(a) if the time in London is 08.00 hours GMT and the local time in Addis Ababa is 12.00 noon on what longitude ts Addis Ababa? (b) Write explanatory notes o...

Answer Details

(a) Longitude of Addis Ababa

The Earth turns \(360^\circ\) in 24 hours, so \(1\) hour of time = \(15^\circ\) of longitude.

Time difference between Addis Ababa (12:00 noon) and London (08:00 GMT):

\[12:00 - 08:00 = 4 \text{ hours}\]

Longitude difference:

\[4 \times 15^\circ = 60^\circ\]

Because Addis Ababa is ahead of GMT (its clock reads later than London's), it lies east of the Greenwich Meridian.

Addis Ababa is on longitude \(60^\circ E\).

(b) Explanatory notes

(i) Time zones: A time zone is a belt of the Earth's surface, about \(15^\circ\) of longitude wide, that keeps the same clock time. The world is divided into 24 such zones (each 1 hour apart) so that places within a zone use one convenient standard time instead of a slightly different local time at every meridian.

(ii) Standard time: This is the single, uniform clock time adopted by a whole country or zone, usually based on a chosen central meridian. It saves the confusion of many local times; large countries that stretch across several meridians (such as the USA or Russia) adopt more than one standard time.

(iii) International Date Line: This is the imaginary line drawn mainly along the \(180^\circ\) meridian in the Pacific Ocean where the date changes. A traveller crossing it going westward (eastern to western hemisphere) gains a day (moves the calendar forward), while going eastward loses a day. The line is bent in places to avoid splitting land areas and island groups into two different dates.