Longitude and time

# Longitude and time Video Lecture - Social Studies (SST) Class 9

## Social Studies (SST) Class 9

51 videos|427 docs|89 tests

## FAQs on Longitude and time Video Lecture - Social Studies (SST) Class 9

 1. What is longitude and how is it measured?
Ans. Longitude is a geographical coordinate that specifies the east-west position of a point on the Earth's surface. It is measured in degrees, with the Prime Meridian (0 degrees) passing through Greenwich, London. Longitude is measured using a device called a sextant, which uses the position of celestial bodies such as the Sun, Moon, or stars to determine the angle between the observer's location and the Prime Meridian.
 2. What is the significance of longitude in determining time?
Ans. Longitude plays a crucial role in determining time as it helps establish different time zones around the world. Each degree of longitude represents 4 minutes of time difference. For every 15 degrees of longitude, there is a time difference of one hour. By knowing the longitude of a particular location, we can calculate the time difference from the Prime Meridian and determine the local time.
 3. How does longitude affect the measurement of time during travel?
Ans. When traveling across different longitudes, the time changes due to the Earth's rotation. As we move eastward, the time becomes later, while moving westward makes the time earlier. This change in time is the basis for crossing time zones. For example, if we travel from London (GMT) to New York (GMT-5), we will experience a time difference of 5 hours, where New York's local time is 5 hours behind London.
 4. How can longitude and time be used in navigation?
Ans. Longitude and time are essential for navigation, especially at sea. By using a chronometer (a precise timekeeping device), sailors can determine their longitude by comparing the local time with the time at the Prime Meridian. The time difference can then be converted into degrees of longitude, allowing sailors to pinpoint their location accurately on a nautical chart.
 5. Are there any countries or regions that do not follow the time zone system based on longitude?
Ans. Yes, there are a few exceptions to the time zone system based on longitude. Some countries or regions, like China, have adopted a single time zone across their entire territory for administrative convenience. Similarly, some countries or regions may have chosen to adjust their time zones for economic or political reasons, deviating from the standard time zone boundaries based on longitude.

## Social Studies (SST) Class 9

51 videos|427 docs|89 tests

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