Question

Why is it 5:30 pm in India when it is 12:00 noon in London?

Answer 1

Hint: Two major movements of the earth attribute to climate and atmospheric conditions on the planet. The first is the rotation of the earth on its axis which is at an age of 23.5° which takes 24 hours for the earth for each complete rotation and results in day and night depending on which side is facing the sun. The other is the revolution of the earth on its orbit around the sun which takes 365.25 days to complete and results in seasons in a year.

Complete answer: Duration of the day also called daytime, is the time when a given location on the planet receives natural illumination from direct sunlight and approximately half of the earth experiences daytime at a given time based on the earth’s rotation. This has led to the designation of time zones so that a uniform standard time is observed at various locations. This is done through longitudes which specify the east-west position on the coordinate system. They are associated with the earth’s rotation and thus, local time varies with the longitude. A difference of 15° longitude corresponds to a one-hour difference in local time. An example of it is that London which is located at the UTC (Coordinated Universal Time and successor of the GMT) is the primary time standard and India with Indian Standard Time located at 82.5° E longitude and it has a time offset of UTC+5:30 meaning that when it is 12 noon in London, it is 5:30 pm in India.

Note: The time in London is decided by the Prime Meridian which passes near the Royal Observatory in Greenwich, England and is considered as the 0° longitude. It is also called the Greenwich Mean Time and denoted commonly as GMT.