Question

How do longitudes help us in calculating time?

Answer 1

* Longitudes help us to calculate time.
* Time is measured by the movement of the earth.
- The earth moves on its axis from West to East. It is called rotation.
* It takes 24 hours for the earth to complete one rotation.
- This means in 24 hours, the earth completes ${360}^{\circ }$.
- Hence, it takes about 4 minutes for crossiing one degree of longitude (or it takes one hour in crossing 15 degrees of longitude)
- Accordingly, the earth has been divided into 24 time zones of one hour each.
- This means each place has different times of sunrise and sunset.
- Places east of the Greenwich Meridian experience day or sunrise earlier than the places lying west of this Meridian. In other words, time is ahead in the East, at the rate of 4 minutes per degree of longitude.