Samacheer Class 6 Social Science - Globe

Local time refers to the time at a specific location on Earth based on the position of the sun. When the sun is directly overhead at noon on a particular line of longitude, it is 12 noon at all places located on that same line of longitude. This is called local time or solar time. Local time varies from place to place depending on their longitude. For example, places located 15° east of a given meridian will have a local time one hour ahead, while places 15° west will have a local time one hour behind. Local time is different from standard time, which is used across entire time zones for practical purposes.

Lines of latitude and longitude are imaginary lines drawn on the globe to help locate places and measure distances and time on Earth. Lines of latitude, also called parallels, are drawn horizontally from east to west and measure distances north or south of the Equator. Lines of longitude, also called meridians, are drawn vertically from the North Pole to the South Pole and measure distances east or west of the Prime Meridian. Together, these two sets of lines form a grid system that allows us to determine the exact geographical position of any location on Earth. Lines of latitude help establish time zones, while lines of longitude help determine local time. By using the coordinates provided by latitude and longitude, we can accurately identify any place on the globe and calculate distances between different locations.

The regions on Earth between the North and South lines of latitude at 66½° and the poles at 90° are called the Frigid Zones. These include the Arctic region from the Arctic Circle at 66½° N to the North Pole at 90° N, and the Antarctic region from the Antarctic Circle at 66½° S to the South Pole at 90° S. In these zones, the sun's rays fall at a very steep angle throughout the year, resulting in extremely low temperatures and harsh climatic conditions. The sun remains below the horizon for several months during winter, and the ground is permanently frozen. These extreme conditions make the Frigid Zones largely uninhabitable, with very sparse vegetation and limited human settlement.

The International Date Line runs in a zigzag pattern rather than following a straight path along the 180° meridian. This zigzag course was deliberately designed to avoid dividing countries and island groups into different calendar dates. If the International Date Line were drawn straight, some countries would have two different dates within their borders, causing confusion in administration, commerce, and daily life. By deviating from the 180° meridian, the line passes through ocean areas and around land masses, ensuring that each country maintains a single date. This arrangement helps maintain consistency and prevents the practical difficulties that would arise if a single nation had to observe two different dates simultaneously.

The globe is a three-dimensional scale model of the Earth that serves several important purposes. Since the Earth is enormous and we inhabit only a small portion of it, we cannot see the entire planet from the ground. A globe allows us to visualize the complete shape and structure of the Earth as it would appear from space. It helps us understand the distribution of continents, oceans, and major geographical features across the planet. The globe displays lines of latitude and longitude, which enable us to locate any place on Earth using coordinates. It also shows the relative positions of countries, their sizes, and their relationships to one another. Additionally, a globe helps us comprehend the spherical nature of the Earth and how different regions experience varying climates and seasons. By studying a globe, we can better understand global geography, plan routes for travel, and appreciate the interconnected nature of our world.

Northern Hemisphere:
Northern Hemisphere. The area of the Earth found between the Equator (Oo) and the North pole (90oN) is called the Northern Hemisphere.Southern Hemisphere:
Southern Hemisphere. The area of the Earth from the Equator (0°) and the South pole (90°S) is called the Southern Hemisphere.Eastern Hemisphere:
Eastern Hemisphere. The part of the Earth between the 0° line of longitude and 180° East line of longitude is known as the Eastern Hemisphere.Western Hemisphere
Western Hemisphere. The part of the Earth from Oo line of longitude and 180° West line of longitude is called as Western Hemisphere.

The significant lines of latitude are
Equator 0°
Tropic of cancer 23 1/2° N
Tropic of Capricorn 23 1/2° S
Arctic Circle 66 1/22°N
Antarctic Circle 66 1/2° S
North Pole 90° N
South Pole 90° S
Based on the amount of heat received from the sun, our world is broadly divided into three heat zones.
1. The Torrid Zone : On both sides of the equator, the region lying between the Tropic of cancer and Tropic of Capricorn is called the Torrid zone. This zone gets the direct rays of the sun all the year round. Hence the climate is hot and humid.
2. The Temperature Zone : This zone is neither hot nor very cold. It lies between the Torrid zone and Frigid zone in both the hemispheres.
3. The Frigid Zone : The region lying between the Arctic circle and North pole and between Antarctic circle and south pole is called the frigid zone. It receives very slanting rays of the sun and is therefore very cold.

Indian Standard Time is the time zone used throughout India for administrative and civil purposes. The longitudinal extent of India spans from 68° 7' E to 97° 25' E, which means approximately twenty-nine lines of longitude pass through the country. If each line of longitude were to have its own local time, it would create confusion and make coordination between different regions extremely difficult. Therefore, the 82½° E line of longitude, which passes through the central part of India, was chosen as the Prime Meridian for calculating Indian Standard Time. This line passes through Mirzapur in Uttar Pradesh and represents the standard reference for the entire nation. By adopting a single standard time based on the 82½° E meridian, India maintains uniformity in timekeeping across all states and territories, regardless of their actual geographical position. This ensures smooth functioning of railways, postal services, telecommunications, and all other national systems that depend on synchronized timing.