: the Northern Hemisphere and the Southern Hemisphere. It marks 0 degrees latitude, while the poles are at 90 degrees north and 90 degrees south, respectively.
• Latitude measures the angular distance of a place, north or south of the Equator, starting from the Earth's center. To measure equal distances from the Equator, circles are drawn 10 degrees apart on both sides. 
• These lines, called parallels of latitude, run parallel to the Equator from west to east. There are a total of 180 parallels of latitude—90 in the Northern Hemisphere and 90 in the Southern Hemisphere.
• Important lines of latitude include the Equator (0 degrees), Tropic of Cancer (23.5 degrees north), Tropic of Capricorn (23.5 degrees south), Arctic Circle (66.5 degrees north), Antarctic Circle (66.5 degrees south), North Pole (90 degrees north), and South Pole (90 degrees south).

Heat Zones

Earth has different climate zones because of the way sunlight falls on it. Near the Equator, it's hot (Torrid Zone), and as we move away, it gets cooler.

Longitudes

Longitude measures the angular distance of a place on Earth's surface, east or west of the Prime Meridian. These lines of longitude, or meridians, are drawn from the North Pole to the South Pole and are of equal length.

• To establish a common reference for measuring east-west distances, the Prime Meridian, passing through Greenwich, England, was agreed upon as the 0-degree line. 
• Meridians are drawn at one-degree intervals on both sides of the Prime Meridian, totaling 180 degrees east and 180 degrees west. The 180th meridian is both the eastern and western extremes, forming a complete circle with the Prime Meridian.
• Together, the Prime Meridian and the 180th meridian create the Great Circle, dividing the Earth into the Eastern Hemisphere and the Western Hemisphere. Any two opposite longitudes also form a Great Circle, always 180 degrees apart.
• Meridians of longitude are drawn at intervals of 10 degrees on globes or maps, each labeled with E or W to denote its position in the Eastern or Western Hemisphere. For example, a meridian three degrees east of the Prime Meridian would be labeled as 3 degrees E.

Comparing latitudes and longitudes:

• Latitudes run parallel to each other and are measured north or south of the Equator.
• Longitudes are farthest apart at the Equator and converge at the Poles.
• Parallels of latitude run east-west, while meridians of longitude run north-south.
• All lines of longitude are of equal length, while the length of lines of latitude varies.
• There are 180 parallels of latitude and 360 meridians of longitude.

Locating Places on Earth

Lines of latitude and longitude on a globe or map create a grid system that helps locate any place on Earth. Parallels of latitude run east-west, while meridians of longitude run north-south. The intersection of these lines at right angles pinpoint the exact location of a place.

For instance, if your city were located where the lines intersect at 30 degrees north latitude and 75 degrees east longitude, your location would be expressed as 30 degrees N and 75 degrees E. Similarly, ships at sea and airplanes in the sky use these lines to describe their exact locations.

For more precise locations, each degree is divided into 60 parts called minutes (written as '), and each minute is further divided into 60 seconds (written as "). For example, the location of Delhi is approximately 28 degrees 38 minutes north latitude and 77 degrees 12 minutes east longitude.w

Longitude and Time

Longitude plays a crucial role in determining the time of a particular place. As the Earth rotates from west to east in an anti-clockwise direction, places to the east experience sunrise earlier than those to the west. Consequently, time varies from one longitude to another. For instance, when people in Delhi are having breakfast, those in London are fast asleep.

• Local time is set when our longitude is directly under the Sun at 12 noon, known as solar noon. Each meridian to the east and west will have its own local time.
• To avoid confusion when moving between locations, a system of time zones was established in 1884. The world is divided into 24 time zones, each covering 15 degrees of longitude. 
• The Prime Meridian, passing through Greenwich, England, serves as the starting point, and the local time there is known as Greenwich Mean Time (GMT).
• Before 1970, time was calculated based on the longitudinal distance from the Greenwich Meridian. 
• However, now, the Coordinated Universal Time (UTC) is used as the basis for digital timekeeping across time zones worldwide. UTC closely approximates GMT and ensures standardized timekeeping internationally.

Standard Time

To avoid confusion in timekeeping across different parts of a country, most nations designate a central meridian as the standard meridian. The local time at this standard meridian becomes the standard time for the entire country.

• In countries with vast territorial extents covering multiple time zones, such as Canada, the USA, and Russia, there may be more than one standard meridian.
• India, with a longitudinal extent from 68°07' E to 97°25' E, is not excessively large. 
• Therefore, the 82°30' E longitude, passing near the center of the country, close to Allahabad (now called Prayagraj), is selected as the standard meridian for the entire nation. 
• The local time at this meridian is known as Indian Standard Time (IST), which is approximately 5 hours and 30 minutes ahead of Coordinated Universal Time (UTC) and Greenwich Mean Time (GMT).

International Date Line

The International Date Line, established by international agreement, follows the 180th meridian and is positioned 180 degrees both east and west. You can observe that the 180th meridian is precisely 12 hours away from the Prime Meridian in either direction.

• When traveling from the right (Western Hemisphere) to the left (Eastern Hemisphere) of the International Date Line, one advances by a day, or loses a day. 
• Conversely, when traveling from the left (Eastern Hemisphere) to the right (Western Hemisphere), one moves back by a day, or gains a day.
• Ships and airplanes crossing the International Date Line, therefore, must adjust the date on their calendar accordingly. This line helps maintain a consistent calendar system globally despite the Earth's rotation and time differences across different longitudes.